FOLIAR AND ROOT INOCULATION OF LETTUCE PLANTS WITH BACTERIA ISOLATED FROM MELIPONIDS IN COMBINATION WITH ARBUSCULAR MYCORRHIZAL FUNGI AND PHOSPHORUS APPLICATION

Resumen

This research evaluated the plant growth-promoting effects of the inoculation of bacterial strains isolated from meliponids (stingless bees) in lettuce. Two bioassays were performed under greenhouse conditions. In the first bioassay, eleven bacterial strains previously isolated from meliponids were inoculated through leaves or roots of lettuce seedlings; greenness index (SPAD units), leaf area, and dry weight (aerial, root and total) were evaluated using a completely randomized design, and the two bacteria with the highest plant- promoting capacity were selected. In the second bioassay, the selected strains were inoculated in combination with arbuscular mycorrhizal fungi (AMF; Claroideoglomus claroideum and Funneliformis mosseae) and three doses of phosphate fertilization (11, 22 and 44 ?g P mL-1); fresh weight, leaf area, dry weight (aerial, root and total), and mycorrhizal colonization were assessed using a 4x2x3 factorial design. In the first bioassay, the results showed that the evaluated bacteria had positive effects on all variables, with Pantoea anthophila and Serratia
nematodiphila being the most prominent strains as plant growth promoters. In the second bioassay, significant differences were observed between the inoculated plants and the control, particularly in dry weight and leaf area. AMF-inoculation did not show significant differences compared to the bacterial combination. In addition, the application of 22 ?g P mL-1 with the combined inoculation of Pantoea anthophila and Serratia nematodiphila had a significant impact on plant growth. Overall, the use of bacteria isolated from stingless bees enhances plant growth and, combined with AMF and/or low or medium doses of P- fertilization, constitutes a good strategy to produce lettuce plants.