Urmil Bansal

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is among the major threats to global wheat production. The common wheat landraces AUS27506 and AUS27894 displayed stripe rust resistance against several commercially prevailing Pst pathotypes. These genotypes were crossed with a stripe-rust-susceptible landrace AUS27229 to understand the inheritance of resistance and to determine the genomic location(s) of underlying gene(s). F3 generations of crosses AUS27506/AUS27229 and AUS27894/AUS27229 showed monogenic segregation for stripe rust resistance under greenhouse conditions. The absence of segregation for stripe rust response among the AUS27506/AUS27894-derived F3 population suggested that both genotypes carry the same gene. The stripe rust resistance gene carried by AUS27506 and AUS27894 was tentatively named YrAW4. A bulked segregant analysis placed YrAW4 in the long arm of chromosome 2B. The AUS27506/AUS27229 F3 population was enhanced to develop an F6 recombinant inbred line (RIL) population for detailed mapping of chromosome 2BL. DArT-based SSR, STS and SNP markers were employed to enrich the 2BL map. DArT-based STS markers sun481 and SNP marker IWB12294 flanked YrAW4 proximally (1.8 cM) and distally (1.2 cM), respectively. Deletion mapping placed sun481 in the deletion bin 2BL-5. All stripe rust resistance genes, previously located on chromosome 2BL, neither express an infection type like YrAW4, nor are they mapped in the deletion bin 2BL-5. Hence, YrAW4 represented a new locus and was formally named Yr72. The usefulness of the markers IWB12294 and sun481 in marker-assisted selection was demonstrated by the amplification of alleles that are different to that linked with Yr72 in 19 common wheat and two durum wheat cultivars.

Puccinia striiformis f. sp. tritici (Pst), the causal agent of stripe rust of wheat, is a highly evolving fungal pathogen and several widely deployed stripe rust resistance genes have been overcome worldwide often through single step increase in virulence. Development of stripe rust resistant cultivars depends on the availability of widely effective sources of resistance. An Indian wheat cultivar ‘VL404’ exhibited high level of resistance against Australian Pst pathotypes. ‘VL404’ was crossed with a susceptible genotype Avocet ‘S’ (AvS) and an F 6 recombinant inbred line (RIL) population was developed. The VL404/AvS RIL population was evaluated at the seedling stage against three Pst pathotypes differing in their virulence profiles. Monogenic segregation for stripe rust response variation was observed in this population and the resistance locus was tentatively named YrVL . Incorporation of stripe rust data into the VL404/AvS genetic map constructed using 40K Wheat‐Barley Illumina XT single‐nucleotide polymorphism (SNP) array placed YrVL in the long arm of chromosome 2B in the 769.1–779.3 Mb region of the Chinese Spring physical map. YrVL was aligned with the previously reported genes in chromosome 2BL ( Yr43, Yr72 and YrAW12 ) using Pretzel, and it was placed distal to all these genes. Hence, YrVL appears to represent a new resistance locus.