| Researches on and exploitation of the two-line hybrid rice were developed based on the discovery of Hubei Photoperiod-sensitive Genie Male Sterile Rice (HPGMR) in China in early 1980s. Numerous studies in this field were carried out and many practically useable sterile lines were developed in past more than 20 years, which has being made China in the lead level on the world. Further studies in this field and the development of the theories and techniques in two-line hybrid rice will provide some new breeding foundation for two-line super hybrid rice.In recent years, several new photo-thermo sensitive sterile germplasms, the characteristics of which are deferent from original Environmental-sensitive Genie Male Sterile (EGMS) Rice, were found or bred. They may be used as breeding tools to develop new types of two-line hybrid rice. Figuring out their genetic character and physiological property is the objective in the study.Two new EGMS lines, D38S and E5-2S, used in the study, which were bred by Gao Yizhi of Yichun Agricultural College, Jiangxi, through crossing between indica and japonica rice. He reported that the characteristics of fertility alterations in D38S and E5-2S were opposite to the original EGMS rice. The characteristics of fertility alteration of D38S and E5-2S were analyzed under the natural photoperiod and temperature conditions in Wuhan. The fertility reactions were identified under controlled photoperiod and temperature treatments in phytotrons. The genetics characteristics were studied through crossing with several normal rice varieties and original EGMS lines. The results showed as follows:1. D38S expressed typical photoperiod sensitive sterility in WuHan. The characteristics of fertility alteration from sterility to fertility and then to sterility was obvious from May to September. In the period of sterility, the pollen fertility was 0.14%, and there was no seed setting. In the period of fertility, the pollen fertility reached to 45.24%, the seed setting varied from 17.22% to 64.54% with an average of 28.28% seed setting. Through analyzing the trend of fertility alteration under the natural photoperiod and temperature conditions, we could find that the fertility rise when temperature became higher and higher, then it descended beyond the optimal temperature. There were same characteristics of fertility alteration in the ratoon plants and seeding plants. Thecharacteristics of fertility alteration of E5-2S were also obvious. The pollen fertility was 48.48% under the long day photoperiod and high temperature conditions.2. Under the controlled conditions, D38S and E5-2S were fertile in the long-day photoperiod treatments and were sterile under short-day photoperiod treatments, but extreme high temperature could cause physiological sterility, D38S, for example, was highly sterile under 35℃/LD condition. The optimal fertile temperature of E5-2S was lower than 30℃. These results indicated that the characteristics of fertility alteration in D38S and E5-2S were short potoperiod-sensitive male sterile.The fertility of D38Sand N5088S was opposite but their growth was identical in the direction of photoperiod reation.3. The genetic analyses showed that the short photoperiod sensitive male sterile characteristics belonged to recessive inheritance and the fertility was controlled by nuclear gene. Normal rice varietis could restore its fertility. The genetic segregation of fertility in F2 population fit in with the model of one or two major genes. But there existed difference among combinations. Pollen fertility of F1 plants crossed by short-day photoperiod sensitive male sterile rice with the long-day potoperiod sensitive male sterile rice was normal fertile, which indicated that these two types of sterile genes were not allelic.4. Some breeding short photoperiod sensitive sterile lines were derived from the offsprings of D38S/C407. E5-2S/Huaxianzhan, E5-2S/PA64S and D38S/N5088S and their backcrosses. The fertility alteration characteristics of these lines were also obvious, and...
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