K. V. Chowdari

Western Psychiatric Institute and Clinic, Pittsburgh, Pennsylvania, United States

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Publications (8)23.85 Total impact

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    ABSTRACT: Two Cytoplasmic Male Sterile lines were crossed with fourteen restorer lines of rice widely grown in the western regions of Maharashtra, India, to produce 28 F1 hybrids which were evaluated for eight agronomically important traits, contributing to yield potential, in replicated field trials. The hybrid performance was recorded along with heterosis and heterobeltiosis. All the rice lines under investigation were subjected to marker-based variability analysis. An attempt was made to correlate genetic distance based on specific markers for each trait individually, as well as average genetic distance based on all specific markers, with hybrid performance and heterosis, by regression analysis. Specific markers could cluster the parental lines in different groups and showed significant correlation with hybrid performance. The data also supports the proposition that epistasis is the basis of heterosis. The analysis, however, revealed a lack of significant predictive values for field application.
    Biochemical Genetics 07/2001; 39(5-6):179-200. · 0.94 Impact Factor
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    ABSTRACT: Genetic diversity among 42 Indian elite rice varieties, which is important for selection of parents for conventional breeding and hybrid program, was evaluated using three different types of DNA markers and parentage analysis. Random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and sequence tagged microsatellite site (STMS) markers resulted in mean heterozygosity values of 0.429, 0.675 and 0.882 over all loci, respectively, and marker index values of 2.21, 4.05 and 5.49, respectively. The three molecular marker systems together provide wider genome coverage and, therefore, would be a better indicator of the genetic relationships among the 42 elite rice cultivars than those revealed using individual molecular markers. A total of 153 bands (91%) were polymorphic out of 168 bands amplified, considering all the markers together. The average genetic similarity coefficient across all the 861 cultivar pairs was 0.70 while the average coefficient of parentage was 0.10. Cluster analysis revealed that there was a very poor correlation (correlation coefficient <0.1) between dendrograms generated using coefficients of parentage and molecular marker generated genetic similarities, which can be attributed to selection pressure, genetic drift, sampling of loci and unknown relationships among supposedly unrelated ancestors.
    Genetica 02/2000; 108(3):269-84. · 1.68 Impact Factor
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    ABSTRACT: Papaya, an economically important fruit plant, is polygamous in nature. The sex of dioecious papaya plants can be deduced only after they attain reproductive maturity (6–8 months). Normally, 50% of the population in a field is composed of unfruitful male plants and almost 45% of these have to be uprooted at the flowering stage. This unnecessary cultivation of unwanted males leads to wastage of resources, which can be avoided if the sex of the plant is determined at juvenile stage. Morphological and cytological studies conducted so far have failed to differentiate between the various sex forms of papaya. Its dioecious nature, occasional sex-reversal of male flowers and the absence of a heteromorphic pair of sex chromosomes make papaya an interesting system to study sex determination at the molecular level. In the present study, highly informative microsatellite and minisatellite probes were employed to identify sex-specific differences in papaya. Among these, only the microsatellite probe (GATA)4 demonstrated sex-specific differences in all the cultivars analysed. The diagnostic potential of this microsatellite marker was exploited to sex papaya plants at the seedling stage. This study also indicates that the genetic material of the X and Y chromosomes of papaya is diverging in a sex-specific manner and hence they are in the process of differentiation.
    Theoretical and Applied Genetics 09/1999; 99(6):1047-1052. · 3.66 Impact Factor
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    ABSTRACT:  The potential of DNA markers such as microsatellites, minisatellites and RAPDs was investigated in pearl millet [Pennisetum glaucum (L.) R. Br] with respect to their abundance and variability. Southern analysis, using 22 different di-, tri-, tetra- and penta-oligonucleotide probes and five minisatellite probes, identified (GATA)4 as the most useful probe for the detection of multiple polymorphic fragments among pearl millet cultivars and landraces from India. The clustering patterns of pearl millet cultivars and landraces based on (GATA)4 and RAPD (randomly amplified polymorphic DNA) markers differed. The landraces, representing eight states in India, could not be grouped based on their geographical distribution with the DNA markers. RAPD analysis revealed a high degree of genetic diversity among the cultivars and landraces employed in this study. The probability of an identical match by chance for any two genotypes using (GATA)4 and RAPDs was 3.02×10-20 for cultivars and 5.2×10-9 for landraces. The microsatellite (GATA)4 and RAPDs provide useful tools for genotype identification and for the assessment of genetic relationships in pearl millet.
    Theoretical and Applied Genetics 06/1998; 97(1):154-162. · 3.66 Impact Factor
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    ABSTRACT: Some somaclonal variants derived from a landrace rice variety, Indrayani, were shown to be high yielding and resistant to multiple diseases in previous analysis carried out in our laboratory. An attempt was made to assess the effect of culturing and regeneration of rice plants on DNA variation at microsatellite loci in R2 progeny of callus-derived rice plants. Different somaclones of the rice line Indrayani differing in yield and disease response (high, low and no change in yield, as compared to the original genotype) were used as genetic material for these analyses. Analysis of microsatellite loci was accomplished by digesting DNA from regenerated rice somaclones and assaying for polymorphisms at microsatellite loci by in-gel hybridization with synthetic oligonucleotide probes such as (GATA)4, (CAC)5 and (TG)10. Specific variation at a PCR-amplified locus containing three internal microsatellite repeats (1E6) using restriction site fingerprinting was also investigated. The locus-specific amplification of a sequence-tagged microsatellite marker followed by digestion with HinfI and Sau3AI restriction endonucleases showed differences in some somaclonal variants. The technique used in this study enables monitoring of DNA changes in successive generations of somaclonal variants as a measure of DNA variability and possibly to identify the regions which are responsible for specific traits.
    Plant Cell Reports 01/1998; 18(1):55-58. · 2.94 Impact Factor
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    ABSTRACT:  Genetic diversity in five cytoplasmic male-sterile and seven restorer lines of pearl millet was determined by DNA fingerprinting using a (GATA)4 microsatellite and randomly amplified polymorphic DNAs (RAPDs). A total of 160 polymorphic loci were generated and, based on the polymorphism data, similarity index values ranged from 0.81 to 0.50. Cluster analysis was performed and relationships among these lines revealed that they were not in agreement with the available pedigree data. The per se performance of parents and hybrids was analyzed for days-to-50% flowering, plant height, productive tillers, ear length, ear width, 1000-grain weight and grain yield per plot. Path co-efficient analysis revealed that productive tillers, ear width and days-to-50% flowering had a relatively large positive effect. The correlation values were mostly not significant with respect to genetic distance, except for days-to-50% flowering, ear length and ear width. Our results have indicated that genetic-distance measures based on the (GATA)4 microsatellite and RAPDs may be useful for the grouping of parents, but not for predicting heterotic combinations, in pearl millet.
    Theoretical and Applied Genetics 01/1998; 97(1):163-169. · 3.66 Impact Factor
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    ABSTRACT:  A high level of genetic polymorphism was detected among Indian isolates of Xanthomonas oryzae pv. oryzae using hypervariable probes such as a microsatellite oligonucleotide, probe (TG)10, a human minisatellite probe, pV47, an avirulence gene probe, avrXa10 and a repeat clone, pBS101. These DNA probes detected multiple loci in the bacterial genome generating complex DNA fingerprints and differentiated all of the bacterial isolates. Analysis of fingerprints indicated that pV47, (TG)10 and pBS101 have a lower probability of identical match than avrXa10 and therefore are potential probes for DNA fingerprinting and variability analysis of Xanthomonas oryzae pv. oryzae pathogen populations. Cluster analysis based on hybridization patterns using all of the above probes showed five groups at 56% similarity. Studies on the methylation patterns of isolates representing the three important races of X. oryzae pv. oryzae indicated more methylation in the most virulent isolate, suggesting a possible role of methylation in pathogenicity.
    Theoretical and Applied Genetics 06/1997; 95(1):103-111. · 3.66 Impact Factor
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    ABSTRACT: The suitability of miniand microsatellite related DNA sequences capable of detecting multiple loci was investigated for their ability to generate DNA fingerprints in rice. These included R18.1, a cattle-derived probe, the M13 repeat probe, pV47, a human minisatellite probe; and repeats in the Per gene, telomere, chi sequence and 3' hypervariable region of apolipoprotein B. With the R18.1, pV47 and M13 repeat probes, the level of polymorphism was high enough to identify all of the cultivars and wild rice species used in this study. R18.1, which showed the highest level of polymorphism, was estimated to identify up to 2.5×10(20) genotypes of rice. In a F2 population of a 'Basmati-370' and 'Taichung-65' cross, loci detected by R18.1 segregated in a Mendelian fashion. DNA fingerprints were somatically stable and the hybridization patterns were identical among different plants of the same cultivar. Application of the above molecular genetic markers for identification of rice genotypes is reported here for the first time.
    Theoretical and Applied Genetics 06/1995; 90(7-8):1000-6. · 3.66 Impact Factor