Studies On Changes Of Nitrate Reductase Activity Of Soybean Cultivars With The Year Of Release In Jilin Province

Soybean yield was increased linearly with the progress of genetic improvement and cultivationtechnology since 1920's. Agronomic character, physiological character and quality characterchanged significantly with the improvement of yield,but we could hardly find the articles aboutthe changes of nitrate reductase activity(NRA)among the soybean cultivars with the released year.Forty-two soybean cultivars released from 1923-2005 in Jilin province were selected and plantedin the field in 2005 and 2006, and the changes of NRA and the relationship between NRA andyield,net photosynthetic rate,chlorophyll content, Specific Leaf Weight(SLW),soluble proteincontent, seed oil content,seed protein content during the genetic improvement of soybean cultivarswith the year of release were studied, probing into nitrogen metabolism and carbonmetabolism, the feasibility if make NRA as a high-yield soybean cultivars' selection indices wasinvestigated.The experiment was conducted at experimental station of Jilin Agricultural University, NRA,netphotosynthetic rate,chlorophyll content,SLW and soluble protein content were measured by thefourth leaf from the top at V₄,R₂,R₄,R₆ growth stages, measured the yield after harvest,thenmeasuring seed oil content and seed protein content in a suitable condition. The results as follows:1 The changes of nitrate reductase activity at different growth stages of soybeanNRA in the leaves of soybean was different significantly at every stage.The order of NRA fromhigh to low was: R₂ stage＞V₄ stage＞R₄stage＞R₆ stage. There were difference in NRA in theleaves of soybean in the same growth stage, the CVï¼…respectively were 17.6ï¼…,8.6ï¼…,8.5ï¼…and12.7ï¼…at V₄ stage, R₂ stage, R₄stage and R₆ stage,there were very significant difference orsignificant difference.2 The changes of NRA in the leaves of soybean with the year of releaseThe nitrate reductase activity at different growth stage was increased linearly from 1923 to2005,and there was significant positive relationship between NRA and the year of release,theorder of relationship level from high to low is: V₄ stage＞R₂ stage＞R₆ stage＞R₄ stage.3 the relationship between NRA and yield of soybean with the year of releaseThere were very significant positive relationship between yield and NRA at V₄ stage, R₂ stage, R₆ stage of soybean with the year of release,there was positive relationship between NRA andyield at R₄ stage,but not significantly.the order is: V₄ stage＞R₂ stage＞R₆ stage＞R₄ stage.4 The relationship between NRA and photosynthetic rate of soybean cultivars with the year ofreleaseThere were positive relationship between NRA and photosynthetic rate at the four growth stagesof soybean, there was very significant positive relationship at R₆ stage,there were significantpositive relationship at R₂ stage and V₄ stage, order of relationship level from high to low is: R₆stage＞R₂ stage＞V₄ stage＞R₄ stage.5 The relationship between NRA and chloroPhyll content of soybean cultivars with the year ofreleaseThere were very significant positive relationship between NRA and chlorophyll content at V₄stage and R₆ stage of soybean with the year of release,there was significant positive relationship atR₄ stage,there was positive relationship at R₂ stage,but not significant.6 The relationship between NRA and SLW of soybean with the year of releaseThere were very significant positive relationship between NRA and SLW at R₂ stage and R₆stage, and there were significant positive relationship at V₄ stage and R₄ stage.7 The relationship between NRA and soluble protein content of soybean with the year of releaseThere were positive relationship between NRA and soluble protein content at the four growthstages of soybean cultivars,but not significant.8 The relationship between NRA and seed oil,protein content of soybean cultivarsThere were very significant positive relationship between NRA and seed oil content at R₂ stageof soybean with the year of release, and there were positive relationship at V₄ stage, R₄ stage andR₆ stage,but not significant.There were negative relationship between NRA and seed protein content at the four growth stagesof soybean cultivars,and there was significant negative relationship between NRA and seedprotein content at R₂ stage,there was very significant negative relationship at R₆ stage.From the above results we could see,at R₄ stage,there was the closest relationship betweenphotosynthetic rate and yield,while at the other growth stages,the relationship level between NRAand yield was closer than the other's;The relationship of increase between all traits and the year ofrelease were studied and showed that the increase of NRA was the nearest compare to yield'sincrease.At R₄ stage,the increase of Pn was higher than that of NRA,but the increase of NRA washigher than the other traits at the other growth stages.The yield,leaf shape,SLW, chlorophyllcontent used to be as index for the high-yield soybean breeding all the time,NRA has not beenconsidered as an index in soybean cultivars genetic improvement programe.But NRA is outstanding by the relationship between traits and yield,measuring NRA in the leaves of soybeanwas not complicated,and canopy constrction at R₂ stage was the best,consequently, NRA at R₂stage in the leaves could be one of indices for high-yield soybean cultivars' selection.