A longitudinal study on morpho-genetic diversity of pathogenic Rhizoctonia solani from sugar beet and dry beans of western Nebraska

Saurav Das,T Plyler-Harveson,Dipak K Santra,Robert M Harveson,Bijesh Maharjan,Kathy A Nielson

doi:10.1186/s12866-020-02026-9

Abstract

BackgroundRoot and stem rot caused by Rhizoctonia solani is a serious fungal disease of sugar beet and dry bean production in Nebraska. Rhizoctonia root rot and crown rot in sugar beet and dry bean have reduced the yield significantly and has also created problems in storage. The objective of this study was to analyze morpho-genetic diversity of 38 Rhizoctonia solani isolates from sugar beet and dry bean fields in western Nebraska collected over 10 years. Morphological features and ISSR-based DNA markers were used to study the morphogenetic diversity.ResultsFungal colonies were morphologically diverse in shapes, aerial hyphae formation, colony, and sclerotia color. Marker analysis using 19 polymorphic ISSR markers showed polymorphic bands ranged from 15 to 28 with molecular weight of 100 bp to 3 kb. Polymorphic loci ranged from 43.26–92.88%. Nei genetic distance within the population ranged from 0.03–0.09 and Shannon diversity index varied from 0.24–0.28. AMOVA analysis based on ΦPT values showed 87% variation within and 13% among the population with statistical significance (p < 0.05). Majority of the isolates from sugar beet showed nearby association within the population. A significant number of isolates showed similarity with isolates of both the crops suggesting their broad pathogenicity. Isolates were grouped into three different clusters in UPGMA based cluster analysis using marker information. Interestingly, there was no geographical correlation among the isolates. Principal component analysis showed randomized distribution of isolates from the same geographical origin. Identities of the isolates were confirmed by both ITS-rDNA sequences and pathogenicity tests.ConclusionIdentification and categorization of the pathogen will be helpful in designing integrated disease management guidelines for sugar beet and dry beans of mid western America.

Highlights

Root and stem rot caused by Rhizoctonia solani is a serious fungal disease of sugar beet and dry bean production in Nebraska
Morphological diversity A total of 38 fungal colonies of the Rhizoctonia_Sugar Beet (RZ_SB) and Rhizoctonia_Dry Bean (RZ_DB) isolates were established in laboratory and these were used for studying morphological characteristics
There were no significant genetic and morphological differences in both sugar beet and dry bean isolates which were collected over 10 years in Nebraska Panhandle

Summary

Introduction

Root and stem rot caused by Rhizoctonia solani is a serious fungal disease of sugar beet and dry bean production in Nebraska. Rhizoctonia root rot and crown rot in sugar beet and dry bean have reduced the yield significantly and has created problems in storage. Vulgaris) [2], dry beans (Phaseolus vulgaris) [2], potato (Solanum tuberosum) [3], and soybean (Glycine max) [4] It is a major problem for the sugar beet and dry bean producers of western Nebraska. Every year Rhizoctonia root rot and crown rot in sugar beet (Fig. 1b) and dry bean (Fig. 1a) have reduced the yield significantly and created problems in storage. In Nebraska, a total of 52 and 42% of yield reduction can be observed in case of dry bean variety viz. Great Northern bean and Pinto bean, respectively due to Rhizoctonia root and crown rot [6]

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