Analysis Of Grain Yield Formation Components Of Extra-heavy-panicle Type Mid-season Indica Hybrid Rice

Increment of panicle weight is the main way of super high yield rice breeding to increase the yield.A two-year field experiment was conducted in Chongqing,a rice-growing area in upper reaches of Yangtze River,to explain the reasons why panicle weight of extra-heavy-panicle type(ET)(Yixiangyou1108,Leyou918,Qianxiangyou677)was significantly higher than heavy-panicle type(HT)(Nei6you138,Yixiangyou2905,Xida5you727)and medium-panicle type(MT)(Shenliangyou5814,Yixiang2115,Nei6you1116)via measuring growth stages duration,tillering dynamics,functional leaves morphology after booting,biomass yield increment dynamics of sigle stem and its organs after booting,grains yield and yield components.The main results are as follows:1.On the basis of the characteristics of sink capacity,the significant increase in yield and panicle weight of ET was attributed to the significant increase in spikelet amount per panicle of ET compared with HT and MT.Compared with HT and MT,the advantage in panicle weight accumulation of ET is reflected after milky stage.2.On the basis of the characteristics of biomass yield accumulation,the biomass yield of ET is significantly higher than that of HT and MT,which is the key factor for the panicle weight of ET to be significantly higher than that of HT and MT.The accumulation dynamics in photosynthate of ET after booting can be simulated by logistic equation,and the maximum photosynthate accumulation rate of ET is about 15-16 days after heading stage.The accumulation rate of photosynthetic of ET was significantly higher than that of HT and MT in the slow increase stage(25~39 d after heading stage),which made the accumulation increment in photosynthetic of ET after milky stage significantly higher than that of HT and MT,which was the direct reason for the significant increase of biomass yield of ET.3.On the basis of the characteristics of photosynthetic products,the higher biomass yield of ET was attributed to leaf area duration(LAD)and specific leaf weight duration(SLWD),which were significantly higher than HT and MT,and leaf drooping angle duration(LDAD),which was significantly lower than HT and MT after the milking stage(MS),which are the basic reasons for the significant increase in biomass yield of ET after booting.LDAD was more effective than LAD or SLWD for characterisation of biomass yield.Therefore,LDAD can be termed a reason to explain why the biomass yield of ET is significantly higher than that of HT and MT.The functional leaf type model diagram of ET was established,in order to provide the quantitative standard of leaf type model for the selection of ET varieties in the future,4.On the basis of the characteristics of photosynthetic translocation,the harvest index of ET was significantly higher than that of HT and MT,which was also the key factor for the panicle weight of ET to be significantly higher than that of HT and MT.The higher harvest index of ET was due to the output amount(OA),output rate(OR)and transformation rate(TR)of photosynthate in the stem after mikey stage,which were significantly higher than HT and MT.TR was more effective than OA or OR of stem in characterising harvest index.Therefore,TR can be termed a reason to explain why the harvest index of ET was significantly higher than that of HT and MT.The main position of photosynthetic products retention in varieties with low panicle weight after milky stage may be 1st and 2nd internodes under panicle.