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Carbohydrates and gamma-amino butyric acid (GABA) have not been studied under the stress of stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) in wheat. Wheat cultivars PBW725 (resistant) and HD2967 (susceptible) were compared at 1, 2 and 4 d of GABA, Pst, and GABA + Pst sprayed to 30-d of seedling growth. Starch was hydrolyzed, and levels of sugars and proteins improved over time of infection in PBW725 however HD2967 improved under GABA + Pst. Proline increased while GABA decreased over the time of infection in HD2967. Progressive increase of diamine oxidase and glutamate decarboxylase was seen in PBW725 during infection. Protease levels became low at 4 d of infection but improved under GABA + Pst in HD2967. Protein carbonyls increased in HD2967 only under Pst but decreased under GABA + Pst. Results concluded that GABA is an essential regulator of carbohydrates under stripe rust. Sustained response over time of infection may be important for resistance. [ABSTRACT FROM AUTHOR]

Globally, leaf and yellow rusts are considered one of the most serious biotic constraints of wheat inflicting huge economic losses in India. Host resistance is the only efficient, economical, eco-friendly way of controlling rust diseases. With this scenario, experiments were carried out to characterize the seedling and adult plant resistance in diverse wheat genotypes. By applying the gene-matching technique using multi-pathotype data, four Yr (YrA, Yr2, Yr9, Yr18) and seven Lr (Lr2, Lr10, Lr13, Lr23, Lr24, Lr26, Lr34) genes in Indian wheat germplasm accessions and five Yr (YrA, Yr2, Yr9, Yr18, Yr27) and nine Lr (Lr1, Lr3, Lr10, Lr13, Lr19, Lr23, Lr24, Lr26, Lr34) genes in Indian wheat cultivars were characterized singly or combinations with other vital genes. Adult plant slow rusting resistance was assessed through host response and different epidemiological parameters. Promising adult plant slow rusting resistance against stripe and leaf rust was observed in different wheat genotypes consistently during the rabi seasons of 2018–19 and 2019–20. All these promising rust-resistant genotypes at the adult plant stage were susceptible at the seedling stage to one or more pathotype(s) including the most prevalent and virulent of both rusts, which indicated the presence of APR gene(s). All the epidemiological parameters were strongly and positively correlated in the study, for which we can strongly conclude that final disease severity, coefficient of infection, and relative area under the disease progress curve followed by infection rate are the most appropriate parameters to assess adult plant slow rusting resistance. The lines identified in this study are useful in the hybridization programs to enhance the levels of resistance. [ABSTRACT FROM AUTHOR]

Thirteen known Yr gene-associated markers pertaining to genes (Yr5,Yr10,Yr15,Yr24/Yr26) were used to identify the genes in selected wheat germplasm which were found resistant under field conditions at two locations in Punjab, India against stripe rust. In field evaluation, 38 genotypes exhibited highly resistant response, with a final rust severity (FRS) ranging from 0 to TR. Seven genotypes expressed a resistant to moderately resistant response with FRS ranging from 5MR–10S. In race-specific phenotying against most prevalent pathotypes of Pucciniastriiformistritici (46S119,110S119 &238S119) by seedling reaction test (SRT) 14 genotypes (29.2%) were found to be immune (IT = 0), 28 genotypes (58.3%) were resistant (IT = 1), and 3 genotypes (6.3%) were moderately resistant (IT = 2). Yr5 was detected in sixteen lines with the help of two markers Xwmc175 and Xgwm120 linked with Yr5. Yr10 was detected in ten lines with the marker Xpsp3000 and Yr15 was detected in fourteen lines with two linked markers; Xgwm413 and Xgwm273. Likewise, Yr24/26 was detected in 15 lines with two linked markers, namely Xbarc181 and Xbarc187. Based on the race specific phenotyping data and marker data, fourteen lines were found to carry a single gene, 16 showed the presence of two gene combinations, and seven genotypes were found to have a combination of three genes. Frequencies of Yr5, Yr15 and Yr26/Yr24 was high among test wheat germplasm in comparison to Yr10. [ABSTRACT FROM AUTHOR]

Thirteen known Yr gene-associated markers pertaining to genes (Yr5,Yr10,Yr15,Yr24/Yr26) were used to identify the genes in selected wheat germplasm which were found resistant under field conditions at two locations in Punjab, India against stripe rust. In field evaluation, 38 genotypes exhibited highly resistant response, with a final rust severity (FRS) ranging from 0 to TR. Seven genotypes expressed a resistant to moderately resistant response with FRS ranging from 5MR–10S. In race-specific phenotying against most prevalent pathotypes of Pucciniastriiformistritici (46S119,110S119 &238S119) by seedling reaction test (SRT) 14 genotypes (29.2%) were found to be immune (IT = 0), 28 genotypes (58.3%) were resistant (IT = 1), and 3 genotypes (6.3%) were moderately resistant (IT = 2). Yr5 was detected in sixteen lines with the help of two markers Xwmc175 and Xgwm120 linked with Yr5. Yr10 was detected in ten lines with the marker Xpsp3000 and Yr15 was detected in fourteen lines with two linked markers; Xgwm413 and Xgwm273. Likewise, Yr24/26 was detected in 15 lines with two linked markers, namely Xbarc181 and Xbarc187. Based on the race specific phenotyping data and marker data, fourteen lines were found to carry a single gene, 16 showed the presence of two gene combinations, and seven genotypes were found to have a combination of three genes. Frequencies of Yr5, Yr15 and Yr26/Yr24 was high among test wheat germplasm in comparison to Yr10. [ABSTRACT FROM AUTHOR]

Stripe rust disease of wheat, caused by Puccinia striiformis f. sp. tritici, (Pst) is one of the most serious diseases of wheat worldwide. In India, virulent stripe rust races have been constantly evolving in the North-Western Plains Zone leading to the failure of some of the most widely grown resistant varieties in the region. With the goal of studying the recent evolution of virulent races in this region, we conducted whole-genome re-sequencing of three prevalent Indian Pst pathotypes Pst46S119, Pst78S84 and Pst110S119. We assembled 58.62, 58.33 and 55.78 Mb of Pst110S119, Pst46S119 and Pst78S84 genome, respectively and found that pathotypes were highly heterozygous. Comparative phylogenetic analysis indicated the recent evolution of pathotypes Pst110S119 and Pst78S84 from Pst46S119. Pathogenicity-related genes classes (CAZyme, proteases, effectors, and secretome proteins) were identified and found to be under positive selection. Higher rate of gene families expansion were also observed in the three pathotypes. A strong association between the effector genes and transposable elements may be the source of the rapid evolution of these strains. Phylogenetic analysis differentiated the Indian races in this study from other known United States, European, African, and Asian races. Diagnostic markers developed for the identification of three Pst pathotypes will help tracking of yellow rust at farmers field and strategizing resistance gene deployment. [ABSTRACT FROM AUTHOR]

In India, systematic wheat yellow rust survey and pathotype (race) analysis work began in 1930. However, information on population structure and genetic diversity of yellow rust pathogen has not been available. To address this, we conducted studies on population structure and genetic diversity of Puccinia striiformis f. sp. tritici (Pst) pathotypes using 38 simple sequence repeat primer-pairs. Bayesian assignment and discriminant analysis of principal components indicated the presence of two distinct Pst subpopu-lations (Popl and Pop2) along with 37.9% admixed pathotypes. The unweighted pair-group method with arithmetic mean also categorized these pathotypes into two major clusters. Principal coordinates analysis explained 20.06 and 12.50% variance in horizontal and vertical In total, 102 alleles were detected, with the expected heterozygosity (Hcxp) per locus ranging from 0.13 to 0.73, with a mean of 0.47. The average polymorphic information content value of 0.40 indicated high genetic diversity among pathotypes. Analysis of molecular variance revealed 12% of the total variance between subpopulations, 11% among the pathotypes of each sub-population, and 77% within pathotypes. A significant moderate level of genetic differentiation (FsT = 0.122, P < 0.001) and gene flow (N,„ = 1.80) were observed between subpopulations. The Pst virulence phenotypes showed a weak positive correlation (R2 = 0.027, P < 0.02) with molecular genotypes. coordinates, respectively. Index of association (IA) and the standardized index of association (fd) values showed that Pst subpopulations reproduced asexually (clonally). [ABSTRACT FROM AUTHOR]

The periodic breakdowns of stripe rust resistance due to emergence of new virulent and more aggressive pathotypes of Puccinia striiformis f. sp. tritici have resulted in severe epidemics in India. This necessitates the search for new and more durable resistance sources against stripe rust. The three bread wheat cultivars PBW 343 (carries Yr9 and Yr27), PBW 621 (carries Yr17) and HD 2967 (gene not known) were highly popular among the farmers after their release in 2011. But presently all three cultivars are highly susceptible to stripe rust at seedling as well as at adult plant stages as their resistance has been broken down due to emergence of new pathotypes of the pathogen (110S119, 238S119). In previous study, the crosses of PBW 621 with PBW 343 and HD 2967 and evaluation of further generations (up to F4) against pathotype 78S84 resulted in resistant segregants. In the present study, the F5 and F6 RIL populations have been evaluated against new pathotypes of Pst. The RILs categorized based on the disease severity on the P (Penultimate leaf) and F (flag) leaf into three categories i.e., high, moderate and low level of APR (adult plant resistance) having 1–200, 201–400 and >400 values of AUDPC, respectively, upon infection with stripe rust. The various APR components (latent period, lesion growth rate, spore production and uredial density) were studied on each category, i.e., resistant, moderately resistant and susceptible. The values of APR parameters decreased as the level of resistance increased. Based on molecular analysis, the lines (representing different categories of cross PBW 621 X PBW 343) containing the genes Yr9 and Yr17 due to their interactive effect provide resistance. Based on BSA using 35k SNPs and KASP markers association with phenotypic data of the RIL population (PBW 621 X HD 2967) showed the presence of two QTLs (Q.Pst.pau-6B, Q.Pst.pau-5B) responsible for the residual resistance and two SNPs AX-94891670 and AX-94454107 were found to be associated with the trait of interest on chromosome 6B and 5B respectively. The present study concludes that in the population of both the crosses (PBW 621 X PBW 343 and PBW 621 X HD 2967) major defeated gene contributed towards residual resistance by interacting with minor gene/QTLs. [ABSTRACT FROM AUTHOR]

All stage resistance to stripe rust races prevalent in India was investigated in the European winter wheat cultivar 'Acienda'. In order to dissect the genetic basis of the resistance, a backcross population was developed between 'Acienda' and the stripe rust susceptible Indian spring wheat cultivar 'HD 2967'. Inheritance studies revealed segregation for a dominant resistant gene. High density SNP genotyping was used to map stripe rust resistance and marker regression analysis located stripe rust resistance to the distal end of wheat chromosome 1A. Interval mapping located this region between the SNP markers AX-95162217 and AX-94540853, at a LOD score of 15.83 with a phenotypic contribution of 60%. This major stripe rust resistance locus from 'Acienda' has been temporarily designated as Yraci. A candidate gene search in the 2.76 Mb region carrying Yraci on chromosome 1A identified 18 NBS-LRR genes based on wheat RefSeqv1.0 annotations. Our results indicate that as there is no major gene reported in the Yraci chromosome region, it is likely to be a novel stripe rust resistance locus and offers potential for deployment, using the identified markers, to confer all stage stripe rust resistance. [ABSTRACT FROM AUTHOR]

• This study presents an extensive systematic literature review on WD recognition. • A set of 94 research articles published between 2005–2022 has been selected for analysis. • A framework has been proposed to classify the research articles into four categories. Due to wheat diseases (WD), the global rate of wheat production is decreasing by 3.6% annually. With the help of computer vision technology, WD recognition is not a challenging task but motivates the concepts of image processing, image segmentation, feature extraction, and AI-based recognition models. The objective of this study is to review and systematically analyze studies that have been published between 2005 and 2022. The authors make an effort to determine the important developments in image segmentation models, tools, datasets, and comparative analysis for the accuracy of the recognition model. The current study follows the standard systematic literature review (SLR) approach and selects 638 studies from five different web source databases. Among 638 studies, 544 studies were discarded in the study extraction process. A total number of 94 studies have been published in 45 reputed journals, and 49 conferences that have been identified with evaluation, validation, proposed, and philosophical criteria. After analysis, ten types of image segmentation models were identified. The most prominent clustering-based image segmentation technique (34.78%) is used for powdery mildew and stripe rust WD recognition. During WD recognition, the accuracy performance parameter is found to be most prominent. China and India are the two countries on the Asian continent that contribute to WD recognition. The current study summarizes the findings of WD research and highlights the need for standard datasets and accuracy. It highlights the importance of exploring and developing more precise and hybrid segmentation classification models for WD recognition. [ABSTRACT FROM AUTHOR]

Wheat variety PBW343, released in India in 1995, became the most widely grown cultivar in the country by the year 2000 owing to its wide adaptability and yield potential. It initially succumbed to leaf rust, and resistance genes Lr24 and Lr28 were transferred to PBW343. After an unbroken reign of about 10 years, the virulence against gene Yr27 made PBW343 susceptible to stripe rust. Owing to its wide adaptability and yield potential, PBW343 became the prime target for marker-assisted introgression of stripe rust resistance genes. The leaf rust-resistant versions formed the base for pyramiding stripe rust resistance genes Yr5, Yr10, Yr15, Yr17 , and Yr70 , in different introgression programs. Advanced breeding lines with different gene combinations, PBW665, PBW683, PBW698, and PBW703 were tested in national trials but could not be released as varieties. The genes from alien segments, Aegilops ventricosa (Lr37/Yr17/Sr38) and Aegilops umbellulata (Lr76/Yr70), were later pyramided in PBW343. Modified marker-assisted backcross breeding was performed, and 81.57% of the genetic background was recovered in one of the selected derivative lines, PBW723. This line was evaluated in coordinated national trials and was released for cultivation under timely sown irrigated conditions in the North Western Plain Zone of India. PBW723 yields an average of 58.0 qtl/ha in Punjab with high potential yields. The genes incorporated are susceptible to stripe rust individually, but PBW723 with both genes showed enhanced resistance. Three years post-release, PBW723 occupies approximately 8–9% of the cultivated area in the Punjab state. A regular inflow of diverse resistant genes, their rapid mobilization to most productive backgrounds, and keeping a close eye on pathogen evolution is essential to protect the overall progress for productivity and resistance in wheat breeding, thus helping breeders to keep pace with pathogen evolution. [ABSTRACT FROM AUTHOR]

Deploying under-utilized landraces in wheat breeding has been advocated to accelerate genetic gains in current era of genomics assisted breeding. Mexican bread wheat landraces (Creole wheats) represent an important resource for the discovery of novel alleles including disease resistance. A core set of 1,098 Mexican landraces was subjected to multi-location testing for rust diseases in India, Mexico and Kenya. The landrace core set showed a continuous variation for yellow (YR) and stem rust (SR) disease severity. Principal component analysis differentiated Mexican landraces into three groups based on their respective collection sites. Linkage disequilibrium (LD) decay varied from 10 to 32 Mb across chromosomes with an averge of 23Mb across whole genome. Genome-wide association analysis revealed marker-trait associations for YR resistance in India and Mexico as well as for SR resistance in Kenya. In addition, significant additive-additive interaction effects were observed for both YR and SR resistance including genomic regions on chromosomes 1BL and 3BS, which co-locate with pleiotropic genes Yr29/Lr46/Sr58/Pm39/Ltn2 and Sr2/Yr30/Lr27, respectively. Study reports novel genomic associations for YR (chromosomes 1AL, 2BS, and 3BL) and SR (chromosomes 2AL, 4DS, and 5DS). The novel findings in Creole wheat landraces can be efficiently utilized for the wheat genetic improvement. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is an important cereal crop globally as well as in India and yield improvement programs encounter a strong impediment from ever-evolving rust pathogens. Hence, durable rust resistance is always a priority trait for wheat breeders globally. Grain weight, represented as thousand grain weight (TGW), is the most important yield-contributing trait in wheat. In the present study high TGW has been transferred into two elite Indian wheat cultivars PBW343 and PBW550 from a high TGW genotype, Rye selection 111, selected from local germplasm. In the background of PBW343 and PBW550, an increase in TGW upto 27.34 and 18% was observed, respectively (with respect to recipient parents), through conventional backcross breeding with phenotypic selections in 3 years replicated RBD trials. Resistance to leaf rust and stripe rust has been incorporated in the high TGW version of PBW550 through marker assisted pyramiding of stripe rust resistance gene Yr15 using marker Xuhw302 , and a pair of linked leaf rust and stripe rust resistance genes Lr57-Yr40 using marker Ta5DS-2754099_kasp23. Improved versions of PBW550 with increased TGW ranging from 45.0 to 46.2 g (up to a 9% increase) and stacked genes for stripe and leaf rust resistance have been developed. This study serves as proof of utilizing conventional breeding and phenotypic selection combined with modern marker assisted selection in improvement of important wheat cultivars as a symbiont of conventional and moderan techniques. [ABSTRACT FROM AUTHOR]

Resistance in modern wheat cultivars for stripe rust is not long lasting due to the narrow genetic base and periodical evolution of new pathogenic races. Though nearly 83 Yr genes conferring resistance to stripe rust have been cataloged so far, few of them have been mapped and utilized in breeding programs. Characterization of wheat germplasm for novel sources of resistance and their incorporation into elite cultivars is required to achieve durable resistance and thus to minimize the yield losses. Here, a genome-wide association study (GWAS) was performed on a set of 391 germplasm lines with the aim to identify quantitative trait loci (QTL) using 35K Axiom® array. Phenotypic evaluation disease severity against four stripe rust pathotypes, i.e., 46S119, 110S119, 238S119, and 47S103 (T) at the seedling stage in a greenhouse providing optimal conditions was carried out consecutively for 2 years (2018 and 2019 winter season). We identified, a total of 17 promising QTl which passed FDR criteria. Moreover these 17 QTL identified in the current study were mapped at different genomic locations i.e. 1B, 2A, 2B, 2D, 3A, 3B, 3D, 4B, 5B and 6B. These 17 QTLs identified in the present study might play a key role in marker-assisted breeding for developing stripe rust resistant wheat cultivars. [ABSTRACT FROM AUTHOR]

Detection and characterization of changes in virulence patterns of pathogen populations is a prelude to effective management of wheat rusts. Such information is useful for the identification of sources of resistance, pre-emptive breeding and judicious deployment of resistant wheat cultivars. During 2013–14, three new Yr9-virulent pathotypes (110S119, 238S119 and 110S84) of Puccinia striiformis f. sp. tritici (Pst) possessing combined virulence to cvs Strubes Dickkopf (Yr2, Yr3a, Yr4a) and Suwon92xOmar (YrSU) were detected in India. These pathotypes were more aggressive and virulent than those reported earlier. Riebesel 47/51 (Yr2, Yr9) and Hobbit (Yr14) hitherto resistant to Indian Pst populations, became susceptible to 238S119 and 110S119, respectively. Moreover, the bread wheat cv. HD2967, currently occupying a 10–12 million ha area, showed a high level of susceptibility to these pathotypes. Stripe rust resistance genes, Yr1, Yr5, Yr10, Yr15, Yr24, Yr28 and YrSP were found effective against the new pathotypes. Phylogenetic relationships of the new and nine other closely related pathotypes were elucidated by comparing sequences of the internal transcribed spacer regions. It appeared that pathotypes110S84 and 110S119 were distinct and evolved independently, whereas 238S119 could have evolved from 46S119 by gaining virulence to cvs Strubes Dickkopf and Riebesel 47/51. Recently developed Indian bread wheat germplasm comprising 56 newly released cultivars and 64 advanced lines (2016–17) were evaluated under controlled conditions at the seedling stage for resistance to the three new and the two already known Yr9-virulent pathotypes 46S119 and 78S84. None of the cultivars was resistant to the new pathotypes. Cultivars DBW88, DPW621–50, HD3043, HD3059, HD3171, HS507, HS542, HS562, MACS6478, PBW723, WH1021 and WH1105, resistant to the erstwhile prevalent pathotypes 46S119 and 78S84, showed susceptibility to the new pathotypes. However, 11 advanced bread wheat lines viz. DBW246, HS645, PBW752, PBW757, PBW777, PBW779, PBW780, UP2993, VL1012, VL3013 and WH1233 were found resistant to all the test pathotypes. [ABSTRACT FROM AUTHOR]

Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is a serious disease of wheat worldwide, including India. Growing resistant cultivars is the most cost-effective and eco-friendly approach to manage the disease. In this study, 70 publically available molecular markers were used to identify the distribution of 35 Yr genes in 68 wheat genotypes. Out of 35 Yr genes, 25 genes amplified the loci associated with Yr genes. Of the 35, 18 were all-stage resistance ASR (All-stage resistance) genes and 7 (Yr16 , Yr18 , Yr29 , Yr30 , Yr36 , Yr46 & Yr59) were APR (Adult-plant resistance) genes. In the field tests, evaluation for stripe rust was carried out under artificial inoculation of Pst. Fifty-three wheat genotypes were found resistant to yellow rust (ITs 0), accounting for 77.94% of total entries. Coefficients of infection ranged from 0 to 60 among all wheat genotypes. Two genotypes (VL 1099 & VL 3002) were identified with maximum 15 Yr genes followed by 14 genes in VL 3010 and HI8759, respectively. Maximum number of all-stage resistance genes were identified in RKD 292 (11) followed by ten genes in DBW 216, WH 1184 and VL 3002. Maximum number of adult-plant resistance gene was identified in VL 3009 (6), HI 8759 (5) and Lassik (4) respectively. Genes Yr26 (69.2%), Yr2 (69.1%), Yr64 (61.7%), Yr24 (58.9%), Yr7 (52.9%), Yr10 (50%) and Yr 48 (48.5%) showed high frequency among selected wheat genotypes, while Yr9 (2.94%), Yr36 (2.94%), Yr60 (1.47%) and Yr32 (8.8%) were least frequent in wheat genotypes. In future breeding programs, race specific genes and non-race specific genes should be utilised to pyramid with other effective genes to develop improved wheat cultivars with high-level and durable resistance to stripe rust. Proper deployment of Yr genes and utilizing the positive interactions will be helpful for resistance breeding in wheat. [ABSTRACT FROM AUTHOR]

The complete genome sequence of leek yellow stripe virus (LYSV) isolate AC-50 from garlic in India was determined and the predicted amino acid (aa) sequence was analyzed. The LYSV RNA genome is 10,131 nucleotides (nt) long excluding the poly(A) tail (KP168261) and has a large open reading frame (ORF) encoding a putative polyprotein of 3152 aa with conserved motifs typical of members of the genus Potyvirus in the family Potyviridae. The pretty interesting Potyviridae ORF (PIPO) coding region was identified in the P3 coding region. LYSV isolate AC-50 shares maximum nt and aa sequence identity of 79.9% and 87.2% with a LYSV isolate from Australia (HQ258895) at the full genome and polyprotein level, respectively, and clusters with clade II isolates from China, Mexico, Australia, Brazil and Spain. The P1 coding region of isolate AC-50 was highly variable with an identity range of 48.9-70.9% with other LYSV isolates and a deletion of 204 nt compared to Japanese and Australian isolates. The ratio of nonsynonymous (dN) and synonymous (dS) polymorphic sites suggested that purifying selection dominates in the evolution of LYSV and the mean dN/dS ratio was highest for P1, confirming that this coding region is under less evolutionary constraints. [ABSTRACT FROM AUTHOR]

Barley has assumed the status of an industrial crop in India over recent years. Once grown as a rain-fed crop with minimum input, presently it is grown under optimum input to produce plump and mealy grains required for malting. The increased use of nitrogenous fertilizer and irrigation is likely to increase the incidence of biotic stresses. Aphids are the most widely distributed and serious threat to this crop under favourable conditions. Among the various diseases infecting barley, yellow rust is the most important in India. Germplasm lines maintained at the Directorate of Wheat Research, Karnal (India) were evaluated both against corn leaf aphid ( Rhopalosiphum maidis ) and yellow rust ( Puccinia striiformis ). Resistant lines were tested over 3 years under field conditions and thereafter under polyhouse conditions to confirm their resistance. One of the lines (BCU 284) was found to be resistant against both corn leaf aphid and yellow rust and is, therefore, potentially of great value to barley breeders. BCU 284 was crossed with highly aphid-susceptible BCU 274 and aphid-resistant EB 921. A single gene in BCU 284 was found to control the resistance against corn leaf aphid, which was different from that in EB 921. [ABSTRACT FROM AUTHOR]

Yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), is economically one of the most important diseases of wheat in India and worldwide. During four wheat-growing seasons (2015-19), a total of 951 yellow rust samples collected from farmers' fields (n = 602) and trap plot nurseries (n = 349) were analyzed for virulence on 30 differentials. From this analysis, 11 distinct Pst pathotypes were identified. The virulence pattern of these pathotypes was also tested on 14 Avocet near-isogenic lines (NILs) and Avocet S. None of the pathotypes were virulent to Yr5, Yr10, Yr15 , Yr16, Yr24 , Yr32, and YrSP. Pathotype 46S119 (46E159) was most prevalent and widely distributed in all the areas and its overall frequency was maximum (56.2%) followed by 110S119 (110E159, 31.9%). However, the frequency of 46S119 has decreased gradually from 62.0% (2015-16) to 48.4% (2018-19). Pathotype 238S119 (238E159) being the most virulent among the identified pathotypes, was detected in 6.8% of samples. Each of the remaining pathotypes was identified in <5% of the samples. Genetic diversity among eleven pathotypes was assessed using novel 89 SSR primer-pairs out of which 24 primers showed polymorphism. Finally, 69 alleles were detected across the loci with an average of 2.87 alleles per locus. Polymorphic information content (PIC) value was in the range from 0.28 to 0.68, with a mean of 0.47. Expected heterozygosity was in the 0.34 to 0.73 range, with a mean of 0.56. Cluster analysis based on both avirulence/virulence pattern and SSR profile categorized the identified pathotypes into two major clades. Generated information will potentially be helpful in rust resistance breeding and deployment of resistant cultivars in yellow rust-prone areas. • Yellow (stripe) rust is economically the most important disease of wheat in India. • Disease is caused by a fungus Puccinia striiformis f. sp. tritici (Pst). • Phenotypic and genotypic variability among the Pst pathotypes was explored. • Novel polymorphic microsatellite markers were also developed. • Generated information is prerequisite for rust resistance wheat breeding. [ABSTRACT FROM AUTHOR]

Seedlings of Indian wheat cultivars (Kalyansona, Sonalika, WL711 and eight others released commercially) were tested with 13 British and four alien races of Puccinia striiformis. The data indicated the probable presence of the resistance gene Yr2 in the three cultivars named above and in six of the others. Reactions of the remaining two cultivars, PWB12 and WL2265, were consistent with the presence of the gene Yr7. The presence of Yr2 in Kalyansona, Sonalika and WL711 was supported by evidence from crosses between them and with Heines VII, which is known to carry Yr2. In crosses of Sonalika with a susceptible cultivar, Kharchia Local and also with WL711, tests of F1, F2 and F3 generations indicated that, in addition to Yr2, Sonalika possesses at least two other genes. Both these genes were difficult to detect but the F3 data supported the hypothesis that there is a single partially recessive gene giving resistance to alien race 6El6 and a different, possibly complementary, gene system effective against another alien race, 39El34. The presence of resistance in addition to Yr2 was also detected in WL711 and HD2329. [ABSTRACT FROM AUTHOR]

The rusts of wheat, caused by three species of Puccinia, are very devastating diseases and are major biotic constraints in efforts to sustain wheat production worldwide. Their capacity to spread aerially over long distances, rapid production of infectious uredospores, and abilities to evolve new pathotypes, makes the management of wheat pathogens a very challenging task. The development and deployment of resistant wheat varieties has proven to be the most economic, effective and efficient means of managing rust diseases. Rust resistance used in wheat improvement has included sources from the primary gene pool as well as from species distantly related to wheat. The 1BL/1RS translocation from cereal rye was used widely in wheat breeding, and for some time provided resistance to the wheat leaf rust, stripe rust, and stem rust pathogens conferred by genes Lr26, Yr9, and Sr31, respectively. However, the emergence of virulence for all three genes, and stripe rust resistance gene Yr27, has posed major threats to the cultivation of wheat globally. To overcome this threat, efforts are going on worldwide to monitor rust diseases, identify rust pathotypes, and to evaluate wheat germplasm for rust resistance. Anticipatory breeding and the responsible deployment of rust resistant cultivars have proven to be effective strategies to manage wheat rusts. Efforts are still however being made to decipher the recurrence of wheat rusts, their epidemiologies, and new genomic approaches are being used to break the yield barriers and manage biotic stresses such as the rusts. Efficient monitoring of pathotypes of Puccinia species on wheat, identification of resistance sources, pre-emptive breeding, and strategic deployment of rust resistant wheat cultivars have been the key factors to effective management of wheat rusts in India. The success in containing wheat rusts in India can be gauged by the fact that we had no wheat rust epiphytotic for nearly last five decades. This publication provides a comprehensive overview of the wheat rust research conducted in India. [ABSTRACT FROM AUTHOR]