Drought stress tolerance and growth promotion in chiltepin pepper (Capsicum annuum var. glabriusculum) by native Bacillus spp

Abstract

Abstract Chiltepin is a semi-cultivated plant of high commercial value and represents a valuable genetic resource. However, several factors, such as drought, limit its production. Treatment with plant growth-promoting bacteria (PGPBs) is an alternative to mitigate drought stress. The present study aimed to evaluate the capacity of Bacillus spp, isolated from soils, to promote growth and induce tolerance to drought stress in chiltepin. A completely random design was established, and the Scott-Knott test was used (α = 0.05). The treated seeds improved germination parameters with increases of 46.42% in Germination Rate (GR), 22.56% in Mean Speed of Germination (MSG), 22.19% in Germination Speed Index (GSI), 65.16% in Vigor Index (VI), and 100.14% in Germination Index (GI). Furthermore, they reduced MGT (Mean Germination Time) by 5.63%. All isolates could solubilize phosphorus and zinc and produce ammonium, siderophores, and exopolysaccharides. Moreover, Bacillus spp. isolates showed resistance to drought at -1.75 MPa. Likewise, the treatments improved in vitro survival of stressed seedlings by 68%. Under greenhouse conditions, treated seedlings exhibited increases in root length (9.6%), stem diameter (13.68%), leaf fresh weight (69.87%), and chlorophyll a (38.15%). They also alleviated severe water stress symptoms and increased Relative Water Content (RWC) by 51%. Isolate Bc25-7 showed the highest potential for promoting growth, enduring water stress, and lessening the drought effect on chiltepin seedlings.