Fine mapping of a preharvest sprouting QTL interval on chromosome 2B in white wheat

Abstract

Fine mapping by recombinant backcross populations revealed that a preharvest sprouting QTL on 2B contained two QTLs linked in coupling with different effects on the phenotype. Wheat preharvest sprouting (PHS) occurs when grain germinates on the plant before harvest, resulting in reduced grain quality. Previous mapping of quantitative trait locus (QTL) revealed a major PHS QTL, QPhs.cnl-2B.1, located on chromosome 2B significant in 16 environments that explained from 5 to 31 % of the phenotypic variation. The objective of this project was to fine map the QPhs.cnl-2B.1 interval. Fine mapping was carried out in recombinant backcross populations (BC1F4 and BC1F5) that were developed by backcrossing selected doubled haploids to a recurrent parent and self-pollinating the BC1F4 and BC1F5 generations. In each generation, three markers in the QPhs.cnl-2B.1 interval were used to screen for recombinants. Fine mapping revealed that the QPhs.cnl-2B.1 interval contained two PHS QTLs linked in coupling. The distal PHS QTL, located between Wmc453c and Barc55, contributed 8 % of the phenotypic variation and also co-located with a major seed dormancy QTL determined by germination index. The proximal PHS QTL, between Wmc474 and CNL415-rCDPK, contributed 16 % of the variation. Several candidate genes including Mg-chelatase H subunit family protein, GTP-binding protein and calmodulin/Ca(2+)-dependent protein kinase were linked to the PHS QTL. Although many recombinant lines were identified, the lack of polymorphism for markers in the QTL interval prevented the localization of the recombination breakpoints and identification of the gene underlying the phenotype.

Improving Genomic Prediction for Pre‐Harvest Sprouting Tolerance in Wheat by Weighting Large‐Effect Quantitative Trait Loci

“…3). Some chromosomal regions reported in the literature as being involved in PHS tolerance were not identified in our study, including the QTL on 2B (Somyong et al, 2014) or 4AL . It is expected that most points will fall along the dotted line, but those furthest to the right will deviate, as they are most likely associated with PHS tolerance.…”

Genome-Wide Association Study for Pre-harvest Sprouting Resistance in a Large Germplasm Collection of Chinese Wheat Landraces

“…We evaluated PHS resistance by performing germination tests of harvest-ripe grain under controlled conditions (Somyong et al, 2014; Zhang et al, 2014; Lin et al, 2015). At each site, wheat spikes were harvested at physiological maturity (i.e., after loss of green pigmentation in the spikes and peduncles).…”

“…These studies have either evaluated PHS resistance directly by testing whole intact spikes in misting chambers or simulated rain events in the field (Somyong et al, 2014; Albrecht et al, 2015), or germination testing of harvest-ripe grain under controlled conditions (Somyong et al, 2014; Zhang et al, 2014; Lin et al, 2015). According to biparental genetic linkage analyses, all 21 chromosomes of wheat reportedly harbor QTL for PHS resistance (Mohan et al, 2009; Cabral et al, 2014; Cao et al, 2016; Fakthongphan et al, 2016), but the most consistently detected regions are located on the group three chromosomes (Kato et al, 2001; Osa et al, 2003; Kulwal et al, 2004; Mori et al, 2005; Liu and Bai, 2010) and Chr 4A (Mares et al, 2005; Chen et al, 2008; Singh et al, 2010; Cabral et al, 2014).…”

Genome-wide association mapping of preharvest sprouting resistance in a diversity panel of European winter wheats

“…Another major PHS resistance QTL on chromosome 2B (QPhs.cnl-2B.1; Munkvold et al 2009) that was separated into two QTL linked in coupling by fine mapping in recombinant backcross populations was associated to possible candidate genes (Somyong et al 2014). Interestingly, Zhang et al (2014) reported a wheat ortholog of the rice dormancy gene OsSdr4 in a region on chromosome 2B similar to the two linked PHS resistance QTL described by Somyong et al (2014). The last among the possible candidate genes for PHS resistance that need to be mentioned here are the Viviparous-1 (Vp-1) genes located on the long arms of the wheat homoeologous group 3 chromosomes.…”