Cucurbit Crops and Their Viral Diseases in Latin America and the Caribbean Islands: a Review
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Journal of Plant Pathology (2014), (2), 227-242 Romay et al. 227 96 Edizioni ETS Pisa, 2014 OFFERED REVIEW CUCURBIT CROPS AND THEIR VIRAL DISEASES IN LATIN AMERICA AND THE CARIBBEAN ISLANDS: A REVIEW G. Romay1,2, H. Lecoq1 and C. Desbiez1 1INRA, UR407 Unité de Pathologie Végétale, 84140 Montfavet, France 2Fundación Instituto de Estudios Avanzados (IDEA). Carretera Nacional Hoyo de la Puerta, Sartenejas, Caracas 1080, Venezuela SUMMARY 83,429,409 tons of melon, watermelon, cucumber and squash, while the USA is the main producer in the West- Cucurbit crops are cultivated throughout the world. ern Hemisphere with 4,602,370 tons (FAOSTAT, 2012). Melon (Cucumis melo L.), cucumber (Cucumis sativus L.), Cucurbit crops are often threatened by diseases of fun- watermelon (Citrullus lanatus (Thumb.) Mat. et Nak.), gal, bacterial and viral origin (Sitterly, 1972) and pests, squash and pumpkin (Cucurbita spp.) are the major crops. such as the pumpkin caterpillars (Diaphania spp.) and the In Latin America and the Caribbean islands (LAC) cucur- melon fly (Bactrocera cucurbitae Coquillet), are also seri- bits are consumed as a part of the daily diet since pre-Co- ous constraints to their cultivation (Peter and David, 1991; lumbian times, when some species such as Cucurbita pepo Duyck et al., 2004; Dhillon et al., 2005; HansPetersen et L., Cucurbita moschata Duch. and Cucurbita maxima Duch. al., 2010). Aphids, whiteflies and thrips can become serious were domesticated by American Indians. In LAC, cucurbit limitations to cucurbit production through the extensive crops have become export commodities and a source of damage they provoke, but also through the transmission of income for several countries, in addition to their role in viral disease (Brown et al., 1995; Morse and Hoddle, 2006; local consumption. The increase of area devoted to cu- Powell et al., 2006). curbit crops and the intensification of production has led At least 59 viruses infecting cucurbits are known to the emergence of severe viral epidemics that threaten (Lecoq and Desbiez, 2012), whose outbreaks have led the sustainability of these cultures. This paper reviews the to significant yield and quality losses to these crops on a cucurbit viruses described in the region and their impact. worldwide basis (Flock and Mayhew, 1981; Desbiez and In addition, the potential of different measures to control Lecoq, 1997; Brown et al., 2001; Lecoq and Desbiez, 2012). the most frequent cucurbit viruses in LAC is discussed. This review examines the current situation of cucurbit production in Latin America and the Caribbean islands Key words: Cucurbitaceae, plant viruses, cucurbit pro- (LAC), with special emphasis on viral diseases that affect duction, Latin American countries these crops, and the perspectives for their control. INTRODUCTION ORIGIN OF MAJOR CUCURBIT PLANTS CULTIVATED IN LATIN AMERICA AND THE CARIBBEAN ISLANDS Cucurbits represent one of the most important vegeta- bles for human consumption throughout the world. Cu- Cucumber (Cucumis sativus). Cucumber is widely curbit species are members of the family Cucurbitaceae grown in cool temperate regions because it is better adapt- that roughly includes 120 genera and 800 species, which ed to low temperatures than other cucurbits (Paris et al., are predominantly tropical plants though some, such as 2012). Cultivated cucumbers are usually monoecious. India Bryonia spp. and Alsomitra spp., are adapted to temperate is the centre of origin of cucumber that has been culti- climates (Teppner, 2004). Four major cucurbit crops are vated there for at least 3,000 years and introduced later in economically important worldwide: melon (Cucumis melo China and Europe (Leppik, 1966) and, in the 15th century, L.), cucumber (Cucumis sativus L.), watermelon (Citrul- in the Western Hemisphere by Columbus (Robinson and lus lanatus (Thumb.) Mat. & Nak.), squash and pumpkin Decker-Walters, 1997). The most closely related species to (Cucurbita spp.) (Robinson and Decker-Walters, 1997). C. sativus is the southeast Asian Cucumis hystrix Chackr. Global production of cucurbits cultivated in the world (Renner et al., 2007; Sebastian et al., 2010). C. sativus is is 151,212,210 tons. China is the main producer with the seventh plant species whose genome (243.5 Mb) has been sequenced. This is expected to provide a remark- Corresponding author: G. Romay Fax : + 58.212.9035003 able increase of new findings for its genetic improvement E-mail: [email protected] (Anonymous, 2009) 228 Cucurbit viruses in Latin America Journal of Plant Pathology (2014), 96 (2), 227-242 Melon (Cucumis melo). Melon is the other important comprises eight species (Bisognin, 2002), among which crop in the genus Cucumis. Its genome has recently been C. lanatus subsp. lanatus (Tsamma and citron type) and sequenced, which will contribute to further investigations C. lanatus subsp. vulgaris (sweet-dessert watermelon group) involving evolution and genetic improvement (García-Mas (Levi et al., 2012). Although a large number of commer- et al., 2012). The C. melo genome has a size of 454 Mb, cial varieties of watermelon are being released each year, while its mitochondrial genome (2,740 Kb) is the largest their genetic diversity is low, increasing the risks of pest among plant mitochondrial genomes, i.e. up to 100 times and disease threats. Hence, the great interest to enhance the size of a typical animal mitochondrial genome (Rodrí- genetic diversity using new germplasm coming from dif- guez-Moreno et al., 2011). The difference in genome size ferent geographical regions (Zhang et al., 2012). between C. melo and C. sativus is probably due in part to transposon amplification in the melon genome (García- Squash (Cucurbita maxima, C. moschata, C. pepo). Mas et al., 2012). Africa is considered as the centre of ori- The genus Cucurbita comprises 12-14 different species gin of melon because of the large number of African wild of American origin and a distribution ranging from the species (Robinson and Decker-Walters, 1997), whereas USA to Argentina (Sanjur et al., 2002). Along with corn Central Asia and China are regarded as secondary cen- (Zea mays L.) and beans (Phaseolus spp), squashes were tres (Leppik, 1966). This assumption was supported by domesticated in the Americas, playing a crucial role for the chromosome numbers: melon and 30 other African the development of American Indian agriculture (Carter, species in the genus Cucumis have a chromosome number 1946). As stated by Paris (2000), six species were origi- of X = 12, whereas C. sativus has a chromosome number nally listed by Linnaeus in the genus Cucurbita on the of X = 7 (Luan et al., 2008). However, recent phylogenet- basis of phenotypic features. Afterwards, four of them ic analyses have shown that C. melo may have an Asian (C. pepo, C. verrucosa, C. melopepo, C. ovifera) were re- rather than an African origin, suggesting the Himalayan assigned to the species C. pepo and the other two were region as the ancestral area for progenitor populations of re-located in the genus Lagenaria and Citrullus. The great melon and cucumber. Moreover, a sister species of melon polymorphism exhibited by C. pepo may have led Linnae- is the Australian Cucumis picrocarpus F. Muell. whose di- us to identify four different species instead of a unique, vergence from melon occurred roughly 2.8 million years but polymorphic, species. Years later, the botanist A.N. ago (Sebastian et al., 2010). Duchesne demonstrated, on the basis of inability to hy- bridize and produce fertile offspring, that several forms Watermelon (Citrullus lanatus). Watermelon is more of Cucurbita belonged to the polymorphic C. pepo and produced than any other cucurbit in the world with that, more interestingly, two other Cucurbita forms were 73,313,777 tons according to latest reports. In Europe, wa- unable to hybridize with C. pepo, therefore, they were termelon production is slightly exceeded that of another considered as distinct species that were named C. maxima cucurbit, cucumber (FAOSTAT, 2012). Watermelon origi- and C. moschata (Paris, 2000). C. pepo is the northern- nates from Africa (Robinson and Decker-Walters, 1997). most species of the three aforementioned Cucurbita, the The presumed ancestor of the modern cultivar C. lanatus northwest of Mexico and the south-east of the USA being includes wild annual forms referred to as C. lanatus subsp. thought to be domestication centres of this species (Cart- lanatus var. caffer (Schrad.) Mansf., which are natives to er, 1946; Nee, 1990; Sanjur et al., 2002). Archeological the Kalahari Desert (Southern Africa). However, the find- studies in Mexico provided evidence of C. pepo and other ing of 5000-year-old seeds of wild watermelon in an ar- wild cucurbits cultivation as early as 8,750 BC, almost chaeological site in southwest Libya raises new discussions 60% of them being wild Cucurbita species and C. pepo about the origin, distribution and domestication history the only cultivated species (Whitaker and Cutler, 1971). of this species (Wasylikowa and van der Veen, 2004). In Three subspecies are recognized: C. pepo subsp. fraterna Asia, watermelon was introduced to India and China in (only found in wild form), C. pepo subsp. pepo (only found about the 9th and 12th century, respectively, in Europe by in cultivation) and C. pepo subsp. texana (found in culti- the Moors during their conquest of Spain (Dane and Liu, vation and wild form). The last two are more genetically 2007) and in the Americas by the Spaniards and rapidly related to each other (Gong et al., 2012). C. moschata is spread throughout the continent (Robinson and Decker- thought to originate from the middle American area, Walters, 1997). According to Romão (2000), a secondary from which it spread southward and northward (Carter, centre of watermelon diversity is northeast Brazil where 1946). The wild ancestor of C. moschata is unknown, slave trading might have reached 18 millions people com- though molecular DNA analyses suggest that it may be ing from Africa in two major groups, Bantu and Sudanese.