Suppression of Rhizoctonia solani Root Rot Disease of Clusterbean (Cyamopsis tetragonoloba) and Plant Growth Promotion by Rhizosphere Bacteria

摘要

Clusterbean (Cyamopsis tetragonoloba (L.) Taub) is a kharif legume crop grown under arid zone. Root rot is the major disease in clusterbean caused by Rhizoctonia solani during rainy season and may result upto 21-60% losses at pre-and post-emergence stages. Rhizobacterial isolates were tested in this study for use as biological control agent for suppression of the root rot disease and to minimize the use of fungicides for disease control. Fifty five rhizobacterial isolates obtained from clusterbean rhizosphere soil were screened for antagonistic interactions against Rhizoctonia solani on PDA medium plates. Rhizobacterial isolates HCS2, HCS4, HCS30, HCS36, HCS43 and HFS12 showed significant antagonistic activity and inhibited the growth of fungi on PDA medium plates. Forty percent of these rhizobacterial isolates utilized ACC on minimal medium plates and five rhizobacterial isolates HCS16, HCS35, HCS42, HCS43 and HFS5 showed significant growth on ACC supplemented plates. Inoculation of Bradyrhizobiumisolate GSA11 with Pseudomonas isolate HCS36/'Bacillus isolate HCS43 and R. solani formed maximum 47 nodules plant-' and increased shoot dry weight by 306.3 and 281.5%, respectively as compared to uninoculated control at 30 days of plant growth under pot house conditions. At 60 days of plant growth, coinoculation of Rhizobium isolate GSA110 with Bacillus isolate HCS43 and R. solani formed 50 nodules plant~(-1) and caused 108.9% increase in shoot dry weight in comparison to uninoculated control. Maximum140.26% increase in shoot dry weight, nodule number (54 nodules plant~(-1)) and nodule weight (346.6 mg plant-') was observed by coinoculation of Pseudomonas isolate HCS36 with Rhizobium strain GSA110 and fungus R. solani. Coinoculation of Bacillus isolate HCS43 and Pseudomonas isolate HCS36 with Bradyrhizobium/Rhizobium isolates also showed 66.7 and 83.7% disease control. Thus, Bacillus isolate HCS43 and Pseudomonas isolate HCS36 could be further tested for disease control and plant growth stimulationunder field conditions.