Abstract

Symptom scoring, dosage of viral DNA and estimation of tolerance level, were three steps successfully used to study the varietal behaviour of five tomato cultivars to the tomato yellow leaf curl (TYLC) disease in Morocco. Forty plant of each cultivar; Cherry, Tres Cantos, Campbell 33, F1 Pepite and the susceptible control Marmand VR, were inoculated mediate Agrobacterim tumefaciens and Bemisia tabaci en separate to scoring symptoms using scale (from 0 to 4) and quantification of viral DNA accumulates on the leaf tissue by molecular hybridization dot-blot 70 day post inoculation. Then, a simple mathematic formula based on symptom scoring, was used to estimate the tolerance level of each cultivar. Symptom severity increased up, was different between the two inoculation methods. Agro-inoculation was more effective and 100 % was obtained in the susceptible control. The symptoms evolution was faster and more uniform (low variability). It can be used in breeding programmes as complementary to inoculation using Bemisia tabaci. Moreover, the dosage of viral DNA at leaf tissues revealed the coexistence of the TYLCV and TYLCSV to plants inoculated via Bemisia tabaci. Considering the tolerance level and agronomic factors, F1 Pepite was the best of the cultivars tested with T (tolerance level) = 0, 54. Whereas Tres Cantos and Cherry were the most sensible with T = 0,32; T = 0,34 respectively