Stimulation of nitrogen fixation and trehalose biosynthesis by naringenin (Nar) and arbuscular mycorrhiza (AM) in chickpea under salinity stress

Abstract

Legumes are extremely susceptible to soil salinity because of high sensitivity of nitrogen‐fixing nodules, where root hair infection and nodulation are particularly salt sensitive. Arbuscular mycorrhiza (AM) inoculation is a promising approach to improve rhizobial symbiosis and hence growth. Flavonoids such as naringenin (Nar), play an imperative role in tripartite symbiosis of rhizobia and AM with legumes by signalling both symbioses. Modulation in flavonoids content is one of the important factors limiting nodulation and mycorrhization in salt stressed plants. Green house study investigated the potential of Nar (4 µM) and mycorrhiza (Funneliformis mosseae) in enhancing nodulation and nitrogen fixation in Cicer arietinum L. genotypes (PBG 5, DCP 92-3) under NaCl (0–100 mM). High sodium concentration in the nodules deleteriously affected nodulation, rate of nitrogen fixation, endogenous Nar and nutrient status, with higher negative effects in DCP 92-3 than PBG 5, which could be directly correlated with higher mycorrhizal dependency and lower colonization. Exogenous Nar partly restored nodulation and mycorrhization indicating its involvement as signal molecule in symbiosis. Mycorrhization and Nar enhanced salt induced trehalose 6-P-synthase and phosphatase and reduced trehalase activity, ensuing higher trehalose biosynthesis in nodules. Relative assessment of AM and Nar indicated a more prominent contribution of AM in reducing Na+ uptake and improving phosphorus, with nodulation and trehalose synthesis exhibiting higher dependency on Nar. Complete amelioration of negative effects of salinity were observed with +Nar+AM, thereby suggesting complementation of Nar and AM in improving symbiotic efficiency of chickpea under salt stress.