Cucurbit Genetics Cooperative Report 13:27-28 (article 10) 1990
Relationship between the Causal Agent of Melon Yellowing Disease in the Southeast of Spain and its
C. Soria and M. L. Gómez-Guillamón
Estación and Experimental "La Mayora". Algarrobo-Costa, (Málaga), Spain
The impossibility of mechanically transmitting melon yellowing disease to melon plants (Cucumis melo L.) (3)
stimulated the design and development of a technique of artificial inoculation that uses the vector of the causal
agent, the greenhouse whitefly Trialeurodes vaporariorum Westwood, to give 100% infection of susceptible plants.
This technique effectively eliminates the problems of variability and escapes that can occur when working under
natural infection conditions and it also allows the investigator to select genotypes with genetic resistance to the
Several parameters of the interrelationship between causal agent of the disease and its vector had to be studied to
develop the technique.
In experiments similar to those of Duffus (1) with Beet Pseudo Yellows Virus (BPYV), and of Hristova and Natskova
(2), the following parameters of the relationship between the causal agent and its vector were studied: Relationship
of numbers of insects to transmission, infection feeding period, and persistence of the causal agent in the vector.
The plant material consisted of healthy plants of C. melo cv. 'Piel de Sapo' at the one to two true-leaf stage that had
been cultivated in a whitefly-free greenhouse.
Greenhouse whiteflies came from colonies bred on healthy melon plants.
Infected melon plants with definite symptoms of yellowing disease were the infection source.
To study the parameters of the causal agent-vector relationships, whiteflies had been allowed to feed for 48 h. on
the yellowing disease source.
Persistence: Transfers of 40 disease bearing whiteflies to healthy melon plants at the 1-2 true-leaf stage were
carried out daily for 7 days. Ten replicates were employed.
Relationship of numbers of insects to causal agent transmission: Disease carrying whiteflies were transferred
individually, and also in groups of 5, 10, 20, 30 and 40, to healthy melon plants on which they were allowed to feed
for 72 h.
Infection feeding period: Groups of 40 disease carrying whiteflies were placed on healthy melon plants and were
permitted to feed for 6, 12, 24, 48 and 72 h.
All the plants were placed in a whitefly-free greenhouse to record symptoms development.
Persistence: T. vaporariorum lost its capacity to transmit the causal agent of melon yellowing disease after the 4th day of feeding on healthy plants. A semi-persistent relationship was observed between the causal agent and the
Relationship of numbers of insects to causal agent transmission: One disease carrying whitefly was capable
of transmitting the disease to a susceptible host. The transmission efficiency increased with the number of insects
employed. Maximum transmission (100%) was obtained with groups of 30 or more whiteflies. When 40 individuals
of T. vaporariorum were employed, symptoms appeared sooner and 100% transmission was recorded 24 days after
inoculation which was 3 days earlier than in the experiment in which 30 whiteflies were employed.
Infection feeding period: T. vaporariorum transmitted the disease to non-infected susceptible plants after six
hours of feeding on them. Transmission of 100% effectiveness was obtained in periods of 72 h. The symptoms
appeared between the 16th and 24th day after inoculation.
Acknowledgments: This work has been financed by the Comisión Asesora Interministerial de Ciencia y
- Duffus, J. E. 1965. Beet pseudo yellows virus, transmitted by the greenhouse whitefly (Trialeurodes
vaporariorum). Phytopathology 55(4):450-453.
- Hristova, D. P. and V. T. Natskova. 1986. Interrelation between Trialeurodes vaporariorum W. and the
virus causing infectious chlorosis in cucumbers. Comptes Rendus de L'Academie Bulgare de Sciences
- Soria, C. and M. L. Gómez-Guillamón. 1989. Transmission of the causal agent of muskmelon yellowing
disease. Cucurbit Genetics Cooperative 12:40-41.