Effect Of Different Planting Density On Population Structure And Yield Formation Of Heavy Panicle Hybrid Rice STA/ILR1

Having the biggest population and limited agricultural resources, China faces great challenge on food security. Therefore, it’s our goal to improve rice yield per unit area and promote rice production by high-yield breeding and cultivation methods. The objectives of this study were to analyze the effects of different plant density on the growth and the dynamics of dry matter and other process of yield formation in heavy panicle hybrid rice. Our results will provide theoretical and practical basis for identifying a suitable density for high yield, explore the yield potential of a new partial interspecific hybrid rice combination.To explore high yielding cultivation method for hybrid rice, a newly bred heavy panicle partial interspecific hybrid rice(STA/ILR1), a three-line indica hybrid rice(Q-you 6), a two-line indica hybrid rice(Feng Liangyou Xiang 1) and an indica/japonica inter-subspecific hybrid rice Yongyou 15 were transplanted in 5 different plant density treatments and three replications, population structure, dry matter production, yield and yield formation were studied. The main results are as follows:1. Environment, climate, cultivation conditions and genetics factors have significant effect on plant height, length and width of the three top leafs and angle of flag leaf of heavy panicle hybrid rice. However, there were no significant differences between different plant densities. The panicle numbers grew slowly at first, then increased rapidly, and then slowly falling in the growth processes, the rates of growth and decline of panicle numbers in in double-plants were faster than that in single-plant. The panicle number per bunch was less impacted by plant density at early period after transplantation, but showed a significant increasing trend with the decreasing of plant density. The panicle number per bunch in the least plant density exceed in 72% than that of the highest plant density. At early and active tillering stage, The total panicle number of group of high plant density was more than that of low plant density, the final tiller number was not significant difference among different densities, tillering ability were:FLYX1﹥QY6≥STA/ILR1﹥YY15.The percentage of effective panicle number declined by the increase of plant density, there was almost 10% difference between high plant density and low plant density.2. Growth and decline dynamic trend of leaf area per bunch and leaf area index are consistent, leaf area per bunch was down by the increase of density. Among different density treatments, the leaf area index was large under high plant density, while was relatively small in low plant density. The SPAD value of flag leaf at full heading stage and after full heading showed a trend of decrease, while the attenuation rate of SPAD value increased with the increase of plant density. There was significant difference of SPAD value and the attenuation between different varieties(or lines). The SPAD value after full heading of the interspecific hybrid rice combination(STA/ILR1) was higher than other materials and the attenuation rate of SPAD value was lower, that is to say, the hybrid rice STA/ILR1 had a good trait on staying green.3. The dry matter of heavy panicle hybrid rice followed an ―S‖ curve increase during the growth process. The difference of dry matter per stem between different varieties was significant, but there was no significant difference observed under different plant density. The dry matter in mature period of the interspecific hybrid rice combination(STA/ILR1) was 14.8% higher than the three-line hybrid indica rice(QY6), 18.5% higher than the two-line hybrid indica rice(FLYX1).The dynamic trend of dry matter accumulation per m2 was similar to the dry matter accumulation per bunch, but it was different under different density treatments. The dry matter weight per bunch increased with the decreasing plant density, while the dry matter weight per m2 decreased. Grain yield correlated significantly with total dry matter accumulation in the whole growth period.4. The response of yield and daily yield of all varieties(or lines) under different density plant treatments was consistent, it showed higher yield were found in high plant densities(30.0 or 26.2 plants per m2) and lower yield were in low plant densities, and the yield and daily yield were different in different varieties, years, and basic seedlings.. The yield and daily yield of the interspecific hybrid rice combination(STA/ILR1) was 15.6% and 20.1% more than the three-line hybrid indica rice(QY6) with the same ripe stage, and it was closed to the two-line hybrid indica rice(FLYX1) with longer growth period relatively in yield, 5.3% higher in daily yield.5. The correlation analysis shows that: the yield per unit area was significantly correlated with total dry matter weight, filled grain number and spikeletes per unit area(the ―R‖ were 0.904, 0.952, and 0.884 respectively), which has no significant correlation with the yield per plant. The results show that yield raising with a vast scale was mainly increasing biomass and filled grains per unit area, rather than emphasizing on the contribution to yield of output per hill. The main component analysis and regression analysis show that biomass accumulation was the crucial factor of yield per plant and the grain full ratio per unit area was the most important factor of yield per unit area, with plant height and other population structure factors also have important contributions. The analysis shows that plant density affected yield per plant by affecting the biomass per plant, then made it had an indirect influence on yield per unit area by affecting filled grains per unit area.6. The effect of density on heavy panicle hybrid rice was studied according to the population quality, dry matter production, yield and yield analysis,showed that it would be more conducive to produce high yield with 26.2-30.0 plants per m2 and one plant per hill under set density range.