Bacteria can help replace chemical inputs in the forestry sector

The number of bacteria with the potential to generate bioinputs suitable for the forestry sector has reached 1.023. This result is the result of the work of Embrapa Florestas (PR), which has been working on building the Collection of Multifunctional Bacteria from Forest Areas since 2018. The collection includes specimens from different soils and forest species and has been instrumental in selecting strains with the potential to develop innovative bioinputs in the form of inoculants. These products can reduce, or even replace, chemical inputs in forest plantations, from seedling production to planting in the field. In addition to ensuring greater sustainability for the sector, it increases efficiency and reduces production costs.

After the isolation and characterization of the bacteria in the laboratory, tests are carried out in nurseries, with application to seedlings. According to Krisle da Silva (photo below), a researcher at Embrapa responsible for forming the collection, several tests have been carried out in nurseries with these bacteria, involving partnerships with forestry companies, to select the strains with the greatest potential to increase rooting rates and phosphorus absorption capacity.

“The production of forest seedlings inoculated with growth-promoting bacteria has shown promise, given the positive effect on rooting, phosphate solubilization, stimulation of plant growth in seedlings and biological pest control that we have found throughout the studies, especially for pine and eucalyptus,” the researcher points out. She hopes that, within two years, the studies will result in the generation of a bioinput in the form of an inoculant from these bacteria.

According to the researcher, all microorganisms in the collection are morphologically characterized in culture medium and 229 have already been genetically characterized. The DNA of these isolates is also stored in the collection.

The collection began with 42 endophytic bacteria (which live inside plant tissue without causing harm to the plant), isolated from a species of jabuticaba tree, due to their growth-promoting characteristics. Later, endophytic bacteria isolated from leaves, meristems (plant tissue responsible for plant growth) and roots of peach palm were introduced into the collection, totaling 222 bacteria to date. The work continued with pine, from which 200 bacteria were isolated, in addition to 90 from eucalyptus, 96 from yerba mate and 145 from araucaria. In the search for a possible biological control, 220 bacteria and actinobacteria (bacteria important for agriculture) were also isolated from leaf-cutter ants (Atta sexdens).

In addition to bioinputs, the collection is the basis for genetic improvement programs and other research actions aimed at developing plants better adapted to the forestry segment, such as pupunha, pine, eucalyptus, yerba mate and araucaria, among others.

How is insulation done?

For the collection, materials were collected from the rhizosphere, an area that is up to four millimeters away from the roots of forest species. The soil samples from the root surface were taken to a laboratory and diluted in a culture medium, where colonies began to proliferate. Then, the bacterial colonies were selected. Subsequently, the bacteria were evaluated for characteristics such as growth time, shape, color, and size of the colonies. To preserve and conserve the bacteria, without frequent handling and without altering their characteristics, three preservation methods are used: one in a solid medium containing mineral oil at a temperature of 20°C; another in water also at 20°C; and the third, in cryopreservation at 80°C below zero.

The identification and multiplication of bacteria are fundamental steps. If the bacteria are considered good for a given characteristic, they are multiplied in large quantities. For those that do not show good results, the study is interrupted. In addition, great care must be taken in the selection. “There are many bacteria in the soil that can potentially harm humans, such as Staphylococcus or Burkholderia cepacea. Therefore, great caution is needed at this stage,” explains Silva.

Collection in constant evolution

Among the researchers' objectives is, for example, identifying bacteria capable of producing phytohormones to stimulate plant growth, or strains with the potential to solubilize nutrients for the plant, among other agronomic benefits. In these cases, they are taken to nurseries for evaluation on the plants. 

According to the researcher, the collection is constantly evolving and should soon yield good results. “Embrapa remains committed to improving the collection of multifunctional bacteria, exploring new possibilities for applying this knowledge, with the aim of boosting the sustainable development of the forestry sector. This is a collection especially designed for forestry species, with preservation of genetic resources, with great potential for the development of new bioinputs,” concludes Silva.