The advancing identification and classification of Rhizoctonia spp. using molecular and biotechnological methods compared with the classical anastomosis grouping

Anamorphic classification of Rhizoctonia spp. has been based on young cell nuclear numbers and hyphal fusion to anastomosis groups (AGs), in addition to the teleomorph classification. The widespread development of molecular biology techniques has added modern tools to support classification of organisms according to their genetics and evolutionary processes. These various methods have also been used in recent years for classification of Rhizoctonia. Data are continuously accumulating in the literature and the sequences in databases, which are readily available for researchers in the network systems. In the present review, attempts were made to describe and compare the advantages and disadvantages of the various methods for the classification of Rhizoctonia spp. Currently, the rDNAinternal transcribed spacer (ITS) sequence analysis seems to be the most appropriate method for classification of Rhizoctonia spp. Data of all the appropriate multinucleate Rhizoctonia (MNR) accumulated in GenBank were analyzed together in neighbor-joining (NJ) and maximumparsimony (MP) trees supplemented with percent sequence similarity within and among AGs and subgroups. Generally, the clusters of the isolate sequences were supportive of the AGs and subgroups based on hyphal fusion anastomosis. The review also indicates inaccuracies in designation of sequences of some isolates deposited in GenBank. The review includes detailed analyses of the MNR groups and subgroups, whereas complementary descriptions of the binucleate Rhizoctonia (BNR), uninucleate Rhizoctonia (UNR), and comprehensive interrelationships among all the currently available MNR, BNR, and UNR groups and subgroups in GenBank are to be discussed in a subsequent review article.