Advances in molecular interactions on the Rhizoctonia solani-sugar beet pathosystem

Rhizoctonia solani is a soilborne pathogen with a broad host range. An anastomosis group (AG) system based on hyphal fusions has been established to distinguish between different R. solani subgroups in this species complex. Members of the AG2-2IIIB subgroup can cause serious problems in sugar beet production, resulting in Rhizoctonia root and crown rot. In this review, we summarize the current molecular advances in the R. solani sugar beet pa-thosystem. The draft genome of R. solani AG2-2IIIB has an estimated size of 56.02 Mb, larger than any of the R. solani AGs sequenced to date. The genome of AG2-2IIIB has been pre-dicted to harbor 11,897 protein-encoding genes, including a high number of carbohydrate-active enzymes (CAZymes). The highest number of CAZymes was observed for polysaccharide lyase family 1 (PL-1), glycoside hydrolase family 43 (GH-43), and carbo-hydrate esterase family 12 (CE-12). Eleven single-effector candidates were predicted based on AG2-2IIIB genome data. The RsLysM, RsRlpA, and RsCRP1 genes were highly induced upon early-stage infection of sugar beet seedlings, and heterologous expression in Cerco-spora beticola and model plant species demonstrated their involvement in virulence. How-ever, despite the progress achieved thus far on the molecular interactions in this pathosystem, many aspects remain to be elucidated, including the development of efficient transformation systems, important for functional studies, and the silencing of undesirable traits in the sugar beet crop.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of British Mycological Society. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).