( 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
CPM, caused by Px , has become one of the most serious diseases of field and greenhouse cucurbits worldwide ( Krístková et al., 2009 ; McGrath, 2017 ; Sitterly, 1978 ). It is a serious fungal disease of BG ( Momordica charantia ), which is an
Anthracnose is a destructive foliage and fruit disease of cucurbits worldwide, particularly on cucumber, watermelon, and cantaloupe. Three fungal taxa have been implicated in the cucurbit anthracnose complex [Colletotrichum orbiculare (CO), C. magna (CM), and the putative teleomorph Glomerella cingulata var. orbiculare (GC)]. In the past 7 years we have assembled a large geographically diverse collection of cucurbit isolates that have been characterized for virulence, vegetative (heterokaryon) compatibility, and mitochondrial and nuclear DNA RFLPs. All isolates that are pathogenic on cucurbit foliage are CO, belong to one of the four VCGs, and belong to a single mtDNA RFLP haplotype. Three races of CO (1, 2, and 2B) can be distinguished by their disease reactions on cucumber (`Marketer' and `H19') and watermelon (`Black Diamond' and `Charleston Gray') differentials. Race 1 (cucumber pathogen) and race 2 (watermelon pathogen) were the most common. Examination of virulence on cucurbit fruit indicates that CM and GC are more aggressive than CO, indicating that they could primarily be fruit-rot pathogens. Race 1 and 2 have been used effectively for screening disease resistance in cucumber and watermelon. Isolates of CM, GC, and Colletotrichum spp. recovered from fruit lesions were not pathogenic or were weakly virulent on cucurbit foliage and were diverse with regard to VCGs, nuDNA, and mtDNA RFLPs. However, CM and GC were more virulent on cucurbit fruit than CO.
Seed production in the family Cucurbitaceae is more complicated than in dry-seeded grain crops because seeds mature within a moist fruit and are often held at high moisture content for several weeks before seed harvest. Muskmelon (Cucumis melo L.), a member of this family, was used as a model system to contrast seed development with crops that are dry at maturity. A detailed time course for `Top Mark' fruit and seed development is presented based on previous studies. In muskmelon fruit, precocious germination is inhibited osmotically by the low water potential of the surrounding fruit tissue. Muskmelon seeds exhibit primary dormancy that affects viability very early in development but has a greater effect on seed vigor and is removed by afterripening during dry storage. Osmotically distended or fish-mouth seeds are dead seeds that occur in cucurbit seed lots after aging kills the embryo without disrupting the semipermeable endosperm that completely surrounds and protects the embryo. Cucurbit seed crops should be harvested before the onset of fruit senescence to prevent aging of the seeds inside. Open-pollinated cucurbit seed crops are frequently once-over mechanically harvested. Mechanical harvesting combines seeds from many stages of development into a single seed lot, which may adversely affect quality and increase seed to seed variability. Hand harvesting cucurbit fruit at the optimal stage of development could improve seed quality in some instances but is more costly and time consuming and would increase production costs.
Early Reports of Didymella bryoniae and Gummy Stem Blight Both Bernhard Auerswald and Karl Fuckel, working independently, described Didymella bryoniae in 1869 from specimens collected on the cucurbit Bryonia growing in Germany ( Corlett, 1981
. Sphaerotheca ) xanthii (Castagne) U. Braun & N. Shishkoff (also known as Sphaerotheca fusca (Fr.) S. Blumer and S. fuliginea (Schlechtend.:Fr.) Pollacci] is an important disease of cucurbit crops throughout the United States ( Zitter et al., 1996 ). The
Arizona in 2006 ( Kuo et al., 2007 ). It occurred in Florida in 2007 and Georgia in 2017 but has not been as severe as in California ( Gadhave et al., 2018 ; Polston et al., 2008 ). Cucurbit chlorotic yellows virus (CCYV; genus Crinivirus , family
In recent years, Phytophthora capsici has become an increasingly severe disease of a wide range of vegetable crops, including cucurbit crops, where it can cause devastating yield losses ( Babadoost, 2004 ; Hausbeck and Lamour, 2004 ). In some
). Cucurbit powdery mildew (CPM) caused by Px is a serious fungal foliar disease of cucurbit production in open fields and greenhouses. Disease outbreak brings reduction in plant growth, premature foliage loss, and reduction in yield and fruit quality
& Shishkoff (syn. Sphaerotheca fuliginea auct. p.p.) can be a severely limiting factor in cucurbit production in open fields and greenhouses. Powdery mildew can result in reduced vigor of the seedlings and, in some instances, death of the seedlings. Powdery