Lack of evidence for sexual reproduction in field populations of Colletotrichum lentis

Species in the genus Colletotrichum have mating systems that deviate from those of other genera in the Ascomycota, and for many species only the anamorph is known. The teleomorph of Colletotrichum lentis is inducible in vitro, but has not been reported in nature. A molecular population study based on amplified fragment length polymorphisms was conducted on 179 field isolates from lentil fields in the Canadian province of Saskatchewan. More than 94% similarity was observed among isolates, and 130 of 131 isolates sampled from a single field shared the same haplotype. Genotypic diversity was equal to 0.47, and association indices IA and r¯d were significantly different from zero. A linkage between mating incompatibility group (mIG) 1 and race 0 was observed among field isolates, but F1 isolates from a cross between an mIG-1/race 0 and an mIG-2/race 1 isolate revealed free recombination of both traits. Results indicate that this fungus does not, or very rarely, sexually reproduces under field conditions.