Analysis Of Main Agronomic Traits And Evaluation Of Breeding Utilization For A RIL And Its Test-crossed Populations In Rice

Most of agronomic traits belong to quantitative characters which controlled by multiple genes in rice. Recombination inbred lines (RIL) are an ideal population for studying the genetic rules of quantitative traits and rice breeding. Minhui 3301 (MH3301) is an elite three-line hybrid restorer. Currently, MH3301’s thirteen cross combinations have passed examination, including five combinations authorized by National Crop Variety Examination and Approving Committee. A population consisting 1529 RIL(F8) constructed by single seed descent from a cross between Mianhui436 and Shuhui527, which parents of Minhui3301.44 excellent lines (named SLSSD) and 236 RIL selected from RIL (F8) population. In the thesis, two test-crossed populations were constructed from cross between RIL and SLSSD and two male sterile lines (Tianfeng A, Huifeng A). The eleven important agronomic traits of RIL, SLSSD and their test-crossed populations were investigated and analyzed. The breeding value of the populations was discussed. It was hoped that the study would be usefulness for the QTL mapping of important agronomic traits and breeding utilization. The main results as follow:1) The frequency of phenotypes of the important traits was approximately Gaussian distributions and showed continuous variation in RIL and its test-crossed populations. The results revealed that all of agronomic traits belonged to quantitative traits which controlled by multiple genes. The broad sense heritability of these traits was between 0.36-0.97, the broad-sense heritability of kilo-grain weight was the highest, up to 0.97, and the broad-sense heritability of effective tillers per plant was the lowest, only 0.36.2) The main agronomic traits of recombinant inbred lines (RIL) showed significant positive correlation with those of two testcross populations, but the correlation degrees of different characters have large difference. Yield per plant (YD), grain number per panicle (GPP) and spikelets density (SD) of RIL population was lower correlated with those of two test groups (Tianfeng combinations and Huifeng combinations), the correlation coefficient of which is in 0.26-0.39. Kilograin weight (KW), grain length (GL), grain width (GW) and Grain length to width ratio (GLWR) of RIL were higher correlated with those of two testcross populations, correlation coefficient in 0.79-0.85. It suggested that selection of kilograin weight and other grain traits in the two kinds of hybrid combination was more reliable than that of yield per plant and other yield characters by selecting the corresponding characters in the restorer.3) Heading date (HD), effective tillers per plant (TP), plant height (PH), YD, panicle length (PL) and GPP were significant difference between the RIL and SLSSD population, which indicated that the selection of SLSSD is very effective on improvement of these traits in the restorer lines. Meanwhile, TP, YD, PL, GPP and SD of the test crosses of RIL and SLSSD with Tianfeng A or Huifeng A showed significant or extremely significant difference, which further indicated that the selection of SLSSD was also effective on improvement of TP, YD, PL, GPP and SD in hybrid combination in rice. The 10 combinations, which were screened in the study and more than Tianyou 3301 by 10% in yield per plant, can be directly used as breeding of hybrid rice by application evaluation.4) In RIL population, variation of HD, TP, GPP, KW, GW and GLWR can explains variation of YD by 90.2%, of which TP and GPP contribute to the YD with 33.5% and 49.7%, respectively. In the TA/RIL group, TP, GPP and KW could explain 67.7% of the variation of the YD, of which the TP and GPP could explain 30.8% and 21.5% of the YD variation, respectively. The HD, TP, GPP and KW contribute to 83.6% of the YD variation in the HA/RIL group, in which TP and GPP with 36.2% and 31.4%, respectively. In summary, mainly factors affecting the YD were the TP and the GPP in both RIL and their different testcross population in this study, though the proportion of them was different in the different population.