Controle biológico de sclerotinia sclerotiorum em sementes e plântulas de girassol ornamental

Abstract

Sunflower (Helianthus annuus L.) is now cultivated worldwide, and among the biotic factors that cause production losses we can highlight the occurrence of Sclerotinia sclerotiorum which is a destructive pathogen of several economically important crops and difficult to control. Thus, this study aimed to evaluate the control of this pathogen through the use of essential oils and bacteria in both in vitro and in vivo tests. The experiment was conducted in an entirely randomized design with 4 repetitions. For the in vitro test, 4 different essential oils were used, Rosmarinus officinalis, Melaleuca alternifolia, Corymbia citriodora and Salvia officinalis, in 4 different concentrations each (0, 500, 1000 and 3000 mg L-1 ), testing the antagonistic effect of Bacillus subtilis x Sclerotinia sclerotiorum and Bacillus amyloliquefaciens x Sclerotinia sclerotiorum, being evaluated the mycelial growth inhibition percentage (PIC %) for all treatments. For the in vivo test, the chosen dose of the essential oils was 1000 mg L-1 and the treatments evaluated were: T1) witness, only substrate and seeds without treatment and without the presence of the fungus; T2) witness, substrate + Sclerotinia sclerotiorum and seeds without treatment; T3) substrate + Sclerotinia sclerotiorum and seeds treated with the essential oil of rosemary (Rosmarinus officinalis); T4) substrate + Sclerotinia sclerotiorum + seeds treated with tea tree (Melaleuca alternifolia); T5) substrate + Sclerotinia sclerotiorum + seeds treated with eucalyptus (Corymbia citriodora); T6) substrate + Sclerotinia sclerotiorum + seeds treated with Salvia dalmaciana (Salvia officinalis); T7) substrate + Sclerotinia sclerotiorum + seeds treated with Bacillus subtilis at a concentration of 3 mL kg-1 seeds; T8) substrate + Sclerotinia sclerotiorum + seeds treated with Bacillus amyloliquefaciens, at a concentration of 3 mL kg-1 of seeds. In the in vitro test, it was found that as the doses of oils were increased, consequently, the control is also increased, ensuring this control also in the in vivo test when compared to the control. The bacteria in the in vitro test did not show as high inhibition of the pathogen, however, in the in vivo test, in addition to ensuring the health of plants, Bacillus amyloliquefaciens promoted plant growth.