Molecular Screening and Characterization of dsRNA from wild-type and Mutant Strains of Rhizoctonia solani Kühn Isolates


Doreen D. Domingo1, Paulina A. Bawingan2,
Seema Bharathan3 and Narayanaswamy Bharathan4

1Associate Professor, Mariano Marcos State University, City of Batac, I.N.
2Professor, Saint Louis University, Baguio City
1,4Professor, Indiana University of Pennsylvania, PA, USA

corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.



Rhizoctonia solani Kühn is a common soil-borne pathogen which infects a diversity of plant hosts. Previous studies have shown that the virulence of Rhizoctonia is affected by the presence of certain dsRNA segments which are of viral origin. This study attempted to screen dsRNA from wild type and mutant isolates of Rhizoctonia solani and characterize them as to size, concentration, and reaction to nucleases. The Rhizoctonia solani isolates were also compared as to color changes in the mycelia and in the culture media, in sclerotia formation and growth rate. There were twelve R. solani isolates utilized in the study: three wild type strains that are heterokaryons (RS29, RS 114 and TE2-4); and nine mutant strains that are homokaryons (RS29.5, RS 29.6. RS29.7, EGR4, EGR7, T2, Tom7, 123e and 115). Results of the study show that only five of the R. solani isolates had dsRNA namely: RS29, RS114, TE2-4, EGR4 and T2. The dsRNAs vary in their sizes and concentration and they showed resistance to nucleases. The R. solani isolates vary in the mycelia pigmentation: white (RS 29.6, RS 29.7, EGR4, EGR7 and 123E), light brown (RS29, RS114, RS 29.5 and 115), brown (TE2-4), and dark brown (T2 and Tom7). Color changes on the potato dextrose agar medium were light yellow (RS 29.5, RS 29.7, EGR4, EGR7), yellow brown (RS 29.6), light brown (RS 29, RS 114, TE2-4), brown (Tom 7, Strain 115) and dark brown (123E, T2).



Many plant pathogenic fungal isolates infected with dsRNA mycoviruses have shown increased virulence (hypervirulence) or reduced virulence (hypovirulence) with the presence of certain dsRNA segments (Tavantzis 2002; Lacksman et al. 1998). For instance, it was shown in previous studies that 3·6-kb dsRNA is associated with suppression of virulence, whereas a 6·4-kb dsRNA is involved with increased virulence in R. solani (Lakshman & Tavantzis 1994; Jian et al. 1997). These dsRNAs are common by-products of viral infection and may result directly from the virus or be produced through transcriptional processes (Karpala et al. 2005). . . .





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