Submitted to: Journal of Forestry and Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2010
Publication Date: 2/1/2011
Publication URL: http://www.academicjournals.org.jhg
Citation: Klas, F.E., Fuchs, M., Gonsalves, D. 2011. Fruit yield of virus-resistant transgenic summer squash in simulated commercial plantings under conditions of high disease pressure. Journal of Horticulture and Forestry. 3(2):46-52. Interpretive Summary: Virus-resistant transgenic summer squash has been commercialized in the U.S. since 1994. These commercial cultivars show transgenic resistance to two important viruses of cucurbits: zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus II (WMV II). In 2006, transgenic squash was planted on an estimated 24% of the summer squash acreage in five of the seven major producing states. Resistance has been durable and these transgenic squash have played a major role in enabling farmers to grow summer squash without damage by ZYMV and WMV II. This work describes a detailed study to measure the fruit yield and marketability of the virus-resistant transgenic squash under simulated commercial conditions under high disease pressure of ZYMV and WMV II. The data clearly showed that under high disease pressure, fruit yield and marketability of the transgenic squash were much higher than comparable nontransgenic summer squash. This work shows that transgenic virus-resistant crops provide a sustainable approach for controlling plant viruses.
Technical Abstract: Fruit yield of transgenic crookneck summer squash ZW-20 resistant to Zucchini yellow mosaic virus (ZYMV) and Watermelon mosaic virus (WMV) and of a susceptible nontransgenic lineage of the same genotype was compared over two consecutive years. Field trials relied on small-scale plantings that reflected commercial settings under conditions of severe disease pressure by ZYMV and WMV with infection achieved via aphid-mediated inoculation from virus source border plants. Across all trials, all transgenic plants were highly resistant to ZYMV and WMV, and the majority (79%, 331 of 421) produced 3 to 9 fruits per plant. In contrast, all control plants had severe systemic symptoms and the majority (80%, 336 of 421) produced 0 to 4 fruits per plant. In addition, all fruits of transgenic squash ZW-20H and ZW-20B were of marketable quality whereas most fruits of nontransgenic controls (96%, 947 of 989) were unmarketable. Differences in fruit number (P = 0.000) and fruit weight (P = 0.000) between transgenic and conventional squash plants were significant but not between ZW-20H and ZW-20B plants (P = 0.933 and P = 0.964, respectively). This is the first report on a comparative analysis of fruit yield of transgenic versus conventional summer squash under conditions approaching commercial plantings in which high infection rates of ZYMV and WMV were achieved via indigenous aphid populations.