Screening rhizobacteria for biological control of Fusarium root and crown rot of sorghum in Ethiopia

Fusarium oxysporum Schlectend causes root and crown rot in several crops including sorghum that results in low grain yield in Ethiopia and other East African countries. Seventy-eight bacterial isolates were obtained and subsequently tested both in vitro and in the greenhouse. Of the 78 isolates tested, 23 displayed between 30 and 66.3% inhibition of in vitro mycelial growth of E oxysporum and also showed significant root colonization ability on sorghum seedlings. These isolates were further tested for their biocontrol ability against F oxysporum in the greenhouse. Four isolates viz. KBE5-7, KBE5-1, KBE2-5 and NAE5-5 resulted in 100% disease suppression and no symptoms of root and crown rot were observed compared to the control. The complete suppression of F. oxysporum by these isolates was also confirmed by root plating on Fusarium-selective medium. The most effective isolates were identified by means of the API system as members of the Genus Bacillus including B. cereus, B. subtilis, B. circulans, B. licheniformis and B. stearothermophilus. Two other isolates, which colonized the sorghum rhizosphere and resulted in more than 70% disease suppression, have been identified as Chromobacterium violaceum. The study demonstrated effective biological control by the rhizobacterial isolates tested, thereby indicating the possibility of application of rhizobacteria for control of soilborne diseases of sorghum in Ethiopia and other countries. (c) 2006 Elsevier Inc. All rights reserved.