SOURCES OF GENETIC-RESISTANCE TO RED RINGSPOT VIRUS IN A BREEDING BLUEBERRY POPULATION

A group of 1031 genotypes representing 245 different crosses from a jo int U.S. Dept. of Agriculture-New Jersey Agricultural Experiment Stati on blueberry breeding program was evaluated for blueberry red ringspot virus (BBRRSV) symptoms after 8 years of field exposure. Among 41 par ents represented by 10 or more progeny, significant differences were o bserved in offspring BBRRSV expression. The species Vaccinium lamarcki i Camp. (4x) and V. amoenum Ait. (6x) and the cultivars Woodard (6x) a nd Earliblue (4x) seem to have high frequencies of alleles for BBRRSV resistance. Significant differences were also found among 21 different crosses. The most resistant cross was 'Elizabeth' x 'Earliblue', whic h had a 23 % BBRRSV incidence. Progeny evaluation revealed that none o f the parents involved produced families in which atl plants were resi stant; hence, resistance to this virus may be under polygenic control.