Pumpkins rank third in acreage among Ohio's fresh market vegetables. Recently, increasing incidence of insect-vectored viruses have threatened the economic potential of this crop. Studies were initiated in 1992 to obtain information on abundance of insect pests, to evaluate the effect of insecticides, reflective mulch and row covers on pest density and yield of marketable fruit. In 1994 and 1995, statewide virus surveys were conducted to determine virus types infecting the pumpkin crop. In 1992 the greatest insect injury of concern was cucumber beetle feeding on fruit rinds, Insecticides lowered pest density, but there was no effect on marketable yield. In 1993, yield of virus-infected fruit was lower were reflective mulch was used than where rowcovers or foliar insecticides were used. Marketable yield and virus incidence in 1994 were not affected by reflective mulch, rowcovers or stylet oil due to the late arrival of the virus. In 1995, aphid infestations at three locations were significantly lower on plants on reflective mulch than on plants on bare ground. Results of the 1994 virus survey showed that watermelon mosaic virus (WMV) was the most common virus in Ohio pumpkins. The watermelon mosaic developed late in the season and fruit deformity was not severe enough to affect marketable yield. There was some incidence of cucumber mosaic and squash mosaic virus but zucchini yellow mosaic virus was not detected in 1994. Results of ELISA testing of samples collected in August/September 1995 at 27 farms were 18 farms positive for watermelon mosaic virus, 5 sites positive for squash mosaic, 4 sites positive for papaya ringspot and 1 site positive for zucchini yellow mosaic.
R. Precheur, C. Welty, R.M. Riedel, and M.R. Breth
T.J.K. Radovich*, R.C. Pratt, L.A. Duncan, N. Welty, and M.D. Kleinhenz
Cucurbita maxima and C. pepo are difficult to hybridize, and it was our objective to generate F1 hybrids between ornamental cultivars of the two species. C. maxima `Lakota' and C. pepo `Jack O'Lantern'; and `OZ'; were selected as parents. `Lakota' (L) is an heirloom, hubbard-type cultivar producing pear-shaped, red-orange fruit with dark green mottling, `Jack O'Lantern'; (J) is an open-pollinated Halloween-type pumpkin cultivar and `OZ' is a Halloween-type hybrid. Sixteen plants of each cultivar were greenhouse-grown in a CRB design during the period July-Sept. 2003. Interspecific crosses were made in both directions, with intraspecific crosses (J × O) and selfs (L) serving as controls. Fruits were harvested about 20 d after pollination. Embryos were excised under aseptic conditions and grown on either full strength Murashige and Skoog (MS) media with 6% sucrose (S6), full strength MS media with 6% maltose (M6), or half strength MS media with 3% sucrose (S3). Fruit set was generally greater in the intraspecific crosses (33%) and selfs (67%) than in the interspecific crosses (15 %), with the notable exception of the interspecific combination L × J (85% fruit set). Embryos of interspecific and control crosses were about 1.5mm and >1cm long, respectively. Hypocotyl and root growth 10 d after plating was better on S3 (3.2 and 1.7 cm) than on S6 (1.6 and 0.25 cm) or M6 (0.35 and 0 cm), and a greater number of functional hybrids were obtained from embryos grown on S3 (6 plants) than on S6 (2 plants) or M6 (2 plants). The interspecific plants were backcrossed to one of the parents and novel combinations of shape, color and variegation in hybrid fruit were observed.