Controle biológico de "Cylindrocarpon" sp. e fusarium sp. em porta-enxertos de videira utilizando Bacillus sp.

Abstract

The Brazilian viticulture has been expanding to different regions and standing out in the national economy. Despite significant advances in recent years, the culture has suffered serious problems with reduced productivity, decline and young death of vines. Many factors are involved in the grapevine decline including soil and crop management, abiotic stresses, pests, viral and fungal diseases. In this context, phytopathogenic fungi are considered the main responsible for damage to the crop and for the need to replant vineyards. Therefore, the use of propagative material with agronomic, physiological and phytosanitary quality is essential. However, healthy plant material may be reinfected when subjected to adverse environmental conditions, such as soils contaminated with phytopathogens. The present study aimed to evaluate the potential of Bacillus sp. strain F62 in the in vitro and in vivo biocontrol of Fusarium sp. and “Cylindrocarpon” sp. These phytopathogens cause serious diseases on grapevine and have been the subject of studies in many wine regions in the world, especially “Cylindrocarpon” sp., which causes black-foot on grapevine. In vitro experiments consisted of the evaluation of the antagonism by volatile and diffusible compounds (paired culture), as well as, the evaluation of the inhibition of conidial germination. In vivo experiments were performed on cuttings and on micropropagated grapevine rootstocks 1103P and SO4, under greenhouse conditions. In the paired culture assay, the bacterium inhibited the mycelial growth of five isolates of “Cylindrocarpon” sp., ranging from 61.09% a 69.98% and four isolates of Fusarium sp., ranging from 35.35% to 63.62%. In antagonism assay by volatile compounds there was no significant difference in relation to the control for both phytopathogens. Regarding the germination of conidia, it was verified that the bacterial suspension and the filtrate metabolites were effective in inhibiting the germination of fungal spores. In the in vivo experiment in cuttings of 1103P, unlike the cuttings of SO4, no statistically significant difference in growth promotion was verified in relation to the control. However, Bacillus sp. F62 reduced the percentage of re-isolation of “Cylindrocarpon” sp. to 27.9% in SO4 and 10.3% in 1103P, in relation to the control. Preventive treatment with Bacillus sp. F62 also reduced the percentage of re-isolation of Fusarium sp. to 17.6% in SO4. Micropropagated rootstocks treated with Bacillus sp. F62 was found to have greater vigor and better vegetative development compared to control. The rhizobacteria reduced the incidence of Fusarium sp. in 52.4% in micropropagated rootstock SO4. In addition, Bacillus sp. reduced the incidence of “Cylindrocarpon” sp. in 36.0% on micropropagated plants of SO4 and Paulsen 1103. In summary, Bacillus sp. F62 was effective in the in vitro and in vivo biocontrol of Fusarium sp. and “Cylindrocarpon” sp. and also stimulated the growth and development of micropropagated plants of both grapevine rootstocks evaluated in this study. [resumo fornecido pelo autor]