Rhizobacteria (Azospirillum brasilense) improves growth of micropropagated vanilla plantlets during acclimatization stage
摘要
Azospirillum brasilense is a plant growth-promoting bacterium that sustainably improves crop development. Thus, this study aimed to evaluate the response of different doses of A. brasilense on the survival percentage and development of micropropagated Vanilla planifolia plantlets during the acclimatization stage under greenhouse conditions. Vanilla plantlets were inoculated with 0, 0.5, 1, and 1.5 × 106 CFU (Colony-Forming Units) per plantlet of A. brasilense during ex vitro conditions. After 12 weeks of acclimatization, survival, dry matter, plantlet development, photosynthetic pigments, and the concentrations of nutrients were evaluated. The dose of 0.5 and 1 × 106 CFU per plantlet of A. brasilense provided adequate development, improving plantlet height (10.33 and 10.60 cm in height, respectively), number of leaves (7.33 and 7.73 leaves per plantlet, respectively), total chlorophyll (0.53 and 0.55 mg g–1 FW per plantlet, respectively) and β-carotene (7.41 and 7.51 mg g–1 FW per plantlet, respectively). While the dose of 1 × 106 CFU per plantlet of A. brasilense improved the number and length of roots (4.10 roots and 7.33 cm in length, respectively), the dose of 1.5 × 106 CFU per plantlet of A. brasilense had a negative response on survival percentage (70%), plantlet height (6.60 cm), number of leaves (4.46 leaves per plantlet), total chlorophyll (0.46 mg g–1 FW per plantlet), and the concentrations of nutrients (N, P, K, Ca, Mg, S, Fe, Cu, Zn, Mn, and B). Vanilla plantlets inoculated with A. brasilense formed a mutualism association with the roots to promote development during acclimatization.