Identification and validation of a major QTL conferring crown rot resistance in hexaploid wheat

Abstract

Crown rot (CR), caused by various Fusarium species, is a chronic wheat disease in Australia. As part of our objective of improving the efficiency of breeding CR resistant wheat varieties, we have been searching for novel sources of resistance. This paper reports on the genetic control of one of these newly identified resistant genotypes, 'CSCR6'. A population derived from a cross between CSCR6 and an Australian variety 'Lang' was analyzed using two Fusarium isolates belonging to two different species, one Fusarium pseudograminearum and the other Fusarium graminearum. The two isolates detected QTL with the same chromosomal locations and comparable magnitudes, indicating that CR resistance is not species-specific. The resistant allele of one of the QTL was derived from 'CSCR6'. This QTL, designated as Qcrs.cpi-3B, was located on the long arm of chromosome 3B and explains up to 48.8% of the phenotypic variance based on interval mapping analysis. Another QTL, with resistant allele from the variety 'Lang', was located on chromosome 4B. This QTL explained up to 22.8% of the phenotypic variance. A strong interaction between Qcsr.cpi-3B and Qcsr.cpi-4B was detected, reducing the maximum effect of Qcrs.cpi-3B to 43.1%. The effects of Qcrs.cpi-3B were further validated in four additional populations and the presence of this single QTL reduced CR severity by up to 42.1%. The fact that significant effects of Qcrs.cpi-3B were detected across all trials with different genetic backgrounds and with the use of isolates belonging to two different Fusarium species make it an ideal target for breeding programs as well as for further characterization of the gene(s) involved in its resistance.

The homoeologous regions on long arms of group 3 chromosomes in wheat and barley harbour major crown rot resistance loci

“…CR resistance of the two novel sources in wheat we analyzed was each controlled by a major 3BL locus Ma et al 2010). The segregating populations used so far do not allow us to clarify if the same gene is involved in these two resistance sources.…”

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.…”

“…A total of 28 publically available PCR-based markers were used in this study and nine polymorphic ones (in red) were filled into the region where the 3B QTL harboured Figure 2 The wheat 3B crown rot QTL identified in the resistant variety Ernie (Li et al, 2010) was remapped using a linkage map constructed using only PCR-based markers. The CR-associated markers are applied in validation study and have the potential value to be used in breeding for CR resistance in wheat Figure 3 The barley 3H crown rot QTL identified in the resistant variety TX9425 (Li et al, 2009) was remapped using a linkage map constructed using only PCR-based markers.…”

“…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).…”