| Drought, as one of the serious ecological environment issues on a world scale, is the most limiting factors effecting rice (Oryza sativa L.) production. However, breeding the strong drought resistant rice varieties and cultivating them with water saving model is an available approach for sustainable delevopment of agriculture, the first and most crucial step is identifying and exploring drought resistance gene resources. Dongxiang wild rice (Oryza rufipogon Griff., hereafter DXWR), recognized as the progenitor of Asian cultivated rice, harbours massive favorable hidden genes, therefore identifying drought resistance gene in DXWR is of great significance to rice breeding program.In this paper, cultivars, DXWR and backcross inbred lines (BILs) R 974//R 974 /DXWR at BC1F5 generation derived from backcross between Indica restorer line R 974 (Oryza sativa L. ssp. indica cv.) and DXWR, were employed to investigate and analyze pheno-physiological drought resistance traits at seedling stage and at whole growth stage. Combined with gray relation analysis, principle component analysis and step wise regression analysis, the sssessment index system of drought resistance were established at seedling stage and at whole growth stage, respectively, and also some intermediate materials with drought resistance were selected for further research. The effects of drought stress on pheno-physiological, root and grain yield traits in rice were further analyzed. This paper also clearly demonstrated the relationship between each trait and rice drought resistance, and briefly expounded some greater differences in drought resistance in various DXWR and its genetic models of drought resistance.The main results were summarized as follows:1. Four accessions of the DXWR chosen among three surviving populations were compared with fifteen cultivars on drought resistance at the seedling stage, by measuring eight traits. The DXWR was more resistant to drought stress than other cultivars indicated by maximum root length (MRL), shoot length (SL), dry root weight (DRW), fresh root weight (FRW), root relative water content (RRWC) and drought resistance index (DRI). Among these eight traits, MRL, SL, DRW, FRW and RRWC contributed more than others to drought resistance for rice seedlings. The four accessions of the DXWR were tremendously differentiated on drought resistance expressed by the comprehensive drought resistance grade value and drought resistance index, and DXWR 3 from Shuitaoshuxia population was the best. The drought resistance of DXWR was related closely with the original habitats. As a result, the DXWR could be precious resources for genetic improvement of drought resistance in cultivated rice. 2. Four upland rice, sixty BILs and their parents were employed to evaluate drought-resistance at seedling stage in greenhouse. Nine traits were recorded for assessment of drought resistance, MRL, NR, SL, DRW, FRW, RRWC, leaf relative water content(LRWC), level for rolling leaf (LRL) and seedling survivability under repeat drought (SSRD). Comprehensive assessment of drought resistance based on the principal component analysis (PCA) indicated the line'1949'showed the highest resistance. The results of the stepwise regression analysis demonstrated that FRW and RRWC significantly influenced the drought resistance, thus could be used as comprehensive index for assessing drought resistance at the seedling stage. The inheritance of drought resistance at seedling stage, based on comprehensive drought resistance value (CDRV), was mostly controlled by two independent genes plus polygene.3. In whole growth period, Twelve pheno-physiological traits correlating with drought resistance were monitored under the water stress and non-stress treatments for a set of 114 BILs, which were plant height (PH), tillers number per plant (TNP), effective tillers number per plant (ETNP), spikelets per panicle (SP), filled spikelets per panicle (FSP), length of panicle (LP), panicle density (PD), 1000-grain weight (TGW), seed setting rate (SSR), grain weight per plant (GWP), LRWC and LRL. GWP is the most sensitive trait which is influenced by drought. Single variable stepwise regression, path analysis and gray correlative analysis were conducted between the relative value of various traits and drought resistance coefficient. The results showed that six traits including LRWC, TNP, ETNP, TGW, PH and ETNP significantly influenced the drought resistance and those six index traits could be feasible to assess and predict the drought resistance in rice at the whole growth stage. The inheritance of drought resistance at whole growth stage based on CDRV was mostly controlled by two independent genes plus polygene. The comparisons between five direct assessment of drought resistance and comprehensive assessment of drought resistance indicated that the drought resistance index was most suitabe for directly assessing drought resistance. |
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