Effects Of Water And Nitrogen And Their Interactions At Grain Filling Stage On Aroma Formation In Aromatic Rice Deng Quanquan

In order to ascertain the effect of water and nitrogen and their interaction on the accumulation of 2-acetyl-1-pyrroline(2-AP)in brown rice of aromatic rice during grain filling stage and find out the best water and nitrogen management measures for the fragrant rice during grain filling period and related mechanism.Field experiments were conducted in the early and late seasons of 2014 on the experimental farm of South China Agricultural University.Indica aromatic rice Basmati385,Nongxiang 18 and Japonica aromatic rice Y-14,OR and RI were used as research materials.Three water treatments were set at full heading stage:Keep the shallow layer 4-6cm(W1),moderate drought-25±5 k Pa(W2)and heavy drought-50±5 k Pa(W3);Three levels of nitrogen treatments were applied at heading stage as follows:0 kg·hm^-2(N1),30 kg·hm^-2(N2)and 60 kg·hm^-2(N3).The content of2-AP of grains,leaves,stem and brown rice at 7 days after heading(7d AFH),14 days after heading(14d AFH),21days after heading(21d AFH)and mature stage(MS)were measured,The content of proline of leaves 7 days after heading,14 days after heading,21days after heading and mature stage were determined.The activity of proline dehydrogenase,pyrroline-5-carboxylic acid synthetase,diamine oxidase and the content of pyrroline-5-carboxylic acid and proline of grains of at 21days after heading and mature stage was detected.The yield and its components and grain quality traits were determined.The main results are as follows:(1)Moderate drought(-25±5 k Pa,W2)during grain filling stage was beneficial for aromatic rice to obtain higher 2-AP content,higher yield and better quality.Under moderate drought treatment(W2),the physiological basis of 2-AP accumulation in brown rice was as follows:The 2-AP content of fragrant rice grains,leaves and stem sheaths;the proline content in leaves;the proline content and the activities of proline dehydrogenase(PDH),pyrrolidine-5-carboxylic acid synthetase(P5CS),ornithine aminotransferase(OAT)and the pyrrolidine-5-carboxylic acid(P5C)content in grains maintained high levels.Moderate drought(-25±5 k Pa,W2)was beneficial to increase the yield of aromatic rice,mainly because filled grain percentage and 1000-grain weight were maintained at high levels.Moderate drought(-25±5 k Pa,W2)was advantageous to keep the brown rice rate,milled rice rate and head milled rice rate at high levels.Moderate drought(-25±5 k Pa,W2)was beneficial to maintain a high level of amylose content in fragrant rice.(2)Nitrogen fertilizer treatment during grain filling stage was beneficial for aromatic rice to obtain higher 2-AP content,higher yield and better quality.Under application of N15 kg·hm^-2(N2),the physiological basis of 2-AP accumulation in brown rice was as follows:The 2-AP content of fragrant rice grains,leaves and stem sheaths;the proline content in leaves;the proline content and the activities of proline dehydrogenase(PDH),pyrrolidine-5-carboxylic acid synthetase(P5CS),ornithine aminotransferase(OAT)and the pyrrolidine-5-carboxylic acid(P5C)content in grains maintained high levels.Improving nitrogen fertilizer(N2)was beneficial to maintain high yield of aromatic rice,mainly because filled grain percentage and 1000-grain weight were maintained at high levels.Improving nitrogen fertilizer(N2)was beneficial to maintain high levels of the brown rice rate,milled rice rate and head milled rice rate of aromatic rice.N2 treatment was beneficial to maintain high levels of protein content and amylose content in fragrant rice.(3)Moderate drought(-25±5 k Pa)and application of nitrogen at rate of 15 kg·hm^-2interactions(W2N2)during grain filling stage was conducive to maintain higher yield,better quality of scented rice and higher 2-AP content in brown rice.Under W2N2treatment,the contents of 2-AP in brown rice of RI in early season and Basmati385,Nongxiang 18 in late season were the highest,reached separately 246.80 ng·g^-1 and 136.29ng·g^-1,66.48 ng·g^-1.The content of 2-AP in brown rice of other varieties maintained at a high level in early and late seasons.The physiological basis of 2-AP accumulation in brown rice was as follows:The 2-AP content of fragrant rice grains,leaves and stem sheaths;the proline content in leaves;the proline content and the activities of proline dehydrogenase(PDH),pyrrolidine-5-carboxylic acid synthetase(P5CS),ornithine aminotransferase(OAT)and the pyrrolidine-5-carboxylic acid(P5C)content in grains maintained high levels.The stable or increased yield of early and late season aromatic rice lies in higher filled grain percent and 1000-grain weight.During grain filling stage,the water-nitrogen interaction treatment can maintain high brown rice,milled rice and head milled rice rate.The protein content of fragrant rice varies greatly among different varieties,amylose content increased partially or not significantly.