| Drought is one of important abiotic factors for the decrease of rice yield. Screening of rice varieties with drought-resistance therefore is the key to the sustainable development of rice production and food supply. In this thesis, a backcross inbred lines (BIL) population including234lines was chosen as the research object, which was derived from an interspecies cross XieqingzaoB(Oryza sativa)//XieqingzaoB/Dongxiang wild rice (O.rufipogon). The morphological, physiological and yield characteristics were investigated in detail under both normal and drought stress conditions at seedling and booting stages. Through subordinate funcation analysis, principal component analysis and step wise regression analysis, the drought-resistance of population was analyzed comprehensively. The assessment index system of drought-resistance was established at both seedling and booting stages. Meanwhile, by using constructed molecular linkage map, we mapped the drought-resistance QTL locus from Dongxiang wild rice at both seedling and booting stages. These results will contribute to futher explore the molecular mechanism of the drought resistance of Dongxiang wild rice.The main results were summarized as follows:1. Upland rice, BILs and their parents were employed to evaluate drought-resistance at seedling stage under PEG6000simulated drought stress. Ten traits were recorded for drought-resistance, such as MRL, NR, SL, DRW, FRW, DSW, BRT, WR,DR. Comprehensive assessment of drought-resistance based on the principal component analysis (PCA) was applied. The result of the stepwise regression analysis demonstrated that MRL、BRT and WR significantly were influenced under drought condition. Therefore, the three index could be used to assess the drought-resistance at seedling stage.2. According to the results of index screening of drought-resistance, we used the established genetic linkage map to analyze the drought-resistance related QTLs for ten traits at seedling stage, including MRL, BRT, WL, etc. A total of16QTLs were detected in eight traits under drought condition. Among them, there were3QTLs for MRL,1QTL for BRT and4QTLs for WR. The addictive genetic effect of qMRL-4, qMRL-7and qBRT-7was negative, indicating the alleles from DongXiang common wild rice. The general contributions of qMRL-4and qMRL-7were11.87%and the contribution of qBRT-7was24.11%, which could be a large effect QTL.Four QTLs detected for WR were located on1,7and11chromosomes,which addictive effect was positive, indicating the alleles from Xieqingzao B and decreasing the drought-resistance ability of population. Meanwhile, the additive genetic effect of QTLs in other traits were all positive, indicating these locus from parent Xieqingzao B. The other traits variations between normal condition and drought condition might be caused by their own genetics.3. Drought-resistance of the BILs population was appraised by the traditional method at booting stage in rainless shed. Nine traits related with drought-resistance were analyzed under drought stress condition and normal condition, including EIPN, SP, FSP, PL, PD, TGW, SR and GWP. The results showed, to different extent, the nine traits were all influenced under drought condition, among which the lines with weak drought-resistance were more seriously influenced than that with strong drought-resistance. PL was not sensitive to drought stress, otherwise TGW expressed sensitive to drought stress.Other yield traits were very sensitive. In addition, by applying subordinate funcation analysis, principal component analysis, and step wise regression analysis, we screened three index, including SR, GWP and TGW, which could be used as evaluation index at booting stage.4. A total of32QTLs for yield traits were detected at booting stage,which located on chromosome1,2,3,7,8,10,11, respectively. Among these traits, SR, GWP and TGW were respectively identified4,2and8QTLs.The contribution of four main effect QTLs including qSR-1, qSR-10, qGWP-1and qGWP-1a was41.30%、43.48%、33.93%and23.35%,respectively.Their addictive effect of QTLs for SR、GWP and TGW were all negative, indicating the alleles from DXWR. These results showed that the most QTLs of the three traits with enhancing alleles came from DXWR, suggesting DXWR had drought-resistance genes.5. We analyzed the correlation between comprehensive index (D value) at seedling and booting stages. The correlation coefficient was0.935, reaching a extremely remarkable level. The lines with strong drought-resistance at booting stage were identical with the lines at seedling stage. Meanwhile, the lines with weak drought-resistance at seedling stage were identical with the lines at booting stage. It indicated that the drought resistance at seedling stage was closely related to that at booting stage. Moreover, ten lines with strong drought-resistance at two stages had been obtained.6. There were pleiotropic or tightly linked QTL regions respectively at two stages by comparing the QTL mapping results of seedling and booting stage. And some QTL regions at booting stage were found to be the co-localized regions at seedling, indicating the seedling was associated with booting stage closely again.7. The physiology and biochemistry properties were studied between strong and weak drought-resistance lines at booting stage under drought condition. The results indicated that soluble sugar and proline content accelerated more rapidly in stronger drought-resistance lines than that in weaker ones with water stress aggravated. The contents of MDA increased in better drought-resistance lines obviously less than that in weaker ones. The above results indicated that the three index were remarkably related to drought-resistance. |
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