Wheat leaf rust caused by Puccinia triticina Eriks is an important disease that causes yield losses of up to 40% in susceptible varieties. Tetraploid emmer wheat (T. turgidum ssp. Dicoccum), commonly called Khapli wheat in India, is known to have evolved from wild emmer (Triticum turgidum var. dicoccoides), and harbors a good number of leaf rust resistance genes. In the present study, we are reporting on the screening of one hundred and twenty-three dicoccum wheat germplasm accessions against the leaf rust pathotype 77-5. Among these, an average of 45.50% of the germplasms were resistant, 46.74% were susceptible, and 8.53% had mesothetic reactions. Further, selected germplasm lines with accession numbers IC138898, IC47022, IC535116, IC535133, IC535139, IC551396, and IC534144 showed high level of resistance against the eighteen prevalent pathotypes. The infection type varied from “;”, “;N”, “;N1” to “;NC”. PCR-based analysis of the resistant dicoccum lines with SSR marker gwm508 linked to the Lr53 gene, a leaf rust resistance gene effective against all the prevalent pathotypes of leaf rust in India and identified from a T. turgidum var. dicoccoides germplasm, indicated that Lr53 is not present in the selected accessions. Moreover, we have also generated 35K SNP genotyping data of seven lines and the susceptible control, Mandsaur Local, to study their relationships. The GDIRT tool based on homozygous genotypic differences revealed that the seven genotypes are unique to each other and may carry different resistance genes for leaf rust.

The mega wheat variety HD2967 was improved for leaf and stripe rust resistance by marker-assisted backcross breeding. After its release in 2011, HD2967 became susceptible to stripe rust and moderately susceptible to leaf rust. The leaf rust resistance gene LrTrk was transferred into HD2967 from the durum wheat genotype Trinakria. Then, HD2967 was crossed with Trinakria to produce F₁ plant foreground selection for LrTrk and background selection for the recurrent parent genotype was carried out in BC₁F₁, BC₂F₁ and BC₂F₂ generations. Foreground selection was carried out with the linked marker Xgwm234, while polymorphic SSR markers between parents were used for background selection. Background selection resulted in the rapid recovery of the recurrent parent genome. A morphological evaluation of 6 near isogenic lines (NILs)—2 resistant to leaf and stripe rust, and 4 resistant to leaf rust only—showed no significant differences in yields among NILs and the recurrent parent HD2967. All of the 6 NILs showed the presence of 2NS/2AS translocation, carrying the linked genes Lr37/Sr38/Yr17 present in HD2967 and the targeted leaf rust resistance gene LrTrk. Two NILs also showed additional resistance to stripe rust. Therefore, these NILs with rust resistance and an at par yielding ability of H2967 can replace the susceptible cultivar HD2967 to reduce yield losses due to disease.

Yellow/stripe rust caused by Puccinia striiformis f. sp. tritici is a major biotic stress in global wheat production. Introgression lines derived from the Triticum spelta accessions PI348764 and IARI276 showed high levels of yellow rust resistance at seedling and adult plant stage. The Yr5 gene located on 2B chromosome was previously the only stripe rust resistance gene described in T. spelta gene pool. By genotyping parental and introgressed material with markers linked with the Yr5 gene, we demonstrate that PI348764 likely carries Yr5, and that it appears to be absent from IARI276. By employing a combination of methods, including screening for adult plant resistance and seedling resistance at multiple field trials, bulked segregant analysis (BSA) on F₅ families, and genotyping using wheat Breeders’ 35K array, we show that Yr^IARI276 is a novel stripe rust resistance gene with putative chromosomal locations on 1BL, 1DL, 5AL, or 7BL. Furthermore, genetic analysis revealed that Yr^IARI276 showed a goodness of fit to Mendelian ratios for a single dominant gene. As the gene is distinct from Yr5 and the chromosomal location is unique from earlier reported Yr genes, it will be useful in improving diversity of Yr gene repertoire in disease resistance breeding programmes.

Utilization of crop wild relatives of wheat can be very effective in building the genetic diversity to cater to the evolving strains of disease pathogens. Aegilops speltoides is a rich source of rust resistance genes however transferring those to wheat genome can be tedious due to co-transfer and preferential transmission of undesirable genes causing gametocidal activity. Such an unholy association was observed in Triticum aestivum-Ae. speltoides derivative line Sel. 2427 which possess the broad-spectrum leaf rust seedling resistance gene (LrS2427). In situ hybridization studies revealed the presence of S genome in Sel. 2427, showing translocations to six telomeric regions involving four chromosomes. This confirms the presence of genes associated with gametocidal activity along with the beneficial LrS2427. QTLs associated with the component traits of gametocidal activity have been localized to 2A, 2D, 3D chromosomes however candidate genes for fertility were identified only in 2A and 2D chromosomes. This is in accordance with the reports of gametocidal genes mapped to 2S chromosomes in Ae. speltoides. To break the inadvertent association, F₁(Agra Local X Sel. 2427) seeds were irradiated with gamma rays and leaf rust resistant mutants lacking gametocidal activity were developed. These mutants showed resistance to different races of leaf rust pathogen and showed superior agronomic performance as well. These mutants could be a great resource in wheat improvement for utilization of the leaf rust resistance gene LrS2427 without any yield penalty.