Analysis Of QTLs Affecting Traits Of Agronomic Importance And Construction Of Near Isogenic-lines With Major QTL

Most of the important agronomic traits in crops are quantitatively inherited. Improvement of these quantitative traits is one of the major objectives in crop genetic breeding program. Before 1980, researchers could not make a deep research on identification and genetic basis of quantitative traits due to lack of tools. However, there is an opportunity to dissect the quantitative traits in rice after 1980 due to the reasons as following: the advent of molecular markers, construction of high density molecular marker linkage map, rapid development of various mapping population, rapid development of powerful statistical software and sequence completion of rice whole genome. Especially the successful examples of QTL fine mapping and cloning in the recent years provide us better understanding the genetic basis of complex traits. QTL cloning era is coming in rice.In this study, a RILs population (F₆ and F₇) derived from a large panicle size parent, HR5 and Zhenshan 97, was used to do QTL analysis. Field experiments with two replications following a randomized complete block design were implemented in 2001 and 2002. Traits scored included yield per plant and components of yield, plant height, heading date and traits related to flag leaf. And analysis of QTL and digenic epistasis was done against these traits. On the basis of QTL analysis, a series of near-isogenic lines of four target traits including spikelets per panicle, grains per panicle, kernel weight and plant height were developed. The main results are summarized as following:1. A genetic linkage map consisting of 263 SSR markers, covering 1559.8 cM in whole genome, was constructed using the RIL population, with an average interval of 6.4 cM. 263 SSR markers were separated into 14 groups. The linear order of markers in the linkage map was in good agreement with that published previously.2. Composite interval mapping was used to detect QTL against all traits. One of these traits, grains per panicle, had the largest number of QTLs identified. The number of QTLs for this trait was 8. For the focusing trait in this study, spikelets per panicle, the number of QTLs identified was 4 and 5 in 2001 and 2002, respectively. One QTL was repeatedly detected in both years. And for grains per panicle, the number of QTLs identified was 6 and 5 in 2001 and 2002, respectively. Three QTLs were repeatedly detected in both years.3. All traits were involved in epistatic interaction. This further confirms that epistasis is one of genetic bases of quantitative trait loci. Genetic effect of single digenic...