Assessment of 3 Tac-I/Beta, an antimicrobial peptide source, in the control of Pseudomonas plant pathogens

E.A. Moya-Elizondo, T. Quezada, M. Reyes Salinas, M.A. Reyes Navarro
Diseases caused by Pseudomonas syringae and other species of Pseudomonas cause severe losses in different fruit crops worldwide. Antimicrobial peptides (AMPs) are small molecules and consist of a variety of proteins that act on the lipid bilayer of the bacterial membrane that is produced by multicellular organisms. The product, 3 Tac-I/Beta, is a biopesticide that bases its action on three Trichoderma strains (T. viride strain T-26, T. harzianum strain T-22, and T. longibrachiatum strain T-397), its total concentration is >25×103 c.f.u. g‑1, which is authorized in Chile to control different fungal diseases in fruit and vegetable crops. In this study we used Transmission Electronic Microscopy (TEM) to assess the possible AMP activity of this product on the bacterial membrane of Pseudomonas syringae pv. syringae (Pss). The effect of two filtered solutions of 3 Tac-I/Beta (commercial and concentrated) on the population of this bacterium was assessed by using in vitro tests. This TEM study showed a marked damage on the membrane of P. syringae pv. syringae, which affected the bacillus shape of the bacterium by changing the continuity of its membrane. In vitro tests on a homogeneous lawn of Pss showed the formation of inhibition halos around discs treated with filtered 3 Tac-I/Beta across the surface of agar King B-medium plates. Bacterial growth, expressed as the optical density of cell culture, was reduced by around 12% when 3 Tac-I/Beta was used, while a concentrated AMP solution of filtered 3 Tac-I/Beta showed a reduction of around 34.8% after 18 h of co-culture. Preventive spraying of 3 Tac-I/Beta on cherry plants cv. ‘Bing’, showed differences in the length of the bacterial canker compared to the untreated control. The biopesticide treatment was not different from the copper based treatments (P<0.10). The potential use of 3 Tac-I/Beta as an alternative to control kiwifruit canker is further discussed below.
Moya-Elizondo, E.A., Quezada, T., Reyes Salinas, M. and Reyes Navarro, M.A. (2019). Assessment of 3 Tac-I/Beta, an antimicrobial peptide source, in the control of Pseudomonas plant pathogens. Acta Hortic. 1243, 33-38
DOI: 10.17660/ActaHortic.2019.1243.6
Pseudomonas syringae pv. syringae, antimicrobial peptides, bacterial fruit canker, biocontrol, 3 Tac-I/Beta

Acta Horticulturae