The sympatric Ascochyta pathosystems of Near Eastern legumes, a key for better understanding of pathogen biology

Abstract

The primary and secondary centres of origin of domesticated plants are often also the places of origin of their pathogens. Therefore, the Near Eastern cradle of agriculture, where crop plants, their wild progenitors, and other con-generic taxa grow sympatrically, may hold some clues on the biology of the pathogens of the respective crops. Unlike the situation in the well-studied Near Eastern cereals and their important diseases, hardly any data are available on basic questions regarding grain legumes. What is the role of genetic diversity at resistance loci of the wild hosts and is it greater compared with the cultigens? Are populations of Ascochyta pathogens infecting wild legumes genetically distinct from populations infecting their domesticated counterparts, and if so, is this differentiation related to differences in host specialization or to adaptation to different ecological conditions? Do isolates originating from wild taxa exhibit a similar level of aggressiveness and have different aggressiveness alleles compared with those originating from domesticated grain legumes? In this review we propose an experimental framework aimed at gaining answers to some of the above questions. The proposed approach includes comparative epidemiology of wild vs. domesticated plant communities, co-evolutionary study of pathogens and their hosts, phenotypic and genetic characterization of fungal isolates from wild and domesticated origins, and genetic analyses of pathogenicity and parasitic fitness among progeny derived from crosses between isolates from wild and domesticated hosts.