Identification of novel QTL for resistance to crown rot in the doubled haploid wheat population ‘W21MMT70’ × ‘Mendos’

Abstract

Crown rot (causal agent Fusarium pseudograminearum) is a fungal disease of major significance to wheat cultivation in Australia. A doubled haploid wheat population was produced from a cross between line ÔW21MMT70Õ, which displays partial seedling and adult plant (field) resistance to crown rot, and ÔMendosÕ, which is moderately susceptible in seedling tests but partially resistant in field trials. Bulked segregant analysis (BSA) based on seedling trial data did not reveal markers for crown rot resistance. A framework map was produced consisting of 128 microsatellite markers, four phenotypic markers, and one sequence tagged site marker. To this map 331 previously screened AFLP markers were then added. Three quantitative trait loci (QTL) were identified with composite interval mapping across all of the three seedling trials conducted. These QTL are located on chromosomes 2B, 2D and 5D. The 2D and 5D QTL are inherited from the line ÔW21MMT70Õ, whereas the 2B QTL is inherited from ÔMendosÕ. These loci are different from those associated with crown rot resistance in other wheat populations that have been examined, and may represent an opportunity for pyramiding QTL to provide more durable resistance to crown rot.

Confirmation of QTL mapping and marker validation for partial seedling resistance to crown rot in wheat line '2-49'

“…This implies that distinct partially resistant genotypes such as W21MMT70 and IRN497 may represent novel sources of partial resistance that can be used to pyramid multiple resistance QTLs together. The recent detection of novel QTLs on 2D and 5D in a W21MMT70 × Mendos doubled haploid population supports this hypothesis (Bovill et al 2006). Further genetic analysis to test these possibilities is currently underway, based on QTL mapping using populations containing these sources, haplotyping of critical regions, and phenotypic screening of half-diallel populations.…”

“…Selection for this trait would be greatly assisted by the development of closely linked molecular markers suitable for deployment in a marker assisted selection (MAS) program. To date, there have been only 3 published reports of the identification of markers associated with crown rot resistance (Wallwork et al 2004;Collard et al 2005;Bovill et al 2006).…”

Pyramiding QTL increases seedling resistance to crown rot (Fusarium pseudograminearum) of wheat (Triticum aestivum)

“…DNA was diluted to a concentration of 10 ng/μL prior to use in PCR. PCR conditions for microsatellite analysis were those detailed in Bovill et al, 2006.…”

“…Partial resistance to crown rot in wheat is a quantitatively inherited trait showing a continuous distribution in all of the segregating populations that have been examined thus far Collard et al, 2005;Bovill et al, 2006;Collard et al, 2006). Quantitative traits are not easily grouped into distinct categories, as the range of appearance of one genotype often overlaps that of others, creating the appearance of a continuous distribution (Kearsey and Pooni, 1996).…”

“…To investigate the effects of combining QTL for partial CR resistance from different sources, we have assessed two doubled haploid populations (2-49/W21MMT70 and Sunco/2-49), involving two previously characterised sources (2-49 and W21MMT70) of crown rot resistance in seedlings (Collard et al, 2005;Bovill et al, 2006) and the Sunco source of adult field resistance. Line 2-49 in particular has rated consistently well in many seedling and field trials for crown rot resistance (Wildermuth and McNamara, 1994) and is widely considered as the current benchmark in the search for a more robust resistance, despite poor agronomic characteristics.…”