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Reduction in chiasma frequency and pollen fertility due to multiple chromosomal associations and univalents in Saxifraga diversifolia from alpine regions of northwest Himalayas (India)
Abstract
Two varieties of Saxifraga diversifolia, diversifolia and parnassifolia, collected from the moist alpine slopes around Gauri Kund, 3930 m (Manimahesh Hills, Himachal Pradesh, India), are studied for detailed male meiosis, chiasma frequency and pollen fertility. Both varieties exist at diploid level (based on x = 8), and show a meiotic chromosome count of n = 8 at diakinesis and metaphase-I, and regular chromosome distributions at anaphases-I/II. The meiotic chromosome count of n = 8 ascertained here represents a new aneuploid cytotype, supplementing the earlier report of a diploid cytotype with 2n = 20 from the north-west Himalayas in India and the Nepal Himalayas. Of the two varieties, var. diversifolia showed the presence of multiple chromosomal associations and univalent chromosomes at diakinesis and metaphase-I of meiosis-I. On the other hand, var. parnassifolia does not have multivalent formation but showed only 2–4 univalent chromosomes at diakinesis and metaphase-I. Occurrence of univalents in pollen mother cells of var. diversifolia and parnassifolia reduced the chiasma frequency significantly and also caused some pollen sterility (7–8%). The paper herein discusses for the first time the occurrence of structural heterozygosity and univalent chromosomes and their apparent affect on chiasma frequency and pollen fertility in S. diversifolia.
... Consequently, 50% non-viable gametes are produced toward pollen side and 50% toward ovule side. Such a phenomenon of structural heteozygosity leading to some sterility of pollen grains has been reported in a number of cases namely, Chrysanthemum coronarium (Gill and Gupta 1981), C. zawadskii (Kim et al. 2008), Lathyrus boissieri (Ghaffari et al. 2009), Artemisia parviflora , Euphorbia pilosa (Saggoo and Farooq 2011), Astragalus chlorostachys (Rana et al. 2012), Tradescantia spathacea (Koul et al. 2013), Saxifraga diversifolia (Kumar and Singhal 2013), Achillea millefolium (Singhal et al. 2014) and Anemone rivularis (Kumar et al. 2015). Complete male sterility due to reciprocal translocations has also been reported in Allium consaguineum (Gohil and Koul 1978) and Allium roylei (Sharma and Gohil 2003, Kohli and Gohil 2011, Kohli and Koul 2013. ...
... Occurrence of high frequency of univalents (up to six) in 15.15% of the analysed meiocytes in the studied diploid taxon of F. acutatum could be attributed to the hybrid constitution of the genome (Stebbins and Pun 1953, Stoyanova 1970, Singhal 1982, Palakarcheva and Dorossiev 1992, Krusteva 1995, Doroszewska and Berbeć 1996, 2000, Legget 1998, Trojak-Goluch and Berbeć 2003, Kumar and Singhal 2013. However, asynapsis/desynapsis resulting into univalent chromosomes in the present case could also originate spontaneously (Kaul and Murthy 1985, Singh 2003, Bala et al. 2010, Sharma et al. 2010, Kumar and Singhal 2011, Ranjbar et al. 2012 or be induced by various factors such as temperature, humidity, nutrients, radiations, mutagens and chemicals influencing chromosomal pairing during meiosis I (Prakken 1943, Ahloowalia 1969, Sjödin 1970, Singh et al. 1977, Koduru and Rao 1981, Vishnuvardhan and Lakshmi 1987, Rao and Kumar 2003, Kumar and Rai 2006, 2007, Gulfishan et al. 2010, Avijeet et al. 2011. ...
... However, asynapsis/desynapsis resulting into univalent chromosomes in the present case could also originate spontaneously (Kaul and Murthy 1985, Singh 2003, Bala et al. 2010, Sharma et al. 2010, Kumar and Singhal 2011, Ranjbar et al. 2012 or be induced by various factors such as temperature, humidity, nutrients, radiations, mutagens and chemicals influencing chromosomal pairing during meiosis I (Prakken 1943, Ahloowalia 1969, Sjödin 1970, Singh et al. 1977, Koduru and Rao 1981, Vishnuvardhan and Lakshmi 1987, Rao and Kumar 2003, Kumar and Rai 2006, 2007, Gulfishan et al. 2010, Avijeet et al. 2011. The studied individuals of this medicinal herb which grows at higher altitudes in the valley where due to low temperature conditions prevailing at a time when plants enter flowering/bud stage might have been responsible for causing synaptic irregularities in chromosomes during meiosis as has been suggested earlier in R. laetus , D. angulatus (Kumar et al. 2012), S. nigrum ) and S. diversifolia (Kumar and Singhal 2013). Consequent to reciprocal translocations coupled with high frequency of univalents, the studied accession of F. acutatum showed some reduction in pollen fertility. ...
Male meiotic studies carried out on the plants of Fagopyrum acutatum (Polygonaceae) collected from the Parvati valley, Kullu district, Himachal Pradesh, India confirms the earlier chromosome reports of 2n=16 from outside of India. The presently recorded chromosome count of n=8 in pollen mother cells (PMCs) is the first ever report of a diploid cytotype for the species from India. The presently studied diploid individuals from the Parvati valley showed the presence of structural heterozygosity for reciprocal translocations. Analysis reveals that multiple associations of four to six chromosomes were noticed in 39-40% meiocytes. A few PMCs in the accession also depicted the presence of two to six univalent chromosomes which could be attributed to the hybrid nature of the taxon or due to synaptic irregularities in chromosomal pairing during meiosis. Consequent to multiple chromosomal associations and univalent chromosomes, the studied plants depicted some pollen sterility.
... Partial homology resulted as a consequence of such exchanges between more than two nonhomologous chromosomes, leading to the pairing of non-homologous chromosomes in a diploid taxon, which is attributed either to the hybrid nature of the taxon or heterozygosity for reciprocal translocations (Singhal 1982). Since the first report of reciprocal translocations in the Stizolobium deeringianum by Belling (1914), their occurrence and consequences have been reported in a number of plants by various workers (Gohil and Koul 1978, Singhal and Gill 1981, Sharma and Gohil 2003, 2008, Talukdar 2008, 2010, 2013, Gupta et al. 2010, Kohli and Gohil 2011, Rana et al. 2012, Kumar and Singhal 2013. Here, we report the existence of structural heterozygosity due to reciprocal translocations in the species for the first time. ...
... However, the PMCs having univalent chromosomes tend to have decreased the value of chiasma frequency. Pollen sterility in a translocation heterozygote largely depends upon whether the orientation of multivalents is of the adjacent or alternate type at M-I (Ghaffari et al. 2009, Gupta et al. 2010, Rana et al. 2012, Kumar and Singhal 2013. In the present case, pollen fertility is high, so the orientation of multivalents at M-I seems to be of the alternate type in a majority of the cases. ...
... The occurrence of univalent chromosomes in some plants of A. millefolium from Dhundi which are not associated with any multiple association seems to be the result of synaptic irregularity (asynapsis/desynapsis) as opined by Singhal (1982), Datta et al. (2010), and Kumar and Singhal (2013). Synaptic irregularity, which influences chromosome pairing during meiosis, may be induced (Prakken 1943, Koduru and Rao 1981, Gulfishan et al. 2010, Avijeet et al. 2011 or originate spontaneously (Kaul and Murthy 1985, Singh 2002, Sharma et al. 2010, Ranjbar et al. 2012, Kumar and Singhal 2013. ...
Presently, A. millefolium, a morphogenetically variable species, has been scored from phytogeographically isolated and unexplored areas of the northwest Himalayas for chromosome counts and male meiotic course. All the studied accessions shared the same meiotic chromosome number of n = 9 and existed at diploid level. A majority of the accessions exhibited the normal meiotic course including microsporogenesis and almost cent per cent pollen fertility. However, three accessions scored from Sangla Valley (Chittkul, 3450 m) and Solang Valley (Dhundi, 3000 m and Palchan, 2480 m) showed the presence of multiple associations of chromosomes in PMCs (pollen mother cells). The quadrivalents formed as a consequence to reciprocal translocations are either chain or ring type (typical ring and zigzag). Meiocytes with multivalents depicted relatively higher chiasma frequency than those with normal bivalent formation. In 4.77% of PMCs, chromosomes remained as laggards during anaphase-I and organized into micronuclei during sporad formation. Consequently sterile/unstained pollen grains were observed. This is the first report of structural heterozygosity for reciprocal translocations in the species.
... Since the first report of such structural changes recorded by Gates (1908) in Oenothera rubinerves, these have been reported in a number of flowering plants. During the last decade or so, the structural heterozygosity for reciprocal translocation has been reported in the wild taxa of many flowering plants from our laboratory , 2018a, b, Malik et al. 2010, Saggoo and Farooq 2011, Rana et al. 2012, Kumar and Singhal 2013, Singhal et al. 2014, 2016, Kumar et al. 2015, Singhal and Kumari 2017, Kumari and Singhal 2018. ...
... physiological conditions (Bennett and Rees 1970), differences in expression of genes (Rees 1962, Wagenaar 1964) and temperature (Swanson 1943, Dowrick 1957. In the present case increase in chiasma frequency in one of the accessions seems to be a consequence of structural heterozygosity for reciprocal translocations as has also been suggested in Saxifraga diversifolia (Kumar and Singhal 2013) and Anemone rivularis (Kumar et al. 2015). ...
Meiotic studies have been carried out on six accessions of Artemisia roxburghiana from four regions of Western Himalayas. The accessions collected from Chamba, Kinnaur and Kullu districts of Himachal Pradesh and Kargil district of Jammu and Kashmir showed a normal meiotic course leading to high pollen fertility. However, the accession collected from Drass region of cold deserts of Ladakh, Jammu, and Kashmir showed abnormal meiosis caused by structural heterozygosity for reciprocal translocations. The present study adds the first report of structural heterozygosity in the species. Chiasma frequency was also calculated in the accessions to see the effect of reciprocal translocations. Besides, reciprocal translocation, the accession also showed various meiotic abnormalities in the form of the early disjunction of bivalents, chromatin bridges and laggards leading to abnormal microsporogenesis. Structural heterozygosity and other meiotic abnormalities in the accession seem to be responsible for a reduction in pollen fertility.
... Such structural heterozygotes occasionally produce duplications or deficiencies in the genome of PMCs, resulting in non-viable and sterile male gametes (Ghosh and Datta 2006). Such a phenomenon of reciprocal translocation leading to sterile pollen grains has also been reported in a number of plants, namely Citrus jambhiri (Singhal and Gill 1981), Chrysanthemum zawadskii (Kim et al. 2008), Artemisia parviflora (Gupta et al. 2010), Astragalus chlorostachys (Rana et al. 2012), Tradescantia spathacea (Koul et al. 2013), Saxifraga diversifolia (Kumar and Singhal 2013) and Achillea millefoilium (Singhal et al. 2014). Kumar and Singhal (2013) have reported multivalent and univalent in the varieties of S. diversifolia. ...
... Such a phenomenon of reciprocal translocation leading to sterile pollen grains has also been reported in a number of plants, namely Citrus jambhiri (Singhal and Gill 1981), Chrysanthemum zawadskii (Kim et al. 2008), Artemisia parviflora (Gupta et al. 2010), Astragalus chlorostachys (Rana et al. 2012), Tradescantia spathacea (Koul et al. 2013), Saxifraga diversifolia (Kumar and Singhal 2013) and Achillea millefoilium (Singhal et al. 2014). Kumar and Singhal (2013) have reported multivalent and univalent in the varieties of S. diversifolia. In the present case, 38.41% of PMCs showed quadrivalent formation at diakinesis and M I. Occurrence of quadrivalents in the wild diploid individuals seems to be the result of the reciprocal translocations (Mahama and Palmer 2003). ...
Cytological investigations have been carried out in one wild accession of Anemone rupicola Cambess. collected from the cold deserts of Ladakh division of Jammu & Kashmir India. The chromosome count of 2n=16 was observed and is the first chromosome record for the species from India. Meiotic analysis showed structural heterozygosity for reciprocal translocations as indicated by the presence of multiple associations of four chromosomes. Detailed meiotic analysis showed Pollen Mother Cells (PMCs) with laggards (32.87%) and chromatin bridges (21.91%) at anaphases I, II (A I, II)/telophases I, II (T I, T II), leading to abnormal microsporogenesis. Consequently, abnormal sporads such as triads (37.14%) and polyads (28.57%) were formed. Structural heterozygosis and other associated abnormal meiotic irregularities in the species showed considerable pollen sterility (32.20%) which could be attributed to the presence of ring/chain shaped multivalent in PMCs.
... Reciprocal translocations, also known as chromosomal interchanges, arise due to the exchange of broken segments of nonhomologous chromosomes (Mahama andPalmer 2003, Talukdar 2013). Ever since the first report of reciprocal translocations by Belling (1914), their occurrence and possible consequences have been reported in a number of flowering plants from N-W Himalayas by various workers (Gohil and Koul 1978, Sharma and Gohil 2003, Gupta et al. 2010, Kohli and Gohil 2011, Rana et al. 2012, Kumar and Singhal 2013. Presently such reciprocal translocations have been noticed in both the 2x and syncyte (4x) PMCs. ...
... However, the PMCs depicted with univalent chromosomes tend to have decreased value of chiasma frequency. Such an increase in chiasma frequency due to structural hetero- zygosity has also been reported in Saxifraga diversifolia by Kumar and Singhal (2013), Achillea millefoilium (Singhal et al. 2014), and Anemone rivularis . ...
Present study records the existence of tetraploid and hexaploid meiocytes and subsequently the formation of large and very large-sized pollen grains for the first time in the diploid individuals of Achillea millefolium. In majority of the diploid accessions, meiocytes exhibited nine bivalents, equal segregation of chromosomes during anaphases, regular tetrads and normal-sized 'n' pollen grain formation. In the accessions scored from Palchan (2400 m) and Dhundhi (3050 m) regions of Solang Valley, two to three proximate PMCs fused during early stages of Prophase-1 and Metaphase-1 resulting into tetraploid (4x) and hexaploid (6x) meiocytes with 18 and 27 bivalents, respectively. Although the frequency of polyploid PMCs was rather low these are detectable due to their larger size compared to diploid PMCs. In both the accessions, the diploid and polyploid PMCs exhibited the multiple chromosomal associations of four to eight chromosomes indicating the existence of structural heterozygosity. Analysis reveals that there is an increase in the chiasma frequency with structural heterozygosity for reciprocal translocations. Syncyte meiocytes followed a regular meiotic course resulting into the formation of normal tetrads but the products of such sporads yielded atypical (large and very large-sized) pollen grains compared to normal sized typical pollen grains. Although the exact cytological status of aforesaid pollen grains could not be ascertained but such fertile larger-sized pollen grains with possible '2n' or '3n' genetic constitution might be involved in fertilization to generate polyploid offsprings and the origin of intraspecific polyploid cytotypes (4x, 6x) which are known to exist in some populations of Himalayas in India.
... In the species, there seems to be a direct correlation of pollen sterility with structural heterozygosity. Similar effects of structural heterozygosity resulting in non-viable pollen grains has been reported in a number of plants, namely, Chrysanthemum zawadskii (Kim et al. 2008), Artemisia parviflora (Gupta et al. 2010), Astragalus chlorostachys (Rana et al. 2012), Saxifraga diversifolia (Kumar and Singhal 2013), Achillea millefolium (Singhal et al. 2014) and Anemone rivularis (Kumar et al. 2015). Gohil and Koul (1978) and Sharma and Gohil (2003) have reported that structural heterozygotes of Allium consanguineum and A. roylei depicted complete gametic sterility due to reciprocal translocations, respectively. ...
... The accessions with higher percentage of chromosomes involved in translocations showed higher values of chiasma frequency and thereby increased recombination value. Kumar and Singhal (2013) in Saxifraga diversifolia, Singhal et al. (2014) in Achillea millefolium, and recently Kumar et al. (2015) have also found direct correlation between chiasma frequency and incidence of translocations. The existence of heterozygosity for translocations in the tetraploid taxon indicates that the species is quite active and has exploited structural chromosomal alterations to create specific gene combinations in addition to intraspecific polyploid chromosomal races (2x, 3x, 4x) and B-chromosomes. ...
An accession-based study carried out on Anthoxanthum odoratum from Kullu district revealed a tetraploid chromosome count of n=10 and the presence of multiple chromosomal associations of up to 10 chromosomes due to structural heterozygosity for reciprocal translocations. Owing to the presence of multivalents, the individuals showed considerable amounts of non-viable male gametes. Structural heterozygosity in the species has also been detected to affect the chiasma frequency significantly, thereby increasing the variability. Similar effects of translocations in increasing chiasma frequency and affecting pollen fertility have been reported by workers in other species.
... Ever since the first report of structural heterozygosity for reciprocal translocations by Belling (1914) in Florida velvet bean (Stizolobium deeriingianum), heterozygosity has been reported to occur in a wide variety of flowering plants (Burnham 1956, Kaul 1977, Gohil and Koul 1978, Sharma and Gohil 2003, Talukdar and Biswas 2006, Kim et al. 2008, Ghaffari et al. 2009, Talukdar 2010, 2013, Kohli and Gohil 2011. From this laboratory, the naturally occurring reciprocal translocations have been reported in individuals of Artimisia parviflora (Gupta et al. 2010), Astragalus chlorostachys (Rana et al. 2012), Saxifraga diversifolia (Kumar and Singhal 2013), Achillea millefolium (Singhal et al. 2014), and Anemone rivularis (Kumar et al. 2015). Kaul (1977) opined that breakage and exchange of heterologous chromosomes in a structural heterozygote are genetically conditioned and controlled, thereby eliminating the chance factor operating for the predominance of either ring or chain or both types of multiple associations of chromosomes. ...
... In the presently studied accession of Tanacetum artemisioides, the majority of the PMCs showed the adjacent type of orientation of quadrivalents/hexavalents (ring or chain) and the alternate (zigzag) orientation was seen in only one PMC, resulting in a considerable amount of pollen sterility (30-35%), which appears to be the result of duplications and deficiencies of genes as mentioned by Ghosh and Datta (2006) in Nigella damascene. Similar effects of structural heterozygosity leading to nonviable pollen grains have been reported in a number of plants, namely, Citrus jambhiri (Singhal and Gill 1981), Chrysanthemum zawadskii (Kim et al. 2008), Artemisia parviflora (Gupta et al. 2010), Astragalus chlorostachys (Rana et al. 2012), Saxifraga diversifolia (Kumar and Singhal 2013), Tradescantia spathacea (Koul et al. 2013), Achillea millefolium (Singhal et al. 2014), and Anemone rivularis (Kumar et al. 2015). Gohil and Koul (1978) and Sharma and Gohil (2003) have reported that structural heterozygotes of Allium consanguineum and A. roylei depict complete gametic sterility due to reciprocal translocations. ...
Male meiotic studies have been carried out on the wild plants of Tanacetum artemisioides Sch. Bip. ex Hook. f. collected from the cold desert regions of Ladakh Division of Jammu and Kashmir. The studied individuals, which existed at the 2x level (2n=18), showed structural heterozygosity for reciprocal translocations as indicated by the presence of multiple chromosomal associations of four to six chromosomes. This is the first report of structural heterozygosity for the species. The structural heterozygotes showed considerable amount of pollen sterility (30-35%) which could be attributed to the presence of ring/chain shaped multivalent in PMCs.
... Such a phenomenon of structural heterozygosity leading to non-viable pollen grains has also been reported in a number of plants, namely Citrus jambhiri (Singhal and Gill 1981), Chrysanthemum zawadskii (Kim et al. 2008), Artemisia parviflora , Astragalus chlorostachys (Rana et al. 2012), Tradescantia spathacea (Koul et al. 2013), Saxifraga diversifolia and Achillea millefoilium ). Kumar and Singhal (2013) have reported multiple chromosomal associations and univalent chromosomes in the varieties of Saxifraga diversifolia. In the present case, 38.41% of PMCs showed quadrivalent formation at diakinesis and metaphase-I. ...
... physiological conditions (Rees 1962), differences in expression of genes (Wagenaar 1964) and temperature (Dowrick 1957;Swanson 1957). In the present case increase in chiasma frequency in one of the accessions seems to be a consequence of structural heterozygosity as has also been suggested in Saxifraga diversifolia by Kumar and Singhal (2013) and Achillea millefoilium . ...
Meiotic studies have been carried out on 12 accessions of Anemone rivularis from different regions of Western Himalaya. The accessions from Chamba, Kullu and Kinnaur districts of Himachal Pradesh and Uttarkashi district of Uttarakhand showed a normal meiotic course leading to high pollen fertility (87–100%). However, the accession scored from Saat Tal, Uttarakhand showed structural heterozygosity for reciprocal translocations. This is the first report of occurrence of structural heterozygosity in the species. Out of the 604 analysed pollen mother cells (PMCs), 38.41% (232) showed quadrivalent formation at diakinesis and metaphase-I. Comparison of chiasma frequency was also performed among selected populations using one-way analysis of variance (ANOVA), which showed significant differences. The occurrence of cytomixis involving inter PMC transfer of chromatin material among neighbouring meiocytes (45.68%) was also observed. PMCs at anaphases/telophases showed laggards (31.25%) and chromatin bridges at A-I/T-I and A-II/T-II (21.02%) leading to abnormal microsporogenesis. Consequently, abnormal sporads such as triads (66.67%), polyads (3.33%) and triads with micronuclei (0.83%) were formed. Structural heterozygosity and inter PMC chromatin material transfer in the individuals of the species seem to be responsible for the reduction in pollen fertility (67.8%) and formation of pollen grains of heterogeneous sizes.
... In the present case, higher chiasma frequency has been recorded in the PMCs having multivalent compared to PMCs with only bivalents. This variation in chiasma frequency among PMCs is correlated to the occurrence of chromosomal associations as has also been suggested earlier by other workers (Kumar and Singhal 2013;Singhal et al. 2014). ...
Alstonia venenata R. Br. (Family: Apocynaceae), a paleoendemic under ex situ conservation in north India has been cytologically investigated for chromosome counts. This study recorded chromosome count (n=11) for the species. The species existed at the diploid level. Multivalents were observed in meiocytes as a consequence of reciprocal translocations Scanning electron microscope (SEM) analysis has also been performed in pollen grains. Here in this paper, we are also presenting a first-time analysis of the meiotic course and occurrence of multivalents in an accession of the species. We also discuss the previous cytological studies done in the genus Alstonia. In spite of the occurrence of high pollen sterility, seed setting is normal which shows that the species has acclimatized to a greater extent in north India climatic conditions.
... Such structural heterozygotes occasionally produce duplications or deficiencies resulting in nonviable and sterile pollen grains as reported in a number of flowering plants viz. Citrus jambhiri (Singhal and Gill 1981), Artemisia parviflora , A. absinthium (Malik et al. 2010), Euphorbia pilosa (Saggoo and Farooq 2011) Astragalus chlorostachys (Rana et al. 2012), Saxifraga diversifolia (Kumar and Singhal 2013), Achillea millefolium (Singhal et al. 2014), Tanacetum artemisioides (Singhal et al. 2016), Anthoxanthum odaratum (Singhal and Kumari 2017), Arthraxon hispidus (Kumari and Singhal 2018), Fagophyrum aculatum and Deutzia staminea (Gupta et al. 2018a, b). ...
Meiotic studies have been carried out on three plants of Leontopodium jacotianum from Cold deserts of Ladakh. The chromosome number of n=24 counted in all the plants adds a new tetraploid cytotype for the species. The plants collected from Zoji-La showed a normal meiotic course leading to high pollen fertility. However, the plants collected from Sankoo region of cold deserts of Ladakh, Jammu, and Kashmir showed abnormal meiosis caused by structural heterozygosity for reciprocal translocations. The structural heterozygosity was observed for the first time in the species. Chiasma frequency was also calculated by using one-way analysis of variance (ANOVA) in the plants to see the effect of reciprocal translocations. Besides reciprocal translocation, the plant also showed various meiotic abnormalities in the form of early disjunction of bivalents, chromatin bridges, and laggards. Structural heterozygosity and other meiotic abnormalities in the plant seem to be responsible for a reduction in pollen fertility.
... Presently reciprocal translocations have been noticed for the first time in some wild individuals of D. staminea. And these structural heterozygotes might have resulted into production of some non-viable pollen grains due to deficien-cies and duplications in chromosomes (Koul et al. 2013, Kumar and Singhal 2013, Singhal et al. 2014. Besides, the accessions with structural heterozygosity for reciprocal translocations also displayed the phenomenon of cytomixis involving inter-PMC transfer of chromatin. ...
Male meiotic studies have been performed on plants basis in Deutzia staminea collected from three localities of Parvati valley, Kullu district, Himachal Pradesh, India. The scored accessions uniformly exhibited the diploid chromosome count of 2n=26 confirming the earlier reports from other regions of North-West Himalayas. The individuals studied from Gurthigarh showed perfectly normal meiosis, microsporogenesis and 100% pollen fertility. On the other hand, plants studied from Pulga and Malana showed the existence of multiple associations of chromosomes due to structural heterozygosity for reciprocal translocations. Analysis of 118 countable pollen mother cells (PMCs) showed that 17.8% meiocytes depicted multivalent of ring or chain type involving 2.87% of the chromosomes. Also these individuals showed the phenomenon of cytomixis (6.57% PMCs), chromatin stickiness, and abnormal spindle activity depicted in form of out of plate bivalents, chromatin bridges and laggards. The existence of some pollen sterility (15-29%) in diploid individuals seems to be the consequence of multivalents during metaphase I (MI) and cytomictically induced meiotic irregularities in the PMCs.
... Variation in chiasma frequency in any taxon has been attributed to several factors such as physiological conditions (Rees 1962), differences in gene expressions (Wa-genaar 1964) and temperature (Dowrick 1957, Swanson 1957). In the grass species, increase in chiasma frequency per meiocyte and bivalents seems to be directly correlated with reciprocal translocations for structural heterozygosity as also been opined in Saxifraga diversifolia (Kumar and Singhal 2013), A. millefolium (Singhal et al. 2014), Anemone rivularis (Kumar et al. 2015) and A. odoratum (Singhal and Kumari 2017). Considering the presence of reciprocal translocations in the wild plants, we opined that the translocation involved in polymorphism of chromosomes might play a role in adaptation to the varied ecological habitats as suggested in Drosophilla by Hoffmann et al. (2004) and Paeonia emodi (Wang 2013). ...
Male meiotic studies have been performed on three wild accessions of Arthraxon hispidus scored from Parvati valley and Solang valley of Kullu district in Himachal Pradesh. The accessions shared the same diploid chromosome number of 2n=30 and added a variable dysploid chromosome report for the species against the earlier reports of 2n=18, 36, 38, 40. Multiple chromosomal associations due to structural heterozygosity for reciprocal translocations involving four to six chromosomes seem to have increased the chiasma frequency in meiocytes. Owing to adjacent type orientation of multiple chromosomal associations coupled with some meiotic irregularities, the studied accessions also related with some pollen sterility.
... Univalents not only interfere with the completion of meiosis, but also survival of the individual through sexual propagation is greatly impaired (Soost 1951). The presence of such univalent chromosomes resulted in a decrease in chiasma frequency and in turn considerably lowers gametic fertility (Kumar et al. 2013). Detrimental effects of univalents on faith of meiosis and pollen fertility have also been documented by several workers (Maity, Datta 2009a;Maity, Datta 2009b;Datta et al. 2010;Goyal, Khan 2010). ...
... Reciprocal translocation involving two pairs of nonhomologous chromosomes is an important cytological event in plant species for transfer of desirable traits (Sears 1956, Gustafsson 1965, raising of trisomics (Sutton 1939, Ramage 1960, Ashraf and Bassett 1987, Lakshmi and Nalini 1989, Auger and Birchler 2002, development of hybrid seeds as well as seedless varieties (Zhang et al. 2012) apart from possessing academic significance (Burnham 1956, Sybenga 1975, Tripathi and Kumar 2009). Since the first report of reciprocal translocation in Stizolobium deeriingianum (Florida velvet bean) by Belling (1914), the phenomenon is found to occur both in natural (Gupta et al. 2010, Rana et al. 2012, Kumar and Singhal 2013, Singhal et al. 2016) and mutagen induced (Hsieh 1961, Sjodin 1971, Driscoll 1965, Kalloo and Das 1971, Biswas and Datta 1985, Verma and Raina 1982, Srivastava and Kumar 2011, Kumar and Dwivedi 2013 population of different plant species including N. sativa (Saha and Datta 2002) and N. damascena (Anindita and Datta 2006) but partial to total gametic sterility (male, female or both) prevailing in them (Burnham 1956, Gohil and Koul 1978, Singhal and Gill 1981, Datta and Biswas 1986, Saha and Datta 2002, Sharma and Gohil 2003, Koul et al. 2013) is a major hindrance for their perspective exploration in the field of cytogenetics. With the view to it, the present communication describes the meiotic configurations and fertility aspect (studied from microsporogenesis) of a translocation heterozygote screened from gamma irradiated R 1 population and from its progeny heterozygote at R 2 of N. sativa L. ...
A translocation heterozygote (without any marker phenotypic trait) is screened in Nigella sativa L. (black cumin) following the exposure of dry seeds (moisture content: 5.0%) to 300 Gy gamma irradiations (one out of twelve). On selfing (53 seeds sown), one heterozygote is detected out of seven survived plants at R2. Compared to 6II formation (2n=12) in PMCs of standard normal plants, the heterozygotes form either a ring or a chain quadrivalents in association to bivalents and univalents (2n=12) in 52.68% (R1) and 30.07% (R2) meiocytes. Ring configuration and adjacent orientation of the multiples are more found to occur predominantly in R1 than R2 heterozygote. Pollen grain fertility and seed setting are found to vary between the translocation heterozygotes irrespective of orientation of the multiples. From the prevalence of ring interchange complexes, it is presumed that the breakpoints are closer to centromere. Furthermore, configurations of the interchange complexes highlight the possibility of two longer pairs of chromosomes to be involved in reciprocal exchanges. A possible genetic control of translocation heterozygote is predicted.
... the Chromosome Counts Database (CCDB; Rice et al., 2015) and from original literature (e.g. Funamoto et al., 1998aFunamoto et al., , b, 2001Funamoto, 2010;Kumar & Singhal, 2013). ...
The driving forces behind evolutionary radiations in mountain ecosystems are only poorly understood. Using the species-rich alpine taxon Saxifraga section Ciliatae, which occurs predominantly in the region of the Qinghai–Tibet Plateau, we explore the driving forces behind elevated diversification rates previously observed in one of three subclades of section Ciliatae (clade 3). We use species distribution models to test for an influence of topographical heterogeneity on the diversity of section Ciliatae and investigate the characteristics of climatic niches in this section. In addition, we expand the dataset of known polyploids of section Ciliatae in order to investigate the effect of polyploidy on diversification in this group and estimate rates of niche evolution. Both polyploidization and topographical heterogeneity were associated with overall species richness in section Ciliatae, but neither was a likely driver of the observed radiation in clade 3 of section Ciliatae. Instead, larger niche breadth and high rates of niche evolution of taxa in clade 3 probably drove rapid diversification via pronounced adaptability for the biologically limiting climatic conditions of the alpine life-zone, presenting an important advantage during past periods of rapid climate change. Our study thus elucidates several aspects of the diversification process in this large alpine taxon and underlines the importance of climatic niche evolution for radiations in mountain regions.
... Many factors can affect pollen development. Kumar and Singhal (2013) reported that the low temperature could cause synaptic irregularities in chromosomes of Saxifraga diversifolia during meiosis. Via do Pico and Dematteis (2012) observed normal meiotic behavior for the diploid species Chrysolaena platensis (Spreng.); ...
Amsonia orientalis Decne. (Apocynaceae) is a medically useful and critically endangered plant which has very restricted distribution world-wide. The root tips and flower buds of A. orientalis were used as an experimental material and they were squashed in aceto-orcein. Fresh flowers and a liquid medium were used for pollen germination tests. In spite of the small size of the cells and chromosomes, all phases of mitosis and meiosis were observed. Generally the phases of mitosis were regular but there were a few abnormalities, such as laggard chromosome in metaphase and bridge formation in anaphase. There was a good relationship between the stages of pollen development and floral bud length. As a result of the cytokinesis, tetrahedral types of tetrads were occurred in microsporogenesis. The tetrad nuclei resulting from the simultaneous type of meiosis were found to be of equal size. Pollen germination had started from the first hour and pollen tube lengths and germination percentages regularly increased with increasing time. This is the first study that identifies mitotic and meiotic cycles and pollen germination in A. orientalis. Our findings about the mitosis and reproduction biology of this critically endangered plant will be useful for in vitro and in situ conservation, taxonomic and genetic studies.
... Many factors can affect pollen development. Kumar and Singhal (2013) reported that the low temperature could cause synaptic irregularities in chromosomes of Saxifraga diversifolia during meiosis. Via do Pico and Dematteis (2012) observed normal meiotic behavior for the diploid species Chrysolaena platensis (Spreng.); ...
Amsonia orientalis
Decne. (Apocynaceae) is a medically useful and critically endangered plant which has very restricted
distribution world-wide. The root tips and
fl
ower buds of
A. orientalis
were used as an experimental material and they
were squashed in aceto-orcein. Fresh
fl
owers and a liquid medium were used for pollen germination tests. In spite of the
small size of the cells and chromosomes, all phases of mitosis and meiosis were observed. Generally the phases of
mitosis were regular but there were a few abnormalities, such as laggard chromosome in metaphase and bridge formation
in anaphase. There was a good relationship between the stages of pollen development and
fl
oral bud length. As a result
of the cytokinesis, tetrahedral types of tetrads were occurred in microsporogenesis. The tetrad nuclei resulting from the
simultaneous type of meiosis were found to be of equal size. Pollen germination had started from the
fi
rst hour and
pollen tube lengths and germination percentages regularly increased with increasing time. This is the
fi
rst study that
identi
fi
es mitotic and meiotic cycles and pollen germination in
A. orientalis
. Our
fi
ndings about the mitosis and
reproduction biology of this critically endangered plant will be useful for
in vitro
and
in situ
conservation, taxonomic
and genetic studies.
Male meiotic studies were carried out on eight different accessions of Hedysarum astragaloides Benth. ex
Baker (Fabaceae), an endemic and threatened species of northwest Himalaya, India. Although genetic factors such as
meiosis, chromosome number, and ploidy level may be causative for the evolution, endemism, rare distribution or
even extinction of the species, no detailed information exists. Keeping this in mind H. astragaloides has been studied
cytologically. Male meiotic investigations revealed diploid level (2n=2x=14) for species and normal meiotic course in
the accessions from the Manali Hills resulting in nearly 100% pollen fertility. However, the accessions scored from the
Manimahesh Hills and Pangi Valley depicted inter-pollen mother cell transfer of chromatin material and structural
heterozygosity for reciprocal translocations. Consequent upon these meiotic anomalies, some pollen sterility (21%)
resulted. On account of this sweeping genetic outcome, the incidence of anomalies such as this in an endemic and
threatened species warrants grave consideration. It is sensible to conclude that conservation measures should include
the collection of germplasm from the localities where plants are meiotically stable with high gametic fertility, to ensure
good germination and healthy plants for future use. Seeds from meiotically normal individuals should be given priority
for inclusion in seed banks.
The present study covers chromosome counts, male meiosis and pollen fertility in 164 species of dicots from the Parvati Valley, Kullu district, Himachal Pradesh. Gathered cytological information generates first ever chromosome counts, new diploid/polyploid cytotypes and varied chromosome counts. As many as 41 species (25%) showed intraspecific euploid cytotypes. Role of aneuploidy causing chromosomal variation is apparent from the existence of 71 species (43.29%) depicting aneuploid/dysploid cytotypes at diploid and/or polyploid levels and 114 genera showing dibasic/polybasic nature. The existence of abnormalities in several species resulted in the production of genetically imbalanced and sterile pollen grains. The viable gametes with variable chromosome numbers might have played a part in the origin of aneuploids, polyploids and species complexes. Also the non-viable gametes produced as a consequence of meiotic irregularities might have resulted in reduction of reproductive success of species through seeds. Consequently, the plants have adopted alternate means of propagation through asexual and vegetative modes which is quite prevalent in the plants of area.
Male meiotic studies in eight Indian Cucumis species, including two newly included species, have been carried out. Gametic chromosome numbers of n = 7 and 12 were recorded in these taxa. Data collected on chromosome associations, chiasma frequency at diplotene/diakinesis/metaphase I revealed the predominant occurrence of bivalents in the majority of the pollen mother cells (PMCs) of taxa having n = 7, suggesting a high degree of homology among the pairing chromosomes. Conversely, species with n = 12 had chromosome associations resulting in a mixed of bivalents and univalents. One of the reasons for such heterogeneity exclusively found in these species may be attributed to chromosome structural alteration at DNA level (duplication/deletion/point mutation) rather than numerical alteration. Multivalents were not encountered in any of the PMCs, indicating the diploid nature of the taxa. A single nucleolus showing affinity towards varying numbers of bivalents (1–4) was the hallmark feature of the PMCs analyzed at diplotene.
Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics Publication details, including instructions for authors and subscription information: (2014): An overview of chromosome and basic numbers diversity in cytologically investigated polypetalous genera from the Western Himalayas (India), Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics, DOI: 10.1080/00087114.2013.856088 makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at
A desynaptic mutant of Corchorus fascicularis Lamk. (Family: Tiliaceae) showing distinctive morphological variations than normal was identified from the natural population (1 out of 27 plants scored) of jute species following male meiotic analysis. Self segregation of the desynaptic plant suggested that desynapsis (mutant trait) was monogenic recessive to normal. Compared to normal plants, the spontaneous desynaptic mutant (medium strong type) demonstrated enhanced univalent frequency per cell (4.05, normal-0.31), reduced number of chiasma (6.67, normal- 7.28) and bivalent (5.12, normal- 6.99) per nucleus, few meiocytes (13.64%, normal-5.36%) with unequal separation at AI, cytologically near normal AII (94.83%, normal- 100.00%) cells and high male fertility (81.77%, normal- 92.06%). Cytomixis (prophase I/ metaphase I) was evident in both normal and mutant plants forming aneuploid (mutant: 2n< 14-1.40%, 2n> 14-2.80%; normal: 2n<14 - 14.20%, 2n>14 - 10.22%) PMCs predominantly at MI (mutant: 4.20%, normal: 24.42%) and rarely in AI (mutant: 1.52%, normal: 1.79%) cells.
The effect of diethyl sulphate (DES) and sodium azide (SA) was studied on the meiotic behaviour of Vicia faba L. var. major in the M1 generation. Five concentrations of SA (0.01%, 0.02%, 0.03%, 0.04%, and 0.05%) were combined with DES (0.02%) to study the synergistic and antagonistic effects of these 2 mutagens. A dose-dependent increase in chromosomal aberrations was recorded in populations treated with both the mutagens individually and their combination doses. The main chromosomal aberrations were stickiness, precocious separations, univalents, multivalents, laggards, unequal separations of chromosomes, micronuclei, disturbed polarity, multinucleate condition, and cytomixis. The stickiness and stray bivalents at metaphase I/II, bridges with or without fragments at anaphase I/II, disturbed polarity, and cytomixis at telophase I/II were the dominant anomalies. The univalents, rod bivalents, and multivalents showed dose-dependent increases, whereas the ring bivalents and chiasma frequency per cell showed dose-dependent decreases both in single as well as in combined mutagenic treatments as compared to the control.
Partial desynaptic plants were isolated from normal population of pearl millet (Pennisetum typhoides S. and H.) inbred T55 and mutagen (EMS and gamma-rays) treated populations of inbreds Tif23A, Tif23B and K560. The pachytene pairing was complete and normal. A variable number (2-14) of univalents occurred at MI. Anaphase I separation was normal in the majority (66-79%) of the cells; many showed 8:6 and 9:5 chromosome separation. The spontaneous desynaptic plant showed laggards and chromatin bridges at anatelophase I, while the induced ones did not show these aberrations. Chiasma frequency in the desynaptic plants was lower than that in the normal controls.
Meiotic analysis performed in nine species of jute (cultivated species - C. olitorius L., C. capsularis L.; wild species - C. fascicularis Lamk., C. aestuans L., C. pseudoolitorius I. and Z., C. pseudocapsularis L., C. tridens L., C. trilocularis L. and C. urticaefolius W. and A. - Family: Tiliaceae) revealed that C. olitorius (mean/cell: 7II), C. capsularis (mean/cell: 6.98 II + 0.03 I), C. tridens (mean/cell: 6.98 II + 0.03 I), C. trilocularis (mean/cell: 7 II) and C. urticaefolius (mean/cell: 7 II) formed 2n=14 chromosomes at metaphase I always with balanced (7/7) segregation at anaphase I; while, C. fascicularis Lamk. (24.42%-MI; 1.79%-AI), C. aestuans L. (33.33%-MI; 28.57%-AI), C. pseudoolitorius I. and Z. (24.69%-MI; 15.73%-AI) and C. pseudocapsularis L. (2.56%-MI; 0.00%-AI) exhibited numerical variations in chromosome number (n=1,2,3,4,5,6,9,10 and 14) in addition to normal (n=7). Average chromosome association per cell at MI was 0.002 VI + 0.006 IV + 6.98 II + 0.31I in C. fascicularis, 6.55 II + 0.60 I in C. aestuans, 6.60 II in C. pseudoolitorius and 7.08 II + 0.21 I in C. pseudocapsularis. Aneuploidy noted in jute species is attributed to cytomixis. Chromosome in the species were mostly bivalents (6.55 - 7.08 mean/cell; random in distribution - p> 0.05) and rarely univalents (0.00 - 0.60 mean/cell; nonrandomly distributed - p<0.001); however, one PMC with a ring and a chain quadrivalent and one with a chain hexavalent were noted only in C. fascicularis. Bivalents in the species were of ring (1.44 ± 0.13 to 4.68 ± 0.14/cell) and rod (2.32 ± 0.14 to 5.44 ± 0.14/cell) configurations. Excepting C. capsularis, the species formed more of rod bivalents than ring. Ring and rod bivalents were nonrandom (p< 0.001); while chiasmata per cell (8.40 - 11.68) and per bivalent (1.20 - 1.67) was random (p> 0.50) in distribution among species as evident from chi - square test of heterogeneneity. Pollen fertility in the species varied from 59.82% - 96.91%.
Th e existence of structural heterozygosity for reciprocal translocations in the wild diploid (n=9) accession of Artemisia parvifl ora collected from the Parvati Valley in Kullu district, Himachal Pradesh, India is reported for the fi rst time. Th e other two Indian accessions studied from Pangi Valley in Chamba district and Pulga, 2300m in Parvati Valley depict normal meiosis with the presence of nine bivalents, regular segregation of chromosomes during anaphases and almost a hundred percent pollen fertility. We studied in detail the male meiosis in pollen mother cells (PMC) and pollen fertility in the accessions showing structural heterozygosity. Th e PMCs exhibited abnormal meiosis due to the presence of multivalents in 62.92% of the analyzed 213 PMCs. A total of 12.31% of the chromosomes are observed to be involved in multivalents and 2.35% remained as univalents. In spite of the presence of multivalents and early/late disjunction of few bivalents, the chromosomes in PMCs are regularly segregated to poles at A-I/A-II resulting into normal tetrad formation. Th e structural rearrangements of chromosomes in A. parvifl ora are responsible for causing some pollen malformation (30%) as has been the case in other species. Another eff ect of structural heterozygosity is the increase in chiasma frequency per PMC from 10.75-12.40.
To circumscribe Saxifragaceae sensu stricto better, as well as to elucidate generic relationships within this group, we sequenced the chloroplast gene rbcL and its 3' flanking region (yielding 1,471 bp) from 19 genera considered to represent core members of Saxifragaceae. In addition, we conducted a restriction site analysis of chloroplast DNA (cpDNA) for 21 core genera using 23 restriction endonucleases. Phylogenetic analyses using both data sets corroborate the results obtained from surveying the distribution of the loss of the intron in the chloroplast gene rp12 in delimiting a well-defined Saxifragaceae sensu stricto. Within the Saxifragaceae s.s. clade, a number of poorly resolved, basal phylogenetic branches supports the hypothesis that Saxifragaceae s.s. radiated rapidly very early in its evolutionary history. Molecular data also indicate the presence of several strongly supported groups of genera, such as the Boykinia group (Boykinia, Suksdorfia, Bolandra, Sullivantia, Jepsonia, and Telesonix), the Heuchera group (Heuchera, Bensoniella, Conimitella, Elmera, Lithophragma, Mitella, Tellima, Tiarella, and Tolmiea) the Leptarrhena/Tanakaea group, and the Darmera group (Darmera, Astilboides, Mukdenia, Bergenia, and Rodgersia). Significantly, molecular data suggest that the very large, taxonomically complex genus Saxifraga may not be monophyletic. DNA data have also helped to resolve the generic relationships of problematic taxa, indicating, for example, that Telesonix and the enigmatic Jepsonia are sister taxa. In addition to its phylogenetic implications, this study provides insight into basic trends in morphological, chemical, and cytological evolution within Saxifragaceae s.s. The molecular-based phylogenies suggest multiple origins and/or losses of several classes of flavonoid compounds, as well as several independent instances of reduction in stamen and petal number, hypanthium-ovary fusion, and aneuploidy. This study also illustrates the ability of rbcL sequence data to resolve generic-level relationships in some taxonomic groups.
Large differences in pollen stainability were observed for 7 cultivars of the pepino (Solanum muricatum Ait.). Viability was measured by staining pollen with cotton blue or fluorescein diacetate and for 4 cultivars by seed set after compatible pollinations. Comparable results were obtained from the two staining methods, although cotton blue over-estimated viability in most cases. Temperature had only a small effect on pollen stainability, although temperatures above 25°C caused high levels of bud and flower drop. Abnormal meiotic behaviour with the formation of variable numbers of univalents was found to be associated with the observed levels of infertility, but other, as yet unknown, factors must also influence pollen fertility in the pepino.
Diploid individuals (2n=18) of Chrysanthemum zawadskii, C. indicum and C. boreale, two or all three of which often occur together in the wild in East Asia, have diverse metaphase karyotypes. We hypothesised that the diverse karyotypes result from chromosome rearrangements. To test this, we investigated chromosomal behaviour during pollen mother cell (PMC) meiosis and pollen fertility, using 33 individuals collected from seven populations in Korea. All individuals contained one or two multivalents (mostly quadrivalents) at late prophase I and metaphase I in some PMCs (approximately 17–37%), and at least one or two bivalents composed of homologous chromosomes of different length and centromere position in all PMCs. This meiotic chromosomal behaviour indicates that chromosome rearrangements, i.e., reciprocal translocation and unequal crossing-over, are prevalent in Chrysanthemum species. Nevertheless, because of successful chromosome segregation in anaphase I and II, they produce ample stainable pollen with different chromosome complements. Fertilization by such gametes should result in diverse somatic karyotypes. We also discuss the possibility that older or relatively recent hybridization events have led to a high rate of irregular meiotic chromosome behaviours and pollen sterility, particularly in C. indicum.
Diploid Lathyrus boissier showed the 7 bivalents in most of pollen mother cells at prophase and metaphase of meiosis. The disturbances in the meiotic stage appeared to have been caused by reciprocal translocation. Meiotic analyses of 232 pollen mother cells indicates occurrence of heterozygotic reciprocal translocation in 94 cells. When the crossing-over and chiasma formation take place in all 4 pairing segments, a ring of 4 chromosomes results, and when the chiasma was absent in one of the 4 pairing segments, a chain of 4 chromosomes results. Of the 94 transtocated MI cells examined, 24 had ring quaderivalents, 55 had open chain quaderivalents and 15 had alternate (zigzag) ring quaderivalents. From the present investigation it appears L. boissier has not acquired stability as yet and translocation has played an important role in its evolution. In this study chromosome count and meiotic behaviour of L. boissieri is presented here for the first time.
The present study was an effort to identify appropriate dose of mutagens for the elevation of specific alkaloids especially thebaine through induced mutagenesis in opium poppy (P. somniferum L.) using two stable high yielding varieties NBRI-1 and NBRI-5. Simultaneously, the study also deals correlation between cytological aberrations and their effects on alkaloid quantity. Among the two varieties NBRI-1 was more sensitive than NBRI-5. The EMS was reported most potent mutagen for creation of chromosomal abnormalities. The treatment kR 10+0.2% EMS and kR10+0.4% EMS possessed high chiasms frequency. The dose 0.2% EMS in combinations with all doses of gamma accelerates the total alkaloid as well as individual alkaloid content.
The large genus Saxifraga, which consists of ≈400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2 500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK-rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well-differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species-rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga, A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium-Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well-separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.
To circumscribe Saxifragaceae sensu stricto better, as well as to elucidate generic relationships within this group, we sequenced the chloroplast gene rbcL and its 3' flanking region (yielding 1,471 bp) from 19 genera considered to represent core members of Saxifragaceae. In addition, we conducted a restriction site analysis of chloroplast DNA (cpDNA) for 21 core genera using 23 restriction endonucleases. Phylogenetic analyses using both data sets corroborate the results obtained from surveying the distribution of the loss of the intron in the chloroplast gene rp/2 in delimiting a well-defined Saxifragaceae sensu stricto. Within the Saxifragaceae s.s. clade, a number of poorly resolved, basal phylogenetic branches supports the hypothesis that Saxifragaceae s.s. radiated rapidly very early in its evolutionary history. Molecular data also indicate the presence of several strongly supported groups of genera, such as the Boykinia group (Boykinia, Suksdorfia, Bolandra, Sullivantia, Jepsonia, and Telesonix), the Heuchera group (Heuchera, Bensoniella, Conimitella, Eìmera, Lithophragma, Mitella, Tellima, Tiarelia, and Tolmiea) the Leptarrhena/Tanakaea group, and the Darmera group (Darmera, Astilboides, Mukdenia, Bergenia, and Rodgersia). Significantly, molecular data suggest that the very large, taxonomically complex genus Saxifraga may not be monophyletic. DNA data have also helped to resolve the generic relationships of problematic taxa, indicating, for example, that Telesonix and the enigmatic Jepsonia are sister taxa. In addition to its phylogenetic implications, this study provides insight into basic trends in morphological, chemical, and cytological evolution within Saxifragaceae s.s. The molecular-based phylogenies suggest multiple origins and/or losses of several classes of flavonoid compounds, as well as several independent instances of reduction in stamen and petal number, hypanthium-ovary fusion, and aneuploidy. This study also illustrates the ability of rbcL sequence data to resolve generic-level relationships in some taxonomic groups.
The large genus Saxifraga, which consists of 400 morphologically and cytologically diverse species, has long been considered taxonomically complex. Phylogenetic analysis of over 2500 bp of chloroplast sequence data derived from matK and rbcL was employed to examine relationships among sections of Saxifraga, the segregate genera Zahlbrucknera, Saxifragopsis, and Cascadia, and the relationships of these taxa to other Saxifragaceae sensu stricto. Phylogenetic trees resulting from separate analyses of the matK and rbcL sequences were highly congruent; phylogenetic analysis of a combined matK–rbcL data matrix was therefore also conducted. Our analyses indicate that Saxifraga is polyphyletic, comprising two well-differentiated clades. One clade, Saxifraga sensu stricto, is the sister to the remainder of the family and consists of Saxifraga sections Irregulares, Heterisia, Trachyphyllum, Cymbalaria, Mesogyne, Xanthizoon, Porphyrion, Ciliatae, Cotylea, Ligulatae, Saxifraga, and Gymnopera. With the exception of Gymnopera, the species-rich sections of this clade are monophyletic. Also part of this clade is the problematic Zahlbrucknera paradoxa, which is allied with members of section Saxifraga. A second major clade of Saxifraga species, Micranthes sensu lato, comprises the large section Micranthes, as well as the segregate genus Cascadia, and S. tolmiei of section Merkianae. This clade is allied with the Heuchera, Darmera, and Chrysosplenium-Peltoboykinia groups of genera. The segregate genus Saxifragopsis is only distantly related to species of Saxifraga, and is instead the sister to Astilbe. The monotypic Oresitrophe is confirmed as a member of the Darmera group of genera. These results suggest that the floral features used to define Saxifraga may simply be symplesiomorphic in these well-separated Saxifraga lineages. Furthermore, the enormous cytological diversity encompassed by Saxifraga likely represents two independent instances of extensive aneuploidy and polyploidy in Saxifragaceae.
Genotoxic effects of two heavy metals viz. mercury (Hg) and cadmium (Cd) on somatic and gametic cells of soybean were investigated. Seeds were treated with different doses of these heavy metals. Treatments with Hg and Cd not only reduced the frequency of dividing cells but a wide spectrum of chromosomal abnormalities were also recorded. Pollen fertility was found to be significantly correlated with meiotic irregularities found in the metal treatment sets. It was found that both of these heavy metals are capable of inducing chromosomal aberrations, but Hg is much more genotoxic than Cd, since it induces greater abnormalities.
The Saxifraga nivalis complex displays significant ecological, morphological and cytological variation. Most European studies suggest that the S. nivalis complex comprises two distinct species: Saxifraga nivalis sensu stricto and Saxifraga tenuis. However, the presence of intermediate morphotypes, inconsistencies in chromosomal counts and variability in morphological keys and descriptions have led to different taxonomic interpretations of the complex in North America. This study investigated the systematics of Canadian Arctic Island members of this complex from 157 specimens using 23 morphological characters. Principal component analysis of the morphological data revealed two adjacent clusters, corresponding to the two taxa and consistent with a close morphological similarity and the presence of hybrids. A preliminary restriction site analysis of five non-coding regions of the chloroplast genome, trnH-trnK, trnT-trnF, trnF-trnV, trnV-rbcL and rbcL-ORF106, was conducted using 21 restriction endonucleases. This analysis indicated a length difference between the trnT-trnF region of S. nivalis and that of S. tenuis, but no difference in restriction sites for any of the assayed regions. These results confirm that in the Canadian Arctic, the S. nivalis complex consists of two closely related, largely sympatric species, with notable morphological variability, and possible hybrids.
Despite the long sized chromosomes of Allium, structural hybridity in this genus is rather rare. Of more than 300 species of Allium studied cytologically so far, reciprocal translocations have been reported only from A. schoenoprasum, A. ammophilum, A. cernum (Levan 1935, 1936–37, 1939), A. scordoprasum var. viviparum (Katayama 1936 and Takenaka 1960), A. ochroleucum (Khoshoo and Sharma 1959), A.fistulosum (Zen 1961), A. cepa, A. atropurpureum (Koul 1963, 1966), A. triquetrum (Rickards 1964) and A. sativum (Konvicka and Levan 1972). During the course of our studies on Indian Alliums a few plants from the Gurez collection of A. consanguineum turned out to be translocation heterozygotes. The meiotic details in these plants are described in the present communication. © 1978, Japan Mendel Society, International Society of Cytology. All rights reserved.
Tetraploidy was induced in Vinca rosea Linn. by treating seeds with. 0.4%/ of aqueous colchinine. By selfing the C1 plants, C2 progeny was raised. The tetraploid is characterised by possessing a stout stem and branches, broader and shorter leaves, larger stomata, slower rate of growth, larger pollen grains and high pollen sterility. The total alkaloid content is more in both generations of the tetraploid plants. Mitosis in the tetraploid is almost normal. Meiosis in both Cl and Cz plants is irregular. It is analysed statistically. The presence of univalents, micronuclei of different shape, spindle abnormalities followed by aggregation of chromosomes into groups at metaphase, and anaphase, irregular anaphase and formation of polyads have been frequently observed in the PMC's.
The coefficient of correlation between the abnormalities at different stages of meiosis and pollen sterility has been determined. There is no significant correlation between these irregularities and pollen sterility.
Seven different types of tetrasomics were isolated and characterized in the advanced selfed generations of seven primary trisomics (2n+1; 2n=15) recovered earlier in diploid (2n=14) grass pea (Lathyrus sativus L.) variety BioR-231. The tetrasomic types (2n+2; 2n=16) could be distinguished instantly from one another by contrasting modifications in shape, number, position and arrangement of leaflets at early seedling stage and also by variations in stipules, stem habit, floral morphology and seed coat color. These variations were distinctive and stable in the seven tetrasomics during successive generations. The extra chromosomes were detected either in bivalent or in trivalent-univalent or in quadrivalent condition at metaphase-I. Presence of a ring like quadrivalent in diakinesis as well as in metaphase-I was the regular feature in the tetrasomic plants. Occurrence of linear or Y-shaped trivalent indicated unmodified nature of the extra chromosomes in the different types of them and they were characterized as primary tetrasomics. As compared to trisomic phenotypes, influences of two extra homologous chromosomes were manifested in more exaggerated way on phenotypes of different tetrasomics. Pollen sterility and reduced yield in these tetrasomics might be the outcome of irregularities at anaphase-I manifested as unequal separation, formation of laggards and bridges.
The present study reports the chromosome number and meiotic behavior of 25 populations belonging to 10 species of Onobrychis sect. Hymenobrychis from Iran. Most populations showed the chromosome number 2n = 2x = 14. However, the chromosome number of two populations belonging to O. michauxii and O. subnitens was 2n = 2x = 16. It seems that the species with x = 7 are derived through aneuploid loss. In addition, intra- and interspecific variations in the chromosome number within O. sect. Hymenobrychis, aneuploidy and polyploidy in Onobrychis with special reference to the section Hymenobrychis and also the evolution of the chromosome number throughout the genus are discussed here. As the result of the present study and by reviewing the chromosome number within the genus, it can be concluded that O. sect. Hymenobrychis includes comparatively highly derived taxa and can be considered as a heterogeneous unit within the genus Onobrychis. Almost all the studied taxa displayed regular bivalent pairing and chromosome segregation at meiosis. However, some meiotic abnormalities observed in different taxa are discussed here.
The locally cultivated material of Rhoeo spathacea (=R. discolor) is totally pollen sterile, irrespective of the time of the year. Meiotic analyses of random samples have shown complete breakdown of the well known Rhoeo system. A fully opened-out ring of 12-chromosomes is not observed, and a chain of twelve occurred only rarely. The chiasmata are not confined only to the pairing segments, but also occur in the interstitial and differential segments which, very often leads to a break-up of the interchange complex into two to five groups. The orientation at metaphase I is basically non-disjunctional, and often unequal distribution occurs at anaphase I. Pollen mitoses revealed sub-haploid, hyper-haploid, diploid and tetraploid pollen. It is suggested that during its long history of cultivation through vegetative means, several mutations may have accumulated upsetting the genetic control on chromosome pairing limited only to the pairing segments. We suggest that most of the pollen sterility is segregational and recombinational in origin; and there is also the probability of the occurrence of mutations causing pollen sterility or the occurrence of some developmental block originating outside the pollen perhaps mediated by environmental factors, as yet unidentified.
To elucidate relationships at deep levels within Saxifragaceae we analyzed phylogenetically a data set of sequences for six DNA regions, four representing the chloroplast genome (rbcL, matK, trnL-trnF, psbA-trnH) and two from the nuclear genome (ITS and expansion segments of the 26S rDNA). A total of 6676 bp was aligned per taxon, 4559 bp and 1878 bp from the chloroplast and nuclear genomes, respectively. Chloroplast and nuclear trees agreed closely, prompting analysis of a combined, six-gene data set. Application of both parsimony and maximum likelihood methods yielded similar topologies. The use of different ITS alignments and the exclusion of hard-to-align ITS regions had little impact on either the final nuclear-based topology, or the shortest trees from the analysis of six genes. The affinities of two monotypic genera (Saxifragella and Saxifragodes) endemic to Tierra del Fuego were elucidated. Saxifragella is an early branching member of the North Temperate genus Saxifranga s. str.; Saxifragodes is sister to Cascadia, a genus endemic to Oregon and Washington. Long-distance dispersal from east Asia or western North America to South America may have played an important role in forming these and ether similar disjunctions in the family. A number of well-supported clades are present, including Saxifroga s. str., Micranthes, Saxifragopsis/Astilbe, Chrysosplenium/ Peltoboykinia, and the Boykinia and Heuchera groups. The use of additional characters has provided greatly increased resolution and internal support at deep levels. Saxifragaceae comprise two major lineages: Saxifroga s. str. (including Saxifragella) and all other genera of the family (the heucheroids). This major split is accompanied by general biogeographical and morphological differences. Whereas Saxifraga s. str. is largely arctic to alpine in occurrence, the heucheroid clade is largely temperate in distribution. Saxifraga s. str. has a relatively uniform floral morphology (generally actinomorphic; 5 sepals, 5 petals, 10 stamens, 2 carpels), whereas the heucheroid clade encompasses actinomorphic and zygomorphic forms, as well as variation in the number of sepals, petals, stamens, and carpels. Deep-level relationships within both Saxifraga s. str. and the heucheroid clade are well resolved and supported. A phylogenetic classification of the family is provided.
Two multiple interchange trisomics one involving all the fifteen chromosomes and other at least seven chromosomes were isolated in the progeny of two tertiary interchange trisomics of pearl millet (Penninsetum americanum (2n=14)). The study of chromosome association of diakinesis in these multiple interchanges showed varying frequencies and type of multivalent formations followed by abnormalities in later stages of meiosis. Secondary association of bivalents was quite frequent in one of the interchange. Aneuploidy together with translocation as the probable cause of further chromosome interchanges has been discussed on the light of the present investigation.
Desynapsis a phenomenon that results in the falling apart of homologous chromosomes after their initial pairing was reported in pearl millet by several investigators (Patil and Vohra 1962, Minocha et al. 1968, Jauhar 1969, Dhesi et al. 1973, Singh et al. 1977) where in mostly mere description and behaviour of univalents were dealt with. Studies from our laboratory revealed that desynapsis was associated with cell wall suppression, chromatin transfer, equational division of univalents and pollen poly-mitosis (Lakshmi and Yacob 1978, Lakshmi and Vishnuvardhan 1984). Dhesi (1980) reported seasonal variation in the expression of the desynaptic gene in disomics. A perusal of data on chromosome pairing in different genera revealed that the influence of environment has not been consistent and uniform. Hence it is felt necessary to conduct more detailed investigations on the effect of environmental factors on desynaptic gene/genes in pearl millet, before coming to definite conclusions. Present study is one such attempt in this direction and for the first time effect of environment has been studied on a desynaptic double trisomic in contrast to the earlier work of Dhesi who made similar investigation on a diploid desynaptic pearl millet. © 1987, Japan Mendel Society, International Society of Cytology. All rights reserved.
To elucidate relationships at deep levels within Saxifragaceae we analyzed phylogenetically a data set of sequences for six DNA regions, four representing the chloroplast genome (rbcL, matK, trnL-trnF, psbA-trnH) and two from the nuclear genome (ITS and expansion ...
Rhoeo spathacea is unusual in that its twelve chromosomes are involved in complex translocations
that results in atypical meiosis with all chromosomes frequently joined end-to-end into a single ring. The detailed
meiotic studies, for the fi rst time, revealed that alignment of chromosomes into a ring and / or a chain
begins at very early prophase I. However, the cells at diakinesis and metaphase I do not exclusively have a ring
or a chain of 12 chromosomes. Instead, they carry a range of chain confi gurations formed due to slipping of the
chiasmata off the pairing segments in complex structures. While in 57.61% cells, at diakinesis, a ring or a chain
was observed, in the rest 2-7 chain confi gurations existed. Similarly, at metaphase I a ring of 12 chromosomes
was observed in 33.87% cells whereas in 66.13 % cells 2-9 chain confi gurations existed. The various groups of
chromosomes in cells at diakinesis generally did not show any specifi c orientation pattern. However, in 17.31%
cells a disjunctional arrangement of chromosomes was observed. At metaphase I also while in 82.26% cells
chromosomes showed more or less non disjunctional orientations, in 17.74% cells regular arrangement of chromosomes
was observed. Owing to non-disjunctional arrangement of chromosomes at metaphase I, the anaphase
I distribution of chromosomes was erratic in 44.18% cells. Three to nine chromosomes were seen at two poles
in 33.06% cells whereas in 11.11% cells 1-8 lagging chromosomes existed. Regular distribution of 6:6 was seen
in 55.82% cells. The Pollen sterility recorded was very high i.e. 81.24% using cotton blue staining procedure.
It is suggested that a wide range of chromosome confi gurations, hitherto unidentifi ed, might exist in Rhoeo
spathacea which awaits to be discovered.
That meiosis is conditioned by a large number of genes majority of which are present in a dominant state, is evidenced by the detection of numerous monogenic recessive mutant genes which affect the premeiotic, meiotic and post-meiotic course of events. These genes are site- and stage-specific, and a few are sex specific. Of these, the most prevalent are the mutant genes affecting male meiosis and causing male sterility (ms genes) and those inhibiting synapsis and chiasma formation (synaptic genes) and leading to gametic sterility. Majority of the mutant genes affect the entire chromosomal complement but a few influence only specific chromosomes of a complement so that the chromosomes behave differentially within a genome of the same species. Some mutant genes alter chromosome form and function, others modify integrity, degree of spiralization, movement and migration of chromosomes. Their cytogenetic behaviour, genetic significance and breeding utility are described and discussed.
Summary The foregoing survey of the literature shows that translocations are of wide-spread occurrence in plants. Most of them have
been found in the angiosperms: in 49 genera of dicots and 47 genera of monocots; but some have been reported in the gymnosperms
(in two genera), also in the fungi. Studies at meiosis will undoubtedly reveal translocations in many other species, either
in occasional plants or in different groups isolated geographically. In certain cases they seem to have played a part in the
evolution of present karyotypes. In a number of cases, the presence of translocations has not been definitely established,
but they are one possible explanation of the observed configurations.
The survey reveals the need for additional detailed studies of interchanges. What accounts for directed segregation in the
interchange rings in certain species? For each of the factors which has been suggested there is one or more species which
does not behave in the predicted manner. Experimentally produced interchanges in other species having these features would
be useful; also in species having directed segregation of the sex chromosomes. A discussion of how they have been and how
they might be used as tools in the investigation of other cytological and cytogenetic problems and also certain applications
to practical breeding have been included.
An accession of A. roylei Stearn, a diploid species with 2n=16, growing in Northwest Himalayas, was studied for reduction division in male track. Multivalent associations involving 3 to 16 chromosomes were observed in cells at diplotene and metaphase-I. Although anaphasic segregations were mostly normal, the pollen stainability was very low. Propagation by bulbs ensures the survival and maintenance of such a complex heterozygosity in this species.
In a study on soybean using gamma rays, we came across with some sterile mutants. Cytological studies of these mutants clearly revealed desynapsis in them. In these sterile plants only few bivalents and a high frequency of univalents have been recorded and they displayed a very high percentage of pollen sterility. Later meiotic stages were also found to be highly disturbed. The plants were identified as male sterile ones as few pods were formed. It might be possible that gamma rays have acted on some genes responsible for synapsis and chiasma formation and resulted in early chiasmate dissociation suggesting that gamma rays can act as a potential tool in the development of male sterile lines. Study of desynaptic mutants is a potentially important source of information on the chiasma maintenance mechanism. These mutants furthermore can provide useful cytological and genetical informations on the male sterility occured in higher plants.
Reciprocal chromosome translocations are important for locating genes to linkage groups (LGs). Identifying the chromosomes involved in translocations is necessary for the isolation of tester sets. Our objectives were (i) to determine the location of translocation breakpoints by testing linkage with loci of Classical Linkage Group (CLG) 6 (Df2 and Y11), CLG 8 (Adh1, Ms1, Wm, Ms6, St5, W1, and Y23), and other CLGs, and (ii) to confirm the orientation of these nine marker loci. The 'KS172-11-3', 'KS175-7-3', 'Clark T/T', 'KS171-31-2', PI 189866, and 'L75-0283-4' soybean lines with homozygous chromosome translocations were crossed to the same genetic marker types. F 2 seed was increased at the University of Puerto Rico/Iowa State University soybean nursery near Isabela, PR. Data for the different characters used as marker traits were collected from F2 populations and +F 2:3 families. Recombination values revealed linkage between the breakpoints in KS172-11-3, KS175-7-3, and Clark T/T, with Df2, Y 11, and several loci of CLG 8. Interestingly, these three translocations had a common breakpoint between Y11 and Ms 1, but no linkage was identified between these loci and the breakpoints in KS171-31-2, PI 189866, and L75-0283-4. Our data further showed that CLGs 6 and 8 are the same LG, with Df2 and Adh1 at the ends of the chromosome segment. KS172-11-3, KS175-7-3, and Clark T/T share a common translocated chromosome which is different from that in KS171-31-2, PI 189866, and L75-0283-4. This information will facilitate the assignment of CLGs and the isolation of a tester set of translocations, and enhance genetic linkage mapping.
Chiasma frequencies in pollen mother cells and megaspore mother cells from both normal and desynaptic (ds-1ds-1) diploid potato clones were estimated on the basis of chiasmate chromosome arm association in metaphase I. In desynaptic mutants both the mean chiasma and bivalent frequencies per cell and the mean chiasma frequency per bivalent proved to be significantly lower. Despite significant differences in within-cell chiasma frequency variation among and particularly between normal and desynaptic clones, no clear effects of the ds-1 gene on the distribution of chiasmata over chromosomes in a cell were detected. The distribution of chiasmata over chromosomes appeared to be more or less random in both normal and desynaptic plants, which suggests that the ds-1 gene similarly affects chiasma frequencies in all chromosomes. Genetic data reported in the literature indicate that the ds-1 gene affects both the overall chiasma frequency and the chiasma distribution along individual chromosomes rather than chiasma maintenance. Sex differences in chiasma formation were not observed among normal plants or among desynaptic mutants, which indicates that chiasma formation in male and female meiosis of potato is governed by a single control system that is similarly expressed in both sexes.Key words: Solanum, desynapsis, chiasma frequency, male meiosis, female meiosis.
One complete asynaptic mutant, MM-19, and two partial ones, MM-4 and MM-16, of Oryza sativa L. induced by N-methyl-N-nitrosourea (MNU) were cytogenetically investigated. No chromosome pairing occurred from zygotene to pachytene and 24 univalents appeared at diakinesis and metaphase 1 in MM-19. On the other hand, a partial lack of chromosome pairing was observed from zygotene to pachytene and various numbers of univalents occurred at metaphase I in MM-4 and MM-16. The mean chiasma frequency per bivalent as well as per cell decreased to different extents in MM-4 and MM-16, and the correlation between both the amount of chromosome pairing from zygotene to pachytene and the chiasma frequency per cell at diakinesis was recognized. Judging from the development of anthers in each meiotic stage, the duration of the stage forming the synizetic knot, at which chromosome pairing took place, was longer in MM-4 and MM-16 than in the normal plant, and was in MM-19 almost as long as in the normal plant. The results of gene analyses indicate that each of the three asynaptic mutants is controlled by a recessive gene and that, at least for MM-4 and MM-16, these genes are located at different loci.Key words: asynaptic, rice, Oryza, chiasma frequency, synizesis.
The existence of structural heterozygosity for reciprocal translocations in the wild diploid (n=9) accession of Artemisia parvifl ora collected from the Parvati Valley in Kullu district, Himachal Pradesh, India is reported for the fi rst time. Th e other two Indian accessions studied from Pangi Valley in Chamba district and Pulga, 2300m in Parvati Valley depict normal meiosis with the presence of nine bivalents, regular segregation of chromosomes during anaphases and almost a hundred percent pollen fertility. We studied in detail the male meiosis in pollen mother cells (PMC) and pollen fertility in the accessions showing structural heterozygosity. Th e PMCs exhibited abnormal meiosis due to the presence of multivalents in 62.92% of the analyzed 213 PMCs. A total of 12.31% of the chromosomes are observed to be involved in multivalents and 2.35% remained as univalents. In spite of the presence of multivalents and early/late disjunction of few bivalents, the chromosomes in PMCs are regularly segregated to poles at A-I/A-II resulting into normal tetrad formation. Th e structural rearrangements of chromosomes in A. parvifl ora are responsible for causing some pollen malformation (30%) as has been the case in other species. Another eff ect of structural heterozygosity is the increase in chiasma frequency per PMC from 10.75-12.40.