University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln U.S. Department of Agriculture: Agricultural Publications from USDA-ARS / UNL Faculty Research Service, Lincoln, Nebraska 1999 Report of the Cucurbit Working Group James D. McCreight USDA-ARS, [email protected] Jack Staub USDA-ARS Follow this and additional works at: https://digitalcommons.unl.edu/usdaarsfacpub Part of the Agricultural Science Commons McCreight, James D. and Staub, Jack, "Report of the Cucurbit Working Group" (1999). Publications from USDA-ARS / UNL Faculty. 483. https://digitalcommons.unl.edu/usdaarsfacpub/483 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Ecological Effects of Pest Resistance Genes in Managed Ecosystems REPORT OF THE CUCURBIT WORKING GROUP1 James D. McCreight, USDA-ARS, Editor Jack Staub, USDA-ARS, Editor Group Members: Noel Keen, University of California-Riverside, disease physiology, bacteriology James D. McCreight, USDA-ARS, breeding Robert Norris, University of California-Davis, weed science, integrated pest management Cal Qualset (Group Leader), Genetic Resources Conservation Program-University of California-Davis, breeding, population genetics Keith Redenbaugh, Seminis Vegetable Seeds, Inc. Jack Staub, USDA-ARS, breeding, population genetics Sue Tolin, Virginia Tech, virology, disease physiology, risk assessment policy Bert Uijtewaal, Nunhems Zaden, breeding, molecular biology CUCURBIT BACKGROUND INFORMATION Hybridization among Cucurbita species is also possible, with various of the 15 or so able to Cucumber (Cucumis sativus L.) originated in hybridize with some difficulty. Diversity in C. India, melon (C. melo L.) and watermelon pepo is rooted in the ancient widespread (Citrullus lanatus) in Africa, and squash, distribution of free-living populations. Today, pumpkin, and gourd (Cucurbita spp.) in the these populations range from northeastern Americas. Thus, cucumber, melon, and Mexico and Texas, east to Alabama and north watermelon (including citron) are relatively through the Mississippi Valley to Illinois. They recent introductions to the New World. Most occupy a diversity of environments and domesticated species of Cucurbita were ecological niches—from upland, seasonally dry introduced from Mexico, Central America, and thornscrub habitat in northeastern Mexico, to South America with the migration of native primarily riverbanks and moist thickets in Texas, Americans centuries earlier. Wax gourd to a variety of riparian and other disturbed (Benincasa hispida (Thunb.) Logr.) is from lowland habitats (e.g., agricultural fields, railroad Southeast Asia. Bottle gourd (Lagenaria tracks, highway embankments, etc.) throughout siceraria (Molina) Stand.) is of African origin. the Mississippi Valley. Different morphological South Asia is the probable center of origin for and physiological adaptations have evolved in cultivated species of Luffa. Bitter melon these areas, including early fruit abscission from (Momordica charantia L.) is a tropical Old the peduncle in response to riverine dispersal in World species. Chayote (Sechium edule (Jacq.) Texas, as well as relatively quick seed Swartz) is a New World species from southern germination in response to a shorter growing Mexico and Central America. season in the more northerly populations (Decker-Walters et al. 1993). Of the New World taxa, only Cucurbita pepo occurs as a significant weed problem in North Wild native taxa in the US and Mexico are listed America. Cucurbita pepo is a morphologically in Table 2. In addition, many Old World and ecologically diverse species composed of cucurbits have been reported as feral species in genetically distinct groups of cultivars and free- the US and Mexico (Table 3), particularly in the living populations (i.e., self-sustaining, including coastal plain from Florida to Texas and into both wild and weedy populations). All of these northern Mexico. The feral variety of Citrullus diverse elements are completely interfertile and lanatus, which originated in Africa, is cross are classified as shown in Table 1. compatible with watermelon and occurs in the 1 Group Report from the “Workshop on Ecological Effects of Pest Resistance Genes in Managed Ecosystems,” in Bethesda, MD, January 31 – February 3, 1999. Sponsored by Information Systems for Biotechnology. 79 Ecological Effects of Pest Resistance Genes in Managed Ecosystems US. The remaining cucurbits in Table 3 are bacterial) continue to be identified. Recently found sporadically to rarely in disturbed areas described pests include sweetpotato whitefly and and are not major agricultural weeds. The same silverleaf whitefly, zucchini yellow mosaic virus, is true for the occasional escapes of melon and lettuce infectious yellows virus, cucurbit aphid- watermelon that have been documented in some borne yellowing virus, cucurbit yellow stunting North American floras (e.g., Steyermark 1963). disorder virus, squash leaf curl virus (= watermelon curly mottle = melon leaf curl), Production Patterns and Cropping bacterial blotch of watermelon and melon, vine Systems in the US decline of melon (causal agent yet to be Cucurbits are grown in several commercial identified), and Monosporascus cannonballus. cropping systems and are popular garden crops. Worldwide, there may be more squashes grown Resistance breeding is the most active area of in home gardens than are grown commercially cucurbit germplasm, breeding, and genetics for sale in local or distant markets. Although research in the US and worldwide. Most consumption figures are not readily available, programs use traditional genetic and plant production estimates are available for the US and breeding procedures. Mapping (phenotypic, many other countries (FAO 1992). isozyme, molecular) of cucumber and melon has begun and progressed, but the maps are not yet Cucurbit production in parts of the desert saturated and few linked markers have been southwest US, e.g., Imperial Valley, California, identified (Pitrat 1998). There has been little is done on a large scale in areas of intensive progress in the development of genetic maps of agricultural production of a broad array of warm watermelon and Cucurbita spp. and cool season vegetables and agronomic crops. Weed control in the immediate vicinity of these Most pest resistance genes have been found in production fields is generally very good, but US or exotic cultivars or in landraces and cross- control along river and canal banks is generally compatible relatives from centers of origin or not carried out. In some of these areas, it is diversity. Unsuccessful attempts have been made possible to find one or more cucurbits, usually a to produce fertile F1 progeny from crosses of Cucurbita sp., grown on a small scale. Cucumis metuliferus with Cucumis melo and Cucumis sativus in order to transfer several pest In the rest of the US, cucurbits are grown on a resistance traits from this distant relative to smaller scale and are not usually part of an melon and cucumber. However, Cucurbita intensive vegetable and/or agronomic crop okeechobeensis ssp. martinezii was successfully production area. They are spatially and used in crosses with Cucurbita maxima and temporally dispersed. Early season production Cucurbita pepo to transfer powdery mildew begins in Florida and moves northward to New resistance to these two species (Contin 1978). York and New England in the East, and Through its Asgrow Seed division, Seminis Michigan and Wisconsin in the mid-west. Weed Vegetable Seeds has introduced transgenic control in these systems may be more difficult resistance to two potyviruses (ZYMV and due to increased rainfall and the resultant native WMV) and one cucumovirus (CMV) in summer plant populations that may often be found squash (Cucurbita pepo). growing immediately adjacent to cucurbit fields. Many sources of pest resistance have been Pests of Cucurbits identified in cucurbits, although relatively few Cucurbits are afflicted with a broad array of have been deployed in commercial cultivars (see insect, pathogen, and nematode pests. With the McCreight 1998). Few of the identified exception of powdery mildew, which is one of resistance genes in the other cucurbits have been few diseases that may be found in most deployed or stacked in commercially available production areas across the US, each production cultivars. area requires a different complement of pest resistances. New pests (insect, fungal, viral, and 80 Ecological Effects of Pest Resistance Genes in Managed Ecosystems Table 1. Major cultivated cucurbit species in the US and worldwide. Scientific name 2n Common name(s); utilization Cucumis sativus 14 Cucumber; fresh, cooked, processed Cucumis melo 24 Cantaloupe, honeydew, exotic; fresh, cooked, juice, confections Citrullus lanatus 22 Watermelon (seeded, seedless); fresh, candied, processed, juice Cucurbita pepoz 40 ssp. pepo Cultivated pumpkins, marrows, a few ornamental gourds (e.g., orange and warted gourds) ssp. ovifera var. ovifera Cultivated crookneck, scallop, and acorn squashes, most ornamental gourd cultivars ssp. ovifera var. texana Free-living populations in Texas ssp. ovifera var. ozarkana Free-living populations in the central Mississippi Valley and the Ozark Plateau ssp.