In vitro Antagonism of Rhizobacteria Isolated from Coffea arabica L. against Emerging Fungal Coffee Pathogens

Abstract

In vitro antagonistic effects of rhizobacteria associated with Coffea arabica L. against some fungal coffee pathogens were studied. The aims were to screen indigenous coffee‐associated isolates for their inherent antagonistic potential against major coffee wilt diseases induced by Fusarium spp. Antagonistic effects, siderophore, HCN and lytic enzyme production were determined on standard solid media. Chemical methods were employed to categorize the major types of siderophores. From a total of 212 rhizobacterial isolates tested, over 10 % (all Pseudomonas and Bacillus spp.) exhibited remarkable inhibition against Fusarium spp. One isolate AUPB24 (P. chlororaphis) showed maximum inhibition of mycelial growth against all fungal pathogens tested, whereas other isolates were mostly inhibitory to F. stilboides and F. oxysporum. The isolate AUBB20 (B. subtilis) was most antagonistic to F. xylarioides. Of the rhizobacterial isolates tested, 67 % produced siderophores and 35 % produced HCN. Many strains (all Pseudomonas spp.) produced siderophores of the hydroxamate type and only a small proportion produced those of the catecholate type. Few antagonists showed chitinase activity. The production of siderophores and HCN by Pseudomonas spp., lipase and protease by all antagonists and β‐1,3‐glucanase by several Bacillus spp. could be considered the major mechanisms involved in the inhibition of fungal growth. The in vitro results provide the first evidence of an antagonistic effect of coffee‐associated rhizobacteria against the emerging fungal coffee pathogens F. stilboides and F. xylarioides and indicate the potential of both bacterial groups for biological control of coffee wilt diseases.

Microbial communities associated with the root system of wild olives (Olea europaea L. subsp. europaea var. sylvestris) are good reservoirs of bacteria with antagonistic potential against Verticillium dahliae

“…isolated from different plant species were the most abundant rhizobacteria showing in vitro antagonism against V. dahliae, with their diversity being both site-and plant-specific (Berg et al 2002(Berg et al , 2005b. Recently, Muleta et al (2007Muleta et al ( , 2009, screened the in vitro antagonistic effect of indigenous cultivable rhizobacteria associated with Coffea arabica, and found that most bacteria showing inhibitory activity against growth of Fusarium spp. were members of Pseudomonas and Bacillus spp.…”

“…to inhibit growth of pathogenic fungi is well known and these bacteria have been reported to be one of the most frequent beneficial rhizobacteria showing broad antifungal effect (Muleta et al 2007). In culturedependent studies, Pseudomonas spp.…”

Beneficial bacteria of agricultural importance

“…The enzymes are usually for defence and they could be cell walldegrading hydrolytic enzymes. The production of enzymes includes chitinase, cellulase, b-1,3-glucanase, protease, lipase can lyse some fungal cells (Muleta et al 2007) and suppress deleterious rhizobacteria. Examples of the best characterized defence enzymes are peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase (Latha et al 2009).…”

Isolation of <i>Pseudomonas flurescens</i> from Rhizosphere of Faba Bean and Screen Their Hydrogen Cyanide Production Under in Vitro Stduy, Ethiopia

“…Pseudomonas spp. that showed remarkable inhibitory effects against the test fungal pathogens produced HCN (Muleta et al, 2007). This compound, although reported as a potential inhibitor of enzymes involved in major plant metabolic processes (Bakker and Schippers, 1987) is currently attracting remarkable attention and wide applications in areas of biocontrol methods.…”