Soil texture affects the efficiency of Bacillus subtilis and Bacillus licheniformis in the physiological and biochemical modulation of sugarcane tolerance to water deficit

Abstract

Using plant growth-promoting bacteria (PGPB) offers a promising strategy to enhance the tolerance of cultivated plants to water deficit (WD). This study investigated sugarcane's physiological, biochemical, and biomass production responses inoculated with Bacillus subtilis (strain FMCH002) and Bacillus licheniformis (strain FMCH001) under WD in two soil types. The experiment followed a completely randomized factorial design (2 × 2 × 2: with and without PGPB, with and without WD, in sandy and clayey soils) with six replicates. In clayey soil, PGPB inoculation increased the effective photochemical efficiency of PSII, stomatal conductance, instantaneous carboxylation efficiency, leaf water potential, relative water content, and chlorophyll a and b levels. Conversely, WD in sandy soil intensified enzymatic activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase alongside elevated malondialdehyde levels. Proline content was approximately 40 % higher in clayey soil. PGPB inoculation resulted in 17.26 % and 15.45 % increases in root dry matter (RDM) and shoot dry matter (SDM), respectively. In sandy soil, RDM and SDM were 68.88 % and 28.63 % higher, respectively. Principal component analysis revealed that intercellular CO₂ concentration and electron transport rate were key contributors to dry matter production, explaining over 90 % of the variance. Positive and significant correlations were observed across evaluation periods before and during WD (119, 126, and 133 DAP). These findings underscore the potential of Bacillus subtilis and Bacillus licheniformis to enhance sugarcane resilience to water deficit, promoting climate-adaptive agricultural practices in sandy and clayey soils.