| Two experiments were conducted to study the inheritance of quality characters and the mutagenic effect of ~?-ray on appearance traits in indica hybrid rice. The main results were as follows:1.The inheritance of quality characters in good-quality hybrid riceTen good-quality parents including 5 CMS lines and 5 restorers were used to make incomplete diallel crosses for studying the inheritance of quality characters in indica hybrid rice. F1 and their parents were sown and planted under early, ratoon and late seasons respectively. To harvest the seeds in near mature date, all stocks were sown in different date for both early and late seasons. Genetic analysis was conducted by using genetic models including genotype >( environment interaction for 1 2 quality characters, i.e. brown rice%(BR), milled rice%(MR), head rice%(HR) , grain length(GL) , kernel length(KL) , length/breadth ratio(LBR), chalky rice% ( CR), chalky score (CS), kernel translucency (KT)1 gelatination temperature( CT), gel consistency( GC)and amylose content (AC). .The results showed that:(1 )The genetic variations(Vg) for each of 12 characters accounted for more than 64% of phenotype variation, especially for traits BR, MR, GL, KL, LBR, GT and GC, which accounted for 92.4%-98.7%, indicating that all of quality traits were mainly controlled by genetic effect.(2)The genetic variations of all characters were mainly attributable to maternal additive (VAin) and direct additive (VA), with maternal additive effect predominating for BR, MR, HR~ GC, KT, GT and AC, while direct additive effect predominating for KL, LBR, CR, CS and Ge. Except for BR and HR, slight cytoplasm effect was also detected in other 1 0 characters.( 3 ) Comparing with genetic main effect , the genotype X environment interaction effects( VGE)were much less important~ although there were some interaction variation components were significant for each character. Among 12 characters, the VGE for HR, CR, CS and KT was higher, which accounted for 33.2%, 35.l%~ 31.3%and 27.1% of phenotype variation respectively.(4) Heterosis were unable to be detected in most of characters except for LBR, GC and GT (ASS) with negative dominances, and AC with positive dominance. The heterosis found for these four traits were unfavorable for quality improvement in indica hybrid rice.(5) Comparing contribution between CMS lines and restorers to F1 quality improvement showed that among 12 characters, eight (BR, MR, HR, LBR, CR, CS, GC, AC) were much more influenced by CMS lines than that by restorers, two ( GL and KT) almost equally affected by both, and only two (KL and GT) showed more influence by restorers than by CMS lines, suggesting that using CMS lines with good quality were crucial in breeding of high quality hybrid rice.(6)The evaluation of genetic effects for parents under three seasons demonstrated that in CMS lines, Jin23A was favorable for improving milling quality, DeshanA and ZhongjiuA were better for appearance quality improvements DeshanA, with low AC( <13%)and high GC ( > 65mm), was also recommended as better parent in cooking quality improvement. In restorers, Yahua No.1 was an ideal stock for developing high quality indica hybrid rice.( 7 ) Significant genetic correlations were uncovered between following traits: MR and HR, GL and KL, GL and LBR, CR and CS, GL and AC. Except for negative genetic correlation between GC and AC, all others showed positive correlation.2.The mutagenic effects of y -ray irradiation on appearance quality inindica riceLongtepuA (TA) and Zhenshan97A (ZA) were two CMS lines with high yield general combining ability and had been utilized broadly in breeding of hybrid rice. However, the grain quality especially for appearance quality in these two CMS lines was unfavorable. Short grain and high chalkiness were two main shortages. In present study, the dry seeds of LongtepuB ( TB) and Zhenshan97B ( ZB), the maintenance lines of TA and ZA, were used for irradiating by Y -ray to investigat...
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