Tratamento biótico e abiótico em sementes de couve de bruxelas para o controle de sclerotinia e indução de resistência

Abstract

among the diseases that affect brussels sprouts, Sclerotinia rot, caused by the fungus Sclerotinia sclerotiorum, can cause damage to the establishment of the culture, causing the rotting of the stem and leaves close to the ground. The pathogen control must be sought, through the use of alternative methods to chemical control. The objective was to verify the efficiency of biotic and abiotic inducers on the physiological quality and incidence of Sclerotinia rot in brussels sprouts seeds and to quantify the resistance responses provided by the treatments in seedlings of this vegetable. Brussels sprouts seeds without chemical treatment were used. The experiment was carried out at UFFS – Campus Erechim, in a completely randomized design, containing 7 treatments, as follows: Saccharomyces cerevisiae; brown propolis ethanol extract; 3% chitosan; acibenzolar-S-methyl; “water” control); “grain alcohol” control; and control “acetic acid” 1%. The seeds were inoculated with S. sclerotiorum by the water restriction technique with the mannitol restrictor, ensuring a water potential of -0.6 MPa. The infection curve of the seeds was calibrated after exposure to the pathogen at the times: 2, 4, 6, 8, 10 and 12 hours, in order to select the best period for infection and maintenance of the germinative potential of the seeds (≥ 80% germination). It was evaluated: i) germination (%); ii) incidence (%) of S. sclerotiorum; iii) field emergency; and iv) incidence (%) of Sclerotinia rot on seedlings. Induced resistance responses were evaluated through the activity of determining total soluble proteins and by the expression of the enzyme Phenylalanine ammonia-lyase (PAL). Data were submitted to analysis of variance and comparison of means by Tukey's test (p ≤ 0.05). For the quantitative variable (times of exposure of seeds to S. sclerotiorum), if significant, polynomial regression analysis was performed. It was found that the best time of exposure of seeds to the pathogen was 4 hours. The results showed that the treatment of brussels sprouts seeds with the different inducers did not provide improvements in relation to germination and pathogen control. The tested inducers also did not ensure an increase in the expression of total proteins as well as the PAL enzyme, indicating that they have a low resistance induction action, at the doses used, when applied to brussels sprouts seeds.