Currently, rDNA-ITS sequence analysis seems to be the most appropriate method for comprehensive c... more 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.
Anamorphic classification of Rhizoctonia spp. has been based on young cell nuclear numbers and hy... more 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 rDNA-internal 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 maximum-parsimony (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.
Virulent Rhizoctonia spp. isolated from strawberry in Israel belonged to anastomosis groups (AG) ... more Virulent Rhizoctonia spp. isolated from strawberry in Israel belonged to anastomosis groups (AG) of: binucleate Rhizoctonia (BNR) AG-A, AG-G, AG-K and AG-F, and to multinucleate Rhizoctonia (MNR) AG 4 subgroup HG-I. In addition, a soil isolate of AG 4 subgroup HG-III was also found to be virulent on strawberry. None of the Israeli isolates obtained in the present study belonged to BNR AG-I, or other MNR AGs. In the cluster analysis of rDNA-ITS sequences, all of the isolate sequences consistently clustered according to their known AGs and subgroups. One AG-F cluster included sequences of 10 strawberry isolates, while another AG-F cluster included sequences of two isolates submitted to GenBank. Additional work is needed to determine whether the isolates of these two clusters may belong to different AG-F subgroups. The current virulence bioassay used for Rhizoctonia spp. isolates on strawberry is based on inoculation of stolon-derived daughter plants with the isolates and estimation of the reduction in plant biomass, rather than on specific distinct disease severity symptoms. The duration of this test is relatively long (ca. 5 weeks or more) and the availability of daughter plants from runners is naturally limited to a certain season. Among the possible alternative methods evaluated in the present study (inoculation of fruits or seedlings developed from germinated strawberry seeds), the method based on seedlings was best. This method has a potential to replace the currently used stolon-daughter plant inoculation bioassay for testing virulence of strawberry root pathogens. This is the first report indicating that Rhizoctonia spp. isolates that belong to AG-F, AG-K, AG 4 HG-I and AG 4 HG-III are virulent to strawberry.
Currently, rDNA-ITS sequence analysis seems to be the most appropriate method for comprehensive c... more 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.
Anamorphic classification of Rhizoctonia spp. has been based on young cell nuclear numbers and hy... more 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 rDNA-internal 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 maximum-parsimony (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.
Virulent Rhizoctonia spp. isolated from strawberry in Israel belonged to anastomosis groups (AG) ... more Virulent Rhizoctonia spp. isolated from strawberry in Israel belonged to anastomosis groups (AG) of: binucleate Rhizoctonia (BNR) AG-A, AG-G, AG-K and AG-F, and to multinucleate Rhizoctonia (MNR) AG 4 subgroup HG-I. In addition, a soil isolate of AG 4 subgroup HG-III was also found to be virulent on strawberry. None of the Israeli isolates obtained in the present study belonged to BNR AG-I, or other MNR AGs. In the cluster analysis of rDNA-ITS sequences, all of the isolate sequences consistently clustered according to their known AGs and subgroups. One AG-F cluster included sequences of 10 strawberry isolates, while another AG-F cluster included sequences of two isolates submitted to GenBank. Additional work is needed to determine whether the isolates of these two clusters may belong to different AG-F subgroups. The current virulence bioassay used for Rhizoctonia spp. isolates on strawberry is based on inoculation of stolon-derived daughter plants with the isolates and estimation of the reduction in plant biomass, rather than on specific distinct disease severity symptoms. The duration of this test is relatively long (ca. 5 weeks or more) and the availability of daughter plants from runners is naturally limited to a certain season. Among the possible alternative methods evaluated in the present study (inoculation of fruits or seedlings developed from germinated strawberry seeds), the method based on seedlings was best. This method has a potential to replace the currently used stolon-daughter plant inoculation bioassay for testing virulence of strawberry root pathogens. This is the first report indicating that Rhizoctonia spp. isolates that belong to AG-F, AG-K, AG 4 HG-I and AG 4 HG-III are virulent to strawberry.
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Papers by Michal Sharon