Seleção de bactérias benéficas para o enraizamento de mudas de videira

Abstract

The production of grapes for fine wines in the southern region of Minas Gerais has become relevant in recent years. Grapevine planting has increased every year in the region and consequently the demand for high quality grafted grapevine has followed the same trend. However, some factors have limited the production, such as the low rooting rate of grafted vines in nurseries. In this sense, although regional research on grapevines at this stage of production is still scarce, the use of microorganisms with beneficial effects has demonstrated positive results in several other crops. Beneficial bacteria are among the most studied and used microorganisms in agriculture nowadays and are the basis of various bioproducts. These microorganisms can occur naturally in soils and are associated with the plant rhizosphere. The objective of this work was to select isolates of gram-positive bacteria capable of promoting rooting and setting of grafted grapevine plants. The isolates were obtained from soil samples collected close to the roots (‘Bulk soil’) and from the rhizospheric environment of grapevine plants. Cuttings of rootstock IAC572 were immersed for 24 h in bacterial suspensions of each isolate and subsequently planted in plastic containers filled with a mixture of sand and substrate and kept in a greenhouse. The plant hormone 1-naphthalene-acetic acid (ANA) was used as positive control and autoclaved distilled water as negative control. The evaluations consisted of quantitative analyses of plant settiing, root and shoot dry mass, branch length and chlorophyll content. The most promising isolates were evaluated in vitro for nutrient solubilization (P, K) and protein hydrolyzation (casein) tests. None of the selected isolates was able to solubilize P (FePO4) and K. Most of the isolates that showed promising results in the in vivo tests were able to hydrolyze casein, releasing nitrogen. The cuttings treated with isolates SY01 and INV did not differ significantly from those treated with the plant hormone in all variables analyzed, demonstrating the potential for biostimulation in grapevine cuttings. In addition to these, the isolates SY18, SY30, BO04 and BO05 also showed results comparable to the hormone treatment in most of the variables tested. The results of this work contributed by providing yet another promising tool for the production of grapevine grafted planting material that may contribute to the sustainability of the process. Finally, it is necessary to carry out more studies to investigate the mechanisms used by these isolates and their combinations to increase setting and growth of grapevines in nurseries.