Cucurbit Genetics Cooperative Report 3:80-81 (article 39) 1980

STOCKS AND GERMPLASM DESIRED OR FOR EXCHANGE

Stocks Desired

T. C. Wehner

Chlorophyll deficient stocks of Cucumis sativus, including lines with any of the following genes: cd, g, gc, ls, pl, v, vvi, yc-1, yc-2, and yp.

Stocks for Exchange

G. W. Bohn, A. N. Kishaba, and J. D. McCreight

Cantaloupe breeding line WMR 29 is a high quality watermelon mosaic virus (WMV) 1-resistant cantaloupe adapted to southwestern desert production areas for use in cantaloupe breeding programs. WMR 29 is also tolerant to high concentrations of minor elements, sulfur dust, WMV race-3 and is heterozygous for resistance to powdery mildew race-2.

WMR 29 was originated at the U.S Imperial Valley Conservation Research Center at Brawley in cooperation with the Boyden Entomology Laboratory at Riverside. The released seed is the 17th inbred generation (Sib₁₇=F) from the fifth backcross (BC₅) to breeding line PMR 29 (a sib of Campo) from the cross PMR 29 x WMV 1-resistant line 90105. Line 90105 was selected from PI 180280, a muskmelon used in soups and stews in southern Asia (1).

Different selection and breeding procedures were used at different locations in different series of generations to combine the several resistances and tolerances with high quality. Resistance to WMV race-1 derived from 90105 was selected in greenhouse tests at La Jolla and Riverside. Watermelon mosaic virus race-1 inoculated plants remain symptomless. Tolerance to WMV race-2 was selected during spring with natural infection in the Imperial Valley. Adaptation to desert culture, freedom from crown blight, high fruit quality, and plant longevity were selected in the field in the Imperial Valley during both spring and summer.

Tolerance to high minor element concentration was tested in the greenhouse ar Riverside by growing plants in a modified Hewitt's solution with the minor elements five times more concentrated than normal. Its source is unknown. Tolerance to sulfur dust for powdery mildew control first observed in a Blythe planting was confirmed in controlled field trails at the University of California Imperial Valley Field Station. Its source is unknown. Resistance to powdery mildew race-2 derived from PMR 29 is controlled by the single gene Pmr-2. WMR 29 is segregating for resistance to powdery mildew race-2 since selection for homozygous resistant plants was not done.

WMR 29 produces well-netted, nearly spherical fruits with well-defined tracks, thick salmon-colored flesh, dry seed cavity and high soluble solids content. Fruits are extremely hard at fully slip and, thus, should withstand mechanical harvest and cross-country shipment.

WMR 29 retains considerable heterozygosity due to mass selection of open pollinated fruits for ten generations. It should be kept under selection pressure for fruit quality.

Muskmelon breeders desiring seed of WMR 29 should submit written requests to Dr. James D. McCreight, U.S. Agricultural Research Station, P.O. Box 5098, Salinas, CA 93915 or to Dr. Albert N. Kishaba, U.S. Boyden Entomology Laboratory, University of California, Riverside, CA 92521.

Literature Cited

1. Webb, R. E. 1979. Inheritance of resistance to watermelon mosaic virus in Cucumis melo L. HortScience 14: 265-266.