Effects Of Nitrogen Supply Rate And Planting Density On Yield And Grain Quality Of Rice With DEP1/dep1

In the process of rice production in China,excessive nitrogen input not only reduces nitrogen use efficiency and increases cost,but also brings huge pollution to agriculture and ecological environment.Therefore,reducing the use of nitrogen fertilizer has become an inevitable choice for modern rice planting.It is hard to reduce the use of nitrogen fertilizer and maintain high yield of rice,because selecting varieties with high nitrogen use efficiency and practicing reasonable cultivation and management measures are equally required.DEP1/depl can not only promote the number of spikelets per unit area,and enhance the photosynthetic efficiency of canopy after heading,but also affect the nitrogen absorption and utilization of rice,improve population ecological environment,and display lodging resistance.The interaction of nitrogen supply rate,planting density and the genotype on yield and grain quality of rice are unclear.To clarify the interactive effect of nitrogen supply rate,planting density and DEP1/depl on rice grain yield,dry matter production and distribution,nitrogen use efficiency and rice quality,we compared a high yielding japonica rice variety Wuyunjing 8(depl)with its DEP1 complementary line through the combination treatment of planting density and nitrogen supply rate.At the same time,the differences of grain quality under different specific gravity of salt water were compared.The results may provide information on how to accurately evaluate the genetic effect,how to rationally use high-yielding genes,and how to optimize the relationship between reducing the use of nitrogen fertilizer and balancing the stable yield and high quality of rice.The main results are as follows:1.Rice grain yieldIncreasing N rate under low planting density,WYJ8(depl)produced higher grain yield than WYJ8-CP(DEP1).The grian yield of WYJ8 did not decrease at N25.5.The response of DEP1/dep1 to nitrogen supply rate has a significant interaction with density.Increasing planting density promoted the panicles per unit area of WYJ8 and WYJ8-CP,and reduced the seed setting rate of WYJ8 and WYJ8-CP.Increasing nitrogen supply rate significantly promoted the panicles per unit area of WYJ8 and WYJ8-CP,and reduced the spikelets per panicle,seed setting rate and 1000-grain weight of WYJ8 and WYJ8-CP.Under the same planting density and nitrogen supply rate,the panicles per unit area,spikelets per panicle,seed setting rate and 1000-grain weight of WYJ8-CP were significantly higher than those of WYJ8.Increasing planting density,the grian yield of WYJ8 was the highest at N8.5,but that of WYJ8-CP was the highest at N172.Dry matter production and distributionThe dry mater production of WYJ8 and WYJ8-CP increased significantly under high nitrogen supply rate.On the contrary,the harvest index decreased.The dry mater production and harvest index of WYJ8-CP were significantly higher than those of WYJ8.The proportion of stem-sheath material production and panicle material production of WYJ8 and WYJ8-CP were negatively correlated with nitrogen supply rate,and the proportion of leaf material production was positively correlated with nitrogen supply rate.The proportion of stem-sheath material production of WYJ8-CP was significantly higher than that of WYJ8.The proportion of stem-sheath material production of WYJ8 increased and the proportion of panicle material production of WYJ8 decreased at mature stage,WYJ8-CP is the opposite.Under high nitrogen supply rate,material accumulation after heading and stem-sheath-leaf material transport of WYJ8 and WYJ8-CP were significantly increased.Material accumulation after heading and stem-sheath-leaf material transport of WYJ8 were higher than WYJ8-CP.Material accumulation after heading of WYJ8 and WYJ8-CP were increased under high planting density,and the increasing range of WYJ8-CP was bigger than that of WYJ8.3.Nitrogen use efficiencyThe nitrogen absorption of WYJ8 and WYJ8-CP at mature stage were significantly increased under high nitrogen supply rate,it reached the maximum at N25.5.The nitrogen absorption of WYJ8-CP was significantly higher than that of WYJ8 under different planting densities or nitrogen supply rates.The nitrogen absorption of WYJ8-CP increased significantly under high planting density,but the nitrogen absorption of WYJ8 did not change The nitrogen grain production efficiency,nitrogen dry matter production efficiency,nitrogen harvest index,agronomy efficiency of nitrogen applied,partial factor productivity of nitrogen and physiological efficiency of nitrogen of WYJ8 and WYJ8-CP were negatively correlated with nitrogen supply rate.The nitrogen grain production efficiency,nitrogen dry matter production efficiency and nitrogen harvest index of WYJ8-CP were significantly higher than those of WYJ8.The nitrogen utilization rates of WYJ8 and WYJ8-CP were increased under high planting density,which showed that there was a bigger increasing range under middle and low nitrogen supply rate,but a smaller increasing range under high nitrogen supply rate.The nitrogen utilization rates of WYJ8 and WYJ8-CP were increased under high planting density,both of which showed a bigger increasing range under middle and low nitrogen supply rate,while a smaller increasing range under high nitrogen supply rate.4.Rice grain qualityThe milling and appearance qualities of WYJ8 and WYJ8-CP did not respond significantly to nitrogen supply rate change.The length of milled grain in WYJ8-CP was significantly longer than that of WYJ8.Gel consistency of WYJ8-CP were similar to those of WYJ8,but the protein content and gelatinization temperature were significantly lowered,so the cooking and eating qualities of WYJ8-CP improved significantly.Our results indicated that utilization of DEP1 instead of depl could improve rice yield and quality at lower N level.There was no significant difference in amylose content,gel consistency and RVA spectrum characteristic valums between WYJ8 and WYJ8-CP under different specific gravity of salt water.Protein content of WYJ8 and WYJ8-CP was negatively correlated with specific gravity of salt water,and the protein content was the highest at lower specific gravity of salt water.5.Transcription levels of certain genes in grain filling stageThe transcription levels of SRS3 and GW2 in WYJ8-CP were higher than in WYJ8 during grain filling.The transcription level of PGL2 in WYJ8-CP was higher than that in WYJ8-CP at N17 level.These may have contributed to the differences of grain size and grain weight between WYJ8 and WYJ8-CP.On the 7th day after flowering,the transcription levels of OsSSI,OsSSⅡa,OsSSⅢa and OsBEⅡb in WYJ8-CP were slightly higher than in WYJ8.On the 14th day after flowering,the transcription levels of these genes in WYJ8-CP were significantly higher than those in WYJ8.These maycontribute the differences of gelatinization temperature between WYJ8 and WYJ8-CP.On the 14th day after flowering,the transcription level of OsBEⅡb in WYJ8 was significantly lower than that in WYJ8-CP,and the synthesis of amylopectin in WYJ8-CP was inhibited.The transcription level of Wx in WYJ8-CP is always lower than that in WYJ8.These may reflect the differences of amylose content between WYJ8 and WYJ8-CP.