Abstract

SANCHEZ, M.V.; AGUERO, R.  and  RIVERA, C.. Plantas hospederas de los virus más importantes que infectan el melón, Cucumis melo (Cucurbitaceae) en Costa Rica. Rev. biol. trop [online]. 1998, vol.46, n.1, pp.13-25. ISSN 0034-7744.

Natural hosts of four melon viruses (cucumber mosaic virus o CMV, papaya ringspot virus o PRSV, watermelon virus 2 o WMV-2 and zucchini yellow mosaic virus o ZYMV) were identified in two commercial melon farms in Costa Rica. The farms differed in management practices. Farm A had a long history of melon production in rotation with corn, sorghum and rice. Weed control was poor. Farm B was previously used as pastureland, had a shorter history of melon production, and was frequently plowed for weed control. Plant species diversity was monitored in 100 m2 quadrants on each farm over a one year period. In addition to the cultivated areas, four distinct plant communities (improved pasture field, drainage ditches, secondary forest and fallow field) in farm A, and three (spontaneus mixed species pasture field, fallow field and secondary forest) in farm B were included in the study. The number of quadrants sampled was dependent on the total cultivated area on each farm. Five sampling dates were selected during rainy and dry seasons and transition periods between seasons. Plants of each species represented in the quadrants were collected at each sampling date and identified using reference collections. Four plants of each species showing virus-like symptoms in the field were tested for the presence of the four viruses by ELISA. The total number of plant species, and the percent ground cover of each species infected at least with one of the viruses were recorded on each of the five sampling dates. A total of 86 and 72 plant species were identified in sites A and B, respectively. Fourteen plant species, 16% of the total plant species represented in site A, and six species in site B (8%) were found to be infected with at least one of the four melon viruses at different times throughout the year. All four viruses were detected in each location at each of the five sampling dates, indicating that weed species naturally occurring in and around areas of commercial melon production serve as reservoirs for the melon viruses and ensure the survival of the viruses from one production season to the next. Several new host species of three of the melon viruses (PRSV, WMV-2 and ZYMV) were identified. Previously unreported hosts of PRSV included Tridax procumbens, Cleome viscosa, Cleome spinosa, Malvaviscus arboreus and Sida rhombifolia. New hosts of WMV-2 included C. viscosa, Crotum argenteus, Musa pardisiaca and Ponsetia heterophylla. New hosts of ZYMV included Guazuma ulmifolia, Rauvolfia tetraphylla, Malachra alceifolia, Boerhavia diffusa, P. heterophylla and C. viscosa.

Keywords : Papaya ringspot virus; watermelon mosaic virus-2; cucumber mosaic virus; zucchini yellow mosaic virus; wild host plants; plant communities; plant species diversity.