Pathogenic potential of Waitea circinata var. zeae

Abstract

Waitea circinata Warcup & P.H.B. Talbot (multinuclear Rhizoctonia spp.) is a widespread, soil-borne plant pathogen causing root rot mainly of monocotyledonous plants. Among five described varieties, the most common and widespread is W. circinata var. zeae Toda, Mushika, T. Hayak., Tanaka, Tani & Hyakum. Besides monocotyledonous hosts, a natural infection of a limited number of dicotyledonous plants, including soybeans, beans, peas, sugar beets and carrots were recorded recently. During 2017, cabbage and oilseed rape plants showing symptoms of root and root neck rot, sampled at the localities of Futog and Rimski Šančevi (Serbia), were proved to be infected with W. circinata var. zeae. This was the first record of natural infection of plants from Brassicaceae family worldwide. Two selected isolates from cabbage (299-17) and oilseed rape (300-17) formed fast-growing orange colonies with red sclerotia and multinucleate hyphae with a characteristic branching pattern. The identification was further confirmed by BLAST analysis of sequences of ITS rDNA, RPB2, LSU and β-tubulin genomic regions. Koch’s postulates were fulfilled after inoculation of cabbage and oilseed rape seedlings, while an experimental host range was determined by inoculations of 14 different plant species from 8 families.