Resumen
- Drought is one of the major worldwide causes of losses in agriculture and livestock farming, including the dry Caribbean zone in Colombia. Therefore, the objective was to determine if a synthetic community of drought-tolerant plant growth-promoting bacteria (PGPB) isolated from the rhizosphere of Guinea grass (Megathyrsus maximus) could improve the plant’s drought tolerance. The PGPB were divided into three groups (A, B, and C) according to their drought tolerance and used for the inoculation of Guinea grass seeds. The treatments consisted of seven combinations of different bacterial groups with non-inoculated watered and drought controls. Forty- day-old plants were exposed to 10 days without water, after which the plant biomass, two antioxidant enzymatic activities, proline accumulation, and membrane stability were determined. The results showed that drought stress significantly decreased the total biomass and membrane stability and increased the glutathione reductase (GR) activity and proline accumulation in non-inoculated plants. Group C bacterial strains were found to be more effective in alleviating drought stress than the other PGPB groups and were identified as Bacillus spp. Group C was evaluated in a 48-h drought-stress simulation using D-sorbitol on 20-day-old plantlets in which the antioxidant responses were measured. The D-sorbitol significantly increased the GR activity and proline accumulation in the non-inoculated plants. The plantlets that were inoculated with the Bacillus spp. group showed significantly reduced GR activity and increased proline accumulation. The results of the study suggested that GR activity and proline accumulation were key mechanisms used by Guinea grass to cope with drought stress. The results also showed that the co-inoculation of Bacillus spp. has the potential to ameliorate drought stress through the modulation of these mechanisms.