Stripe rust and leaf rust resistance in CIMMYT wheat line “Mucuy” is conferred by combinations of race-specific and adult-plant resistance loci

Abstract

Developing wheat varieties with durable resistance is a core objective of the International Maize and Wheat Improvement Center (CIMMYT) and many other breeding programs worldwide. The CIMMYT advanced wheat line “Mucuy” displayed high levels of resistance to stripe rust (YR) and leaf rust (LR) in field evaluations in Mexico and several other countries. To determine the genetic basis of YR and LR resistance, 138 F5 recombinant inbred lines (RILs) derived from the cross of Apav#1× Mucuy were phenotyped for YR responses from 2015 to 2020 at field sites in India, Kenya, and Mexico, and LR in Mexico. Seedling phenotyping for YR and LR responses was conducted in the greenhouse in Mexico using the same predominant races as in field trials. Using 12,681 polymorphic molecular markers from the DArT, SNP, and SSR genotyping platforms, we constructed genetic linkage maps and QTL analyses that detected seven YR and four LR resistance loci. Among these, a co-located YR/LR resistance loci was identified as Yr29/Lr46, and a seedling stripe rust resistance gene YrMu was mapped on the 2AS/2NS translocation. This fragment also conferred moderate adult plant resistance (APR) under all Mexican field environments and in one season in Kenya. Field trial phenotyping with Lr37-virulent Puccinia triticina races indicated the presence of an APR QTL accounting for 18.3–25.5% of the LR severity variation, in addition to a novel YR resistance QTL, QYr.cim-3DS, derived from Mucuy. We developed breeder-friendly KASP and indel molecular markers respectively for Yr29/Lr46 and YrMu. The current study validated the presence of known genes and identified new resistance loci, a QTL combination effect, and flanking markers to facilitate accelerated breeding for genetically complex, durable rust resistance.

Phenotyping and Identification of Molecular Markers Associated with Leaf Rust Resistance in the Wheat Germplasm from Kazakhstan, CIMMYT and ICARDA

“…The Lr37 and Lr34 genes differed in the highest frequency of occurrence (24.3 and 22.8%, respectively). The Lr37 gene still provides a sufficient level of resistance, which indicates the need for its introduction into breeding programs [69][70][71][72][73]. The Lr46 gene provides "slow-rusting", although it is a less effective gene compared to the Lr34 gene.…”

Exploring the Genetic Variation of Stripe Rust Foliar and Head Infection in Egyptian Wheat as an Effect of Climate Change

“…The isoline set evaluated in this study was very useful to shed light on the possible resistant genes to both symptoms under Egyptian conditions. This set is widely used in identifying the possible resistant genes to stripe rust [44,45]. Ten isolines carrying at least nine different resistant genes (Yr3, Yr5, Yr18, Yr25, Yr31, Yr37, Yr51, YrAld, and YrSP) were resistant to PstFI and PstHI (Figure 6a,b).…”

Genomic Regions Associated with Resistance to Three Rusts in CIMMYT Wheat Line “Mokue#1”

“…Lr46/Yr29/Sr58/Pm39 occurs frequently in the CIMMYT breeding program and is an important contributor of durable resistance against multiple diseases [24][25][26]. Over 90% of the CIMMYT breeding lines now possess this gene and its presence was reported in multiple genetic mapping studies involving the CIMMYT germplasm [27][28][29][30][31]. This gene is also associated with a morphological marker, leaf tip necrosis (LTN), in adult plants, which is also expressed in the resistant parent in all environments, suggesting that QLrYr.cim-1BL was in fact Lr46/Yr29.…”

“…APR gene Yr36 was mapped at 153 cM of the genetic map [58], whereas Yr78 was mapped at 92.4 Mb on 6BS [57], suggesting that QYrKEN.cim-6BS can be different from Yr36 and Yr78. Several other QTLs were reported on 6BS: Qyr.sicau-6BS, mapped between 80.4 Mb and 84.8 Mb on the physical assembly [59]; Qyr.sun-6B, mapped at the interval of about 150 Mb [60]; QYrst.wgp-6BS.1, mapped closer to Yr36 on the basic SSR marker position [61]; QYrsk.wgp-6B, mapped to the centromere region of 6B [62]; and QYr.cim-6BS, considered to be Yr78 based on the positioning of closely linked markers [30]. These results suggest that QYrKEN.cim-6BS could be different from previously reported genes/QTLs.…”