Screening and evaluation of rice germplasm resources with low nitrogen tolerance

<bold>Objective</bold> Nitrogen is an important nutrient element that affects the growth，development，yield and quality of rice.Improving the low nitrogen tolerance of rice varieties contributes to the green and efficient development of agricultural production.The identification and screening of rice germplasms with low nitrogen tolerance is a key method for cultivating varieties that can withstand low nitrogen conditions. <bold>Method</bold> A total of 3，000 rice germplasms from southern rice-growing areas were used as experimental materials.From 2017 to 2018，biological yield per plant and grain weight per plant at the maturity stage were used as indexes to identify low nitrogen tolerance.Combined with field performance，624 low nitrogen tolerant rice germplasms were preliminarily selected.In 2019，the panicle and yield correlation traits of the primary screening germplasm were determined for the accurate identification of low nitrogen tolerance.A total of 153 germplasms demonstrating excellent yield performance and low nitrogen tolerance were screened.On this basis，the plant height，number of effective tillers per plant，panicle length，spikelets per panicle，full spikelets per panicle，1 000-grain weight，grain density and theoretical yield were investigated in 2020.<italic>Tianyouhuazhan</italic>，the control variety of Jiangxi rice regional trial，was used as the control to identify and evaluate the 153 low nitrogen tolerant rice germplasms under low nitrogen stress. <bold>Result</bold> There are significant differences in plant height，number of effective tillers per plant，panicle length，spikelets per panicle and theoretical yield among different nitrogen application treatments.However，there are no significant differences in the full spikelets per panicle，1，000-grain weight and grain density.Under different nitrogen treatments，theoretical yield is significantly or extremely significantly positively correlated with the number of effective tillers per plant，panicle length and spikelets per panicle，but not significantly correlated with plant height and 1，000-grain weight.This indicates that low nitrogen stress has a significant impact on the number of effective tillers per plant，panicle length，spikelets per panicle，and theoretical yield.The coincidence rate between the two methods—clustering analysis and the membership function method—is 86% when applied to evaluate the low nitrogen tolerance characteristics of 153 excellent germplasms，using panicle number，panicle length，total grain number per panicle，and theoretical yield as evaluation indexes. <bold>Conclusion</bold> A total of 30 cultivars with strong low nitrogen tolerance have been identified using two methods，and the results of comprehensive evaluation may be more reliable.The selected germplasms with strong low nitrogen tolerance will have important application value not only in the study of molecular genetic mechanism of low nitrogen tolerance in rice，but also in the breeding of rice cultivars with low nitrogen tolerance and green efficiency.