Heritability of Morphological and Vegetative Traits in Corylus spp.

A breeding program aimed to obtain new varieties suitable for processing was started at the end of the 1970s. The population studied included 20 parental genotypes and about 1000 seedlings obtained from 19 cross combinations in which the local cultivar ‘Tonda Gentile delle Langhe’ (‘TGL’) has been used as female parent in 84% of crosses. High percent kernel and Big Bud Mite resistance are the most interesting parameters needed to improve ‘TGL’. Eleven morphological traits of the nut together with four phenological, and four vegetative traits of the tree, were observed for two years. Each parameter was rated on a specific scale. The aim of the research was to estimate narrow-sense heritability by regression of progeny means on mid-parent values and the estimation of phenotypic correlation coefficients. Narrow-sense heritability ranged from r = 0.21 for shell thickness to r = 0.95 for nut height. Among phenological traits, Big Bud Mite susceptibility was highly heritable (r = 0.78). Big Bud Mite susceptibility was negatively correlated with time of bud break and tree vigour and positively correlated with sucker production. Of the carpological traits, percent kernel showed high heritability (r = 0.68) and was negatively correlated with shell thickness, nut weight and volume.