The effect of drought stress on yield and panicle traits of different type super rice varieties during panicle initiation to grain filling stage

With experiment cultivated in pots and contrived simulation of drought stress,method to determine soil moisture by electronic balance(made in Shanghai) and W.E.T Sensor(ML2x type,made in USA),the effect of drought stress on panicle traits and yield components of different panicle type rice varieties(more or middle grains per panicle) was studied.The results showed that middle level drought stress of different stage from panicle initiation to grain filling had various degree of influence on rice panicle characteristics,yield and its components,and caused the reduction of grain yields(more than 20% of each variety).Water treatment from 15 to 30 days after panicle initiation had the greatest influence,followed by 0～15 d and 15～30 d after flowering,however,0～15 d after panicle initiation had the least influence.Compared with normal water supply,drought stress during panicle growth and development stage led to panicle length decrease obviously and numbers of the secondary branches and total spikelets per panicle reduce significantly,and drought stress during grain filling led to great reduction of filled grain numbers,fertility rate and 1000-grain weight, which caused the reduction of grain yields.The affecting degree of drought stress on panicle traits and yield components varied from these varieties because of different sensitivity to water stress,and the influence on super rice varieties was less compared with common hybrid rice variety(Shanyou 63) in general The rice varieties with more grains per panicle(eg.Guodao 6,Liangyoupeijiu and Ⅱyou 7) showed lower degree influence of drought stress on yield components and panicle traits than those with middle grains per panicle(eg.Tianyou 998,Ⅱyou 602 and Shanyou 63).