Evaluation of Oryza sativa growth and yield to endophytic beneficial bacterial inoculation in acid-sulfate soil

Abstract

Coastal agriculture in Malaysia faces significant challenges due to acid-sulfate soils, which are highly acidic and contain excessive amounts of harmful minerals such as aluminium and iron, negatively impacting rice (Oryza sativa) growth and yield. While the use of beneficial endophytic bacteria to promote plant growth is well-established, their effects on rice in acid-sulfate soils remain underexplored. This study aimed to isolate endophytic bacteria from rice roots cultivated in acid-sulfate soils, assess their plant growth-promoting traits, and evaluate their potential to enhance rice growth and productivity in these challenging environments. Endophytic bacteria were isolated from surface-sterilized roots collected from a rice plot in Nenasi, Pekan, Pahang. Molecular identification through 16S rRNA sequencing and phylogenetic analysis revealed six distinct bacterial genera, including Chromobacterium, Bordetella, Burkholderia, Bacillus, Klebsiella, and Moraxella. The isolates were evaluated for key plant growth-promoting traits such as nitrogen fixation, phosphate solubilization, and indole acetic acid (IAA) production. A nursery experiment was conducted, applying three different rates (100%, 75%, and 50%) of NPK fertilizer and inoculating with the two most promising isolates. Among the isolates, Burkholderia sp. and Falsibacillus sp. exhibited the strongest plant growth-promoting activities and were selected for further testing. The results showed that the combination of endophytic bacteria and fertilizers significantly enhanced rice growth and yield compared to the control. Specifically, Falsibacillus sp. (BAC 2) resulted in a 53.60% increase in grain yield, 11.69% higher grain filling, and 3.56% greater grain weight. This study demonstrates that beneficial endophytic bacteria can effectively enhance the growth and yield of rice in acid-sulfate soils, providing a sustainable and cost-effective approach to improving agricultural productivity.