Genetic evidence for natural hybridization between the Dutch elm disease pathogens Ophiostoma novo-ulmi ssp. novo-ulmi and O. novo-ulmi ssp. americane

摘要

The Dutch elm disease pathogen Ophiostoma novo-ulmi is separated into subspecies novo-ulmi, formarly known as the Eurasian (EAN) race, and subspecies americana, formerly known as the North American (NAN) race. Both subspecies occur in Europe, and hybrids betweent hem are suspected to have emerged in aprts of Europe where their ranges overlap. Authenticated isolates of both subspecis were eamined in order to determine whether fixed mutations occur in the cerato-ulmin (cu) and in the colony type gene (col1). One and six mutations were detected between subspp. novo-ulmi and americana in cu and col1, repectively. The mutation in cu and one mutation in col1 proved to be located within restriction sites, and were used for PCR-RFLP. this method provides a quick and reliable diagnostic method to differentiate the two subspecies. Seven islates of O. novo-ulmi from Austria were supected to be hybrids between subspp. novo-ulmi and americana, and were tested by PCR-RFLP of their cu and col1 genes. two fo the suspected hyrids from Austria (isolates AT37 and AT146) had the cu PCR-RFLP profile fo ssp. emericana and the col1 PCR-RFLP profile of ssp. novo-ulmi. Furthermore, a ssp. novo-ulmi tester isolate from Poland (P150) showed a similar hybrid pattern. This is the first evidence revealing recombination betweent wo genes and thus hybridization betweent he two subspecies of O. novo-ulmi in nature.