Sweetpotato whitefly, Bemisia tabaci (Gennadius), adversely affects yield and quality of a wide range of vegetable and agronomic crops worldwide directly through feeding damage or indirectly as virus vectors (Henneberry et al., 1998). It is known to transmit 111 virus species (Jones, 2003). Six sweetpotato whitefly-transmitted begomoviruses of melon (Cucumis melo L.) have appeared in commercial melon fields in the southwestern United States, western Mexico, and Central America since 1977 (Table 1). Squash leaf curl virus (SLCV), first reported in 1977 (Flock and Mayhew, 1981), is notable among the group for the fact that melon was not a host in open commercial fields or experimentally in controlled-inoculation greenhouse tests (Cohen et al., 1983), but SLCV was recently detected with polymerase chain reaction (PCR) using SLCV-specific primers in commercial melon plants in Imperial Valley (R.L. Gilbertson, pers. comm.). Cucurbit leaf crumple virus (CuLCrV) (Guzman et al., 2000) and cucurbit leaf curl virus (Brown et al., 2000) are identical geminiviruses, with more than 98% similarity based on percent nucleotide and amino acid similarities for open reading frames, and are distinct from SLCV and melon chlorotic leaf curl virus (≤92% and 91% respectively) (Brown et al., 2002). None of the six viruses has caused significant, widespread economic losses to melon production in these areas (T.A. Turini, unpublished). Genetic resistance has not been reported to any of these six viruses, with the possible exception being the original SLCV strain, which did not infect melon.
Six begomoviruses of melon in the North and Central Americas.
Cucurbit leaf crumple virus symptoms include chlorotic leaf spots and terminal buds, leaf curling and crumpling, and interveinal yellowing. In addition, plants may be stunted in size (Fig. 1). When severe and widespread CuLCrV symptoms were observed in commercial melon fields early in the season in several succeeding years, the fields recovered with no observable reduction in yield (T.A. Turini, unpublished). Experimental melon plantings in Fall 2003 at the University of California, Desert Research and Education Center (DREC), El Centro, CA, and the University of Arizona, Yuma Agricultural Research Center, Yuma, AZ, exhibited severe and uniform symptoms similar to SLCV and CuLCrV. We report here the identification of CuLCrV at these two sites, resistance in field and greenhouse tests to CuLCrV in a limited number of melon cultigens [cultivars, breeding lines, and plant introductions (PIs)], and inheritance of resistance in melon.
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