Genetic analysis of leaf trichome density using mixed major gene plus polygene inheritance model in Brassica rapa ssp. chinensis

Leaf trichome is an important trait for stress-resistance breeding in Brassica crops, but its scientific evaluation and identification are rarely reported. To investigate the inheritance of leaf trichome in non-heading Chinese cabbage, two inbred lines, '14XS23W' (glabrous) and '14XS23Y' (hirsute), were used to generate F-1 and F-2 populations for joint analysis using a mixed major genes plus polygene inheritance model. The density of adaxial leaf trichomes was controlled by two pairs of additive-dominance-epistasis major genes plus additive-dominance polygenes. The broad-sense heritabilities of the major genes were 93.8% and 85.51%, respectively, for greenhouse and open-field conditions. However, the density of the abaxial leaf trichome was controlled by two pairs of additive-dominance-epistasis major genes plus additive dominance-epistasis polygenes. The broad-sense heritabilities of the major genes were 91.45% and 72.20%, while the polygenes were 0% and 14.5%, respectively, for greenhouse and open field environments. These results indicated that trichome density in non-heading Chinese cabbage was primarily controlled by two pairs of major genes with high heritability, implying that this trait is suitable for rapid selection in early generations.