Abstract
Seedling growth is one essential component of reliable crop establishment, and greater early vigor is often associated with
greater drought tolerance, biomass and grain yield. Chuanmai 42 derived from synthetic hexaploid wheat has been widely used
as an elite wheat-breeding parent in wheat breeding program of Southwest China. In this study, 127 recombinant inbred lines
(RILs) developed from Chuanmai 42 were used to dissect the molecular basis of its great early vigor by QTL mapping, and
seven early vigor related traits including number of all expanded leaves, total leaf area, shoot fresh weight, shoot dry weight,
number of the main roots, root dry weight and relative growth rate were evaluated for this RILs after 21-day and 28-day growth
under a modified Hoagland nutrient solution, respectively. Based on a linkage map containing 148 SSR and 644 DArT makers,
a total of 40 QTLs for these traits were detected on 14 chromosomes. Among the 25 QTLs with the phenotypic variance
explained more than 10%, 17 QTLs enhanced the related traits through Chuanmai 42 alleles. A total of 4 genomic regions with
QTL clusters were detected on chromosomes 5A, 6A, 6B and 7A, respectively. Among them, the genomic regions with QTL
clusters on 6B and 7A from Chuanmai 42 enhanced early vigor of seedling, and the other two were from Chuannong 16.
Moreover, QTL cluster in Xgwm154-Wpt7846 of chromosome 6B was the important genomic region with the strongest
phenotypic effects that were also strengthened during elongation of the growth period. The findings of this study are relevant
to the molecular improvement of early vigor when using Chuanmai 42 as a breeding parent.
