Genetic Diversity of Endospore-forming Nitrogen-fixing Bacteria and Their Future Application as Biofertilizers in the Central Dry Zone of Myanmar

Abstract

In Myanmar, the application of both nitrogen-based chemical fertilizers and biofertilizers is limited and this low input has caused poor agricultural yields. The present study aimed to isolate indigenous endospore-forming nitrogen-fixing bacteria (EFNFB) and examine their potential for co-inoculation with agricultural waste. A total of 387 isolates were obtained from 42 different soil samples in the central dry zone of Myanmar using nitrogen-free Rennie medium. Nitrogen-fixing activity (NFA) assessed with the acetylene reduction assay was positive in 102 isolates. A phylogenetic ana­lysis based on 16S rRNA sequences identified 25 different species, including the genera Paenibacillus, Priestia, Bacillus, Brevibacillus, Sporolactobacillus, Niallia, and Neobacillus. Among these genera, Paenibacillus spp. was the predominant genus, comprising 51 isolates (64%) across 16 different species (64%) that were prevalent in soils rotated with rice and pulses. Paenibacillus spp. showed different NFA levels in Rennie medium. Eleven species belonging to different genera had not been previously documented as nitrogen-fixing bacteria. NFA levels were evaluated in soil inoculated with EFNFB and rice straw or mung bean residue. The results obtained demonstrated that NFA levels were dependent on isolates and the type of agricultural waste. NFA in soil was significantly increased by inoculations with some isolates, suggesting their potential as biofertilizers. The inoculation of Priestia aryabhattai S10 with rice straw or mung bean resulted in significantly higher NFA levels in soil. These results indicate the potential of EFNFB as biofertilizer inoculants in Myanmar.