Relationship between inbreeding coefficients and plant height of 1-year-old seedlings in crosses among Japanese pear (Pyrus pyrifolia Nakai) cultivars/selections

Plant height, a vigor trait, in 1-year-old seedlings made from Japanese pear (Pyrus pyrifolia) cultivars/selections was measured using 994 individuals from 29 families. The family mean of plant height was negatively correlated (r = -0.72**) to the inbreeding coefficients (F). The regression of the family mean (Fm) on the F value (Fm = 130 - 104F) showed that inbreeding depressions were 8%, 20%, and 40% for F = 0.1, 0.25, and 0.5, respectively. According to the regression, the family mean at F = 0 was estimated at 130 cm. These results showed that the vigor was greatly influenced by inbreeding in Japanese pear. Within-family variances, the genetic segregation of offspring in a family, differed according to family. The proportions of offspring with plant height above 130 cm (estimated Fm for F = 0) were extremely low, i.e., 0-17% for 0.5 <= F < 0.60 and 0-8% for F = 0.75. (c) 2008 Elsevier B.V. All rights reserved.