Effect of drought stress at different growth stages on grain yield of indica hybrid rice

[Objectives]Many of the rice-growing areas lack adequate irrigation facilities.This study explored the effect of drought stress at different growth durations on grain yield of indica hybrid rice in the plateau mountain region of southwest China.[Methods]We excepted to provide very useful information to cope with seasonal drought which occurred frequently in the local areas.Three indica hybrid rice cultivars including‘Liangyou 585' ‘Jinyou 785 'and ‘Ziyou 93 ' were used as materials for tanks-experiment in two years.Ten days after transplanting,water was controlled by relative water content of soil at a 20cm depth around 70% in six growth periods,i.e.,productive tillering stage(PTS),unproductive tillering stage(NPTS),early stage of panicle initiation(EPDS),late stage of panicle initiation(LPDS),ear sprouting stage(ESS),grain filling stage(GFS) and continuous flooding as control check(CK).Each of six stress treatments was flooded after 20 days of drought treatment,respectively.[Results]Compared with CK,grain yields of all six drought stress treatments decreased by 3.6%-31.1%.Among these drought stress treatment,the highest grain yield was achieved by the drought stress at unproductive tillering stage.And the lowest grain yields were achieved by drought stress at productive tillering stage or early stage of panicle initiation,followed by drought stress at heading period,late stage of panicle initiation and grain filling stage.Compared with CK,productive panicles per unit area were reduced by drought stress treatment in productive tillering growth period,the number of spikelet per panicle and seed setting rate was reduced by drought stress in panicle initiation growth period,and 1 000-grain weight was reduced by drought stress in grain filling period.In the rice population forming process,tiller growth was restrained by drought stress in productive tillering period,which caused smaller biomass accumulation de-spite higher effective spike rate.The top three leaves and productive leaves were restrained by drought stress in panicle initiation period,lower LAI caused smaller dry matter accumulation,and dry matter translocation and distribution was reduced by drought stress in heading and grain filling periods.[Conclusions]Long period(20d) moderate drought stress at different development stages led to the yield losses of hybrid indica rice in varing degrees,which could not be completely compensated even by rewatering.