Study On The Effect Of Morphological Traits On Sheath Blight Resistance And Yield In Rice

Study on the effect of morphological traits on sheath blight resistance and yield in rice Postgraduate: Han Yuepeng Advisor:Zhang Hongxi Pan Xuebiao Abatract Sheath blight, caused by Rhizoctonia solani, is one of the major diseases of rice. This study was conducted with a recombinant inbred lines (RILs) population consisting of 241 recombination lines, derived from an elite combination, Zhenshan 97B X Shanyou 63. A genetic map was constructed from the RILs. Field experiments were implemented in 1999 and 2000. Agronomic traits were investigated, including 17 morphological traits such as plant height, heading date, tiller angle, plant compaction, the angles and sizes of leaves from the flag to the fourth, and sheath blight response rating (SBR) and individual plant yield and its component traits. The analysis methods of partial correlation and interval mapping for quantitative traits were used to study the relationship between morphological traits and SBR as well as between morphological traits and yield and its component traits. The main results are summarized as following: 1. Transgressive separation was observed for all the investigating traits including morphological traits and SBR and yield and its component traits in the RILs. This showed that the RILs was a valid population for the inheritance study of quantitative traits. 2. The field experiment accuracy of SBR identification could be enhanced by adding replicates, adjusting sowing date in order to shortening the difference of heading date among RILs and combining the inoculation of insertion of R. solani infected short toothpicks. 3. Most of traits had major QTL, but the number greatly varied according to different traits. Major QTL could be located on the same interval in different environments, while minor QTL couldn抰. 4. The major QTLs controlling plant height and heading date were simultaneously located on the same interval of chromosome 7 in two years. Two major QTLs contributing to tiller angle were located on the chromosome 9, one of them was at the same site for plant compaction. Two major QTLs for the second leaf angle were located on chromosome 5 and chromosome 6 respectively. The QTLs for 1000-grain-weight and filled grain percentage could be detected in different environment, while the number of panicles per plant and yield were on the contrary. 5. Two QTLs for sheath blight resistance were simultaneously detected in two years. They were located on chromosome 5(qSB-5) and chromosome 7 (qSB-9), respectively. The QTLs could both approximately explain 10% of phenotype variation and the genotype of MH63 had negative additive effects. The qSB-9 was next to the QTL contributing to tiller angle, while the qSB-5 was close to the QTL for the second leaf angle. The result suggested that the QTLs for sheath blight, tiller angle, plant compaction and the second leaf angle could be linked. 6. Accounding to the analysis of partial correlation, most of morphological iraits appeared to be independent of SBR. The traits, which significantly correlated with sheath blight resistance at 5% or 1% of levels only in one year, included plant height, heading date, plant compaction, uniformity of panicles?height, leaf...