Differences In Yield,Quality,and Aroma Of Southern Fragrant Japonica Rice And Their Response To Nitrogen And Zinc Fertilizer Combined Application

The middle and lower reaches of the Yangtze River are the main production areas of southern japonica rice in China,with abundant temperature and light resources and high yield levels.In recent years,with the breeding and promotion of high-quality japonica rice varieties,the market competitiveness of southern japonica rice products has been improved.However,there is still a certain gap compared with well-known rice such as Daohuaxiang and Basmati,among which the gap of aroma quality is particularly significant.Therefore,the research on the selection of high-quality varieties and supporting cultivation measures of southern fragrant japonica rice is beneficial for the comprehensive enhancement of the quality and market competitiveness of southern fragrant japonica rice.For this purpose,this study extensively collected 42 fragrant japonica rice varieties in the middle and lower reaches of the Yangtze River.The differences in yield,quality and aroma among different growth types of fragrant japonica rice varieties were systematically compared.On this basis,the representative varieties with high yield,good quality,and strong aroma were selected.Furthermore,four fragrant japonica rice varieties with high yield,good quality,and strong aroma suitable for planting in southern regions were chosen as experimental materials(late maturing medium japonica rice:Nanjing 9108,Yangnongxiang 28;early maturing late japonica rice:Ningxiangjing 9,Nanjing 46).The effects of nitrogen and zinc fertilizer combined application on the yield,quality,and aroma of southern fragrant japonica rice were investigated,thus providing a basis for the optimization and aroma enhancement of southern fragrant japonica rice.The main results are as follows:1.Yield,quality,and aroma among different varieties of southern fragrant japonica rice:According to the total growth days,fragrant japonica rice varieties were divided into three growth types:medium maturing medium japonica,late maturing medium japonica,and early maturing late japonica,whose average yield were 8.31 t/hm2,9.73 t/hm2,and 10.06 t/hm2,respectively.The brown rice rate of all fragrant japonica rice was above 79%.The average milled rice rate of medium maturing medium japonica,late maturing medium japonica and earlymaturing late japonica fragrant japonica rice varieties were 70.62%,71.16%,and 73.22%,respectively.The number of varieties with head rice rate above 63%were 5,12,and 18,respectively.In terms of appearance quality,the average chalky grain rate of three growth types of fragrant japonica rice varieties were 10.75%,19.46%,and 29.13%,respectively.The number of fragrant japonica rice varieties with chalkiness degree below 6%were 10,11,and 14,respectively.In terms of taste quality,the taste value of early maturing late maturing southern japonica rice varieties was higher than that of late maturing medium japonica varieties,and the taste value of medium maturing medium japonica rice was the lowest.The content of amylose and protein in early maturing and late maturing fragrant japonica rice varieties was lower than that in late maturing medium japonica rice,while medium maturing medium japonica rice had the highest content.In terms of aroma,the average content of 2acetyl-l-pyrroline(2AP)in three growth types of fragrant japonica rice varieties were 20.81 ng/g,33.59 ng/g,and 53.29 ng/g,respectively.2.The effects of nitrogen and zinc fertilizer combined application on the yield of southern fragrant japonica rice:Without zinc fertilizer application,the yield of fragrant japonica rice increased with nitrogen fertilizer application.The yield of fragrant japonica rice varieties under the 270 kg/hm2 nitrogen fertilizer treatment combined with zinc fertilizer was the highest,which increased by 15.81%-26.14%compared with the 180 kg/hm2 nitrogen fertilizer treatment combined with zinc fertilizer,and increased by 63.49%-82.46%compared with 0 kg/hm2 nitrogen fertilizer treatment combined with zinc fertilizer.The combined application of nitrogen and zinc fertilizer increased the number of tillers in the early growth stage of fragrant japonica rice,increased the leaf area index,and guaranteed the synthesis and accumulation of photosynthetic products in the later stage of fragrant japonica rice.At the same time,the mutual promotion effect of nitrogen and zinc in fragrant japonica rice increased the absorption and utilization of nitrogen fertilizer,promoted the synthesis of chlorophyll,improved the synthesis and transportation efficiency of photosynthetic products,promoted grain filling and fruiting,and improved the seed setting rate and thousand grain weight of fragrant japonica rice to a certain extent.3.The effects of nitrogen and zinc fertilizer combined application on the quality of southern fragrant japonica rice:Among different nitrogen fertilizer combination zinc fertilizer treatments,the processing and appearance quality of fragrant japonica rice under 270 kg/hm2 nitrogen fertilizer combination zinc fertilizer treatment showed the best performance.Under the combined application of nitrogen and zinc,the amylose content of fragrant japonica rice significantly decreased and the protein content significantly increased with the increase of nitrogen fertilizer dosage.Adding zinc fertilizer on the basis of nitrogen fertilizer resulted in a decrease in amylose content and an increase in protein content.The taste value of fragrant japonica rice under the combined application of nitrogen and zinc was significantly decreased with the increase of nitrogen fertilizer application.The application of zinc fertilizer improved the taste value of fragrant japonica rice compared with samples without zinc application,improving the taste quality of fragrant japonica rice.The peak viscosity,trough viscosity,final viscosity,breakdown and consistence of rice rapid visco-analyzer profile(RVA profile)were significantly decreased and the setback was significantly increased by the combined application of nitrogen and zinc compared with the application of nitrogen or zinc alone.4.Effects of nitrogen and zinc fertilizer combined application on the aroma of southern fragrant japonica rice:Without zinc fertilizer application,compared with the samples under 0 kg/hm2 nitrogen fertilizer treatment,the 2AP content in rice of fragrant japonica rice under 180 kg/hm2 and 270 kg/hm2 nitrogen fertilizer treatments increased by 0.86%-103.38%and 12.34%-146.56%,respectively.The 2AP content in brown rice increased by 3.21%-82.56%and 3.25%-113.02%,and the 2AP content in milled rice increased by 7.91%-283.33%and 16.24%-469.77%,respectively.Under the same nitrogen fertilizer conditions,compared with treatments without zinc fertilizer application,the 2AP content in rice,brown rice and milled rice of fragrant japonica rice with zinc fertilizer application increased by 0.86%-47.55%,0.69%-21.71%,and 2.00%-176.84%,respectively.The 2AP content in rice,brown rice,and milled rice of fragrant japonica rice reached maximum under 270 kg/hm2 nitrogen fertilizer treatment combined with zinc fertilizer.In summary,based on a comprehensive analysis of the differences in yield,quality,and aroma among different growth types of southern fragrant japonica rice,it was found that among the 42 varieties of fragrant japonica rice,Songzaoxiang 1,Huai 666,Nanjing 9108,Jinxiangyu 1,Yangnongxiang 28,Wuxiangjing 113,Nanjing 46,Suxiangjing 100,Ningxiangjing 9,Yangjingnuo 2,and Quanxiangnuo 3 were found to have higher yield,better quality,and stronger aroma.Thus,the above southern fragrant japonica rice varieties were suitable for promotion and planting in the southern japonica rice region.Applying zinc fertilizer under the condition of 270 kg/hm2 nitrogen fertilizer significantly increased the number of tillers,leaf area index,dry weight accumulation,and yield of southern fragrant japonica rice.And it improved the processing and appearance quality of southern fragrant japonica rice,enhanced the cooking and eating quality of fragrant japonica rice,increase the 2AP content of grains,which achieved a synergistic improvement in yield,quality,and aroma of southern fragrant japonica rice,and could be used for optimizing and enhancing aroma cultivation for southern fragrant japonica rice.