Systematics and mating systems of two fungal pathogens of opium poppy: the heterothallicCrivellia papaveraceawith aBrachycladium penicillatumasexual state and a homothallic species with aBrachycladium papaverisasexual state

Abstract

This paper presents a systematic revision of the fungal opium poppy (Papaver somniferum L.) pathogens formerly known as Pleospora papaveracea (de Not.) Sacc., along with allied asexual states formerly placed in Dendryphion . The revision is based on analysis of phylogenetic relationships, comparative morphology, and analysis of mating systems. Using morphology, 18S and ITS rDNA, we established that these species belong to the Alternaria group rather than to Pleospora, a conclusion supported by the Shimodaira–Hasegawa test. For these fungi, we erect the new genus Crivellia , with Crivellia papaveracea as type. ITS rDNA analyses suggested with moderate support Alternaria brassicicola (Schw.) Wiltshire, Alternaria japonica Yoshii, and Ulocladium alternariae (Cooke) Simmons as Crivellia’s closest relatives. Combined ITS, partial GPD and EF-1 alpha analyses confirmed earlier studies that show that asexual isolates in the Crivellia lineage of poppy pathogens represent two closely related species. Because Dendryphion was determined to be polyphyletic, the former genus Brachycladium was resurrected for B. penicillatum Corda and B. papaveris (K. Sawada) Shoemaker & Inderbitzin, the Crivellia asexual states that had been in Dendryphion. Molecular and morphological comparison with isolates from field-collected ascomata and morphological comparison with the type specimen of P. papaveracea indicated that B. penicillatum , and not B. papaveris , is the anamorph of C. papaveracea. The mycelia from single conidium or single ascospore isolates, including mycelia from 14 single ascospores from one field-collected C. papaveracea ascoma, either have a MAT1-1 or MAT1-2 gene and are thus heterothallic. In contrast, each single-conidium isolate of B. papaveris has an incomplete MAT1-2 gene fused to a MAT1-1 region and is inferred to be homothallic. We speculate that ancestral MAT fusion might have led to speciation in Crivellia.