Heterosis and genetic analysis of branching in cut-flower chrysanthemums

The single-head cut-flower chrysanthemum is one of the most important and popular varieties of Chinese export cut flowers, but the less collateral varieties are very rare in the market. To produce new, high-quality varieties, we generated two hybrid combinations from the varieties Fukashi (SZ), Jinba (SM), and FengWofen (FW; "SM x SZ" and "SZ x FW", respectively). A detailed analysis of morphological tests revealed the heredity and variation in the F-1 populations. Hybrid plant height showed significant negative heterosis. Flower diameter and the number of small flowers were both diminished, but the ornamental traits of the population overall showed wide variation. The results provided a basis of genetic differences for subsequent analysis. In both crosses, Fukashi played an important regulatory role in determining branching traits in the middle zone and basal zone of the progeny plants: it reduced hybrid branching traits in the middle zone to a certain extent, however, it increased those in the basal zone and there were some transgressive progeny. These results indicate that hybridization is an effective way to contribute to the phenotypic variation of cut-flower chrysanthemums. The inheritance of branching traits identified in this study will be important in improving the plant architecture of chrysanthemum cultivars.