Thermal stress in the acclimatization of micropropagated banana plantlets, supplemented with plant growth-promoting rhizobacteria

Micropropagated banana plantlets need acclimatization to reduce the stresses caused by the change from in vitro to ex vitro environment. The objective of this study was to evaluate the influence of thermal stress on the acclimatization of micropropagated plantlets of banana cultivar ‘Prata Catarina’, supplemented with plant growth-promoting rhizobacteria. Four applications of the LPPC159 strain, belonging to the genus Bacillus were performed every 15 days. Inoculated plantlets did not show differences in the biometric variables compared to fertilized plantlets. Plantlets acclimatized for seven days under controlled conditions, seven days in tunnel and 46 days in greenhouse showed greater pseudostem diameter, fresh and dry mass, and higher accumulations of N, P, K, Ca, Mg, S, Na, B, and Cu. No significant differences were observed between inoculated and non-inoculated plantlets. Inoculations had positive and negative effects only on the accumulations of N and Cu, respectively. The lowest thermal indices were observed for plantlets of T5 (7 days in a controlled environment + 7 days in a tunnel + 46 days in a greenhouse) and T1 (14 days in a shade tunnel + 46 days in a greenhouse), promoting better thermal comfort for plantlets of these treatments. Using shade in the acclimatization phase combined with plant growth-promoting rhizobacteria promoted gains in pseudostem diameter, fresh mass, dry mass, and nutrient accumulation in the plantlets. These conditions also allowed reductions in thermal stress in the acclimatization phase of micropropagated plantlets of banana cultivar ‘Prata Catarina’.