Assessment of Genetic Variability and Evolutionary Relationships of Rhizoctonia solani Inherent in Legume Crops

Abstract

Rhizoctonia solani is one of the most common soil-borne fungal pathogens of legume crops worldwide. We collected rDNA-ITS sequences from NCBI GenBank, and the aim of this study was to examine the genetic diversity and phylogenetic relationships of various R. solani anastomosis groups (AGs) that are commonly associated with grain legumes (such as soybean, common bean, pea, peanut, cowpea, and chickpea) and forage legumes (including alfalfa and clover). Soybean is recognized as a host for multiple AGs, with AG-1 and AG-2 being extensively investigated. This is evidenced by the higher representation of sequences associated with these AGs in the NCBI GenBank. Other AGs documented in soybean include AG-4, AG-7, AG-11, AG-5, AG-6, and AG-9. Moreover, AG-4 has been extensively studied concerning its occurrence in chickpea, pea, peanut, and alfalfa. Research on the common bean has been primarily focused on AG-2, AG-4, and AG-1. Similarly, AG-1 has been the subject of extensive investigation in clover and cowpea. Collectively, AG-1, AG-2, and AG-4 have consistently been identified and studied across these diverse legume crops. The phylogenetic analysis of R. solani isolates across different legumes indicates that the distinct clades or subclades formed by the isolates correspond to their specific anastomosis groups (AGs) and subgroups, rather than being determined by their host legume crop. Additionally, there is a high degree of sequence similarity among isolates within the same clade or subclade. Principal coordinate analysis (PCoA) further supports this finding, as isolates belonging to the same AGs and/or subgroups cluster together, irrespective of their host legume. Therefore, the observed clustering of R. solani AGs and subgroups without a direct association with the host legume crop provides additional support for the concept of AGs in understanding the genetic relationships and evolution of R. solani.

Biofungicides Based on Plant Extracts: On the Road to Organic Farming

“…Matsum & Nakai var. Lanatus) [119]. Al-Rahmah et al [100] evaluated the fungicidal activity of five methanol extracts of the following plants: Lantana camara L., Salvadora persica L., Thymus vulgaris L., Zingiber officinale Roscoe, and Ziziphus spina-christi L. on the phytopathogenic fungi Fusarium oxysporum, Pythium aphanidermatum, and Rhizoctonia solani.…”

Unveiling the Genetic Tapestry: Exploring Rhizoctonia solani AG-3 Anastomosis Groups in Potato Crops across Borders

“…Breeding-resistant potato cultivars are regarded as an environmentally safe and successful technique for R. solani management [ 21 ]. Understanding the genetic diversity of R. solani is crucial for the development of innovative management strategies, such as creating varieties resistant to Rhizoctonia [ 22 , 23 , 24 ]. The division of R. solani into anastomosis groups explains its genetic variability and, presently, 14 anastomosis groups have been identified (AG 1-13 and AG-BI), delineated based on hyphae fusion, shape, aggressiveness (pathogenicity), physical appearance, and DNA homogeneity [ 25 , 26 , 27 ].…”

“…The division of R. solani into anastomosis groups explains its genetic variability and, presently, 14 anastomosis groups have been identified (AG 1-13 and AG-BI), delineated based on hyphae fusion, shape, aggressiveness (pathogenicity), physical appearance, and DNA homogeneity [ 25 , 26 , 27 ]. Certain AGs are further classified based on the type of anastomosis, physiological and morphological features, pathological, biochemical, biomolecular, inherent, and DNA resemblance qualities [ 22 ]. For instance, AG-1 contains six subgroups, viz., IA, IB, IC, ID, IE, and IF, whereas AG-4 is divided into three subgroups, e.g., (HGI, HGII, and HGIII), while AG-2 is divided into nine (1, 2, 3, 4, t, Nt, 2IIIB, 2IV, and 2LP) subgroups [ 22 ].…”

“…Certain AGs are further classified based on the type of anastomosis, physiological and morphological features, pathological, biochemical, biomolecular, inherent, and DNA resemblance qualities [ 22 ]. For instance, AG-1 contains six subgroups, viz., IA, IB, IC, ID, IE, and IF, whereas AG-4 is divided into three subgroups, e.g., (HGI, HGII, and HGIII), while AG-2 is divided into nine (1, 2, 3, 4, t, Nt, 2IIIB, 2IV, and 2LP) subgroups [ 22 ]. Infection of potatoes with R. solani AG3-PT may cause typical disease signs such as stem canker and black scurf and various molecular indicators have been employed for detection and characterization, including techniques like ISSR (inter-simple sequence repeats), SSR (simple sequence repeats), SNPs (single nucleotide polymorphisms), AFLP (amplified fragment length polymorphisms), RFLP (restriction fragment length polymorphisms), RAPD markers derived from randomly amplified polymorphic DNA, EK (electrophoretic karyotyping), sequence analysis involving rDNA ITS1-5.8 S, and DNA-DNA hybridization [ 28 ].…”

“…Due to the presence of multiple recurrent tandem copies within the genetic content of all fungi, the examination of the rDNA ITS1-5.8 S-ITS2 region through sequence analysis has proven to be a superior method for investigating genetic diversity and the evolutionary connections within AG groups and AG subgroups of R. solani [ 22 , 29 ]. The verification of AG classification relies on conventional hyphal anastomosis responses, while the sequences of the rDNA ITS1-5.8S-ITS2 region evolve rapidly and are flanked by highly conserved nucleotide sequences, situated within the 18S and 5.8S rRNA genes (ITS1), as well as the 5.8S and 28S rRNA genes (ITS2) [ 22 ]. Genetic variability of R. solani causing potatoes black scurf and stem canker has been found in all areas of the world; however, there has been a dearth of effort to explore R. solani AG’s worldwide variation in genetics and geographical distribution related to potatoes [ 8 ].…”