Resistance of Cucumis melo var. agrestis against Melon-Yellowing Disease

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Cucurbit Genetics Cooperative Report 17:74-75 (article 20) 1994

C. Soria and M.L. Gomez-Guillamon
Estacion Experimental “La Mayora” CSIC, 29750 Algarrobo-Costa, Malaga SPAIN

Several accessions of Cucumis melo L. with different degrees of resistance to melon yellowing disease whose causal agent is a closterovirus transmitted by Trialeurodes vaporariorum Westwood (1) have been selected (4). One will accession, Cucumis melo var. agrestis belongs to the same species as the cultivar and so can be exploited without difficulty in a breeding program designed to find varieties of melon with tolerance or resistance to yellowing disease.

Nevertheless, this accession has shown variable responses to the melon yellowing disease regarding the results when controlled or natural conditions of infection are used. So, under natural conditions, around the 16% of the plants became non-infected and the rest showed mild symptoms which appeared later than on susceptible genotypes (2, 3). This behavior suggested that this genotype should have some kind of resistance against muskmelon yellowing disease. When controlled inoculations are carrie out, the response of this genotype is quite irregular because in some experiments all the plants showed mild symptoms while in others some plants showed no symptoms (2). Probably, factors depending on the virus and/or its vector are involved.

Because of that, the behavior against the melon yellowing virus of Cucumis melo var. agrestis was compared under controlled-infection conditions with other accessions known to be either resistant: C. dipsaceus and C. metuliferus of susceptible: C. melo var. ‘Piel de Sapo’, cv. ‘Bola de Oro’, and PI-505601 (2, 4). Each plant at two-leaf stage was inoculated by 40 whiteflies inside a clip-on cage attached to the first true leaf (5). Table 1 shows that, although C. melo var. agrestis developed the characteristic symptoms of the disease, these appeared ten days later than in the susceptible accessions.

C. melo var. agrestis showed itself susceptible to the virus responsible for yellowing disease. The fact that the symptoms emerged later could be due to the existence of a certain degree of resistance to the spread or multiplication of the virus particles, or to both these factors.

The fact that no infection occurred under natural conditions when the virus vector was not forced to feed on a particular genotype could suggest a certain degree of resistance to the vector to be present in C. melo var. agrestis.

Both, tolerance to the virus causing yellowing disease and possible resistance to its vector T. vaporariorum found in this genotype could be useful in melon breeding.

Table 1. Incidence of melon yellowing disease.

Days after inoculations

Genotypes
20
25
30
35
C. melo cv. ‘Piel de Sapo’ 8/10z 10/10 10/10 10/10
C. melo cv. ‘Bola de Oro 4/10 10/10 10/10 10/10
C. melo PI 505601 2/10 9/10 9/10 9/10
C. melo var. agrestis 0/10 0/10 3/10 9/10
C. dipsaceus 0/10 0/10 0/10 0/10
C. metuliferus 0/10 0/10 0/10 0/10

a/bz a: plants with sumptoms; b: plants inoculated

Literature Cited

  1. Jorda-Guiterrez, C., M.L. Gomez-Guillamon, M. Juarez and A. Alfaro-Garcia. 1993. Clostero-like particles associated with a yellows disease of melons in southeastern Spain. Plant Pathology 42:722-727.
  2. Soria, C. 1991. Amarilleo del melon (Cucumis melo L.), causas, teenicas de inoculacion y fuentes de resistencia. Doctoral Thesis, Univ. Malaga (Spain).
  3. Soria, C. and M.L. Gomez-Guillamon. 1993. Respuesta al amarilleo de hibridos F1 entre dos variedades botanicas de Cucumis melo. Actas de Horticultura 10:1359-1363.
  4. Soria, C., M.L. Gomez-Guillamon, J. Esteva, and F. Nuez. 1989. Search for sources of resistance to yellowing disease in Cucumis spp. Cucurbit Genetics Cooperative Report 12:42-43.
  5. Soria, C., M.L. Gomez-Guillamon, and J.E. Duffus. 1991. Transmission of the agent causing a melon yellowing disease by the greenhouse whitefly Trialeurodes vaporariorum in southeast Spain. Neth. J. Pl. Path. 97-289-296.