Potencial biotecnológico de bactérias para o controle de diferentes patógenos da cultura do tomate, Solanum lycopersicum L

Abstract

Tomato (Solanum lycopersicum L.) belongs to the Solanaceae family and is native to the Andean region, comprising Peru, Bolivia and Ecuador. Among the fruits characterized as vegetables, tomato is the most consumed in the world, in addition to being a source of antioxidants, such as lycopene. However, several diseases of bacterial and fungal origin can compromise tomato production. Bacterial wilt caused by R. solanacearum, sclerotium wilt caused by Sclerotium rolfsii and target spot caused by Corynespora cassiicola (Bert & Curt) Wei are the main diseases that limit the productivity of Solanaceae in tropical regions. Brazil, despite having the ideal environmental conditions for the proliferation of the main pathogens of tomato, also offers the necessary environmental variables to succeed in the production of tomato that can be produced commercially in all Brazilian regions. Pathogens such as R. solanacearum, C. cassiicola and S. rolfsii, as they are the most important in tomato crops, are therefore interesting targets for biological control. Therefore, this research aimed to select, identify and evaluate in vitro and in planta biocontrol based on antagonistic bacteria with potential for the development of bioinputs that contribute to sustainable agricultural development against these pathogens. The phytopathogen C. cassiicola and S. rolfsii were obtained from tomato plants showing symptoms of target spot and sclerotium wilt, respectively. The screening of antagonistic bacteria was performed based on 60 isolates from the collection of microorganisms from the Molecular Biology laboratory at Embrapa Amazônia Ocidental, with the three most promising isolates being selected for each pathogen. In the case of R. solanacearum the isolates SOL 195, SOL 101.1 and PcA1. For C. cassiicola the isolates PcA1, SOL 194 and SOL 195 and S. rolfsii the isolates PcA1, SOL 112 and SOL 101.1. All isolates were identified based on the 16S region or complete genome and evaluated for biocontrol in vitro and in planta. Molecular identification revealed that PcA1, based on phylogenomics, belongs to the species Bacillus amyloliquefaciens, and the other isolates were identified based on the nucleotide identity of the 16S region in genus: SOL 101.1 (Bacillus sp.), SOL 112 (Bacillus sp.), SOL 194 (Microbacterium sp.) and SOL 195 (Stenotrophomonas sp.). The in vitro tests indicated that the SOL 195 isolate obtained the highest percentage of inhibition of the growth of R. solanacearum, with 75.62% and showing a progressive increase in the antagonist activity during the experiment. The isolate PcA1 maintained the highest percentage of growth inhibition of the fungus S. rolfsii, ranging from 78.18% (seven days) to 67.40% (21 days). PcA1 was also the most efficient against C. cassiicola with 75.73% inhibition at 21 days. In the in-plant evaluations, the isolates SOL 195, SOL 101.1 and PcA1 were effective in the biocontrol of bacterial wilt in tomato. Isolates SOL 101.1, SOL 112 and PcA1 were ineffective in controlling sclerotium wilt independently if inoculated before the pathogen (preventive effect) along with the pathogen, or after the establishment of the disease (curative effect). In the biocontrol of C. cassiicola, the isolates SOL 195 and PcA1 were the most efficient in reducing the severity of the target spot when used preventively. In addition, PcA1 was the most efficient when inoculated after the established disease (curative effect).