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

Abstract

Crown rot of wheat (Triticum aestivum), predominantly caused by the fungus Fusarium pseudograminearum, has become an increasingly important disease constraint in many winter cereal production regions in Australia. Our group has previously identified a range of quantitative trait loci (QTL) for partial resistance to crown rot in various bread wheat sources. Here we report on work that has assessed the effectiveness of pyramiding QTL to improve resistance to crown rot. Two doubled haploid populations were analysed -one from a cross between two previously characterised sources of partial seedling resistance (2-49 and W21MMT70; n = 208) and one from a cross between 2-49 and the commercial variety Sunco, a source of adult field resistance (n = 134). Both populations were phenotyped for seedling resistance to crown rot. Microsatellite and DArT markers were used to construct whole genome linkage maps for use in composite interval mapping (CIM) to identify QTL. Three QTL were detected in both trials conducted on the 2-49/W21MMT70 population. These were located on chromosomes 1D (QCr.usq-1D.1), 3B (QCr.usq-3B.1) and 7A. QCr.usq-1D.1 and the previously undetected 7A QTL were inherited from 2-49. QCr.usq-3B.1, inherited from W21MMT70, was the most significant of the QTL, explaining up to 40.5 % of the phenotypic variance. Three QTL were identified in multiple trials of the Sunco/2-49 population. These were located on chromosomes 1D (QCr.usq-1D.1), 2B (QCr.usq-2B.2) and 4B (QCr.usq-4B.1). Only QCr.usq-2B.2 was inherited from Sunco. QCr.usq-4B.1 was the most significant of these QTL, explaining up to 19.1 % of the phenotypic variance.In the 2-49/W21MMT70 population several DH lines performed significantly better than either parent, with the best recording an average disease severity rating of only 3.8 % of that scored by the susceptible check cultivar Puseas. These lines represent a new level of seedling crown rot resistance in wheat.

Development of near-isogenic lines for a major QTL on 3BL conferring Fusarium crown rot resistance in hexaploid wheat

“…A QTL at a similar location was found to be the sole QTL responsible for the resistance from the genotype Ernie . A QTL on 3B was also the most significant among those detected in the resistant genotype 'W21MMT70' (Bovill et al 2010). However, the 3B QTL in this third resistant genotype was not detected in a different population where the same resistant genotype was involved (Bovill et al 2006) and it is likely that the expression of the QTL from 'W21MMT70' is a product of a specific interaction.…”

Culm discolouration as an indicator of Fusarium pseudograminearum biomass

“…Rating of crown rot disease using seedling leaf sheath tissues has become widely used due to its rapid nature and the ability to grow large quantities of seedlings in controlled growth environments (Wildermuth and McNamara 1994;Mitter et al 2006;Li et al 2008). While these assays have been reported to correlate with ratings performed on adult plants in the field, they cannot replace field grown trials, particularly since some adult plant resistances have been demonstrated (Wildermuth et al 2001;Wallwork et al 2004;Bovill et al 2010). …”

Development and Validation of Markers Closely Linked to Crown Rot Resistance in Wheat and Barley

“…They were found on five different chromosomes. However, recent studies have identified a major QTL on the long arm of chromosome 3B for CR resistance in three different wheat genotypes (Li et al, 2010a;Ma et al, 2010, Bovill et al, 2010. The magnitude of the 3B CR QTL identified in these genotypes explained up to 34.6%, 40.2%, and 46.2% of the phenotypic variance with detection in each of the trials in the three independent studies.…”

“…Fortunately, recent studies have identified a major QTL on the long arm of chromosome 3B conferring CR resistance in three different wheat genotypes, two of them belong to T. aestivum (Li et al, 2010a;Bovill et al, 2010), another belong to T. spelta (Ma et al, 2010). The magnitude of the 3B CR QTL identified in the wheat genotypes 'Ernie' and 'CSCR6' explained up to 34.6% and 46.2% of the phenotypic variance with detection in each of the trials with the use of two different F. pseudograminearum and F. graminearum isolates.…”

“…The magnitude of the 3B CR QTL identified in these genotypes explained up to 34.6%, 40.2%, and 46.2% of the phenotypic variance with detection in each of the trials in the three independent studies. Although the three genotypes are totally different, one is a modern wheat variety from USA, another is an Australian breeding line, and the third is an old landrace from India; a major QTL was identified in each of these resources and they were mapped to a very similar position on 3BL (Li et al, 2010a;Ma et al, 2010;Bovill et al, 2010).…”