Construction Of Two Chromosme Segment Substitution Line Populations And Detection Of QTL For Yield Related Traits In Rice (Oryza Sativa L.)

Chromosome segment substitution lines (CSSLs) is a series of near-isogenic lines, which were bred by hybridizing, backcrossing, selfing and molecular marker-assisted selection method, covering whole genome of donor parent. The use of genetic background relative homozygous CSSLs can improve the accuracy of QTL mapping. By crossing CSSLs with the same genetic background, many elite alleles located on different fragments can be rapidly pyramided and new varieties with more favorable traits can be bred. Rice is one of the world’s most important food crops feeding half of the world’s population. Rice growing area in China is30,700,000ha each year. Among them, indica rice planting area is22,400,000ha. Indica hybrid planting area is17,330,000ha and accounts for78percent of China’s indica rice cultivated area and57%of China’s rice growing area. Relative to the tremendous achievements of indica hybrid rice, japonica hybrid rice development is very slow. Japonica rice planting area is8.30million hectares and the area planted with japonica hybrid rice only occupied5%of the total area of japonica rice in China. There is still much room for the development of hybrid japonica rice. The key is to improve yield competitive heterosis and unit area yield of F1seed-making. Therefore, this study was carried out in three sets of investigations:(1). using the japonica rice restorer R254as the donor parent, high yielding popular cultivar Ningjing1as the recipient parent, a set of CSSLs (CSSL-R) containing R254chromosome fragments in Ningjing1genetic background was constructed;(2). using this CSSL-R population, QTLs underlying nine yield-related traits were mapped; And (3). Using large flag leaf angle japonica variety A7444as the donor parent,9311as the recipient parent, a set of9311genetic background A7444chromosome segment substitution lines population (CSSL-A) was constructed. Characteristics of the two CSSLs constituted and yield-related traits QTL mapping results are summarized below.1. CSSL-R population was composed of86substitution lines, and covered87.26%of R254genome. Among the86lines, four lines had five donor segments, fifteen lines had six donor segments, seventeen lines had seven donor segments, sixteen lines had eight donor segments, twelve lines had nine donor segments, four lines had ten donor segments, six lines had eleven donor segments, seven lines had twelve donor segments and five lines had more than twelve donor segments. Through two replications in randomized block experiment in2years, we have identified four excellent breeding materials in the CSSL. The four excellent breeding materials were NingR-97, NingR-114, NingR-128and NingR-140. Their grain yield was significantly higher than Ningjing1. We found28japonica semi-erect panicle restorers from the CSSLs by test cross with BT type CMS6427A in japonica rice. Among them, Ning R-97, NingR-128and NingR-140were excellent semi-erect panicle restorer lines obtained in this study.2. Fifty three QTLs controlling yield related traits were detected in CSSL-R population by one way ANOVA and substitution mapping in both the first and second year. Among the53QTLs, there were twelve QTLs for heading date, one plant height QTL, seven plant length QTLs, one spikelets per panicle QTL, one grains per panicle QTL, six seed setting rate QTLs, seventeen1000-grain weigh QTLs, seven single panicle weigh QTLs and one grain yield per m2QTL.3. The CSSL-A population, composed of68substitution lines, covered the entire genome of the donor A7444. Among the68CSSL lines, eight substitution lines contained only one donor segment,11CSSLs two donor segments, eight substitution lines contained the three donor segments,10CSSLs contained four donor segments, the12CSSLs contained five donor segments, four substitution lines contained six donor segments, four substitution lines contained seven donor segments, four substitution lines contained eight donor segments and seven CSSLs lines contained segments of more than8donor segments. The CSSL-A population provides basic materials for studying expression characteristics of favorable alleles carried by A7444, a special japonica rice germplasm, in the indica genetic background.