Genome Analyses of the Less Aggressive Rhizoctonia solani AG1-IB Isolates 1/2/21 and O8/2 Compared to the Reference AG1-IB Isolate 7/3/14.

Daniel Wibberg,Andreas Schlüter,Oliver Rupp,Franziska Genzel,Rita Zrenner,Alexander Goesmann,Jochen Blom,Bart Verwaaijen,Alfred Pühler,Rita Grosch

doi:10.3390/jof7100832

Abstract

Rhizoctonia solani AG1-IB of the phylum Basidiomycota is known as phytopathogenic fungus affecting various economically important crops, such as bean, rice, soybean, figs, cabbage and lettuce. The isolates 1/2/21 and O8/2 of the anastomosis group AG1-IB originating from lettuce plants with bottom rot symptoms represent two less aggressive R. solani isolates, as confirmed in a pathogenicity test on lettuce. They were deeply sequenced on the Illumina MiSeq system applying the mate-pair and paired-end mode to establish their genome sequences. Assemblies of obtained sequences resulted in 2092 and 1492 scaffolds, respectively, for isolate 1/2/21 and O8/2, amounting to a size of approximately 43 Mb for each isolate. Gene prediction by applying AUGUSTUS (v. 3.2.1.) yielded 12,827 and 12,973 identified genes, respectively. Based on automatic functional annotation, genes potentially encoding cellulases and enzymes involved in secondary metabolite synthesis were identified in the AG1-IB genomes. The annotated genome sequences of the less aggressive AG1-IB isolates were compared with the isolate 7/3/14, which is highly aggressive on lettuce and other vegetable crops such as bean, cabbage and carrot. This analysis revealed the first insights into core genes of AG1-IB isolates and unique determinants of each genome that may explain the different aggressiveness levels of the strains.

Highlights

IntroductionRhizoctonia solani Kühn (teleomorph Thanatephorus cucumeris [Frank] Donk) belongs to the phylum Basidiomycota and is a soilborne plant-pathogenic fungus that causes diseases in many economically important crops [1]
Rhizoctonia solani Kühn belongs to the phylum Basidiomycota and is a soilborne plant-pathogenic fungus that causes diseases in many economically important crops [1]
The pathogenicity and in particular aggressiveness of the R. solani AG1-IB isolates used in this study were tested based on their impact on lettuce growth

Summary

Introduction

Rhizoctonia solani Kühn (teleomorph Thanatephorus cucumeris [Frank] Donk) belongs to the phylum Basidiomycota and is a soilborne plant-pathogenic fungus that causes diseases in many economically important crops [1]. The ability for hyphal fusion (anastomosis) is used to characterize R. solani isolates [2]. Differences include a distinct degree in host specificity of the respective AG, as well as the subdivision of AGs into subgroups. Infection of rice by AG1-IA isolates results in severe sheath blight symptoms, while AG1-IC are non-pathogenic regarding this host plant. R. solani AG1-IB isolates cause diverse disease symptoms such as sheath blight, leaf blight, foliar blight, root rot, damping-off and bottom rot on a number of agriculturally and horticulturally important crops and plants including corn, sugar beet, rice, common bean, soybean, lettuce, cabbage, figs and hortensia [6]. Previous comparative analyses of available R. solani genomes of various pathogenic AGs (AG1-IA, AG1-IB, AG3 and AG8)

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