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ARS Home » Pacific West Area » Pullman, Washington » Plant Germplasm Introduction and Testing Research » Research » Publications at this Location » Publication #77834
Title: ASCOCHYTA FABAE AND ASCOCHYTA LENTIS: HOST SPECIFICITY, TELEOMORPHS (DIDYMELLA), HYBRID ANALYSIS, AND TAXONOMIC STATUS

Author
item Kaiser Jr, Walter
item WANG, B. - WASHINGTON STATE UNIV.
item ROGERS, J. - WASHINGTON STATE UNIV.

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Studies were conducted on two important ascochyta blight pathogens of faba bean and lentil incited by Ascochyta fabae and A. lentis, respectively. Both fungi require the pairing of two compatible isolates for the sexual state to develop. When certain isolates of A. fabae and A. lentis were crossed, hybrid sexual fruiting bodies developed. Growth, sporulation, colony appearance, morphology, and pathogenicity of hybrid progeny frequently differed greatly from the parent isolates. Inoculations with spores from matings among compatible isolates of A. fabae caused disease in faba bean, but not lentil. Inoculations with spores from matings among compatible isolates of A. lentis incited disease in lentil, but not faba bean. Inoculation with spores from crosses between faba bean and lentil isolates did not induce disease in either r host. Molecular tests demonstrated that isolates of the ascochyta blight pathogen from faba bean and lentil are distinct. The pathogenicity tests, morphological characteristics, and molecular tests indicate that A. fabae and A. lentis represent distinct species. Didymella lentis, with its asexual state, A. lentis, is proposed as a new species, distinct from D. fabae and its asexual state, A. fabae.

Technical Abstract: Isolates of Ascochyta fabae from faba bean (Vicia faba) and A. lentis (Lens culinaris) collected from different countries were used in this study. Both fungi are heterothallic and the two mating types have been designated MAT1-1 and MAT1-2. When certain isolates of A. fabae and A. lentis were crossed, hybrid pseudothecia developed. Inoculations with ascospores from matings among compatible isolates of A. fabae caused disease in faba bean, but not lentil; inoculations with ascospores from matings among compatible isolates of A. lentis incited disease in lentil, but not faba bean. Inoculations with ascospores from pseudothecia produced in crosses between faba bean and lentil isolates did not induce disease in either host. Random amplified polymorphic DNA (RAPD) banding patterns of Ascochyta isolates from faba bean and lentil are clearly different, and banding patterns of ascospores from hybrid pseudothecia give hybrid banding patterns. The pathogenicity tests, morphological characteristics, and RAPD markers indicate that A. fabae and A. lentis represent distinct taxa. Didymella lentis, with its anamorph, A. lentis, is proposed as a new species, distinct from D. fabae, with its anamorph A. fabae.