GENETIC CORRELATION BETWEEN RIPENING TIME AND WEIGHT OF FRUITS IN JAPANESE PEAR (PYRUS-PYRIFOLIA NAKAI)

This study was conducted to obtain estimates of genetic parameters on ripening time of fruits and fruit weight, using a Japanese pear seedling population of sixteen families and their parental cultivars. High correlations (r=0.759**) were observed between ripening time and fruit weight among families(Fig.1). In the case that the average of the ripening time of fruits of seedlings in a family was early, the average of fruit weight was low, and the reverse case as for the ripening time, the average of fruit weight was relatively high (Fig.1). High correlations (r=0.793**) were also observed between mid-parent of ripening time and the family mean of fruit weight (Fig.2). In the case that the ripening time of fruits of parents was early, the average of fruit weight of offsprings was low comparing with that of the offsprings of late-ripening parents (Fig.2). Significant correlations were observed also with in families, and in most of families early-ripening seedlings tended to bear a small fruit (Fig.3, Table 2). Heritabilites of ripening time and fruit weight were estimated to be about 0.9-1 and 0.6-0. 7, respectively (Table 3). Both phenotypic and genetic correlation coefficients were estimated to be about 0.8 (Table 3). Breeding method of early-ripening Japanese pear cultivars and the use of indirect selection for fruit weight through ripening time were discussed.