Emails: n.qureshi@cgiar.org; s.bhavani@cgiar.org

Changing climate patterns across the globe poses various challenges necessitating new wheat varieties that are resilient to transboundary pests and diseases to ensure future agriculture sustainability. Wheat rusts remain economically important diseases causing substantial yield losses to wheat production worldwide. Mining rust resistance genes remains an integral component in several wheat breeding programs.

Understanding the complex genetics of resistance is crucial for varietal development and deployment. The current study focuses on unraveling the genetic basis of rust resistance in CIMMYT line, “Kasuko”. A RIL population comprising 181 lines was developed using resistant variety Kasuko and a triple rust susceptible parent Apav. This population was phenotyped under artificial epidemics of leaf rust (LR) and yellow rust (YR) in Mexico and yellow rust and stem rust (SR) in Kenya.

Quantitative trait loci (QTL) mapping studies were conducted using the DArTSeq genotyping to map the QTL associated with rust resistance. The analysis revealed two significant pleotropic loci associated with leaf rust, yellow rust and stem rust resistance, QLrYr.cim-1BL and QLrYr.cim-2AS on chromosomes 1BL and 2AS, respectively. QLrYr.cim-1BL was identified as Lr46/Yr29, whereas QLrYr.cim-2AS represented Yr17/Lr37 region.

Another consistent and stable minor leaf rust QTL, QLr.cim-2DS was observed on chromosome 2DS explaining 9-11% phenotypic variation (PVE). Two minor QTLs were identified for yellow rust resistance in Kenya on chromosomes 3DS and 6BS, QYrKen.cim-3DS and QYrKen.cim-6BS, respectively with minor effects of less than 10% PVE.

In addition to these, four minor QTLs were detected for the stem rust resistance on chromosomes 2BS (QSr.cim-2BS), 5AL (QSr.cim-5AL), 6AS (QSr.cim-6AS) and 6AL (QSr.cim-2BS). The comparison of average severities among RILs carrying these QTL in various combinations indicated significant disease reduction.

These QTL and their closely linked markers are being developed which will be useful for fine mapping and marker-assisted selection (MAS) in breeding for durable resistance to multiple rust diseases.