Characterization of Cultural and Morphological Variability in Rhizoctonia solani Isolates Associated with Root Rot of Ajwain (Trachyspermum ammi L.)

Rhizoctonia solani (teleomorph: Thanatephorus spp.) is a plant pathogenic fungus which had a wide host range. It is best known to cause many diseases in plants such as collar rot, root rot, damping- off, sheath blight, stem canker, web blight and wire stem throughout the world. In vitro study of the various isolates of R. solani for morphological and cultural characters and results revealed that this experiment the various isolates of R. solani differed in colony characters and showed black brown colored cultures with 90.0 mm colony diameter on 7th day of incubation under uniform environmental condition. The highest growth reported was isolates CHIRs-5 and sclerotial formation was recorded in all the isolates of R. solani. Morphology of sclerotia varied from 1.9×1.5 mm of DCHIRs-1 and 1.8×1.5 mm of RUDPRs-2.

Current Status and Prospect of Web Blight of Cowpea: A Review

Pulses in India have been considered as the poor man’s only source of protein. Among them Cowpea (Vigna unguiculata) is an important food legume which is also known as vegetable meat due to high amount of protein in the grain with better biological value on dry weight basis. Various factors viz., diseases and insect pests are mostly responsible for its low production. Among diseases, web blight caused by Rhizoctonia solani is one of the most important disease of cowpea. The web blight appears every year at varying intensity and causes heavy losses in yield. Web blight disease is most severe at seedling and vegetative stage. The disease is characterized by oval or spindle shaped brown black lesions having length ranging from 0.2-8 cm at soil level near collar region and girdling the basal portion of the stem and lesions developed by basidiospores of Thanatephorus cucumeris which are 2-4 mm in diameter, circular and appear as brown necrotic spots with light brown centre. Cob web like symptoms also noticed hence, the name web blight.

Influence of Temperature on the Pathogenesis and Gene Expression of Rhizoctonia solani Causing Web Blight/Wet Root Rot Disease in Mungbean

Background: Mungbean (Vigna radiata L. Wilzeck) is one of the most important pulse crops and grown in almost all parts of the India. Web blight/wet root rot disease of mungbean is caused by Rhizoctonia solani Kühn. Crop environmental factors plays a vital role in the development of web blight disease caused by R. solani. An understanding of the role of environmental factors on the infection and survival of the pathogen is necessary to develop disease management practices. Methods: The effect of different temperatures (4oC, 20oC, 25oC, 30oC and 35oC) on mycelial growth of seven different R. solani isolates belonging to different anastomosis group were evaluated under in vitro conditions. Effect of different temperatures on the development of root rot/web blight disease of mungbean was also evaluated under phytotron conditions at various temperatures with constant relative humidity (85%) and illumination (alternate dark and light period of 12 h). Effect of temperatures on the expression of selected pathogenicity related genes was evaluated through real time PCR. Result: Maximum radial growth in R. solani isolates was observed at 25 and 30oC after 48 hrs of incubation. Maximum disease incidence was observed with R. solani isolate RUPU-18 (73.11%) followed by R-17 (68.75%), RDLM-1 (63.45%) at 25oC on mungbean genotype Pusa Vishal. Expression of genes like ABC transporter was observed only at 35oC, while other genes like 1, 3 glucan hydrolase expressed maximum at 25oC after 24, 48 and 72 hrs post inoculation. Present study suggested that the expression of pathogenicity related genes in mungbean-R. solani system is dependent on the temperature and time interval post pathogen inoculation.