Studies On Screening Of Identification Method, Physiological Characteristics And Combining Ability Analysis Of Pre-harvest Sprouting Tolerance In Rice

The phenomenon of pre-harvest sprouting(PHS) exists widely before the hybrid rice harvested.It brings bad effects on seed quality and comercial value and limits the exploitation of hybrid rice.At present,the most of male sterile lines in seed production are sensitive to PHS.It is even worse if meeting the rainy days before harvesting.It has been one of the most important problems to control the PHS in rice breeding.In this study,we reported the screening of the identification methods of PHS tolerance,the study of PHS physiological characteristics of hybrid seeds and the analysis of combining ability of PHS. The detail results were summarized just as follows:1.The screening of the identification methods of PHS toleranceThree methods,the plastic sack sprouting test,the grains petri dish sprouting test and artificially induced sprouting test,were selected to identify the resistance of PHS of the hybrid seeds of 10 combinations.The result indicated that all the three methods were able to identify the resistance of PHS in rice,but the plastic sack sprouting test was the most simple and reliable one.While using the plastic sack sprouting test to identify PHS resistance,the best period was in 20 days,25 days and 30 days after pollination and three times weighted germination percentage was the appropriate identification indexs.While using the grains petri dish sprouting test to identify PHS resistance,the best period was in 15 days and 20 days after pollination and two times weighted germination percentage was the appropriate identification indexs.2.The studies of physiological characteristics of PHSTwo combinations,D69A(a high-sprouting CMS)/R527(a restorer line) and D23A(a low-sprouting CMS)/R527,were used to study the physiological characteristics of PHS. The results indicated that the hybrid seeds of D69A/Shuhui 527 that pre-harvest sprouting percentage was 44.84%,was higher than that of D23A/Shuhui527(5.59%).The amylase activity of the hybrid seeds of D69A/Shuhui 527 were higher than that of D23A/Shuhui527,while in the treatment of higher temperature and higher humidity.And also indicated that ABA/GA content ratio of D69A/Shuhui527 was shown a parabolic trend, but that of D23A/Shuhui527 was shown anti-parabolic trend.During late stage of maturity, GA content advantage of endogenous ABA/GA and a higher level of amylase activity in grains may be the major physiological basis of PHS in the production of hybrid rice.3.Analysis of combining ability of susceptibility of pre-harvest germinationThe combining ability for susceptibility of pre-harvest germination was studied with 6 male sterile lines and 5 restorer lines by the method of p×q incomplete diallel cross design.The results indicated that the susceptibility of pre-harvest germination was affected by additive and non-additive gene effect,but the effect of additive genes was predominant.The correlation coefficients between susceptibility of pre-harvest germination value of parents and GCA effects was 0.6189.In other words,the higher susceptibility of pre-harvest germination value of parents,the greater the GCA effect in progeny population.The susceptibility of pre-harvest germination was influenced more greatly by female than that of male.The estimates of broad-sense and narrow-senes heritability were 92.75%and 54.64%,respectively,which indicated that selection for the resistance could be carried out in early-middle generation of the hybrids.