Rust Reaction Research Articles

GG HPS-2: A high yielding and large seeded Virginia bunch groundnut (Arachishypogaea L.) variety for Gujarat state

A Virginia bunch large seeded groundnut variety GG HPS 2 was developed from the cross JVB HPS 2 and GG 20. It recorded a higher mean pod yield (2835 kg/ha) and kernel yield (1945 kg/ha) as compared to the checks.GG HPS 2 recorded an average 100 kernel weight of 66.71 g, shelling out-turn of 68.61% and oil content of 48.82%. GG HPS 2 showed restistance reaction to tikka (leaf spot) and rust reaction, whereas it showed comparableresistance to stem rot, collar rot, damages due to leaf defoliators and thrips under field conditions with check varieties. Based on the superior performance, it has been released for kharif groundnut growing areas of the Gujarat State.

Evaluation of Yellow Rust Reactions in some Bread and Durum Wheat Varieties by Using Spectral Band Regions

Yellow rust (caused by Puccinia striiformis f. sp. tritici) is an important fungal disease affecting wheat production and quality. The purpose of this study was to identify the spectral band regions that influence how the disease changes throughout the year by determining how the plant responds to yellow rust when it is applied to test materials at various doses (0%, 25%, 50%, and 100%). Eser, Bayraktar 2000 and Demir 2000 varieties showed high correlation in the early-mid period of the study for bread varieties, while Kenanbey variety exhibited high correlation in the mid-late period. Effective band region for all bread types are The Red+Red Edge+ Near Infrared (NIR) range and NIR range of the Kenanbey variety both showed an increase (+) in disease severity values. Eminbey and Çeşit-1252 varieties for durum varieties displayed high correlation in the early period, followed by Mirzabey 2000 variety in the early to medium period and Kızıltan-91 variety the mid to late period. Kızıltan 91 variety in Red+Red Edge+NIR region, Çeşit-1252 variety in Green+Red region, Eminbey and Mirzabey 2000 varieties in Green+Red+Red Edge were effective in band ranges in the region and showed an increase (+) in disease severity reactions.

Potential Source of Resistance in Introgressed, Mutant and Synthetic Brassica juncea L. Lines against Diverse Isolates of White Rust Pathogen, Albugo candida

The existing resistance genes against white rust disease are often ineffective due to racial variation of the causal fungal pathogen, Albugo candida. Therefore, new sources of resistance effective against multiple races are needed for durable resistance. Large-scale phenotyping of advanced introgressed (ILs), mutant, and resynthesized (RBJ) lines of Brassica juncea L., under artificial inoculation at cotyledonary and true leaf stages, against thirteen diverse isolates of Albugo candida and simultaneously at the adult plant stage under multi-location field evaluation from 2019–2022, revealed significant differences in white rust reactions. Amongst 194 introgressed lines, three lines, namely ERJ 39, ERJ 12, and ERJ 15, and three lines among 90 resynthesized and 9 mutant lines, including RBJ 18, DRMR 18-36-12, and DRMR 18-37-13, were identified as potential sources of resistance against multiple isolates at all three developmental stages of the plant. Furthermore, correlation and principal component analysis revealed a positive correlation between white rust resistance at true leaf and adult plant stages for ILs as well as mutant and RBJ lines. These novel sources of host resistance will play vital roles are required for the mustard improvement program and to establish a strong genetic and molecular foundation for identifying white rust resistance linked marker(s), QTLs, or gene(s) for sustainable disease management in India.

Identification of genetic immunity to the warrior race and local population of stripe rust using conventional techniques in winter wheat genotypes

Wheat stripe rust caused by the Puccinia striiformis f. sp. tritici (Pst) is a major and devastating biotic stress inducing notable product losses in wheat (Triticum spp.). Possibility of the breakdown of important genes conferring resistance against to stripe rust and the threat of emergence of new aggressive races remain a concern in all wheat growing areas around the world. Therefore, breeding programs must continue screening of wide genetic diversity to improve new varieties with different gene combinations against race changes. Within this scope, 140 wheat genotypes obtained from various countries and programs were evaluated in terms of their reactions to stripe rust at both seedling and adult-plant stages in 2020 and 2021 growing seasons. The adult-plant stage evaluations of these genotypes were conducted under artificial inoculation of PstS7 (Warrior) race at Haymana location of Field Crops Central Research Institute in Ankara and under naturally occurring local stripe rust population at Menemen location of Aegean Agricultural Research Institute in Izmir. Whereas the seedling stage tests were carried out using the PstS7 race under controlled conditions at Pest and Disease Resistance Unit of the Field Crops Central Research Institute. More than 80% of the genotypes tested at both locations exhibited immune, resistant, and moderately resistant reactions at the adult-plant stage, while only 36.4% of the genotypes exhibited resistance reactions at the seedling stage. The coefficients of infection (CI) of the genotypes were calculated by using the stripe rust reaction and disease severity of each genotype. Following scales were used for classification of the genotypes based on the CI: 0 = Immune; 0.1-5.0 = Resistant; 5.01-20.0 = Moderately Resistant; 20.1-40.0 = Moderately Susceptible; 40.1-100 = Susceptible. In conclusion, 101 genotypes (72.1%) evaluated at both locations were found to be immune, resistant, and moderately resistant to both the PstS7 race and local stripe rust population. These genotypes have been proposed as resistance gene sources for cultivars to be developed.

Nebraska winter wheat unexpected flowering in Egypt: New improvement opportunities

AbstractThe University of Nebraska has bred some of the most winter hardy wheat (Triticum aestivum L.) cultivars in the United States. With the advent of a new race of stem rust in Africa, the breeding program identified a testing site in northern Egypt, a Mediterranean environment, for seedling disease resistance screening. Quite surprisingly, the Nebraska winter wheat lines flowered when grown in northern Egypt, indicating the lines were vernalized. To confirm this result, a panel of 112 Nebraska winter wheat genotypes and three commercially grown Egyptian spring wheat check cultivars were grown in three replicates in a randomized incomplete block design at two locations for 3 years (2016/2017–2018/2019) in Egypt. Seven traits were measured on all genotypes (the number of days to flowering; total chlorophyll content; plant height; leaf, stem, and stripe rust reaction; and grain yield). The winter wheat genotypes flowered and several of them were not significantly different in grain yield from the spring cultivars. A multi‐trait stability index identified 22 genotypes (20% selection intensity, the local checks, and 19 lines from the United States) for good performance. This study provides novel evidence that winter wheat can flower in northern Egypt, can be used for adult plant resistance screening, and provide a grain yield comparable to the commercially grown spring wheat cultivars. Our findings are expected to facilitate future efforts to hybridize winter‐by‐spring lines to develop new genotypes with unique combinations of genes to improve grain yield production, adaptation, disease resistance, and climate resiliency.

Searching for Novel Oat Crown Rust Resistance in Diploid Oat Avena strigosa Schreb. Reveals the Complexity and Heterogeneity of the Analyzed Genebank Accessions

Crown rust, one of the most destructive diseases of oat, regularly occurs worldwide and leads to significant yield losses. The constant evolution of the Puccinia coronata f. sp. avenae pathogen causes a rapid decline in the effectiveness of currently used crown rust resistance genes, so new ones are urgently needed. In this study, 39 accessions of Avena strigosa Schreb. from ten countries gathered from the Polish National Genebank were evaluated at the seedling stage for crown rust reaction using a detached leaf assay and five isolates of P. coronata with diverse virulence profiles. Ten plants of each accession were tested, and 28 diverse infection profiles (IPs) were defined. One hundred and sixty-eight out of 390 plants revealed an IP of unidentified resistance. Thirty-eight (97%) of the accessions studied showed a heterogeneous infection pattern, none of the accessions displayed homogeneous susceptibility, and one (51887) was homogeneously resistant to all races used. The obtained results confirmed the complexity and heterogeneity of the accessions gathered in the genebanks. A. strigosa preserved as complex populations could be a valuable source of resistance to crown rust and potentially other pathogens. The variability of the analyzed populations was ascertained by a detailed diversity analysis of the transformed resistance/susceptibility data. The averaged resistance rating for the genebank specimens available in the databases may be an obstacle in revealing the beneficial alleles of genes hidden among the plants representing accessions preserved as complex populations. Potential donors of effective resistance may be discovered even in accessions with general susceptibility, which is a promising alternative at a time when making new collections of wild and weedy accessions is under threat from agricultural practice and climate change.

Impact of Asian soybean rust on vegetable soybean, considering two stages of development

AbstractDiseases can cause negative impacts during all stages of development of soybean [Glycine max (L.) Merr.] Asian soybean rust (ASR) (caused by Phakopsora pachyrhizi) is the most destructive. The impact of ASR on vegetable soybean (consumed when the seeds are still immature) have not been studied rigorously. Thus, in a 2‐yr study, we assessed 42 F6 lines from crosses of soybean vegetable genotypes and three commercial cultivars (‘BRS 257’, ‘BRS 267’ and ‘IAC 100’) in two sites. During the R6 and R8 development stages, the genotypes were evaluated for 10 traits. The joint analysis showed that the interactions were significative for the most traits. The significance of the rust effect allowed us to identify the genotypes in which the losses were nonsignificant. We observed that ASR affected two stages of plant development. However, information about ASR losses quantified by the rust reaction rate (RRR) enabled the researchers to select lines that could be used in breeding programs aiming towards ASR tolerance. We found three lines that were superior to one of the cultivar checks. Furthermore, cluster analysis for RRR was useful in establishing the most promising groups of vegetable soybean genotypes for use in hybridization aiming to expand the genetic base for vegetable soybeans and integrate new genetic resources of vegetable soybean in the Brazilian genetic pool to ensure genetic gain.

Fine mapping of a stripe rust resistance gene YrZM175 in bread wheat.

A stripe rust resistance gene YrZM175 in Chinese wheat cultivar Zhongmai 175 was mapped to a genomic interval of 636.4 kb on chromosome arm 2AL, and a candidate gene was predicted. Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), is a worldwide wheat disease that causes large losses in production. Fine mapping and cloning of resistance genes are important for accurate marker-assisted breeding. Here, we report the fine mapping and candidate gene analysis of stripe rust resistance gene YrZM175 in a Chinese wheat cultivar Zhongmai 175. Fifteen F1, 7,325 F2 plants and 117 F2:3 lines derived from cross Avocet S/Zhongmai 175 were inoculated with PST race CYR32 at the seedling stage in a greenhouse, and F2:3 lines were also evaluated for stripe rust reaction in the field using mixed PST races. Bulked segregant RNA-seq (BSR-seq) analyses revealed 13 SNPs in the region 762.50-768.52Mb on chromosome arm 2AL. By genome mining, we identified SNPs and InDels between the parents and contrasting bulks and mapped YrZM175 to a 0.72-cM, 636.4-kb interval spanned by YrZM175-InD1 and YrZM175-InD2 (763,452,916-764,089,317bp) including two putative disease resistance genes based on IWGSC RefSeq v1.0. Collinearity analysis indicated similar target genomic intervals in Chinese Spring, Aegilops tauschii (2D: 647.7-650.5Mb), Triticum urartu (2A: 750.7-752.3Mb), Triticum dicoccoides (2A: 771.0-774.5Mb), Triticum turgidum (2B: 784.7-788.2Mb), and Triticum aestivum cv. Aikang 58 (2A: 776.3-778.9Mb) and Jagger (2A: 789.3-791.7Mb). Through collinearity analysis, sequence alignments of resistant and susceptible parents and gene expression level analysis, we predicted TRITD2Bv1G264480 from Triticum turgidum to be a candidate gene for map-based cloning of YrZM175. A gene-specific marker for TRITD2Bv1G264480 co-segregated with the resistance gene. Molecular marker analysis and stripe rust response data revealed that YrZM175 was different from genes Yr1, Yr17, Yr32, and YrJ22 located on chromosome 2A. Fine mapping of YrZM175 lays a solid foundation for functional gene analysis and marker-assisted selection for improved stripe rust resistance in wheat.

Variation in biochemical attributes and rust reaction in response to crop geometry in mono-picking garden pea for mechanical harvesting

The present study was conducted on single-harvest gardenpea to standardize the agronomic practices for mechanizedcultivation in India. The experiment was laid out in split plotdesign with 30 treatments comprising five dates of sowing,viz. 20th October, 5th November, 20th November, 5thDecember and 20th December in main plots and 2 differentplanting methods (flat and bed) sown at three differentspacing (20 × 5 cm, 20 × 7.5 cm and 20 × 10 cm) in subplotsand replicated three times. The bed size was standardizedaccording to front loading width of the pea combine. Thesowing of garden pea cv. Punjab-89 on 5th November atintermediate spacing of 20 × 7.5 cm resulted into significantlyhigher green pod yield of 136.2 q/ha (in single harvest) whichwas statistically at par with same sowing date i.e. 5thNovember at wider (135.0 q/ha) and closer spacing (131.4 q/ha), which was due to cool temperature during plant growth,moderate temperature during pod development and fillingstage. The significant interactions were observed betweendate of sowing and spacing for total yield, protein contentand rust incidence. However, for all the traits, there is nonsignificantinteraction for date of sowing with sowingmethod, spacing with sowing method and 3-way interactionbetth December) crop resulted lowest total yieldbut less incidence of rust incidence which was due to hightemperature and low relative humidity at pod developmentand filling stage.ween date of sowing, spacing and sowing method. The late sown (20

Discovery and Chromosomal Location a Highly Effective Oat Crown Rust Resistance Gene Pc50-5.

Crown rust, caused by Puccinia coronata f. sp. avenae, is one of the most destructive fungal diseases of oat worldwide. Growing disease-resistant oat cultivars is the preferred method of preventing the spread of rust and potential epidemics. The object of the study was Pc50-5, a race-specific seedling crown rust resistant gene, highly effective at all growth stages, selected from the differential line Pc50 (Avena sterilis L. CW 486-1 × Pendek). A comparison of crown rust reaction as well as an allelism test showed the distinctiveness of Pc50-5, whereas the proportions of phenotypes in segregating populations derived from a cross with two crown rust-susceptible Polish oat cultivars, Kasztan × Pc50-5 and Bingo × Pc50-5, confirmed monogenic inheritance of the gene, indicating its usefulness in oat breeding programs. Effective gene introgression depends on reliable gene identification in the early stages of plant development; thus, the aim of the study was to develop molecular markers that are tightly linked to Pc50-5. Segregating populations of Kasztan × Pc50-5 were genotyped using DArTseq technology based on next-generation Illumina short-read sequencing. Markers associated with Pc50-5 were located on chromosome 6A of the current version of the oat reference genome (Avena sativa OT3098 v2, PepsiCo) in the region between 434,234,214 and 440,149,046 bp and subsequently converted to PCR-based SCAR (sequence-characterized amplified region) markers. Furthermore, 5426978_SCAR and 24031809_SCAR co-segregated with the Pc50-5 resistance allele and were mapped to the partial linkage group at 0.6 and 4.0 cM, respectively. The co-dominant 58163643_SCAR marker was the best diagnostic and it was located closest to Pc50-5 at 0.1 cM. The newly discovered, very strong monogenic crown rust resistance may be useful for oat improvement. DArTseq sequences converted into specific PCR markers will be a valuable tool for marker-assisted selection in breeding programs.

High-temperature wheat leaf rust resistance gene Lr13 exhibits pleiotropic effects on hybrid necrosis

High-temperature wheat leaf rust resistance gene Lr13 exhibits pleiotropic effects on hybrid necrosis

Mutation breeding in six rowed barley: Screening for stem rust resistance in certain induced mutants

During the induced mutagenesis in six rowed barley, 18 mutant lines were isolated from the M2 and M3 generations. Thirteen lines were induced by gamma rays, four by EMS and one by HA. These lines were screened for resistance to stem rust and loss assessment. Mutants were grown in field as well as in earthen pots. Artificial inoculums were provided in condition suitable for rust occurrence. Rust reaction was recorded according to modified Cabb’s scale and the rust intensity was classified as 0,5, 10, 25, 40 and 65 percent. Lines K50-38, K50-97, K50-102 and K40-73 were completely free from infection (0 %) and thought to be immune lines(I). K50-47, KE-4-47 and G50-47 exhibited traces of symptoms and placed under 5% intensity and were very resistant(R). Line KE2-63 exhibited 10% intensity and classified as moderately resistant(MR). Line K50-44; K40-11, K40-67, K30-91, KE3-75, G50-35 and GH3-32 showed 25% intensity of pustules and were put into moderately susceptible(MS) class. One line K30-82 showed 40% intensity and classified as susceptible(S), while line KE4-87 exihibited 65% intensity and was classified as heavily susceptible. Class 100 percent was not observed. Immune, very resistant and moderately resistant were identified as resistant lines and selected for further study, while moderately susceptible and heavily susceptible lines were identified as susceptible lines and discarded. Reduction in yield contributing traits i.e. number of grains/spike, test weight, seed yield and biological yield was also observed which was positively correlated with disease intensity.

Molecular mapping of a new recessive wheat leaf rust resistance gene originating from Triticum spelta

TSD276-2, a wheat genetic stock derived from the cross Agra Local/T. spelta 276 showed broad spectrum resistance against leaf rust pathogen. Genetic analysis was undertaken using F1, F2, F2:3 and BC1F1 generations derived from the cross TSD276-2/Agra Local. The results revealed a single recessive gene for leaf rust resistance, tentatively named as LrTs276-2, in TSD276-2. Molecular mapping of leaf rust resistance gene LrTs276-2 in TSD276-2 was done using SNP-based PCR and SSR markers. For Bulked Segregant Analysis (BSA), two bulks viz. resistant bulk and susceptible bulk, and the parents TSD276-2 and Agra Local were genotyped for SNPs using AFFYMETRIX 35K Wheat Breeders' AXIOM array. T. spelta 276 was also genotyped and used as a check. BSA indicated that the gene for leaf rust resistance in TSD276-2 is located on chromosome arm 1DS. Putatively linked SNPs on chromosome arm 1DS were converted into PCR-based markers. Polymorphic SSR markers on chromosome arm 1DS were also identified. Final linkage map was constructed using one SNP-based PCR and three SSR markers. The rust reaction and chromosomal location suggest that LrTs276-2 is a new leaf rust resistance gene which may be useful in broadening the genetic base of leaf rust resistance in wheat.

Genetic basis of spring wheat resistance to leaf rust (Puccinia triticina) in Kazakhstan and Russia

Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB) was established in 2000 to conduct multi-location cooperative yield trials for the exchange of breeding material and to evaluate agronomic traits such as grain yield and disease resistance. In 2016, aggregated KASIB data were analyzed and 120 cultivars and breeding lines demonstrating different degrees of resistance to leaf rust selected. They were tested for leaf rust and agronomic traits in Omsk, Russia; Almaty, Kazakhstan and Sakarya, Turkey in 2017–2019. This germplasm was grouped into four categories based on leaf rust reaction: 31 resistant (R), 27 moderately resistant (MR), 37 intermediate (M) and 25 moderately susceptible (MS) entries. Lr genes were postulated based on tests using pathotypes with known virulence profiles and molecular markers. The most frequent Lr genes alone or in combination were Lr10 (31 entries), Lr26 (24), Lr9 (23), Lr1 (18), Lr17 (11), Lr34 (11) and Lr19 (7). Genes Lr1, Lr9, Lr10 and Lr17 reduced the leaf rust severity to M or MS across environments. The presence of Lr26 alone or in combination with other major genes reduced the leaf rust severity to MR-M in Omsk and R in Sakarya. The only gene with the large effect on leaf rust was Lr19, which provided a high level of resistance at all sites both alone and in combination with Lr26. Leaf rust severity in 52 entries with adult plant resistance (APR) was compared to 68 entries possessing effective seedling resistance genes. The leaf rust severity in entries with APR compared to seedling resistance was similar at low infection pressure at Sakarya, 2018 and Omsk, 2019. However, at higher leaf rust infection pressure at Omsk in 2017 and 2018, Almaty in 2019, there was a clear advantage for the germplasm possessing major genes. High level of stem rust infection in Omsk in 2019 confirmed effectiveness of the Sr31/Lr26 gene. A set of 33 genotypes was selected combining resistance to leaf and stem rust with superior agronomic performance.

Marker assisted stacking/pyramiding of stem rust, leaf rust and powdery mildew disease resistance genes (Sr2/Lr27/Yr30, Sr24/Lr24 and Sr36/Pm6) for durable resistance in wheat (Triticum aestivum L.)

Wheat being a staple food crop is essential for food security. Rust diseases like stem and leaf rust continues to be a serious threat to wheat production at national and international level. In recent years, powdery mildew disease is emerging as a threat to wheat production due to the climate change and intensive crop cultivation practices. Development of resistant cultivar is the most economical, reliable and sustainable way to control rusts and powdery mildew diseases. Stem rust, leaf rust and powdery mildew resistance genes viz., Sr2/Lr27/Yr30, Sr24/Lr24 and Sr36/ Pm6 were pyramided using marker assisted backcross breeding approach. Based on phenotypic observations, five populations were selected at BC4 F6 with respect to yield traits, leaf and stem rust and powdery mildew reactions. These populations were subjected to molecular marker analyses. Out of the five populations, Sr2+ were present in all the populations, while Sr24/Lr24 and Sr36/Pm6 was present in the fourth and fifth population. The identified population carrying Sr24/Lr24, Sr36/Pm6 and Sr2+ genes were stabilized at BC4 F7 generation. The use of gene stacks/pyramids of major (Sr24/Lr24 and Sr36/Pm6) and minor gene (Sr2+) that confer resistance to most of the pathotypes of stem rust, leaf rust and powdery mildew could impart durability and sustainability to the cultivars than single gene deployment.

Genetics of white rust resistance in Indian mustard (Brassica juncea L.) and its validation on using molecular markers

White rust resistance loci (AcB1-A4.1 and AcB1-A5.1) associated with intron polymorphic (IP) markers i.e. At5g41560 and At2g36360, respectively, were used for validation of P1, P2, F1, F2, BC1F1 and BC2F1 generations. The donor parents namely, Bio-YSR and BEC-144 produced desired banding pattern of 430 and 750 bp while recipients viz., NRCHB 101 and DRMR-150-35 exhibited different pattern from donors confirming white rust resistance loci 4.1 and 5.1 with marker At5g41560 and At2g36360, respectively. Confirmation of these set of two IP markers in the parents and F1s lead us to further screening of selected F2, BC1F1 and BC2F1 populations. Available data on white rust reaction in different generations under study revealed that single dominant gene is responsible for white rust resistance. Potential of molecular markers in developing white rust resistant genotypes is proved under present study.

Screening of CIMMYT Wheat Genotypes to Stem Rust Disease under Field Conditions in Egypt غربلة التراکیب الوراثیة لقمح السیمیت ضد مرض صدأ الساق تحت ظروف الحقل فی مصر

Among 190 wheat genotypes (CIMMYT), 51 lines were evaluated for adult plant resistance (APR) to stem rust infection at Sakha, Kafr El-Hamam and Nubaria locations, as the new sources of this resistance. Extensive and high significant differences of stem rust reaction among the tested wheat lines were obtained, at the three locations under study. Out of 51 wheat genotypes, only eight promising lines; no's 1, 9, 12, 14, 20, 25, 47 and 49 had the highest resistant potentiality at adult stage (completely resistant) and utilized as the new sources to increase stem rust resistance. Twenty nine wheat lines were characterized as partially resistant (PR), at the three locations of the study. The phenotypic variations were attributable to genetic structures of the lines due to high heritability estimates (up to 99%) and high values of genetic advance. The importance of all the selected disease parameters was confirmed through the correlation analysis especially final rust severity (FRS %). It is considered to be the more appropriate indicator, rather than area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) for screening large numbers of breeding materials to stem rust resistance and facilitate the success of selection process, during a national breeding program.

Preliminary screening of Avena sterilis L. for resistance to crown rust

The best source of crown rust resistance genes (Pc) in genus Avena is a wild hexaploid A. sterilis L. In this study, accessions of A. sterilis gathered from European and North American gene banks, originated from 21 countries were evaluated at the seedling stage for crown rust reaction using the host–pathogen test and two Puccinia coronata f. sp. avenae isolates. Of the 45 oat accessions analyzed, 12 were resistant to one crown rust race (3.2). Resistance to both pathotypes used in the study was observed in two of the accessions, first of which was collected in Libya (AVE 2532) and second in Portugal (CN 26036). Further research is required to evaluate the genetic background of the discovered resistance, however, obtained results provide a valuable first step in the identification of new promising crown rust resistance sources.

A novel leaf rust resistance gene introgressed from Aegilops markgrafii maps on chromosome arm 2AS of wheat.

A novel leaf rust resistance gene, LrM, introgressed from Aegilops markgrafii and mapped on chromosome 2AS using SSR- and SNP-based PCR markers will aid in broadening the genetic base of rust resistance in wheat. A new leaf rust resistance gene tentatively named LrM was introgressed from the diploid non-progenitor species Ae. markgrafii (2n = 2x = 14, genome CC) into common wheat using the nulli-5B mechanism. The introgression line ER9-700 showed a high degree of resistance against a wide spectrum of Puccinia triticina pathotypes. Genetic analysis was performed using the F1, F2, F2:3 and BC1F1 generations derived from the cross ER9-700/Agra Local. The results showed a single dominant gene for leaf rust resistance. The resistance gene LrM was mapped on chromosome arm 2AS using SSR- and SNP-based PCR markers. Preliminary mapping with SSR markers in the F2:3 population from the cross ER9-700/Agra Local identified two SSR markers flanking the LrM. SNPs were identified in the genomic region flanked by SSR markers, and SNP-based PCR markers were developed to construct the final map. Three SNP-based PCR markers co-segregated and mapped closest to the resistance gene at a distance of 2cM. The gene LrM was distinguished from all the other genes designated and mapped on chromosome arm 2AS by molecular markers and rust reaction. All five markers used in the mapping amplified identical alleles in the donor Ae. markgrafii accession and introgression line ER9-700. The chromosomal location and rust reaction suggest that LrM is a novel leaf rust resistance gene that may be useful in broadening the genetic base of leaf rust resistance in wheat.

Identification of effective sources for spot blotch and stripe rust in barley

Stripe rust and spot blotch are major biotic constraints in yield maximization in barley. Stripe rust is caused by fungus, Puccinia striiformis f. sp. hordei and wide spread in northern hills, foot hills and in the states of Punjab, Haryana and Rajasthan. Spot blotch ( Bipolaris sorokiniana ) is one of the major diseases in north eastern Indo-Gangetic plains having warm and humid climate. The resistant sources for stripe rust are available but the genetic resources for spot blotch are indeed meagre. Therefore, the present investigation was carried out to identify combined sources for stripe rust and spot blotch in barley. The experiments for stripe rust were conducted at Durgapura and Karnal during 2015-16 to 2017-18. While, spot blotch evaluation was carried out for two years at Faizabad and Karnal centres during 2015-16 and 2016-17. The indigenous genotypes namely DWRB127, DWRB128, DWRB136, DWRB137, DWRB143, RD2786 and Dolma showed resistance for stripe rust. Based upon stripe rust and spot blotch reactions the genotypes namely, DWRB136, Notch-2, Orosus and Bella Union were found promising. Similarly, the cross combination viz., Lbiran/Una80//Lignee640/3/Bbsc/4/Chamico and P.sto/3/Libran/Una80//Lignee640/4/Bllu/5/ Petunia1 were also considered promising for barley stripe rust and spot blotch. Therefore, these identified genotypes are suggested to be incorporated in future barley breeding programmes for gainfully utilization. DOI.10.25174/2582-2675/2020/88973