Actinobacteria associated with vineyard soils of Algeria: classification, antifungal potential against grapevine trunk pathogens and plant growth-promoting features
Résumé
Grapevine trunk diseases (GTDs) are among the most destructive diseases of vineyards worldwide, including Algeria. In the fungal complex involved in GTD symptoms, referred as grapevine trunk-pathogens,Paeomoniella chlamydosporaandPhaeoacremonium minimumhave a determining infecting role as pioneer fungi. Due to the lack of efficiency of conventional disease management practices, a search for alternative strategies, such as biocontrol, is needed. Taking the approach of looking for biocontrol candidates in the environment surrounding the plant, the present study explored actinobacteria diversity within vineyard soils of six grape-producing regions in Algeria. Based on their 16S rRNA gene sequence, identification and phylogenic analysis were performed on the 40 isolates of actinobacteria obtained. Forty percent of strains were attached toStreptomyces, including two evidenced new species, and 32.5% were affiliated toSaccharothrix. The other less represented genera wereActinoplanes,Nocardia,Nocardiopsis,Lentzea,Nonomuraea,Promicromonospora,SaccharopolysporaandStreptosporangium. Screening based on antagonistic and plant growth promotion (PGP) abilities of the strains showed that 47.5% of the isolates exhibited appreciable antagonistic activities against bothPa.chlamydosporaandPm.minimum,with the two best strains beingStreptomycessp. Ms18 andStreptomycessp. Sb11. Screening for plant growth promoting properties demonstrated that majority of the strains were able to produce indole acetic acid, siderophores, ammonia, ACC deaminase, cellulase and amylase, and fix N-2. Through a PGP-traits-based cluster analysis, the most interesting strains were highlighted. Taking into account both antagonistic and PGP properties,Streptomycessp Sb11 was selected as the most promising candidate for further evaluations of its efficiency in a GTDs context.