Classification of Rhizoctonia spp. using rDNA-ITS sequence analysis supports the genetic basis of the classical anastomosis grouping

Abstract

Currently, rDNA-ITS sequence analysis seems to be the most appropriate method for comprehensive classification of Rhizoctonia spp. Our previous review article was concerned with detailed analysis of multinucleate Rhizoctonia (MNR), and the current review complements the previous one with detailed analysis of binucleate Rhizoctonia (BNR) (teleomorphs: Ceratobasidium spp. and Tulasnella spp.) and uninucleate Rhizoctonia (UNR) (teleomorph: C. bicorne). Data of all the appropriate BNR and UNR accumulated in GenBank were analyzed together in neighbor-joining (NJ) trees supplemented
with percent sequence similarity within and among the anastomosis groups (AGs) and subgroups. Generally, the clusters of the
isolate sequences supported the genetic basis for the AG based on hyphal fusion anastomosis. Comprehensive interrelationships
among all the currently available MNR, BNR, and UNR groups and subgroups in GenBank were subsequently analyzed in NJ and maximum-parsimony
(MP) trees, showing the genetic relatedness among the different groups and indicating possible bridging groups between MNR,
BNR, and UNR. The review also indicates serious inaccuracies in designation of sequences of some isolates deposited in GenBank.
Several additional teleomorph genera with Rhizoctonia spp. anamorphs have also been reported in the literature. However, as they have not been intensively studied, there were
no available data on their rDNA-ITS sequences that could be included in this review.