| It was estimated that about 20% of cultivated land was affected by salinity in the world. High concentration of salt would not only retard the growth and development of crops, but also affect the yield and quality of crop products. Rice is one of the most widely grown crops in the world with moderate sensitivity to salinity. The most effective approach to improve rice salt tolerance was breeding salt tolerance variety. Raising and popularizing rice variety tolerant to salt would be helpful to utilize effectively salt land, enlarge rice planting area and increase rice yield .Jiucaiqing(JCQ), a japonica landrace from Taihu valley, was an excellent salt tolerance germplasm which could head and set seed under 0.5% NaCl stress.To understand inheritence and identify molecular markers linked to QTLs for rice salt tolerance, the following experiments were conducted.1.Determination of salt concentration and indices during the screening of rice varieties with salt toleranceThe seedlings of three varieties with tolerant, moderate and sensitive to salt stress were grown in nutrient solution with control. 0.5%, 0.6%, 0.7%, 0.8%, 0.9% NaCl to determine the suitable salt concentration and indices. It indicated that the treatment with 0.8% NaCl is suitable to distinguish the difference of salt tolerance among rice varieties. Under 0.8% NaCl stress, there was significant correlation between Na+:K+ in roots and rating of salt tolerance.It was suggested that the best way to identify rice salt tolerance is to measure rating of salt tolernce combining Na*:K" in roots under 0.8% salt stress. 2.The inheritence and QTL analysis of salt tolerance at rice seedling stageA F2 population from the cross JCQ (japonica} and lR36(indica) was used to analyze inheritence of rice salt tolerance by genetic model of major-gene and polygene. under 0.8% NaCl stress, the five traits including rating of salt tolerance(STR), Na+:K+ in roots(Na+:K+X fresh weight of shoots(FWS), dry weight of shoots(DWS) and root length(RL) were controlled by two major genes and with effect of polygenes. Heritability of major genes of five traits were 17.8%, 53.3%, 82.3%, 52.3% and 59.4%, respectively. Both additive and dominance effect were important in the inheritence of all traits studied.Using 147 F2 progenies derived from the cross JCQ and IR36, a SSRs genetic mapwas constructed. On this map 57 markers distribute among 12 rice chromosomes and span about 1,142 cM in the whole rice genome with the average distance of 20.0cM between markers. Twenty three markers which linked with traits of salt tolerance were indentified by ANOVA . Fifteen QTLs for seven traits were detected by interval mapping approach, among of them, three QTLs for STR on chromosome 1, 5 and 9; two QTLs for FWS and DWS in the same interval region of chromosome 8 and 9; two QTLs for RL on chromosome 4 and 5 ; two QTLs for Na+:K+ on chromosome 2 and 6; two QTLs for Na content on chromosome 4 and 7; two QTLs for K content on chromosome 4 and 5. Fifteen QTLs accounted for 6.4-19.3% of phenotypic variation. In addition, additive and dominance effects for all detected QTLs were also analyzed. 3.The effects of salt stress on agronomic traits and their QTLs at rice adult stageThe effects of salt stress on agronomic traits of same F2 population were investigated. The result showed that the plant height and length of main panicle were retarded,heading time delayed, the numbers of spikelets in main panicle and seed set percentage were reduced. Under the salt stress the numers of spikelets in main panicle, seed set percentage and grain weight were reduced by 40.8%, 53.0% and 33.9%, respectively. Variation coefficient of seed set percentage was 36.1% under no salt stress , while 90.3% under salt stress.QTLs for five agronomic traits were indentified under salt stress or not. The result showed that thirteen QTLs were indentified under no salt stress, among of them, four QTLs for plant height on chromosome 7, 8, 9 and 11; four QTLs for heading time on chromosome 4, 8. 9 and 12; two QTLs for...
|
PDF Full Text Request