Cucurbit Genetics Cooperative Report 7:45 (article 20) 1984

Evidence of a Recessive Powdery Mildew Resistance Gene in Muskmelon PI 414723

J. D. McCreight

U.S. Department of Agriculture, Agricultural Research Service, P.O. Box 5098, Salinas, CA

Plant Introduction (PI) 414723 (melon aphid, Aphis gossypii Glover, resistant inbred of PI 371795) is a source of aphid resistance (1) and zucchini yellow mosaic virus resistance in muskmelon. Observations of greenhouse plantings indicated that it was also resistant to powdery mildew caused by Sphaerotheca fuliginea (Schlecht.) Poll. PI 414723 was crossed with 'Topmark' which is susceptible to S. fuliginea races 1, 2, and 3. Twenty-five seedlings of PI 414723 and F₁ (PI 414723 x 'Topmark') were inoculated 3X over a 13-day period beginning at the cotyledon stage of growth. The inoculum, cultured on 'Hales Best Jumbo' and 'Topmark', was previously identified on a set differential hosts as S. fuliginea race 1 (unpublished data). The plants were rated for powdery mildew 3 and 4 weeks after the 1st inoculation.

PI 414723 was resistant. The F₁ (PI 414723 x 'Topmark') was susceptible, which indicates that the resistance in PI 414723 is conditioned by a recessive gene(s).

Literature Cited

1. Kishaba, A.N., G.W. Bohn and H.H. Toba. 1971. Resistance to Aphis gossypii in Cucumis melo from India. J. Econ. Entomol. 64:935-937.
2. Pitrat, M. and H. Lecoq. 1984. Inheritance of zucchini yellow mosaic virus resistance in Cucumis melo L. Euphytica 33 (In press).