| Cotton is considered as an important economic fiber crop in China.The growth and development of this crop are not only affected by inherent varietal characteristics but also environmental factors.Nitrogen is an essential macronutrient that required most consistently and in larger volumes than other nutrients for cotton production.The utilization rate of nitrogen fertilizer is low and sometimes it causes serious environmental pollution.Screening nitrogen efficient varieties as well as improving nitrogen use efficiency is indispensable to recover the ecological atmosphere.This article was studied on differences of nitrogen efficiency among 80 cotton varieties in hydroponic experiment.12 different traits of various cotton germplasm were analyzed in the seedling stage under hydroponic condition.A field experiment was also conducted concurrently at the farm of Cotton research Institute,Chinese Academy of Agricultural Sciences,2017-2018 to determine the feasibility of screening cotton efficient varieties.The main results are as follows:Under the condition of hydroponic in the seedling stage,the growth of the tested cotton varieties was inhibited to a different extent compared with the normal nitrogen treatment.In the seedling stage,significant differences were observed among the tested cotton under different nitrogen levels 0.25 mM or 5 mM.After principal component analysis,it is considered that the difference among seedling varieties depends on total dry matter weight,dry weight of shoots,root dry weight,total nitrogen accumulation,above-ground nitrogen accumulation,nitrogen absorption efficiency,etc.,and the 6 traits are significant correlation,can be used as a screening indicator.The clustering analysis was carried out with the tolerance values of the six traits.At the same time,according to the N efficiency comprehensive index at seedling stage,two varieties of Lu05R59 and CCRI-69 were selected as low nitrogen tolerance and nitrogen-efficient germplasm,Coker201,XLZ30 belongs to the low nitrogen sensitive,double inefficient germplasm.There were significant differences in germplasm among the traits at the two nitrogen levels in the field trials,and the coefficient of variation was large.There were significant differences in germplasm between the two treatments in the two years,and the coefficient of variation was large.Correlation analysis of the traits in the field experiment showed that the yield was significantly correlated with plant height,total number of bolls,boll weight,total dry weight,total nitrogen accumulation,nitrogen harvest index,nitrogen utilization efficiency,and nitrogen absorption efficiency.Principal component analysis of traits,nitrogen harvest index,total dry matter weight,total nitrogen accumulation,nitrogen utilization efficiency,nitrogen absorption efficiency,yield,can be used as screening indicators.Comprehensive N efficiency comprehensive index and yield,Lu05R59 and CCRI-69 are divided into double efficient materials,Coker201,XLZ30 is divided into double efficient materials,which can be used as a study on the mechanism of cotton tolerance to low nitrogen.These varieties can be used as an ideal material for studying the mechanism of cotton tolerance to low nitrogen,and breeding parents of cotton resistant new varieties with low nitrogen.In summary,the results obtained from the hydroponic trial at seedling stage and pot as well as field experiments showed that the root length,root volume,field yield,field nutrient accumulation and photosynthetic rate of Lu05R59 and CCRI-69 were significantly higher than that of Coker201,XLZ30.Hence,it was proved that the seedling stage and field screening results are effective and Lu05R59 and CCRI-69 were found nitrogen efficient,while,Coker201,XLZ30 is nitrogen inefficient germplasm.Moreover,these germplasm can be used as an ideal material for studying the mechanism of cotton tolerance to low nitrogen,and breeding purpose to develop new germplasm with high nitrogen use efficiency and resistant to low nitrogen. |
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