'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 Md-ACS1: A DNA MARKER FOR PREHARVEST FRUIT DROP IN APPLE T. SATO, Y. WAKASA, N. NIIZEKI, T. HARADA Faculty of Agriculture and Life Science, Hirosaki University, 036-8561 Japan

An allele of the apple ripening-specific 1 aminocyclopropanr-1-carboxylate (ACC) synthase gene (Md-ACS1) has a 5’-flanking region possessing an inserted retroposon-like sequence.  Apple cultivars can be classified into three groups that are heterozygous or homozygous for the ACS1-1 and ACS1-2 alleles, and the homozygousity of ACS1-2 results in low levels of ethylene production in the ripening fruit.  Therefore, it was predicted that ACS1 genotypes might influence fruit characters. We investigated the relationship between ACS1 genotype and preharvest fruit drop.  Almost all of the ASC1-2 homozygous cultivars monitored were significantly lower drop than for ACS1-1 cultivars.  These results indicate that ACS1 genotypes can be useful as a DNA marker for early selection of low preharvest fruit drop in apple breeding.