Interactions between common scab-inducing strains on potato suberin.

Potato tuber periderm is armored with suberin, that consists of two domains, an aliphatic domain composed of fatty acid polyesters and an aromatic domain composed of cinnamic acids. Streptomyces scabies 87.22, a predominant causal agent of potato common scab, was compared for adaptation to tuber suberin with Streptomyces acidiscabies ATCC 49003 and Streptomyces turgidiscabies Car8 belonging to emerging pathogenic species. S. scabies 87.22 showed higher growth in the suberin supplemented medium than the two other strains. When co-cultured on rich nutrient medium, S. acidiscabies ATCC 49003 produced the antibiotic oxanthromicin, which inhibited growth and mycelium development of the other strains. Exposure of S. scabies 87.22 and S. acidiscabies ATCC 49003 to suberin was accompanied by the secretion of enzymes degrading cellulose, hemicellulose, fatty acids and glycerol derivatives. Compared to the two other strains, S. scabies 87.22 showed higher esterase activity in suberin-supplemented medium and strong induction of cellulase gene expression. Both S. acidiscabies ATCC 49003 and S. turgidiscabies Car8 exhibited a poor utilization of trans-ferulic and p-coumaric acids, suggesting almost no ability to degrade the aromatic moiety of suberin. This work suggests that S. scabies 87.22 is better adapted to the potato periderm degradation than the emerging pathogens. The elucidation of pathogenic Streptomyces strains interaction may contribute to the improvement of ecologically oriented agronomic strategies for common scab management.