Improving the crown rot resistance and tolerance of wheat using marker-assisted recurrent selection

Abstract

Crown rot disease (Fusarium pseudograminearum) of wheat causes significant yield losses across Australia. However, the genetic control of crown rot resistance and tolerance is complex and traditional breeding strategies have proven ineffective. Marker Assisted Recurrent Selection (MARS) was examined as a strategy to more effectively pyramid the many minor genes controlling plant response to crown rot. Populations were developed from three-way crosses to (i) optimize screening procedures for crown rot, (ii) examine the relationship between resistance and tolerance, (iii) identify quantitative trait loci (QTL) linked to resistance and tolerance, (iv) pyramid QTLs using MARS and (v) confirm response to selection. Disease severity in greenhouse pot tests was less reliable than field screening using managed inoculum; hence field screening was used for all subsequent evaluations. In the MARS approach, materials from each population were genotyped and phenotyped by F4 for crown rot response and QTLs linked to crown rot resistance and/or tolerance identified. Consistent QTL, mapped to unique chromosomal regions, were then recombined in crossing to pyramid markers. Following two cycles of recombination, the progeny from both cycles of MARS, the base population and the original parents were compared for resistance and/or tolerance depending on the population. Resistance and tolerance (determined as reduced yield loss in the presence of crown rot) were independently inherited. A significant and positive response to selection was observed with some recombinants significantly more resistant and higher yielding than their parents. The genotypes identified and developed in this study combine multiple sources of resistance and tolerance and these materials and their associated markers can be used by the Australian wheat industry to improve wheat yield in the presence of crown rot.