Genetic Resistance to Cucurbit Leaf Crumple Virus in Melon.

Cucurbit leaf crumple virus (CuLCrV) is a geminivirus transmitted by Bemisia tabaci (Gennadius) biotype B (SPW-B) and common in melons (Cucumis melo L.) planted from July through September in the desert southwestern United States. Symptoms include chlorotic leaf spots, leaf curling and crumpling, and interveinal yellowing, and plants may be stunted. Melon breeding line MR-1, and six plant introductions (PIs; PI 124111, PI 124112, PI 179901, PI 234607, PI 313970, and PI 414723) exhibited partial resistance to CuLCrV in naturally infected field tests and controlled inoculation greenhouse tests. PI 236355 was completely resistant in two greenhouse tests. Partially resistant plants exhibited chlorotic spots, or mild expression of other typical CuLCrV symptoms; all such plants were positive for presence of virus using polymerase chain reaction analysis with a CuLCrV-specific primer pair from the BC1 region. Genetic resistance to CuLCrV in melon was recessive. Field and greenhouse data from F1, F2, and backcrosses of the F1 to 'Top Mark' and PI 313970 demonstrated a single, recessive gene for resistance to CuLCrV. Progenies from crosses of four partially resistant cultigens with 'Top Mark' were susceptible. Resistance in PI 313970 appeared to be allelic, with resistance in the other six cultigens based on F1 data. The name cucurbit leaf crumple virus and symbol culcrv are proposed for this gene. [ABSTRACT FROM AUTHOR]