Abstract
Mapping major quantitative trait loci (QTL) responsible for rice seed germinability under low temperature (GULT) can provide valuable genetic source for improving cold tolerance in rice breeding. In this study, 124 rice backcross recombinant inbred lines (BRILs) derived from a cross indica cv. Changhui 891 and japonica cv. 02428 were genotyped through re-sequencing technology. A bin map was generated which includes 3057 bins covering distance of 1266.5 cM with an average of 0.41 cM between markers. On the basis of newly constructed high-density genetic map, six QTL were detected ranging from 40 to 140 kb on Nipponbare genome. Among these, two QTL qCGR8 and qGRR11 alleles shared by 02428 could increase GULT and seed germination recovery rate after cold stress, respectively. However, qNGR1 and qNGR4 may be two major QTL affecting indica Changhui 891germination under normal condition. QTL qGRR1 and qGRR8 affected the seed germination recovery rate after cold stress and the alleles with increasing effects were shared by the Changhui 891 could improve seed germination rate after cold stress dramatically. These QTL could be a highly valuable genetic factors for cold tolerance improvement in rice lines. Moreover, the BRILs developed in this study will serve as an appropriate choice for mapping and studying genetic basis of rice complex traits.
Highlights
Low temperature germination is a major determinant for stable establishing of the cultivated rice in tropical or subtropical area where optimum temperatures for rice growth during germination and seedling stages are from 25 to 35◦C (Fujino et al, 2004; Xu et al, 2015)
A backcross recombinant inbred lines (BRILs) (BC1F6) population consisting of 124 individuals derived from Changhui 891/02428//02428 was developed for subsequently analysis
Near-isogenic lines (NILs) (CSSLs) and chromosome segment substitution lines can overcome this issue and ideal for quantitative trait loci (QTL) detection (Kubo et al, 1999; Bian et al, 2010), but they are time consuming and labor-intensive which limited the acceleration of gene cloning
Summary
Low temperature germination is a major determinant for stable establishing of the cultivated rice in tropical or subtropical area where optimum temperatures for rice growth during germination and seedling stages are from 25 to 35◦C (Fujino et al, 2004; Xu et al, 2015). The low temperature existing during seed germination stage results poor plants survival rate and alternatively cause reductions in the final yield. Cold tolerance improvement at germination stage is necessary for yield stability and an increase in crop productivity (Fujino et al, 2008). Paddy field with direct seeding become one of the choice with low labor and cost to overcome the damage of low temperature in rice cultivars (Mao et al, 2015). Improving cold tolerance in rice varieties with conventional breeding methods is labor-and time consuming as cold tolerance. Better understanding of the complexity of QTL underlying cold tolerance at the seed germination stage is estimated to accelerate the progress of cold-tolerant cultivars development by using molecular assisted breeding technology (Koseki et al, 2010)
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