Classification, Inheritance Of Environmentally Enduced Genetic Male Sterile (EGMS) Lines And Parent Selection For Breeding Of Inter-Subspecies Hybrid Rice

The hybrid rice breeding using two lines method and utilization of heterosis of inter-subspecies are important research subjects in the rice genetics and breeding field. Some theoretical fundaments for breeding of two lines hybrid rice and inter-subspecies hybrid rice were studied. They include the classification of environmentally enduced genetic male sterile (EGMS) lines of rice based on the fertility response to photoperiod and temperature, inheritance of photoperiod sensitive genetic male sterility (PGMS), plant type model and cross methodology for breeding of super high yielding hybrid rice, etc. The stability of EGMS lines to be used into breeding of two lines hybrid rice was analyzed and available cross method for breeding of inter-subspecies hybrid rice with strong heterosis and ideal plant type was evaluated. Fertility responses to photoperiod and temperature were studied in 101 EGMS lines under nine controlled regimes combining three photoperiods (15.0, 14.0 and 12.5h) X three temperatures (30.1, 24.1 and 23.lC) and natural conditions at Hangzhou. According to the variance analysis of seed-setting data, 96% of the total EGMS lines studied could be divided into three types as follows: photoperiod-sensitive genetic male sterility (PGMS), thermosensitive genetic male sterility (TGMS) and photo-thermosensitive genetic male sterility (P-TGMS). Among the japonica EGMS lines studied, PGMS, TGMS and P- TGMS accounted for 32.3, 9.7 and 51.6%, respectively. However, among the indica EGMS lines, no PGMS lines were detected and most of them were TGMS or P-TGMS (61.4 and 35.7%, respectively). Ecological pressure of daylength and temperature on selection of PGMS or TGMS was analyzed under the environments of different latitude regions i.e. Guangzhou (230 08?N). Fu.zhou (260 05?N). Changsha (280 12?N). Hangzhou (300 19?N). Nanjing (32 0 N) and Shenyang (410 49?N). It was shown that both selection pressure on male sterility under long-day/low temperature and male fertility under short- day/high temperature is unsuitable under all sites. The male sterility change was observed in the segregation generations of six crosses of Nongken 58S, a PGMS line and normal lines. The continuing distribution curve of seed-setting in the F2 generations was detected. The male sterility in most of the F3 lines derived from the male sterile plants in F2 was inheriting stable, but in few lines was unstable. There was distinct discrepancy in seed-setting segregation among different crosses or yearly discrepancy in the same cross, which is iii j) attributed to the effects of genetic background and environmental factors on expression of PGMS. The results suggest that it is important to select the PGMS or TGMS lines suitable for practical utilization under multi-sites or under the controlled conditions and pay attention to breeding hybrid rice using EGMS for temperature change. Some plant type components were observed and compared among 65396 (Peiai64SIE32), 65002 (Peiai64S/93 II), newly developed super high-yielding hybrids of inter-subspecies rice using two-lines, and Xieyou93OB, using three- lines. From the results the rational model of plant type components are refined for reference of breeding of super high-yielding hybrids of inter-subspecies rice with yield potential over 12t/hni2. The development of wide compatible male sterile lines of in...