Abstract
ABSTRACT The present study assessed the efficacy of formulated biocontrol agents and nitrogen fertilization on southern blight control. Antagonism test in vitro was performed to assess the inhibitory activity of Bacillus methylotrophicus and Trichoderma asperellum against the growth of Sclerotium rolfsii. Tomato seedlings were transplanted into the substrate added with ammonium nitrate doses and inoculated with the formulated biocontrol agents Onix (B. methylotrophicus) or Quality (T. asperellum). Subsequently, seedlings were inoculated with S. rolfsii. Plant mortality, shoot and root weight were assessed 11 days after the last inoculation. Agents had effective inhibitory activity against S. rolfsii; thus, they could reduce southern blight severity when combined with ammonium nitrate. However, plant mortality was not reduced by them.
Highlights
Sclerotium rolfsii, the pathogen of southern blight, causes root and crown rot, wilt and damping off in plants
Experiments in vivo assessed the efficacy of antagonistic microorganisms amended with ammonium nitrate doses in reducing southern blight severity in tomato plants
Treatments without biological control were not colonized by Trichoderma and/or Bacillus
Summary
Sclerotium rolfsii, the pathogen of southern blight, causes root and crown rot, wilt and damping off in plants. The sclerotium of S. rolfsii has a melanized outer layer, cortex and a medulla consisting of thread-like hyphae It is round-shaped and its size ranges from 0.5 to 3 mm in diameter. The secretion of oxalic acid triggers the infectious process and reacts to calcium in the cell wall, which first produces calcium oxalate, the pathogen secrets pectinase and endopolygalacturonase (enzymes). It enables plant tissue penetration by fungal mycelium (PUNJA, 1985; SARMA et al, 2002; SERRA; SILVA, 2005)
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