Analysis On Combining Ability And Heterotic Group Of Inbred Lines From 5 Synthetic Maize Populations

In present study,15 inbred lines derived from 5 synthesized maize populations were used as males to make a total of 120 NCⅡtestcrosses with 8 often used inbred lines in southwest China.The combing ability,heterosis and genetic indexes of main traits of 15 inbred lines were estimated.The heterosis groups and heterosis pattern of 27 inbred lines,including the 15 inbred lines derived from 5 synthesized maize populations,8 testers and 4 temperate inbred lines(Mo17,Huangzaosi,Dan340 and Ye478),were studied with SSR markers.The main results were summarized as follows:1.Genetic variance was significant in the 15 observed traits in 120 hybrid combinations. The combing ability analyses according to NCⅡdesign indicated that the GCA and SCA of all traits were significant at 0.05 or 0.01 level except for the GCA for the yield of testers and the SCA for the kernel depth.The inbred line GP2-1 shows the highest GCA for yield, followed by GP5-2 and GPS-5,and the GCA for yield component traits of the 3 lines was high.The GCA of tester 48-2 and ES40 for 6 traits show highly positive effective.They have better utilization value to combing with the tested lines.2.The combination 48-2×GP3-3 shows the max SCA effective for yield and ear weight. The combination ES40×GP1-2 shows the maximum SCA effect for ear length and ear diameter,and SCA for yield/plant rank the 2nd place.The combination 18-599×GP5-4 shows the min SCA effective for yield and ear weight.The 1^st and 2^nd highest combinations in yield/plant were ES40×GP2-1 and 48-2×GP3-3,the lowest combination was RP128×GP4-4. This results indicated that the heterosis of the hybrids combination were determined by the GCA of each parents along with the SCA between them,It is more effective to estimated the utilization value of lines by using the GCA and SCA together.3.The GCA for yield/plant of the lines GPS-2,GPS-5,GP5-1,GPS-4 and GPS-3,which were derived from GPS,rank the 2^nd,4^th,5^th,6^th and 11^th in the 15 newly selected lines, respectively.4 of 5 lines derived from GP5 were involved in the 15 combinations which were the highest in SCA for yield/plant.All the 5 lines were involved in the 15 combinations which were superiority over CK 12%for 7 times,with an average of 1.40 for each line.This result indicated that the GCA effect for yield component traits of lines derived from GP5 was positively high,and the SCA between them and the testers were high,and we conclude that GP5 was a population of better utilization value.4.The broad sense heritability and narrow sense heritability of ear diameter,axis diameter,rows/ear,kernels/ear,axis weight and were high,and the additive effect was bigger than the non-additive effect,they were affected by the environments slightly,they should be selected at early generations when a population was used to derive inbred lines.The situation of ear weight and kernel weight/plant were just the opposite,they should be selected at later generations.The ear length,sterile length,100-kernel weight,plant height and ear height were higher in broad sense heritability but lower in narrow sense heritability,and they were accessible to the environment,so they were not to be selected in early generations.5.The genetic distance of 15 newly selected lines range from 0.23 to 0.70,with an average of was 0.651.It indicated that there are abundant genetic variations in 5 populations, it effective to resolve the problem of the narrow base of germplasm.The genetic distance of 27 inbred lines,including the 15 inbred lines derived from 5 synthesized maize populations,8 testers and 4 temperate inbred lines(Mo17,Huangzaosi,Dan340 and Ye478),ranges from 0.15 to 0.74,with an average of 0.595.The 27 inbred lines were classified to 5 groups,and the group2 contains 4 sub groups.Most of the newly selected lines were belong to group2 which included the template tester Dan340,few of then belong to the group4 which included the template tester Ye478 and the group 3 which included no template testers.2 lines derived from gp4 and gp5 belong to a same sub-group,which indicated that the two populations have same genetic background partly.6.The combing pattern of the hybrid combinations which were superiority over CK 12% were analysis,the result shows that they were combined with lines belong to different groups or sub-groups,and the genetic distance between parents was big,the result also proved the reliability of heterosis grouping by SSR markers.The heterosis of Lancaster×Luda Red Cob was high,especially the pattern Lancaster×Luda Red Cob1 and Lancaster×Luda Red Cob4.It is more possible to obtain high field hybrid combinations by using 18-599 and R08 which presented Lancaster cross with lines belong to Luda Red Cob.The genetic distance between parents of the 15 combinations which were the highest in yield was analysis,10 of them was bigger than the average genetic distance of all lines and 5 of them was smaller than he average genetic distance of all lines.It indicated that the heterosis was related to the genetic distance calculate by SSR markers.