Studies On Complete Diallel Cross Of Eight Inbred Lines In Zinnia Elegans

Zinnia elegans has been very popular due to its long-lasting bloom and flower colors. The breeding technique has been mature abroad, but due to the protection of intellectual property rights, the breeding methods has been merely reported only on interspecific hybridization and tissue culture. In this paper,8 inbred lines including A3、S5、J6、J8、J10、A1、J12、J17 of 10-13 generations by pedigree technique were selected as parents. By Griffing completely diallel cross method I,64 combination were designed, which included 56 hybrid crosses and 8 selling crosses. So in the 56 hybrid crosses, the seed setting rate, initial bloom stage and 13 main ornamental traits were analysed and the genetic regularity of 13 main ornamental traits was calculated. The main results were showed as follows:(1) analysis of seed setting rate and initial bloom stage The analysis of seed setting rate showed that all crosses could fruit and average seed setting rate was 60.63%, ranging between 32.86% and 88.35%. Seed setting rates of A3xJ6, J6xA3, J10xA3 and J12×A1 were higher than other crosses, which was above 80%. Seed setting rates of Al, J8 as famale parents were higher than that as male parents, which indicated that they were suitable for famale parent. Seed setting rates of S5 and J6 as parent respectively were higher than its parents, in which included S5xA3, J8xS5, J10xS5 J6xA1, J6xA3, A3xJ6 and J12XJ6 crosses. Seed setting rates of J10xA3 and J8XJ10 crosses were higher than that of J10. The analysis of initial bloom stage showed that average stage was 49.7d and initial bloom stage of direct and reciprocal cross had differences. In A3 offspring, either direct cross or reciprocal, the initial bloom stage was shorter than which of other hybrid offsprings, however in J6 offspring, the initial bloom stage was longer than which of other hybrid offsprings. In the previous two offspring, the initial bloom stage was not more than a week, which indicated that heterosis of each crosses had not been particularly different.(2) Analysis of heterosis of main ornamental traits Analysis of heterosis of 13 main ornamental traits indicated that plant height and crown size had mid-parent heterosis, while inflorescence diameter, number of branches, pedicel length and number of whorls of ray florets across capitulum had transgressive heterosis, all of which indicated that target traits changed greatly in specific hybrid crosses. In J6XA3, S5xA3 and J6XJ8 crosses, the number of whorls of ray florets across capitulum had transgressive heterosis, which showed that hybrid offspring had strong double flower traits. In J6×A1, J6xJ12, J10xS5, J6xS5 and J12×A1 crosses, the plant height, number of branches and pedicel length had obvious transgressive heterosis, which traits satisfied breeding objectives of cut flowers, such as high plant, long pedicel and many branches, and in J6×A1, J6XJ12 and J6XS5 crosses, number of whorls of ray florets across capitulum had obvious transgressive heterosis, which indicated that hybrid offspring had strong double ray florets traits.(3) Analysis of genetic regularity The analysis on genetic parameters of the main ornamental traits showed that genetic variance of plant height, inflorescence diameter, pedicel length, crown size and number of whorls of ray florets across capitulum was higher than their environment variance, which indicated that goal traits were mainly affected by genetic gene rather than the environment. Among these traits, plant height, inflorescence diameter, pedicel length and crown size had higher dominant variance than additive variation, and the difference between broad sense heritability and narrow sense heritability was greater than narrow sense heritability, which indicated that non-additive effects of these traits were higher than additive effects, namely their inheritances were mainly controlled by non-additive effects. Both broad sense heritability and narrow sense heritability of number of whorls of ray florets across capitulum were relatively high, which indicated that it had strong ability of genetic transmission for offspring and was suitable for early-generation selection in breeding work.(4) Evaluation of parents and hybrid crosses The comprehensive analysis results of general combining ability and special combining ability showed A3 and J8 inbred lines were the ideal parents for potted flowers, and J6, J10 and J12 inbred lines were the ideal parents for cut flowers and in which J6 was suitable for famale parent due to strong double flower trait. Analysis of special combining ability among hybrid crosses showed that the J6xA3, J6XJ8 and S5×A3 crosses were the primary combinations for potted flowers, and A3×A1, A3xJ12 and J8×J10 crosses were the secondary combinations; J6×A1, J6xJ12 and J6xS5 crosses were the primary combinations for cut flower, and J1O×S5 and J12×A1 crosses was secondary combinations.