CANTALOUPE LINE CZW-30 CONTAINING COAT PROTEIN GENES OF CUCUMBER MOSAIC-VIRUS, ZUCCHINI YELLOW MOSAIC-VIRUS, AND WATERMELON MOSAIC VIRUS-2 IS RESISTANT TO THESE 3 VIRUSES IN THE FIELD

Cantaloupe line CZW-30 containing coat protein gene constructs of cucu mber mosaic cucumovirus (CMV), zucckini yellow mosaic potyvirus (ZYMV) , and watermelon mosaic virus 2 potyvirus (WMV-2) was investigated in the field over two consecutive years for resistance to infections by C MV, ZYMV, and/or WMV-2. Resistance was evaluated under high disease pr essure achieved by mechanical inoculations and/or natural challenge in oculations by indigenous aphid vectors. Across five different trials, homozygous plants were highly resistant in that they never developed s ystemic symptoms as did the nontransformed plants but showed few sympt omatic leaves confined close to the vine tips. Hemizygous plants exhib ited a significant delay (2-3 weeks) in the onset of disease compared to control plants but had systemic symptoms 9-10 weeks after transplan ting to the field. Importantly, ELISA data revealed that transgenic pl ants reduced the incidence of mixed infections. Only 8% of the homozyg ous and 33% of the hemizygous plants were infected by two or three vir uses while 99% of the nontransformed plants were mixed infected. This performance is of epidemiological significance. In addition, control p lants were severely stunted (44% reduction in shoot length) and had po or fruit yield (62% loss) compared to transgenic plants, and most of t heir fruits (60%) were unmarketable. Remarkably, hemizygous plants yie lded 7.4 times more marketable fruits than control plants, thus sugges ting a potential commercial performance. This is the first report on e xtensive field trials designed to assess the resistance to mixed infec tion by CMV, ZYMV, and WMV-2, and to evaluate the yield of commercial quality cantaloupes that are genetically engineered.