Genetic Diversity and Pathogenicity of Rhizoctonia spp. Isolates Associated with Red Cabbage in Samsun (Turkey).

Ismail Erper,Muharrem Turkkan,Elif Yildirim,Ruslan Kalendar,Mehtap Alkan,Sirin Avci,Goksel Ozer

doi:10.3390/jof7030234

Abstract

A total of 132 Rhizoctonia isolates were recovered from red cabbage plants with root rot and wirestem symptoms in the province of Samsun (Turkey) between 2018 and 2019. Based on the sequence analysis of the internal transcribed spacer (ITS) region located between the 18S and 28S ribosomal RNA genes and including nuclear staining, these 124 isolates were assigned to multinucleate Rhizoctonia solani, and eight were binucleate Rhizoctonia. The most prevalent anastomosis group (AG) was AG 4 (84%), which was subdivided into AG 4 HG-I (81%) and AG 4 HG-III (3%), followed by AG 5 (10%) and AG-A (6%), respectively. The unweighted pair group method phylogenetic tree resulting from the data of 68 isolates with the inter-PBS amplification DNA profiling method based on interspersed retrotransposon element sequences confirmed the differentiation of AGs with a higher resolution. In the greenhouse experiment with representative isolates (n = 24) from AGs on red cabbage (cv. Rondale), the disease severity index was between 3.33 and 4.0 for multinucleate AG isolates and ranged from 2.5 to 3.17 for AG-A isolates. In the pathogenicity assay of six red cabbage cultivars, one isolate for each AG was tested using a similar method, and all cultivars were susceptible to AG 4 HG-I and AG 4 HG-III isolates. Redriver and Remale were moderately susceptible, while Rescue, Travero, Integro, and Rondale were susceptible to the AG 5 isolate. The results indicate that the most prevalent and aggressive AGs of Rhizoctonia are devastating pathogens to red cabbage, which means that rotation with nonhost-crops for these AGs may be the most effective control strategy. This is the first comprehensive study of Rhizoctonia isolates in red cabbage using a molecular approach to assess genetic diversity using iPBS-amplified DNA profiling.

Highlights

Turkey is the world’s fourth-largest vegetable producer with approximately one million hectares of cultivation area and an annual yield of 24.1 million tons [1]
The aims of this study were the following: (i) to conduct the molecular characterization of anastomosis group (AG) and their subgroups of Rhizoctonia isolates recovered from diseased red cabbage plants showing root rot and wirestem symptoms; (ii) to apply DNA-profiling PCR methods based on Inter Primer Binding Site (iPBS) amplification to discriminate AGs of Rhizoctonia spp.; (iii) to determine the pathogenicity of the isolates belonging to AGs determined in this study in red cabbage cv
It has been reported in several studies that AG 4 HG-I is dominant in warmer periods, while AG 2-1, AG 1-IB, and AG-BI are dominant during colder periods [68,69,70]

Summary

Introduction

Turkey is the world’s fourth-largest vegetable producer with approximately one million hectares of cultivation area and an annual yield of 24.1 million tons [1]. Rhizoctonia spp. is an important and difficult-to-treat group among the myriad of fungal pathogens and associated with damping off, root rot, wirestem, foot rot, and the head rot disease complex of brassicas, which result in economic yield losses [5,6,7,8,9,10,11]. This phytopathogen as a complex group shows significant differences in cultural, molecular, and biochemical properties, and pathogenicity

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