[show abstract][hide abstract] ABSTRACT: Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, is one of the most devastating foliar diseases on wheat (Triticum aestivum L.) in the northern Great Plains of North America. This study was conducted, under controlled environmental conditions, to elucidate the genetics and map the resistance to SNB caused by spore inoculum and culture filtrate of P. nodorum isolate Sn2000. A hard red spring wheat population was developed from a cross between the susceptible cultivar Steele-ND and the resistant line ND 735 for this study. Two-leaf seedlings of the parents, F1 and F2 generations, and F2:6 recombinant-inbred lines (RILs) were inoculated with spore suspensions while independent two week old seedlings of segregating generations were infiltrated with culture filtrate. Disease reaction was assessed 8 days after inoculation based on a lesion-type scale while plants were evaluated for culture filtrate response four days after infiltration for the presence or absence of necrosis. Genetic analysis revealed that a single recessive gene, Tsn1, in ND 735 confers resistance to both spore suspension and culture filtrate of P. nodorum isolate Sn2000. Mapping analysis using Diversity Arrays Technology (DArT) and simple sequence repeat (SSR) markers indicates the gene, Tsn1, is located on the long arm of chromosome 5B and is flanked by the DArt markers wPt-8285 and wPt-3049 at a distance of 7.0 cM and 2.9 cM, respectively. This gene also controls resistance to tan spot caused by Pyrenophora tritici-repentis race 2. Results of this study reveal that wheat-P. nodorum interaction follows the toxin model of gene-for-gene hypothesis. Additionally, the finding of single gene control in the line ND 735 for both tan spot and SNB enhances the utility of the line ND 735 in wheat breeding program as a source of multiple disease resistance.
[show abstract][hide abstract] ABSTRACT: Tan spot, caused by Pyrenophora tritici-repentis, is an economically important disease of wheat worldwide. Isolates of P. tritici-repentis are presently classified into eight races on the basis of their virulence (ability to induce necrosis and (or) chlorosis) on a set of wheat differential cultivars. A total of 337 isolates of P. tritici-repentis from leaves of common wheat (Triticum aestivum), durum wheat (Triticum durum), einkorn wheat (Triticum monococcum), canary grass (Phalaris canariensis), and weedy grasses infected with tan spot were collected in wheat fields across Saskatchewan, Canada, from 2000 to 2002. Single-spore isolates were developed and tested on an expanded set of differential lines. Races 1, 2, 3, and 4 of P. tritici-repentis were identified in Saskatchewan. Race-2 isolates were the most prevalent on both common and durum wheat in all 3 years. Races 1, 2, and 4 were isolated from common wheat, and races 1, 2, and 3, from durum wheat. All race-3 isolates were detected from durum wheat, and while all race-4 isolates were from common wheat. Race 2 was isolated from canary grass, and races 1, 2, 3, and 4 were isolated from T. monococcum and wild grasses. To our best knowledge, this is the first report of the occurrence of P. tritici-repentis on canary grass and of race 3 on T. monococcum and wild grass.
Canadian Journal of Plant Pathology 03/2010; June 2007(Vol. 29):166-171. · 1.12 Impact Factor
[show abstract][hide abstract] ABSTRACT: Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, is a major component of the leaf-spotting disease complex of wheat (Triticum aestivum L.) in the northern Great Plains of North America. This study was conducted, under controlled environmental conditions, to determine the inheritance of resistance to SNB in a diverse set of hexaploid and tetraploid wheat genotypes and to decipher the genic/allelic relationship among the resistance gene(s). Plants were inoculated at the two to three-leaf stages with a spore suspension of P. nodorum isolate Kelvington-SK and disease reaction was assessed 8 days after inoculation based on a lesion-type scale. Tests of the F1 and F2 generations and of F2 : 3 or F2 : 5 families indicated that a single recessive gene controlled resistance to SNB in both hexaploid and tetraploid resistance sources. Lack of segregation in intra-specific and inter-specific crosses between the hexaploid and the tetraploid resistant genotypes, indicated that these genetically diverse sources of resistance possess the same gene for resistance to SNB. Results of this study suggest that the wheat-P. nodorum interaction may follow the toxin model of the gene-for-gene hypothesis.
[show abstract][hide abstract] ABSTRACT: Stagonospora nodorum blotch (SNB) is an important foliar disease of durum wheat (Triticum turgidum var. durum) worldwide. The combined effects of SNB and tan spot, considered as components of the leaf spotting disease complex,
result in significant damage to wheat production in the northern Great Plains of North America. The main objective of this
study was the genetic analysis of resistance to SNB caused by Phaeosphaeria nodorum in tetraploid wheat, and its association with tan spot caused by Pyrenophora tritici-repentis race 2. The 133 recombinant inbred chromosome lines (RICL) developed from the cross LDN/LDN(Dic-5B) were evaluated for SNB
reaction at the seedling stage under greenhouse conditions. Molecular markers were used to map a quantitative trait locus
(QTL) on chromosome 5B, explaining 37.6% of the phenotypic variation in SNB reaction. The location of the QTL was 8.8cM distal
to the tsn1 locus coding for resistance to P. tritici-repentis race 2. The presence of genes for resistance to both SNB and tan spot in close proximity in tetraploid wheat and the identification
of molecular markers linked to these genes or QTLs will be useful for incorporating resistance to these diseases in wheat
[show abstract][hide abstract] ABSTRACT: Triticale (X Triticosecale), a Man-made cereal grass crop obtained from hybridization of wheat (Triticum spp) with rye (Secale cereale). The hope was that triticale would combine the high yield potential and good grain quality of wheat, and the resistance/tolerance
to the biotic and abiotic stresses of rye. Triticale grains can be used for human food and livestock feed. Since the last
century, triticale has received significant attention as a potential energy crop. Today, research is currently being conducted
includes the use of this crop biomass in bio-energy production. The aim of a triticale breeding programs mainly focuses on
the improvement of economic traits such as grain yield, biomass, nutritional factors, plant height, as well as traits such
as early maturity and high grain volume weight. Intense breeding and selection have made very rapid genetic improvements in
triticale seed quality. The agronomic advantages and improved end-use properties of the triticale grains over wheat achieved
by research and development efforts make triticale an attractive option for increasing global food production particularly,
for marginal and stress-prone growing conditions. Details of the different breeding approaches utilized to enhance modern
triticale cultivars for various uses are discussed in this chapter.
[show abstract][hide abstract] ABSTRACT: Wheat (various species of the genus Triticum) is a grass originating from the Levant area of the Middle East. However, only hexaploid common wheat (Triticum eastivum), and tetraploid durum wheat (Triticum turgidum ssp. durum) are presently cultivated worldwide. Not only is wheat an important crop today, it may well have influenced human history.
Wheat was a key factor enabling the emergence of civilization because it was one of the first crops that could be easily cultivated
on a large scale, and had the additional advantage of yielding a harvest that provides long-term storage of food. Today, there
are different classes and uses of wheat. Although, it is mainly used as a staple food to make flour for leavened, flat and
steamed breads, wheat can also be used as livestock feed, for fermentation to make beer and other alcoholic liquids, and recently,
as a source of bio-energy. Global wheat production must increase at about 2% annually to meet future demands. The potential
of increasing the global arable land is limited; hence, future increases in wheat production must be achieved by enhancing
the wheat productivity to the land already in use. The objectives of most breeding programs include: high and stable yields,
superior end-use quality, desirable agronomic characteristics, biotic (mainly, pests) resistance, and abiotic (environmental
stresses) tolerance. While it is virtually impossible to combine all these characteristics into a single ‘perfect’ variety,
continuous breeding efforts toward achieving these objectives will ensure that new varieties possess as many desirable and
economic traits as possible. Details of the different breeding approaches to enhance modern wheat breeding are discussed in
[show abstract][hide abstract] ABSTRACT: Tan spot of wheat, caused by the fungus Pyrenophora tritici-repentis, is a destructive disease worldwide that can lead to serious losses in quality and quantity of wheat grain production. Resistance to multiple races of P. tritici-repentis was identified in a wide range of genetically diverse genotypes, including three different species Triticum aestivum (AABBDD), T. spelta (AABBDD), and T. turgidum (AABB). The major objectives of this study were to determine the genetic control of resistance to P. tritici-repentis races 1 and 5 in 12 newly identified sources of resistance. The parents, F(1), F(2), and F(2:3) or F(2:5) families of each cross were analyzed for the allelism tests and/or inheritance studies. Plants were inoculated at the two-leaf stage under controlled environmental conditions and disease reaction was assessed based on lesion-type rating scale. A single recessive gene controlled resistance to necrosis caused by P. tritici-repentis race 1 in both tetraploid and hexaploid resistant genotypes. The lack of segregation in the inter- and intra-specific crosses between the resistant tetraploid and hexaploid genotypes indicated that they possess the same genes for resistance to tan necrosis and chlorosis induced by P. tritici-repentis race 1. A single dominant gene for chlorosis in hexaploid wheat and a single recessive gene for necrosis in tetraploid wheat, controlled resistance to P. tritici-repentis race 5.
[show abstract][hide abstract] ABSTRACT: Stagonospora nodorum blotch, caused by Phaeosphaeria nodorum, is considered one of the most destructive foliar diseases of wheat in the United States. However, relatively little is known about the population biology of this fungus in the major wheat-growing regions of the central United States. To rectify this situation, 308 single-spore isolates of P. nodorum were analyzed from 12 populations, five from hard red spring wheat cultivars in Minnesota and North Dakota and seven from soft red winter wheat in Indiana and Ohio. The genetic structure of the sampled populations was determined by analyzing polymorphisms at five microsatellite or simple-sequence repeat (SSR) loci and the mating type locus. Although a few clones were identified, most P. nodorum populations had high levels of gene (H(S) = 0.175 to 0.519) and genotype (D = 0.600 to 0.972) diversity. Gene diversity was higher among isolates collected from spring wheat cultivars in North Dakota and Minnesota (mean H(S) = 0.503) than in those from winter wheat cultivars in Indiana and Ohio (H(S) = 0.269). Analyses of clone-corrected data sets showed equal frequencies of both mating types in both regional and local populations, indicating that sexual recombination may occur regularly. However, significant gametic disequilibrium occurred in three of the four populations from North Dakota, and there was genetic differentiation both within and among locations. Genetic differentiation between the hard red spring and soft red winter wheat production regions was moderate (F(ST) = 0.168), but whether this is due to differences in wheat production or to geographical variation cannot be determined. These results suggest that sexual reproduction occurs in P. nodorum populations in the major wheat-growing regions of the central United States, and that geographically separated populations can be genetically differentiated, reflecting either restrictions on gene flow or selection.
[show abstract][hide abstract] ABSTRACT: Tan spot of wheat, caused by the fungus Pyrenophora tritici-repentis, is a destructive disease worldwide that can cause serious losses in quality and quantity of wheat grain production. The fungus induces two distinct symptoms; tan necrosis and extensive chlorosis, on susceptible wheat cultivars. The major objective of this study was to determine the genetic control of resistance to tan spot, caused by multiple races of P. tritici-repentis in the newly identified sources of resistance. Plants were inoculated at the two-leaf stage under controlled environmental conditions and disease assessment was based on lesion-type rating scale. The segregating generations of each cross were analysed for the allelism and/or inheritance studies. A single recessive gene controlled resistance to tan necrosis caused by race 1 in both tetraploid and hexaploid resistant genotypes studied. The lack of segregation in the inter- and intra- specific crosses between the resistant tetraploid and hexaploid genotypes indicates that they possess the same genes for resistance to tan necrosis and extensive chlorosis induced by P. tritici-repentis race 1. Two independent genes, a single dominant gene for extensive chlorosis in hexaploid wheat and a single recessive gene for tan necrosis in tetraploid wheat, controlled resistance to tan spot induced by race 5. Genetic analysis of inter- and intra-specific crosses among Triticum species confirms that wheat-P. tritici-repentis host-pathosystem follows the toxin model of gene-for gene hypothesis.
[show abstract][hide abstract] ABSTRACT: ABSTRACT Race 3 of the fungus Pyrenophora tritici-repentis, causal agent of tan spot, induces differential symptoms in tetraploid and hexaploid wheat, causing necrosis and chlorosis, respectively. This study was conducted to examine the genetic control of resistance to necrosis induced by P. tritici-repentis race 3 and to map resistance genes identified in tetraploid wheat (Triticum turgidum). A mapping population of recombinant inbred lines (RILs) was developed from a cross between the resistant genotype T. tur-gidum no. 283 (PI 352519) and the susceptible durum cv. Coulter. Based on the reactions of the Langdon-T. dicoccoides (LDN[DIC]) disomic substitution lines, chromosomal location of the resistance genes was determined and further molecular mapping of the resistance genes for race 3 was conducted in 80 RILs of the cross T. turgidum no. 283/Coulter. Plants were inoculated at the two-leaf stage and disease reaction was assessed 8 days after inoculation based on lesion type. Disease reaction of the LDN(DIC) lines and molecular mapping on the T. turgidum no. 283/Coulter population indicated that the gene, designated tsn2, conditioning resistance to race 3 is located on the long arm of chromosome 3B. Genetic analysis of the F(2) generation and of the F(4:5) and F(6:7) families indicated that a single recessive gene controlled resistance to necrosis induced by race 3 in the cross studied.
[show abstract][hide abstract] ABSTRACT: Tan spot of wheat is caused by the fungus Pyrenophora tritici-repentis. On susceptible hosts, P. tritici-repentis induces two phenotypically distinct symptoms, tan necrosis and chlorosis. This fungus produces several toxins that induce tan necrosis and chlorosis symptoms in susceptible cultivars. The objectives of this study were to determine the inheritance of insensitivity to necrosis-inducing culture filtrate of P. tritici-repentis, race 2, and to establish the relationship between the host reaction to culture filtrate and spore inoculation with respect to the necrosis component. The F1, F2, and BC1F1 plants and F2:8 lines of five crosses involving resistant wheat genotypes ‘Erik’, ‘Red Chief’, and line 86ISMN 2137 with susceptible cultivars ‘Glenlea’ and ‘Kenyon’ were studied. Plants were spore-inoculated at the two-leaf stage. Four days later, the newly emerged uninoculated third leaf was infiltrated with a culture filtrate of isolate Ptr 92–164 (race 2). Reactions to the spore inoculation and the culture filtrate were recorded 8 days after spore inoculation. The segregation observed in the F2 and BC1F1 generations and the F2:8 lines of all crosses indicated that a single recessive gene controlled insensitivity to necrosis caused by culture filtrate. This gene also controlled resistance to necrosis induced by spore inoculation.
[show abstract][hide abstract] ABSTRACT: Leafspotofwheat(TriticumaestivumL.)inNorthAmericaconsists of a group of diseases involving tan spot (Pyrenophora tritici-repentis (Died.) Drechs.), Stagonospora nodorum blotch (Phaeosphaeria nodorum (E.Muller) Hedjarroude), and Septoria tritici blotch (Mycosphaerella graminicola (Fuckl) J. Schrot. in Cohn). A complex of these diseases occurs in nature hence managing leaf spots is diffi- cult. Use of resistant cultivars is the most effective and economical means of controlling leaf spot; however, none of the widely grown wheatcultivarsinNorthAmericashowhighlevelsofresistancetothese diseases. Hence, this study aimed to identify new sources of resistance to leaf spotting diseases. To achieve this objective, 975 accessions of wheat and its relatives were evaluated for P. tritici-repentis, race 1, resistance under controlled environments. Of these 975 accessions, 40 selected accessions were further screened against six virulent races (1, 2, 3, 5, 10, and 11) of P. tritici-repentis and to foliar pathogens P. nodorum and M. graminicola. New sources of resistance effective against the three leaf spotting disease were identified in accessions of T. monococcum L., T. turgidum L., T. dicoccum Schrank ex Schubler, T.dicoccoides(Korn.exAschandGraebner)Schweinf.,T.timopheevii (Zhuk.) Zhuk., T. spelta L., and T. aestivum L. including synthetic wheat. Resistance was observed in all three ploidy levels of the wheat genome and presently efforts are being made to transfer the leaf spot resistance into adapted wheat and durum cultivars. I
[show abstract][hide abstract] ABSTRACT: The fungus Pyrenophora tritici-repentis, causal agent of tan spot of wheat, produces two phenotypically distinct symptoms, tan necrosis and extensive chlorosis. The inheritance of resistance to chlorosis induced by P. tritici-repentis races 1 and 3 was studied in crosses between common wheat resistant genotypes Erik, Hadden, Red Chief, Glenlea, and 86ISMN 2137 and susceptible genotype 6B-365. Plants were inoculated under controlled environmental conditions at the two-leaf stage and disease rating was based on presence or absence of chlorosis. In all the resistant×susceptible crosses, F1 plants were resistant and the segregation of the F2 generation and F3 families indicated that a single dominant gene controlled resistance. Lack of segregation in a partial diallel series of crosses among the resistant genotypes tested with race 3␣indicated that the resistant genotypes possessed␣the same resistance gene. This resistance gene was effective against chlorosis induced by P.␣tritici-repentis races 1 and 3.
[show abstract][hide abstract] ABSTRACT: Tan spot, a major foliar disease of wheat (Triticum aestivum L.), is caused by an ascomycete Pyrenophora tritici-repentis. Both culture filtrates and conidiospore inocula induce disease symptoms in susceptible wheat genotypes. The objectives of
this study were to determine and map the genetic control of resistance to spore inocula and culture filtrates of P. tritici-repentis races 2 and 5. The F1 and F2 generations and an F2:6 recombinant inbred lines (RIL) population were developed from a cross between the resistant ND735 and the susceptible Steele-ND.
Disease assessments of the segregating generations were done at the seedling stage using culture filtrates and spore inocula
under controlled environmental conditions. Genetic and mapping analyses of the F1 and F2 generations and the RIL by both methods indicated that the same single recessive gene, Tsr1, located on chromosome 5BL, controlled resistance and insensitivity to necrosis induced by race 2. A second recessive gene,
designated Tsr6, located on chromosome 2BS, conferred resistance/insensitivity to chlorosis induced by spore inocula or culture filtrates
of race 5. Diversity Arrays Technology markers wPt-3049 (2.9cM) and wPt-0289 (4.6cM) were closely linked to Tsr1 and Tsr6, respectively. The results further indicated that culture filtrates can be used as surrogates for spore inoculation. Tsr1 and Tsr6 can be selected by marker-assisted selection in breeding for resistance to tan spot.
KeywordsYellow spot-Necrosis-Chlorosis-Diversity arrays technology (DArT) and simple sequence repeat (SSR) markers-
[show abstract][hide abstract] ABSTRACT: Tan spot and Stagonospora nodorum blotch caused by Pyrenophora tritici-repentis (Died.) Drechs. and Phaeosphaeria nodorum (E. Müller) Hedjarroude, respectively, are the major components of the leaf spotting disease complex of durum wheat (Triticum turgidum L.). These diseases induce significant quality and yield reductions and control through host plant resistance is the most
effective and economical method. The objectives of this study were to determine the chromosomal locations of major genes conferring
resistance to P. tritici-repentis races 1–3 and 5, toxins Ptr ToxA and Ptr ToxB, and P. nodorum isolate Sn2000 in a set of Langdon- Triticum dicoccoides (Israel A) durum substitution lines. Plants were evaluated for disease reaction at the two-leaf stage under controlled environmental
conditions. Based on the reactions of the substitution lines, the chromosomal locations of the resistance genes for P. tritici-repentis races 1 and 2, and 3 and 5, were determined to be chromosomes 5B and 3B, respectively. Resistance to toxin Ptr ToxA was located
on chromosome 5B whereas toxin Ptr ToxB failed to induce symptoms in the tetraploid genotypes, including the substitution
lines. Resistance to P. nodorum isolate Sn2000 was located on chromosome 5B. This is the first study to reveal the chromosomal locations of major genes for
resistance to tan spot and Stagonospora nodorum blotch in tetraploid wheat using the Langdon-T. dicoccoides (Israel A) substitution lines.
[show abstract][hide abstract] ABSTRACT: Tan spot, caused by an ascomycete fungus Pyrenophora tritici-repentis, is one of the most devastating foliar diseases of wheat. This fungus induces two distinct symptoms, tan necrosis and extensive
chlorosis, on susceptible wheat cultivars. Besides causing average yield losses of 5–10%, tan spot also causes significant
losses in grain quality by grain shriveling, red smudge, and black point. Conservation agriculture in combination with wheat
monoculture involving cultivation of susceptible cultivars has resulted in frequent onset of tan spot epidemics worldwide.
Development of new resistant wheat cultivars, in conjunction with crop rotation, will provide an effective, economical, and
environmentally safe means of controlling tan spot. Presently, eight races of P. tritici-repentis have been identified worldwide based on the ability to induce necrosis and chlorosis symptoms on a set of differential wheat
cultivars. P. tritici-repentis is a homothallic fungus having both sexual and asexual reproduction resulting in high genetic diversity worldwide. Both quantitative
and qualitative mode of inheritance for resistance to tan spot of wheat has been reported. The tan spot fungus produces multiple
host-specific toxins and host resistance is highly correlated to insensitivity to toxins. Genetic studies have further confirmed
that wheat–P. tritici-repentis follows the toxin model of gene-for-gene hypothesis although other mechanism of host–pathogen interaction may exist and exploitation
of all resistance phenomenon is to be adopted to develop durable resistant cultivars.