Leaf Stay-Green Traits in Chinese Maize Inbred Lines and Their Relationship with Grain Yield

Abstract

Leaf stay-green trait is one of the major targets in maize(Zea mays L.) breeding.Although sugar concentration in culm,green leaf number,leaf area,and chlorophyll content at maturity have been used to evaluate the stay-green trait of maize in earlier studies,there is no a common criterion.To further study the evaluation system for stay-green in maize and disclose the relation-ship of stay-green with grain yield,we sampled 75 inbred lines from common parents of Chinese maize cultivars.At silking stage and 10,20,30,40,50,and 60 d after silking,the leaf area(LA),leaf area duration(LAD),relative leaf area,and relative green-leaf area(RGLA) were measured.The results showed that the changes of RGLA after silking accorded with the equation of y = aeb-cx/(1+eb-cx).On the basis of correlation analysis,the green leaf number,chlorophyll content at physiological maturity,and mean decreasing rate of RGLA(Vm) were selected as the key indices to discriminate the stay-green and non-stay-green maize genotypes.According to relative green leaf area at physiological maturity(MRGLA),the maximum decrease rate of RGLA(Vmax),and the mean decreasing rate of RGLA(Vm),the 75 inbred lines were classified into stay-green and non-stay-green two types with Hiechical clustering analysis.The stay-green type was composed of 12 inbred lines with the following common characteristics:MRGLA of more than 60%,Vm of 0.687% d-1,no significant decrease of RGLA during the whole growing period(67.07% at maturity),and high green leaf number(8.8 leaves) and chlorophyll content(4.43 mg dm-2) at physiological maturity.The non-stay-green type,consisting of 63 inbred lines,was further categorized with quick-leaf-senescence(50 inbred lines) and slow-leaf-senescence(13 inbred lines) subgroups.In the quick-and slow-leaf senescence subgroups,the RGLA at maturity,Vm,green leaf number at maturity,and chlorophyll content at maturity were 17.75% and 33.55%,1.89% d-1 and 1.44% d-1,3.2 and 6.2,and 2.06 mg dm-2 and 3.17 mg dm-2,respectively.At physiological maturity,the RGLA was positively correlated with LAD(r = 0.8861,P 0.01) and yield per plant(r = 0.8221,P 0.01).The LAD and yield per plant were 20.02-23.87% and 50.44-59.38% higher in the stay-green type than in the non-stay-green type,respectively.Thus,the stay-green type had higher yield potential due to larger green leaf area,higher chlorophyll content and photosynthesis efficiency as well as longer photosyn-thesis duration.