Standard Seedlings Research Articles

TESTING A MICROSATELLITE MARKER FOR SELECTION OF COLUMNAR GROWTH HABIT IN PEACH [PRUNUS PERSICA (L.) BATSCH

Tree fruit breeding requires large numbers of seedlings in the field for selection. These trees occupy large land areas and are expensive to maintain. Most seedlings are discarded, thus the investment in these trees is lost. Selection in the greenhouse would spare much of this expense. Marker-assisted selection offers this possibility. A microsatellite marker was tested for selection of columnar (also termed “pillar or “broomy”) growth habit (brbr). Columnar trees are being tested for highdensity production systems. Seventy-five genotypes were used for this study. These included compact (CT), dwarf (DW), standard (ST), and 2 sources of columnar; showy-flowered (SFP) with small, melting-, white-flesh fruit, and non-showy flowered (NSP) with large, non-melting-, yellow-flesh fruit. The microsatellite marker pchgms1 has been previously assigned a position 12.5 cM from the br locus in SFP trees. Using pchgms1 in this study, 2 fragments were obtained. One fragment was present only in SFP trees, the other was present in all other trees, including NSP. Hybrids of SFP with NSP and with all other growth habits contained both fragments. These results indicate that trees heterozygous for SFP can be selected, using pchgms1. At the seedling stage, prior to field planting, ST seedlings (BrBr) cannot be readily distinguished from trees heterozygous for br based on morphological traits. The efficiency of breeding programs developing brbr (columnar) or heterozygous Brbr (upright) trees could be improved by discarding ST trees prior to field planting. Using pchgms1, trees carrying the columnar trait, homozygous or heterozygous, could be selected from crosses using SFP as a parent. While this study demonstrates the usefulness of a satellite marker for selecting columnar growth habit in peach, the AFRS breeding program is utilizing NSP for cultivar development because of its higher fruit quality. The development of a microsatellite marker specifically for NSP or for both SFP and NSP sources of columnar growth habit is underway.