Classifi cation 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 classifi cation 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 neighborjoining (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.

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.

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In an attempt to increase the insecticidal effect of the ␦-endotoxin crystal protein CryIC on the relatively Cry-insensitive larvae of Spodoptera littoralis, a combination of CryIC and endochitinase was used. CryIC comprising the first 756 amino acids from Bacillus thuringiensis K26-21 and endochitinase ChiAII encoded by Serratia marcescens were separately produced in Escherichia coli carrying the genes in overexpression vectors. The endochitinase on its own, even at very low concentrations (0.1 g/ml), perforated the larval midgut peritrophic membrane. When applied together with low concentrations of CryIC, a synergistic toxic effect was obtained. In the absence of chitinase, about 20 g of CryIC per ml was required to obtain maximal reduction in larval weight, while only 3.0 g of CryIC per ml caused a similar toxic effect in the presence of endochitinase. Thus, a combination of the Cry protein and an endochitinase could result in effective insect control in transgenic systems in which the Cry protein is not expressed in a crystalline form.

Pseudomonas protegens strain Pf-5 is a soil bacterium that was first described for its capacity to suppress plant diseases and has since been shown to be lethal to certain insects. Among these is the common fruit fly Drosophila melanogaster, a well-established model organism for studies evaluating the molecular and cellular basis of the immune response to bacterial challenge. Pf-5 produces the insect toxin FitD, but a ΔfitD mutant of Pf-5 retained full toxicity against D. melanogaster in a noninvasive feeding assay, indicating that FitD is not a major determinant of Pf-5's oral toxicity against this insect. Pf-5 also produces a broad spectrum of exoenzymes and natural products with antibiotic activity, whereas a mutant with a deletion in the global regulatory gene gacA produces none of these exoproducts and also lacks toxicity to D. melanogaster. In this study, we made use of a panel of Pf-5 mutants having single or multiple mutations in the biosynthetic gene clusters for seven natural products and two exoenzymes that are produced by the bacterium under the control of gacA. Our results demonstrate that the production of rhizoxin analogs, orfamide A, and chitinase are required for full oral toxicity of Pf-5 against D. melanogaster, with rhizoxins being the primary determinant.