Diversity in Seasonal Bloom Time and Floral Development among Apple Species and Hybrids

Abstract

Timing of flowering is a fundamental developmental transition that has great ecological and agricultural importance. For perennial plants, seasonal timing of bloom and anthesis, which is the ultimate stage of flowering, can be determined by the net effect of several preceding developmental steps: seasonal timing of floral initiation, rate and extent of floral development before winter dormancy, duration of dormancy, and rate of floral development after release from dormancy. In the domestic apple (Malus ×domestica), fruit production has generally favored cultivars that bloom relatively early in the season. However, floral tissues are easily damaged by freezing temperatures, and freeze injury is especially problematic in years when abnormally warm temperatures in early spring lead to rapid floral development. To facilitate identification of genes/alleles that govern bloom time, and that could add versatility to production systems for apple, we evaluated seasonal bloom time for accessions of M. ×domestica, wild apple species (Malus sp.), and Malus hybrids maintained in a large germplasm diversity collection.