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  • Author or Editor: David Drews x
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`Pavo', a commercially grown, virus-susceptible squash (Cucurbita pepo L.) hybrid, and two experimental virus-resistant transgenic squash hybrids, XPH-1719 and XPH-1739, were tested for field performance. The two transgenic squash hybrids possess the desired fruit and plant characteristics of their parental line, `Pavo', plus resistance to zucchini yellow mosaic virus and watermelon mosaic virus 2 (XPH-1719), and resistance to zucchini yellow mosaic virus, watermelon mosaic virus 2, and cucumber mosaic virus (XPH-1739). Percent emergence and days to flowering were similar among the three hybrids. XPH-1719 and XPH-1739 were equally effective in producing a high percentage of quality marketable fruit and yields with 90% and 13,800 kg·ha–1 and 87% and 16,500 kg·ha–1, respectively. XPH-1719 and XPH-1739 demonstrated their outstanding virus resistance over `Pavo' by producing only 3% and 14% symptomatic plants, respectively, compared to 53% for `Pavo'. They also produced the lowest percentage of infected fruit, 0% and 7%, respectively, with `Pavo' at 26%.

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Sixty-one cultivars of geraniums, including zonal, regal, ivy, and scented, were tested for susceptibility to three strains of Ralstonia solanacearum: a race 1, biovar 1 (R1B1) strain P597 isolated from tomato in Florida, a R1B1 strain P673 obtained from pothos originated from Costa Rica, and a race 3, biovar 2 (R3B2) strain UW551 isolated from geranium imported from Kenya. These three strains represent populations of R. solanacearum found in the United States or imported with infected plant propagative material. A genomic comparison of the geranium cultivars was also done using amplified fragment length polymorphisms. Both R1B1 strains were more virulent than the R3B2 strain, producing wilt symptoms on most cultivars of zonal, regal, and ivy types. Variation in susceptibility of geranium cultivars to the two R1B1 strains was observed. The R3B2 strain UW551 had a much more restricted host range and was not able to infect most regal geranium cultivars when applied as a soil drench. Many of the scented cultivars were found to be resistant to all three strains of R. solanacearum when tested using the drench inoculation method. However, most scented cultivars were found to be susceptible when plants were wound-inoculated. The greatest variation in type of resistance was observed between the scented geranium cultivars and specific strains of R. solanacearum.

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Two of Asgrow's experimental virus resistant transgenic lines, XPH-1719 and XPH-1739, and their parental line, Pavo, a commercially grown virus susceptible hybrid, were tested for field performance at the Texas A&M University Experimental Farm in the summer of 1993. The two transgenic squash lines possessed the desired fruit and plant characteristics of Pavo plus resistance to ZYMV and WMV2 (XPH-1719), and resistance to ZYMV, WMV2 and CMV (XPH-1739). Under the conditions of this test it was determined that the two transgenic hybrids, were equally effective in producing high quality marketable fruits/ha with 89.64 % and 86.84 % respectively and marketable yields with 13,762 kg/ha and 16,525 kg/ha respectively. XPH-1719 and XPH-1739 also demonstrated their outstanding virus resistance by producing only 3.44% and 14.35% symptomatic plants/ha, and 0.00% and 7.17% infected fruits/ha respectively compared to 53.55% symptomatic Pavo plants/ha, and 25.73% infected Pavo fruits/ha.

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