The Effect Of U.S.germplasm On The Improvement Of Domestic Maize Inbred Lines W9706 And CA667

The introduction of elite maize inbred lines from the United States and other developed countries is helpful to widen domestic maize germplasm basis and to accelerate the development of new varieties.W9706 and CA667,belonging to group Lancaster and Sipingtou,respectively,are two important inbred lines in Chinese maize breeding program,with high combining ability,good seed set rate and so on,but with shortcomings such as poor lodging resistance,susceptibility to stem rot,low kernel producing-rate and slow moisture rate.Therefore,both lines are difficult to meet the demand of modern breeding and need to be futher improved.Maize inbred lines in the United States generally have characteristics such as high density tolerance,lodging resistance,and fast dehydration rate.In this paper,elite U.S.lines MPBM,PHT77,6M502,LH213 and PHBA6,which belong to group NSS,were used as donors of favorable alleles to improve domestic lines W9706 and CA667,and 100 S4 families were selected to conduct analysis of agronomic traits.The hybrid combinations of these lines with their respective testers were made by NCII genetic mating design.The field trials were carried out in Harbin,Heilongjiang province and Gongzhuling,Jilin province through α-lattice design,and the combining ability for yield and other agronomic traits of the improved lines was analyzed to evaluate the effect of U.S.germplasm on the improvement of domestic W9706 and CA667.The main results were as follows:(1)According to the comprehensive analysis of yield and major agronomic traits,the improved lines of W9706 including WM-2,WM-6,WM-7,WP-5,WP-6,W6-6,WL-4,WL-6,WL-8,WL-9,and WB-8,and the improved lines of CA667 including CM-2,CM-9,CP-3,CP-7,and C6-8 had excellent performance.(2)The U.S.line MPBM could be used as donors to improve days to silking,kernel row number,kernel number per row and yield and enhance GCA effects for kernel row number,kernel number per row and harvesting mositure content of W9706,and to improve days to silking,kernel row number,kernel number per row,100-kernel weight,seed-producing rate and yield and enhance GCA effects for lodging resistance,kernel row number,kernel number per row and harvesting moisture content of CA667.PHT77 could be used to improve days to silking,ear height,kernel row number,kernel number per row and enhance GCA effects for ear height,lodging resistance and kernel row number of W9706,and to improve days to silking,kernel number per row,100-kernel weight,seed-producing rate and yield and enhance GCA effects for days to silking,lodging resistance,kernel number per row,seed-producing rate of CA667.6M502 could be used to improve days to silking,ear height,kernel row number,kernel number per row and yield andenhance GCA effects for yield,days to silking,ear height,lodging resistance,kernel row number,100-kernel weight and the harvesting moisture content of W9706,and to improve days to silking,kernel row number,100-kernel weight,seed-producing rate and yield and enhance GCA effects for ear height and harvesting moisture content of CA667.LH213 could be used to improve days to silking,kernel row number,kernel number per row,100-kernel weight and yield and enhance GCA effects for ear height,100-kernel weight,seed-producing rate of W9706,and to improve days to silking and kernel row number and yield and enhance GCA effects for kernel number per row of CA667.PHBA6 could be used to improve days to silking,kernel row number,kernel number per row and yield and enhance GCA effects for lodging resistance,kernel number per row,harvesting water content and seed-producing rate of W9706,and to improve days to silking,ear height and kernel number per row and enhance GCA effects for yield,days to silking,ear height,lodging resistance,kernel number per row and 100-kernel weight of CA667.(3)According to the analysis of gerneral combining ability for yield and major agronomic traits of the improved lines,WM-2,WP-1,WP-4,W6-1,W6-4,W6-6,W6-9,WB-2,CM-7,CL-3,CL-5,CB-1,CB-2,CB-4,CB-7 and CB-9 had good comprehensive GCA performance in agronomic traits and could be further used in maize breeding.(4)Based on the SCA analysis for yield,WP and W6 had relatively high SCA and strong heterosis responses for yield with Lx736.WB and CP had relatively high SCA and strong heterosis responses for yield with CA749.CL and CP had relatively high SCA and strong heterosis responses for yield with CA193.CM,C6 and CB had relatively high SCA and strong heterosis responses for yield with 4144.(5)Overall,the U.S.lines LH213 and 6M502 have great potential in improving multiple traits of W9706,and PHT77,6M502 and PHBA6 have potential in improving multiple traits of CA667.Especially 6M502 could improve the comprehensive performance of the receptor lines.