Virulence and genetic diversity of Colletotrichum Lindemuthianum isolates collected from common bean varieties of Turkey

Abstract

The common bean (Phaseolus vulgaris L.) is the most widely distributed and consumed legume species of the genus Phaseolus. As one of the major producer in the world, common bean production is highly dominated by the Black Sea Region of Turkey. Among diseases of the common bean, anthracnose, caused by the hemibiotrophic fungus Colletotrichum lindemuthianum, is a potentially devastating seed-borne disease that affects the yield. The present disease management strategies mostly fail in production areas due to lack of information about pathogenic and genetic diversity of this fungus in Turkey. Availability of such knowledge is considered vital prior to development of resistance breeding programs using lines selected for necessary resistance gene combinations. Therefore in this thesis using pathogen isolates of Turkey we aimed to (i) evaluate virulence, (ii) characterize the races based on CIAT-binary code system, (iii) determine geographical distribution and (iv) assess genetic diversity based on marker system. Forty seven pathogen isolates collected from four geographical regions of Turkey were used in this study. Race characterization based on universal set of 12 differential cultivars demonstrated the presence of 37 races. Unusually high pathotype diversity (78%) with no bias distribution to geographical regions was observed among isolates. In addition, very high genetic diversity (100% polymorphism) was also detected using Rep-PCR, RAMS and RAPD marker systems with no relation to pathotype diversity. Predominantly high virulence among the isolates were observed towards both Andean and Mesoamerican genepool varieties have indicated the presence of both Andean and Mesoamerican pathotype populations in Turkey. Two of the Andean pathotypes (races 1 and 2) and two of the Mesoamerican pathotypes (races 3 and 64) were also detected both in Southeast American and European countries. The rest of the 33 races determined were not reported by any other countries. Unusually high pathotype and genetic diversity of isolates enforced us to confirm identity of isolates as C. lindemuthianum species using specific molecular detection approaches. The results indicated that only four of the isolates with races of 2, 32, 64 and 96 from Blacksea region were C. lindemuthianum species. Based on these confirmed C. lindemuthianum isolates, this study is the first report of race 32 and race 96 in the world.