Rhizobacteria Influence Potato Tuberization Through Enhancing Lipoxygenase Activity

Abstract

Many rhizobacteria are known to influence several plant growth parameters in many crop species. The influence of rhizobacteria on potato tuber production was reported in few earlier studies but none of the studies explored the molecular mechanism involved in such effects. In the present study, we isolated and identified 13 bacteria from potato rhizosphere and these isolates were tested for their influence on potato tuberization under in vitro and ex vitro conditions. Under in vitro conditions, mini-tubers formed as a result of sub-apical swelling of stolons in control while mostly sessile tubers formed in the axils of nodal segments in few of the bacterial treatments. Among all the isolated strains, bacterial isolate 6 induced highest average tuber yield followed by isolate 4 and 5 under both in vitro and ex vitro conditions. As lipoxygenase (LOX) expression is associated with plant-microbe interactions and suggested involvement of LOX in potato tuberization, we tested the hypothesis on LOX activity related role of these rhizobacteria on tuber induction and tuber yield in potato through studying the LOX1 gene expression and LOX activity. Significant increase in LOX1 mRNA expression and LOX enzyme activities were detected in stolons and tubers from the rhizobacterial treatments as compared to untreated control. Also a strong positive correlation between rhizobacteria-induced LOX1 gene expression and enhanced tuber induction and tuber yields were observed.