First exploration of seed endophytic bacteria from Artocarpus lakoocha Roxb., revealing Mammaliicoccus sp. and Enterobacter sp. with plant growth-promoting and rice seed priming potential

Abstract

Seed endophytes are gaining attention for their beneficial roles in plant growth, nutrient assimilation, and stress tolerance. Intensive efforts are made to identify beneficial endophytic bacteria for sustainable crop improvement. Despite its ecological, medicinal, and biochemical importance, the seed endophytes of Artocarpus lakoocha Roxb. remain unexplored.

Fifteen bacterial isolates were recovered, and five (Als1, Als2, Als3, Als13, and Als15) were selected for further study based on their IAA production at a concentration of 9.19 μg/ml, 7.36 μg/ml, 17.73 μg/ml, 15.26 μg/ml, and 8.71 μg/ml, respectively. The 16S rRNA gene sequencing confirmed Als1 and Als2 as Mammaliicoccus sp. and Als3, Als13, and Als15 as Enterobacter sp.

All isolates were able to grow under nitrogen-limiting conditions on Jensen's medium and formed biofilms. Als2 showed the highest biofilm production potential (0.34 ± 0.02 at 590 nm). Als3, Als13, and Als15 demonstrated the ability to solubilize phosphate and potassium, and also produced siderophores. Maximum phosphate (with PSI of 2 ± 0.5) and potassium (with KSI of 1.15 ± 0.21) solubilizing capabilities were exhibited by Als3. Isolates Als1 and Als2 were only capable of producing ammonia with 1.97 ± 0.29 μg/ml and 1.85 ± 0.39 μg/ml, respectively.

Biopriming rice seeds with each isolate significantly enhanced seedling growth in both petri plate and pot experiments. Als3 exhibited maximum root length stimulation, while treatment with Als1 displayed the highest shoot length increment. Treatments also enhanced root hair length and density, thus improving nutrient uptake capacity.

All our findings suggest that bioprospecting bacteria from A. lakoocha seeds offers a sustainable alternative to improve crop productivity and soil health.