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Different Ecological Affinities and Aggressiveness Patterns Among Didymella rabiei Isolates from Sympatric Domesticated Chickpea and Wild Cicer judaicum

First and third author: The Levi Eshkol School of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel; second author: Genomics Department, The Volcani Center, Agricultural Research Organization, Bet Dagan 50250, Israel; and fourth author: Department of Plant Pathology and Weed Research, The Volcani Center, Agricultural Research Organization, Bet-Dagan 50250, Israel.

Domesticated chickpea (Cicer arietinum) and its wild relative C. judaicum grow in sympatric distribution in Israel and both are susceptible to Ascochyta blight caused by Didymella rabiei. C. arietinum was grown for millennia in drier and hotter Levantine spring conditions while C. judaicum grows in the wetter and milder winters. Accordingly, it is possible that D. rabiei isolates originated from C. arietinum are adjusted to the less favorable spring conditions. Here, 60 isolates from both origins were tested in vitro for their hyphal growth at 15 and 25°C. Isolates from C. arietinum had a significantly larger colony area at 25°C than at 15°C (P < 0.001) while no such differences were detected between isolates from C. judaicum. D. rabiei isolates from wild and domesticated origins were used to inoculate nine C. judaicum accessions and two domesticated chickpea cultivars and their aggressiveness patterns were determined using five measures. On domesticated chickpea, isolates from domesticated origin were significantly more aggressive in four out of the five aggressiveness measures than isolates from wild origin. On C. judaicum, isolates from wild origin were generally more aggressive than isolates from domesticated origin. The results suggest that the habitat segregation between wild and domesticated Cicer influences the pathogens ecological affinities and their aggressiveness patterns.

Additional keywords:comparative epidemiology, ecological requirements, incubation period, sympatric pathosystems, wild hosts.