Drought Resistance Identification Of HFB And HH2B And Preliminary QTL Analysis Using Their F_3-4 Families

Drought is one of the most important abiotic stress factors limiting rice production in many countries and regions, development and adoption of drought resistant and high-yielding rice varieties is an effitive method to solve this problem. Drought resistance of rice is very complex, it is important to study drought resistance mechanism and find more genes involved in drougth response in rice.Huhan2B (HH2B) is a new japonica CMS maintainer, developed from BC breeding procedure that introduced drought resistance into HanfengB (HFB) as a CMS maintainer with good grain quality, the hybrid combination Huhan2A/Xiangqing has been released by Shanghai Municipal Government. The experiment was carried out to learn the differences in drought resistance between HH2B and HFB under both well-watered and drought conditions; The expression level changes of15predicted genes was analyzed in five different tissues of HFB and HH2B plants under simulated drought stress condition; the F3.4popolation was developed between HFB and HH2B, parents and phenotyped under well-watered and drought in order to conduct QTL analysis, and to explore genetic components underlying the breeding gain in drought resistance in the future.1. The comparison of drought resistance between two parents in PVC under well-watered and drought conditions revealed that:Under more severe drought stress, in early tillering stage and adult stage, the leaf relative water content, of HH2B was significantly higher than HFB, In adult stage, photosynthesis and leaf osmotic potential of HH2B were significantly higher than HFB, single tiller withered leaf number andof HFB was significantly higher than HH2B. In addition, the recovery rate of leaf rolling of HH2B was significantly faster than HFB.2. The agronomic traits of HFB and HH2B were evaluated under normal and drought conditions, spikelet length, spikelet number, grain number per panicle of HFB and HH2B were reduced under drought stress, the reduction of the grain yield was mainly due to the reduction of the grains number per panicle, spikelet number, grain number per panicle, spikelet fertility percentage of HH2B were significantly higher than HFB.3. In this study, principal component analysis showed that the relative photosynthesis, relative plant height and relative length of the last third leaf before rehydration were mutually independent indicators, and had lager role in drought resistance of HFB and HH2B. These indicators could probably be useful for drought resistance identification of HFB, HH2B and their progenies groups.4. HFB and HH2B were used as materials, the study analysed expression level variation of15predicted genes in leaves, leaf sheaths, spike, root tip and root hair zone under25%PEG stress. It was observed that some genes had significantly higher expression under a longer time stress than the control in HH2B.5. In the study, a population was derived from a cross between HFB and HH2B, the ratio of the phenotypic data in well-watered and drought conditions of7traits (relative panicle numbers, relative panicle length, relative spikelets’s number per panicle, relative grains number per panicle, relative fetility percentage, relative100-grain weight, relative grain yield) of parents and pupolation combined with SSR information for QTL analysis, there were4additive QTLs and4epistatic QTLs were detected.