Evaluation of resistance sources to Alternaria disease in tomato collection of National Plant Gene Bank of Iran by green house method.

Alternaria species are important pathogens of tomato that cause ring spot on the leaf, stem and fruit. Utilization of resistante cultivar is one of the most cost effective method of controlling of this disease. In this research 48 samples of tomato accessions of National Plant Gene-Bank of Iran were chosen that three accessions from every tomato growing provinces of country presented base on availability of enough regenerated seed. The samples were planted in the experimental field of genetic department and National plant genebank of Iran which annual infection has benn reported. Recording of reactions started as soon as symptoms were observed at eight days interval for five times. According to analysis of AUDPC index, 30 samples with higher tolerance were chosen to be evaluated in greenhouse for resistance. During 2010 samples of infected leaves were collected from tomato fields of Isfahan, Azerbaijan garb, Tehran, Lorestan, Fars, Khuzestan, Hamedan, Markazi, Khorasan razavi provinces. Based on morphological characterization 51 fungi isolates were belonging to Alternaria genus that species were: A. alternata, A. tenuissima, A. arborescens, A. infectoria, and A. dumosa. Pathogenicity test of isolates were conducted on susceptible variety to choose an isolate with highest virulence and an Alternaria arborescens isolated from Gorgan was selected for future study. Resistance evaluation on 30 resistant and moderately resistant varieties along with susceptible check was done in greenhouse on accessions chosen from first part of research. Accessions A72-1033, A72-1058, A72-1076 with less disease development were more resistant after them three accessions A72-1052, K72-1033, and A72-1079 were moderately resistance. Other accessions with high disease development were categorized in semi susceptible to susceptible groups. Accession K72-982 with 90% disease development and then accessions A72-907, A72-1075 and A72-1032 were most susceptible. Two accessions A72-1033, A72-1058 that were resistant both in greenhouse and in the field were recommended for future investigation and utilization in tomato breeding program to develop resistant variety.