Cross Compatibility Analysis to Identify Suitable Parents of Tagetes erecta and T. patula for Heterotic Hybrid Breeding

Seven interspecific crosses of Tagetes erecta x T. patula were conducted in this study. The cross compatibility index, seed setting rate, germination rate, phenotype, ploidy level, heterosis over male parent and field performance were tested. The results showed that different cross compatibility indices of Tagetes vary greatly, from 10.44 similar to 114.41, which is far less than that of the intraspecific hybridization S-121 x I-506 index. The seed setting rate of each cross ranged from 15.67% to 49.0%, and the cross S-121 x TP-512 scored the highest seed setting rate, which was higher than that of the intraspecific cross S-121 x I-506 (35.85%). Compared with the male parent, F-1 has higher plant height, wider crown width, larger flower diameter and more ray florets and earlier bloom with two exceptions. The S121 of T. erecta was diploid. All of the male parents of T. patula were tetraploids, and the combinations were triploids. The traits of plant height, plant width, flower size and number of ray florets showed positive heterosis over the male parents, and the days leading to flowering showed both positive and negative ones. Finally, S121 x TP-379 and S121 x TP-512 were selected as the two best combinations. This study confirmed that the two species of marigold could be crossed for better F-1 varieties with improved performance.