A QTL located on chromosome 4A associated with dormancy in white- and red-grained wheats of diverse origin

Abstract

Improved resistance to preharvest sprouting in modern bread wheat (Triticum aestivum. L.) can be achieved via the introgression of grain dormancy and would reduce both the incidence and severity of damage due to unfavourable weather at harvest. The dormancy phenotype is strongly influenced by environmental factors making selection difficult and time consuming and this trait an obvious candidate for marker assisted selection. A highly significant Quantitative Trait Locus (QTL) associated with grain dormancy and located on chromosome 4A was identified in three bread wheat genotypes, two white- and one red-grained, of diverse origin. Flanking SSR markers on either side of the putative dormancy gene were identified and validated in an additional population involving one of the dormant genotypes. Genotypes containing the 4A QTL varied in dormancy phenotype from dormant to intermediate dormant. Based on a comparison between dormant red- and white-grained genotypes, together with a white-grained mutant derived from the red-grained genotype, it is concluded that the 4A QTL is a critical component of dormancy; associated with at least an intermediate dormancy on its own and a dormant phenotype when combined with the R gene in the red-grained genotype and as yet unidentified gene(s) in the white-grained genotypes. These additional genes appeared to be different in AUS1408 and SW95-50213.

Maximizing the identification of QTL for pre-harvest sprouting resistance using seed dormancy measures in a white-grained hexaploid wheat population

“…Noda et al (2002) investigated another ABA responsive gene located on the long arm of chromosome 4A. QPhs.spa-4A, located in interval barc170-gwm397-wmc617a on 4A, is in a region associated with dormancy and preharvest sprouting resistance in numerous other QTL studies of hexaploid wheat (Flintham et al 2002;Torada et al 2005;Mares et al 2005;Tan et al 2006;Ogbonnaya et al 2008;Imtiaz et al 2008;Munkvold et al 2009;Rasul et al 2009;Kulwal et al 2010;Singh et al 2010Singh et al , 2012Lohwasser et al 2013). The locus was also identified in tetraploid ) and diploid (Nakamura et al 2007) wheat populations, and in an association mapping study (Kulwal et al 2012).…”

“…Heritability of the various traits varied from 0.59 to 0.93. Identification and incorporation of genetic factors underlying resistant genotypes is a key to improve resistance to pre-harvest sprouting Flintham 2000;Mares et al 2005;DePauw et al 2012).…”

“…Also, the effects of QTL range from minor to major corresponding to a range in phenotypic expression from susceptible to resistant. As with DePauw and McCaig (1991) in the study of heritability, in order to deal with the complexity of pre-harvest sprouting resistance and identify associated QTL, different tests such as wetting spikes in an artificial rain simulator, threshed seed germination counts for dormancy, and alpha-amylase activity measured by falling number have been conducted (Roy et al 1999;Mares et al 2005;Imtiaz et al 2008;Rasul et al 2009). Knox et al (2012) reported GI, GR and PG measures each at 7, 14 and 21 days intervals from the start of germination across multiple environments.…”

Quantitative trait loci for resistance to pre-harvest sprouting in US hard white winter wheat Rio Blanco

“…Recently, QTLs from white wheat germplasm have received increased attention. A major QTL on 4AL has been reported in white wheat from China and Africa (Chen et al 2007;Mares et al 2005). In another study, two markers, Xbarc55 and Xbcd1434, were found to be associated with PHS resistance in a U.S. white wheat cultivar Clark Cream (http:// maswheat.ucdavis.edu/protocols/PHS).…”

“…Kato et al (2001) detected a major QTL for PHS resistance on 4AL of a red wheat cultivar, and Mares and Mrva (2001) reported the same QTL, but with smaller eVect, for seed dormancy in white wheat. Several recent studies demonstrated that the major QTL on 4AL is present in both white and red wheat cultivars of diverse origins (Chen et al 2007;Lohwasser et al 2005;Mares et al 2005;Torada et al 2005). Although QTLs for PHS resistance have been identiWed on many chromosomes in diVerent studies, chromosome 4A and all long arms of group 3 chromosomes appear to be more critical for PHS resistance (Flintham and Gale 1996;Groos et al 2002;Kato et al 2001;Kulwal et al 2004;Mori et al 2005;Osa et al 2003).…”