CHARACTERIZATION AND ASSESMENT OF PLANT GROWTH PROMOTING RHIZOBACTERIA ON SOYBEAN UNDER SALINE ENVIRONMENT

ABSTRACT

The agricultural sector is continuously facing myriad of problems such as yield loss due to abiotic stress as well as phytopathogen infestation. Soil salinity is a major problem in agriculture that limits plant growth and causes significant loss of crop productivity worldwide. The aim of this study was to characterize and assess plant growth promoting rhizobacteria on soybean under saline environment. Standard bacteriological methods were used to enumerate the total bacterial count of the soybeans rhizosphere soil using pour plate methods after serial dilution. The bacterial isolates were characterized and identified using morphological and biochemical methods and sugar fermentation test. The percentage distribution and frequency of the isolates were evaluated using statistical method. The results showed that the enumeration of microbial population in soil was at 53.3 x 102 cfu/g. The bacterial isolates used were characterized and identified using morphological, biochemical methods and sugar fermentation test. Following the cultural, morphological and biochemical characteristics of bacteria, the isolates obtained were Citrobacter fruendii and Yersinia pestis. The two rhizobacteria were isolated, and their capacity to generate indole acetic acid and hydrogen cyanide was tested. It was found that the isolates had different capacities for producing indole acetic acid (IAA). Compared to isolate Citrobacter, Yersinia pestis was negative to HCN test but both were positive to IAA. there was no growth observed after soybean seedlings were planted using the plant growth promoting rhizobacteria isolated in saline conditions, therefore measurement of plant characteristics could not be done. Soil salinity imposes ion toxicity, osmotic stress, nutrient (N, Ca, K, P, Fe, Zn) deficiency and oxidative stress on plants, and thus limits water uptake from soil.