Relationships between Parental, Seed, and Seedling Chilling Requirement in Peach and Nectarine

Abstract

Attempts to select for flower bud chilling requirement (CR) at the seed stage were made in 58 families obtained from crosses and open-pollination of low chill selections and cultivars of peach and nectarine [Prunus persica (L.) Batsch] from the Florida breeding program. A nonsignificant correlation (r = 0.08) between midparent bud CR and family seed CR was obtained. A low significant correlation (r = 0.21**) was obtained between individual seed CR and the CR of the resultant seedling. Seed coat removal had no effect on these correlations. Narrow sense heritability for bud CR as determined by parent-offspring regression was 0.50 ± 0.06. The small range in CR of the seed and pollen parents, 300 to 450 and 200 to 400 chill units, respectively, may explain the low correlation values obtained. The data suggest that it is impractical to screen for seedling CR based on seed CR where the CR for climatic adaptability must be held within a range of less than 300 chill units.

Breeding of Low-chill Peach and Nectarine for Mild Winters

“…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. A lthough seed chilling requirement was shown not to predict seedling chilling requirement accurately (13), time of autumn growth cessation was generally related to chilling requirement of clones (10). The highest chilling requirement clones ceased growth first in the presence of shortening days.…”

“…In areas of inadequate winter chilling, successful culture of tem- perate-zone fruit is dependent on cultivars with a low chilling re quirement; desiccation and/or chemicals to terminate growth and assist defoliation; and appropriate rootstocks, irrigation, and/or chemicals to hasten and synchronize bud burst in the next growth cycle (6,7,13,16). In equatorial regions where winter chilling is rare, the effect of altitude on temperature (Fig.…”