Plant Growth-Promoting Rhizobacteria for Sustainable Agricultural Production.

Rhizosheric bacteria with several abilities related to plant growth and health have been denominated Plant Growth-Promoting Rhizobacteria (PGPR). PGPR promote plant growth through several modes of action, be it directly or indirectly. The benefits provided by these bacteria can include increased nutrient availability, phytohormone production, shoot and root development, protection against several phytopathogens, and reduced diseases. Additionally, PGPR can help plants to withstand abiotic stresses such as salinity and drought and produce enzymes that detoxify plants from heavy metals. PGPR have become an important strategy in sustainable agriculture due to the possibility of reducing synthetic fertilizers and pesticides, promoting plant growth and health, and enhancing soil quality. There are many studies related to PGPR in the literature. However, this review highlights the studies that used PGPR for sustainable production in a practical way, making it possible to reduce the use of fertilizers such as phosphorus and nitrogen and fungicides, and to improve nutrient uptake. This review addresses topics such as unconventional fertilizers, seed microbiome for rhizospheric colonization, rhizospheric microorganisms, nitrogen fixation for reducing chemical fertilizers, phosphorus solubilizing and mineralizing, and siderophore and phytohormone production for reducing the use of fungicides and pesticides for sustainable agriculture.

Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture.

Plant growth-promoting bacteria (PGPB) and humic substances (HSs) are promising options for reducing the use of pesticides and mineral fertilizers. Although many studies have shown the effects of PGPB and HSs separately, little information is available on plant responses to the combined application of these biostimulants despite the great potential for the simultaneous action of these biological inputs. Thus, the objective of this review is to present an overview of scientific studies that addressed the application of PGPB and HSs to different crops. First, we discuss the effect of these biostimulants on biological nitrogen fixation, the various effects of the inoculation of beneficial bacteria combined with the application of HSs on promoting the growth of nonleguminous plants and how this combination can increase bacterial colonization of plant hosts. We also address the effect of PGPB and HSs on plant responses to abiotic stresses, in addition to discussing the role of HSs in protecting plants against pathogens. There is a lack of studies that address the role of PGPB + HSs in biocontrol. Understanding the factors involved in the promotion of plant growth through the application of PGPB and HSs can assist in the development of efficient biostimulants for agricultural management. This approach has the potential to accelerate the transition from conventional cultivation to sustainable agrosystems.

Efficacy of alginate- and clay-encapsulated microorganisms on the growth of Araçá-Boi seedlings (Eugenia stipitata)

The present work aimed to evaluate the effects of encapsulated microorganisms on seedlings of Eugenia stipitata, popularly known as araçá-boi, to evaluate the interaction between the inoculum and encapsulating agents such as clay and alginate. The experiment was carried out in a completely randomized design using a 3×2 factorial scheme. The treatments were control, inoculum, clay without microbial inoculum, clay with microbial inoculum, alginate without microbial inoculum, and alginate with microbial inoculum. The seedlings were grown under nursery conditions over a period of 3 months. No treatment increased the height, stem diameter, shoot dry matter or root dry matter of the araçá-boi seedlings. The use of alginate increased the ammonium content compared to the clay and control treatments. Alginate and clay increased the nitrate content in relation to the control. Alginate increased the total number of bacteria in relation to the clay and control treatments. The application of inoculum combined with alginate increased the nitrate content only in relation to the clay and control treatments. Although the application of inoculum promoted an increase in the nitrate content compared to the uninoculated treatments, there was no effect for the other parameters analyzed. The results suggest that clay and alginate encapsulating agents with the presence or absence of microorganisms may improve some soil parameters.

Porta-enxertos e fixadores de enxerto para enxertia hipocotiledonar de maracujazeiro azedo / Rootstocks and tying materials for hipocotyledonar grafting of yellow passion fruit

RESUMO:Avaliou-se a enxertia hipocotiledonar de maracujazeiro azedo em porta-enxertos de Passiflora alata, P. edulis, P. cincinnata e P. gibertii utilizando-se, como fixadores para envolvimento da região da enxertia, fita adesiva tipo crepe, grampo metálico de cabelo e grampo de enxertia a mola. O delineamento experimental foi em blocos ao acaso, em esquema fatorial 4 x 3 (porta-enxerto x fixador), com 12 tratamentos, três repetições e oito plantas na parcela. Utilizou-se a enxertia hipocotiledonar pelo método de garfagem de topo em fenda cheia. Avaliaram-se diâmetro de caule, altura de planta e número de folhas do porta-enxerto no momento da enxertia, percentagem de sobrevivência da enxertia, diâmetro do caule, número de folhas e altura do enxerto aos 30, 60 e 90 dias após a enxertia. A sobrevivência do enxerto de maracujazeiro azedo foi elevada, em geral, sendo equivalente para todos os porta-enxertos avaliados, demonstrando a eficiência da técnica. O uso dos fixadores de enxertia resultou em elevada percentagem de sobrevivência dos enxertos sem se verificarem diferenças entre os fixadores. Aos 90 dias após a enxertia, o maracujazeiro azedo, enxertado em P. alata apresentou menor crescimento em relação àqueles enxertados em P. edulis e P. gibertii.

ABSTRACT:The hipocotyledonar grafting of yellow passion fruit was evaluated onto Passiflora alata, P. edulis, P. cincinnata and P. gibertii with masking tape, metallic hair clip and spring plastic graf clip as tying materials. Experimental design was randomized blocks in a factorial 4 x 3 (rootstock x tying material) with 12 treatments, three replications and eight plants in the unit. The hipocotyledonar grafting method utilized was apical cleft grafting. Collected data included stem diameter, plant height and leaf number of rootstocks at grafting, and graft survival rate, stem diameter, leaf number and height 30, 60 and 90 days after grafting. Graft survival rate was high in general and equivalent among the evaluated rootstocks, indicating that apical cleft hipocotyledonar grafting was an efficient technique. All tying materials led to similar graft survival rates. Yellow passion fruit grafted onto P. alata presented lower canopy growth in relation to plants grafted onto P. edulis and P. gibertii, 90 days after grafting.