Selection of antagonistic bacteria isolated from the Physalis peruviana rhizosphere against Fusarium oxysporum

Aims: Cape gooseberries (Physalis peruviana) have become increasingly important in Colombia for both domestic consumption and the international export market. Vascular wilting caused by Fusarium oxysporum is the most damaging disease to P. peruviana crops in Colombia. The control of this pathogen is mainly carried out by chemical and cultural practices, increasing production costs and generating resistance. Therefore, the objectives of this study were to test rhizobacteria isolates from P. peruviana rhizosphere against F. oxysporum under in vitro and in vivo conditions. Methods and Results: Over 120 strains were isolated, and five were selected for their high inhibition of F. oxysporum growth and conidia production under in vitro conditions. These strains inhibited growth by 41-58% and reduced three-to fivefold conidia production. In the in vivo assays, all the tested isolates significantly reduced fungal pathogenicity in terms of virulence. Isolate B-3.4 was the most efficient in delaying the onset of the first symptoms. All isolates were identified as belonging to the genus Pseudomonas except for A-19 (Bacillus sp.). Conclusions: Our results confirmed that there are prospective rhizobacteria strains that can be used as biological control agents; some of them being able to inhibit in vitro F. oxysporum growth and sporulation. Significance and Impact of the Study: Incorporating these bacteria into biological control strategies for the disease that causes high economical losses in the second most exported fruit from Colombia would result in a reduced impact on environment and economy.