High-density Nursery System for Breeding Peach and Nectarine: A 10-year Analysis

Abstract

A 10-year analysis of the high-density nursery (HDN) in the breeding of low-chilling peach and nectarine [Prunus persica (L.) Batsch] cultivars indicated selection was effective during the first cropping year for chilling requirement, fruit development period, size, color, shape and firmness but not for crop load, which needs to be evaluated at normal spacing over several years. The HDN system effectively has advanced the breeding program by promoting short generation time, reducing labor and space, and allowing for rating of some characters within 2 years from seed.

Breeding of Low-chill Peach and Nectarine for Mild Winters

“…The highest chilling requirement clones ceased growth first in the presence of shortening days. A correlation matrix among chilling requirement, length of fruit development period, crop load, fruit color, fruit size, fruit shape, and fruit firmness showed a few low, but significant relationships (15). None of the correlations were high enough to be of use in seedling selection.…”

“…This relationship must be close enough for high genetic progress to be made in advancing potential commercial selections. Recent stud ies have shown that expression of traits in the fruiting nursery, such as chilling requirement, fruit development period, fruit size, and flower bud set is highly correlated with expression in mature clones of the same selections in simulated commercial plantings (15). Chilling requirement was slightly higher and fruit size slightly lower in young seedlings selections in the fruiting nursery than in mature trees of the sam e selections in sim ulated com m ercial plantings.…”

“…The late season is fixed as the rainy season begins in early June. The 100-to 350-CU zone represents central Florida and the subtropics (1,11,15,19). The 400-to 600-CU zone represents northern Flor ida and some low-chill areas in the world's temperate zones, such as southern Spain and northern Argentina.…”

“…Seedling marker genes for early ripening have been de scribed in peach, and evidence has been presented for major genes controlling time of ripening (23). Genetic progress in reducing days from bloom to maturity and increasing fruit size was obtained among selections (15). The increase in fruit size and short fruit develop ment period were obtained while maintaining high ratings in the same selections for fruit color, firmness, and shape.…”