Etiology of seedling blight and root rot of faba bean (Vicia faba) in Manitoba
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A severe seedling blight and root rot of faba bean (Vicia faba L.) has been observed since 1978 in experimental plots at the University of Manitoba (U of M) and in some commercial faba bean fields in Eastern Manitoba. Aphanomyces euteiches Drechs. was found to be the main agent of the disease at the U of M Campus farm, where faba bean root rot was consistently severe. Rhizoctonia solani Kuehn. was isolated from plants of faba bean and other crops infected at different locations. The pathogenic isolates of R. solani caused damping-off of faba bean plants except for one isolate recovered in Eastern Manitoba. The latter caused a soft rot of the stem and roots and was more aggressive than any of the other isolates. A Fusarium tentatively identified as F. avenaceum (Fr.) Sacc. was recovered from mature faba bean plants in Eastern Manitoba and found to be pathogenic to faba bean and peas in the greenhouse. In addition to V. faba, 12 leguminous species were infected by A. euteiches. The following species were infected and do not appear to have been reported as hosts of this fungus: Lathyrus ochroleucus Hook., L. sativus L., Lens culinaris Medic., Vicia calcarata Desf., V. cracca L., V. disperma D.C., V. narbonensis L. and V. tetrasperma Schreber. The faba bean type isolate (AE1) differed in pathogencity from Wisconsin pea isolate (P14). The latter was avirulent on faba bean. Three pathotypes were identified among the Manitoba isolates of A. euteiches. Pathotypes AE1, AE2 and AE3 were pathogenic to peas; pathotypes AE1 and AE2 were distinguished by a pea cultivar and AE3 was not virulent on faba bean and lentils...