Dose-responses of Bacillus cereus RS87 for growth enhancement in various Thai rice cultivars

Abstract

To achieve the goal of reducing the levels of chemical fertilizers applied in rice production, there is a need to develop microorganisms with the capacity to enhance plant growth. Previous studies have demonstrated that Bacillus cereus RS87 promotes growth of various plants in greenhouse and field trials. The objectives of this study were to (i) evaluate the efficacy and determine the optimum concentration of B. cereus RS87 to enhance growth of various Thai rice cultivars, (ii) measure the chlorophyll content in leaves affected by strain RS87, and (iii) investigate the capacity of strain RS87 to solubilize phosphate and produce siderophores. Three concentrations of strain RS87 (log 6.0, log 7.0, and log 8.0 CFU/mL) were applied to each rice cultivar. Superior responses (i.e., enhanced development of roots and shoots of all rice cultivars) were observed using RS87 at log 8.0 CFU/mL compared with lower bacterial concentrations and the water-treated control treatment. In addition, log 8.0 CFU/mL of RS87 provided the greatest root length and plant height of all rice cultivars 45 days after planting in the greenhouse. Rice leaves treated with log 8.0 CFU/mL of RS87 yielded the highest total chlorophyll, specifically chlorophyll a and chlorophyll b, compared with the control. Strain RS87 also solubilized phosphate and produced siderophores. The results of these studies demonstrate that log 8.0 CFU/mL is the optimum concentration of strain RS87 for growth promotion of various Thai rice cultivars.

Molecular Characterization of Stress Tolerant Plant Growth Promoting Rhizobacteria (PGPR) for Growth Enhancement of Rice

“…Bacillus is known as potential elicitor of ISR and exhibits significant reduction in the incidence or severity of various diseases on diverse crops including rice (Kloepper et al 2007;Choudhary et al 2007;Jetiyanon and Plianbangchang, 2010).…”

Potential of Bacillus cereus strain RS87 for partial replacement of chemical fertilisers in the production of Thai rice cultivars

“…Fages and Arsac36 observed that maximum increases in germination and yield often occur in crops inoculated with PGPR strains isolated from the plants native rhizosphere 37. On the other hand, the prominent feature of strain RS87 was able to stimulate plant growth and yield of different crop systems including the rice cultivars studied in this paper 13, 21. Even though strain RS87 is isolated from the rhizosphere of Green Kuang Futsoi ( Brassica chinensis Jusl var parachinensis (Bailey) Tsen & Lee), other plant families such as pepper, cucumber, and rice respond to strain RS87 with greater growth promotion than the plant of which the strain was isolated (unpublished data).…”

“…Various mechanisms of plant growth promotion, including nitrogen fixation for plant use;22, 23 production of plant hormones, such as auxins14, 24 and cytokinin25, 26 affecting root growth and morphology or gibberellic acid involving the modification of plant morphology by extension of plant tissues, especially stem tissue;27 provision of bioavailable phosphorus for plant uptake;28, 29 production of siderophore to sequester iron for plant;30, 31 and production of 1‐amino‐cyclopropane‐1‐carboxylate deaminase enzyme to inhibit ethylene production during seed germination32 have been associated with PGPR actions. Our previous studies demonstrated that strain RS87 was able to perform at least three modes of action: namely, indole‐3‐acetic acid production, phosphate solubilisation, and siderophore production 13, 21. Some of these actions by strain RS87 could together contribute to plants resulting in compensation of at least 50% chemical fertiliser replacement for plant growth promotion.…”

“…Bacillus cereus strain RS87 (the strain used in this study) has previously been reported to promote growth in various Thai rice cultivars under greenhouse conditions 21. Growth enhancement by strain RS87 may be due to a combination of indole‐3‐acetic acid production, phosphate solubilisation, and siderophores released by the bacterium 13, 21. Therefore, the objective of this study was to investigate the efficacy of strain RS87 for the partial replacement of chemical fertiliser in rice production.…”