Search Results
Abstract
Genetic and environmental components of variance were estimated in 2 seedling populations of plum and prune at the University of California, Davis, California; the first population comprised 90 progeny of 14 open-pollinated parents, the second, 430 progeny of 50 controlled crosses among 28 parents. The estimates of phenotypic and genotypic variability associated with these traits in these 2 populations were nearly identical. Heritabilities, estimated by regressing the 500 progeny from the second population on their 50 mid-parents, were very high (0.80–1.0) for fruit size measurements and ripening dates, but zero for fruit yield. Also high (0.49) was the maximum heritability of percent soluble solids, estimated by the genetic variance/phenotypic variance. Phenotypic correlations among the traits fruit size, ripening date, and percent soluble solids are also small but significant in this seedling population. These results indicated that the rates of gain to be expected from mass selection on such populations are substantial.
Abstract
Estimates were obtained of the means, variances, and heritabilities of 10 commercially important traits from approx 200 parents and their more than 2,000 offspring observed over a period of 8 years. After adjustment of measurements for the effects of yearly variations in climate, heritabilities were found to be very high for ripe date; high for bloom date, amount of bloom, fruit length, suture, and cheek; modest for fruit firmness and acidity; and low for percent soluble solids and crop. The implications of these results on the design and execution of breeding programs in such crops are discussed.
Abstract
Five peach rootstock selections show immunity to root-knot nematode disease caused by Meloidogyne incognita (Kofoid and White) Chitwood and M. javanica (Treub) Chitwood. These are the first peach rootstocks which remain free from galls when exposed to both these root-knot nematode species. They are derived from a 1949 cross in Chico, California, of Prunus davidiana Franch with a Chinese Peach.
Resistance to the species M. incognita and M. javanica depends on different genes. Resistance to the former was inherited as a monofactorial dominant. Resistance to M. javanica appeared dependent on 2 or more dominant genes in both ‘Okinawa’ and P. davidiana, but P. davidiana progenies were completely free from visible galls.
A third type of root-knot nematode was discovered in Florida in 1966. It reproduces readily on ‘Okinawa’, ‘Nemaguard’ and the other lines which have been selected for resistance or immunity to M. incognita and M. javanica.