Variability of Cuban and International Populations of Alternaria solani from Different Hosts and Localities: AFLP Genetic Analysis

As causal agent of early blight disease in tomato and potato, Alternaria solani is an internationally important horticultural pathogen. Genetic variability was surveyed by amplified fragment length polymorphism analysis in a total of 112 isolates from potato and tomato, representing pathogen populations from different Cuban provinces together with isolates from the USA, Brazil, Turkey, Greece and China. Also included in the analysis were isolates from catenulated Alternaria spp. from Brazil, Canada, Greece and Russia, along with single isolates of Alternaria porri, Alternaria alternata and a Curvularia sp. UPGMA clustering revealed a differentiation between the isolates of A. solani and all other species with the exception of A. porri which could not be distinguished from A. solani. Among the isolates of A. solani, two distinct subclusters were formed, with high genetic significance revealed by bootstrapping, corresponding to a general subdivision based on the respective solanaceous host. The results are discussed with regard to potential host specificity of A. solani on tomato and potato, and in terms of the comparative contributions of regional and international genetic variability in populations of this ubiquitous plant pathogen.