大豆氮高效种质苗期筛选与鉴定

氮高效利用种质资源的筛选与鉴定是大豆高产育种的重要前提。本研究以78份大豆种质资源为材料，采用水培养法，分析正常氮（氮浓度为7.5 mmol/L）和低氮（氮浓度为0.75 mmol/L）条件下大豆生物量和耐低氮指数。根据地上部干重、总干重、耐低氮胁迫指数初步筛选出3份耐低氮材料（2011-X-559、2011-X-618、2011-X-639）、3份低氮敏感材料（2011-X-472、2011-X-531、2011-X-547）和2份中间型材料（吉育86、东农53）。进一步复筛测定8份大豆种质材料的叶绿素含量、生物量、氮含量和根系形态构型等17个氮利用相关指标，通过对性状指标的变异系数、相关性和主成分分析，筛选出总干重、整株氮含量、整株总氮、总根长、根体积和根表面积6个指标可作为大豆苗期耐低氮评价关键指标，并依此鉴定出耐低氮材料2011-X-618和低氮敏感材料2011-X-531。本研究为大豆耐低氮机制解析和氮高效育种提供了优异种质资源和理论指导。

Distinguishing and evaluating high nitrogen-use-efficient soybean germplasm at seedling stage

Distinguishing elite germplasm with high nitrogen-use-efficiency is critical to high-yield breeding in soybean. In this study, we employed hydroponic assay and evaluated biomass and tolerance index of low nitrogen stress of 78 accessions at two nitrogen levels, i.e. normal (7.5mmol/L) and low (0.75mmol/L). Based on performance of aboveground dry weight, whole-plant dry weight and low nitrogen tolerance index, 8 elite accessions, including 3 low-nitrogen-tolerant genotypes (2011-X-559, 2011-X-618, 2011-X-639), 3 low-nitrogen-sensitive genotypes (2011-X-472, 2011-X-531, 2011-X-547) and 2 intermediate genotypes (Jiyu 86, Dongnong 53), were distinguished. Furthermore, we focused on the 8 accessions and examined 17 traits, covering chlorophyll content, biomass, nitrogen percentage and root morphology. By means of variation coefficient, Pearson correlation and principal component analysis, 6 traits （composing of dry biomass, total nitrogen percentage, total nitrogen accumulation, total root length, root volume and root surface area） could be considered as the main indicators for screening low nitrogen tolerant soybean germplasm at seedling stage. Consequently, a low nitrogen tolerant accessions 2011-X-618 and a low nitrogen sensitive accessions 2011-X-531 were further validated. We hoped to shed light on deciphering the mechanism of nitrogen use efficiency and provide excellent germplasm for high yield breeding in soybean.