| It is significant for improving the accuracy and prediction of maize breeding to research the heterotic groups of maize and the heterotic patterns.The heterotic groups of maize were clustered by the genetic distance with the SSR markers;this study,by using Chinese main maize hybrid parents as materials.By crossing tropical maize inbred lines and representative temperate inbred lines from different heterotic groups and analyzing their heterosis,the value of tropical germplasm was appraised.Combining abilities of different maize germplasm were analyzed by crossing above representative inbred lines and tropical populations(testers).The research is beneficial to guide the selecting of inbred lines and promote efficiency of crossing hybrids.The study gives the following conclusions:546 polymorphic amplified fragments were detected among the 30 kinds of maize inbred lines with the 110 SSR primers.The variation in PIC ranged from 0.1115 to 0.91(average: 0.652) and concentrated on 0.5-0.8.The results showed that these inbred lines had great genetic deviations at molecular marking level.Based on the results of SSR and molecular genetic distance analysis,the 30 inbred lines can be clustered into seven heterotic groups: First,Group P,including seven inbred lines:P007,Qi319,Dan599,Shen137,178,P138 and 87-1;Second,Group Tangsipingtou,including six inbred lines:K12,Q1261,Huanyesi-3, Huangzao4,Ji35 and Chang7-2;Third,Group Reid,including five inbred lines:478,B73, K14,Huang C and Shen5003;Fourth,Group Zi330,including four inbred lines:Zhongzong3, Zhongzong31,Zi330 and 340;Fifth,Group E28,including E28 and its second cycle line-Zheng22;Sixth,Group Lancaster,including Mo17,Huotanghuang17 and Qi205; Seventh,the left lines,including Luyuan92,Ji63 and LU28.Heterosis was analyzed by crossing five tropical inbred lines(CML27,CML40,CML92, CML107,CML116) with 4 temperate inbred lines from above heterotic groups(Dan340,B73, Mo17,Huangzao4).The results showed:hybrids from tropical and temperate germplasm have significant predominance in yield per plant,100-kernel weight and kernel volume weight.No heterosis in row kernels.Germplasms from the tropics can improve the yield and ear traits. The pattern of some CIMMYT inbred lines×Dan340 is valuable in temperate maize breeding.Combining abilities of 10 above temperate inbred lines(Dan340,87-1,178,K12,Mo17, P138,Huangzao 4,Luyuan92,Qi319,Zi330) were analyzed by using tropical population Poo125,Pop66,Pob21 and Suwanl as testers.The analysis on general combining ability(GCA) of yield per plant,ear length,ear diameter,ear rows,row kernels and 100-kernel weight was done.The result showed that Dan340,Huangzao4,Pob21 and Suwanl had high positive GCA value in yield per plant. which is 11,6.5,24,and 25 respectively,but 178,Mo17,P138,Poo125 and Pop66 had high negative GCA value.Luyuan 92,Qi319,Zi330,Pob21 and Suwan1 had high GCA value in ear length.Dan 340 had the highest GCA value,87-1,K12 had higher GCA value,and in ear diameter and ear rows.Pop66 is the only one line which had higher GCA value(3.36) in row kernels,others are lower or negative.87-1,K12,Qi319,Poo125 and Suwanl had higher positive GCA value in 100-kernel weight.Further analysis of the specific combining ability(SCA) of yield per plant showed that 23 of 40 combinations had positive SCA values.Among them,the SCA values of Dan340×Poo125(7.84),Luyuan92×Poo125(9.22),Mo17×Pop66(8.38),87-1×Pob21(11.39),K12×Pob21(9.99),Luyuan92×Pob21(15.48),Mo17×Suwanl(7.41) and Z330×Suwanl(7.28) were high.
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