Outcrossing in a Diverse Peach Rootstock Seed Block

Abstract

Over a 3 year period incidence of evident outcrosses (heterozygous redleaf) was recorded in open-pollinated seedlots of 'Nemared' and 'Rutgers Redleaf' collected in a rootstock repository. Since this block is made up predominantly of green-leaf cultivars this technique should detect most outcrossing events. Outcrossing averaged 6 percent. However, rootstock cultivar had a highly significant effect on the number of outcrossing events; in 'Nemared' such events occurred on average at more than three times the rate observed in 'Rutgers Redleaf.' In the absence of sufficient isolation to prevent undesirable outcrossing, rootstock cultivars need to have some readily identifiable 'marker' to reveal out-crosses so that they may be discarded.