Groundnut (Arachis hypogaea L.) Growth and Yield Enhancement by Non-rhizobial Root Nodule Endophytic Bacteria

Abstract

Limited attention has been given to non-rhizobial root-nodule bacterial endophytes in relation to the growth and yield of Arachis hypogaea. This study evaluated two non-rhizobial endophytes, Pseudomonas aeruginosa strain OG1 and Alcaligenes faecalis strain OT1, isolated from root nodules of A. hypogaea and identified through cultural, morphological, biochemical and molecular characterisation. The isolates were applied as a combined soil inoculant to two groundnut varieties, SAMNUT 25 and SAMNUT 26, under greenhouse conditions. The treatments comprised uninoculated control, NPK fertiliser and Pseudomonas-Alcaligenes inoculation in 4000.0 g of soil per pot. After 120 days, growth and yield parameters and selected soil chemical properties were assessed. Across the uninoculated, NPK and Pseudomonas-Alcaligenes treatments, respectively, germination time was 5.2, 6.0 and 4.3 days; shoot length was 53.5, 58.4 and 61.9 cm; root length was 22.7, 19.1 and 34.9 cm; nodule number was 240.0, 37.8 and 506.2; and pod number was 11.3, 3.3 and 16.7. Compared with the uninoculated and NPK treatments, the Pseudomonas-Alcaligenes treatment improved several growth and yield-related traits. The treatment also enhanced soil organic matter and nitrogen content, while soil pH, available phosphorus and cation exchange capacity were not significantly altered. The findings indicate that combined inoculation with selected non-rhizobial root-nodule endophytic bacteria may support groundnut growth, nodulation, yield-related performance and selected soil fertility indicators under greenhouse conditions.