Culm Morphophysiological Traits Related With Lodging Tolerance And QTLs Mapping In Rice(Oryza Sativa L.)

Rice is one of the most important grain crops in the world. Most of the important agronomic traits in rice are quantitative such as plant height, internodes length, and resistance to diseases etc. Improvement of these quantitative traits is one of the major objectives in rice cultivating and breeding. Lodging has negative effects on the yield, grain quality and mechanical harvesting efficiency in the rice production. Although it has been well recognized that culm characters are significantly correlated to lodging tolerance in rice, little work was done on the inheritance of these traits.The recombination inbred lines (RILs) including 247 lines derived from an indica-indica rice cross Zhengshan97B/Miyang46, as well as the parental lines, were grown in the paddy field of China National Rice Research Institute (CNRRI), Hangzhou, China, using random complete block design with 2 replications and 20 plants per line per replication. Sixteen traits related to lodging tolerance were scored and used for correlation analysis, stepwise regression analysis and path analysis by SPSS, including pushing resistance per plant (PRpt), plant height (PH), panicle length (PL), length of upper first elongated internode (LUFI) and so on. A complete and well-distributed molecular linkage map with 207 DNA markers distributing on the 12 chromosomes of rice was employed for QTL mapping by using software QTL Mapper 1.6 of mixed linear model. The results are summarized as below.1. The significant correlations were found between PRpt and all the tested traits except length of upper third elongated internode (LUTI). The PRpt had the biggest positive correlations with first elongated internode thick (FIT) and second elongated internode weight per unit (SIWu), 0.37 and 0.36, respectively. No significant correlations were found between PRpt and PH, LUTI by correlation analysis, while the path coefficients of PH, LUFI with PRpt were significant. Meanwhile, path analysis result showed PH, LUFI, second elongated internode thick (SIT), FIT, SIWu contributed to PRpt 17.64%, 3.61%, 2.56%, 21.16%, 9.00%, respectively. The above results indicated selection of higher FIT, SIT and SIWu in rice breeding might be advantageous for enhancing lodging resistance.2. For all the tested traits, except PL, LUFI, FIT, and SIWu, transgressive segregation was detected. There were significant differences between Zhenshan 97B and Miyang 46 for all the traits.3. A total of 21 QTLs showing significant additive effects and 31 significantly additive by additive (AA) interactions were detected for PH and its component traits. While the contributions to the phenotype variance due to additive effect of a single QTL had a wide range of 3.57%~28.21%, the contributions due to epistatic effect of a single AA interaction showed a smaller range of2.06%~10.95%.4. Sixteen additive QTLs were detected for the characters of the basal I > II elongating...