Microbial inoculants with inorganic fertilizers slacken the chlorosis impact on Kalmegh [Andrographis paniculata (Burm. F.) Wall ex., Nees] improve yields and quality traits

Abstract

A common problem witnessed in Kalmegh [Andrographis paniculata (Burm. F.) Wall ex., Nees] plants are yellowing of leaves, when cultivated during rainy season which drastically affects the yield and quality of andrographolide. In the present study, four strains of bioinoculants (Pseudomonas monteilii, Cedecea devisae, Cronobacter dublinensis, Advenella species) were scrutinized along with combinations of inorganic fertilizers to identify the best bioinoculant-fertilizer combination which can curb the effect of yellowing in Kalmegh plants most efficiently as well as enhance its biomass and secondary metabolite content. Minimum percentage of yellowing of leaves was recorded in the plantlets inoculated with bioinoculants (Cedecea devisae) and N:P:K applied at the ratio of 80:60:40 kg ha−1. Among all the treatments, Cedecea devisae (T5) gave maximum fresh and dry herb yields. The results showed a significant variation in photosynthetic pigments along with the treatments. Maximum andrographolide yield was recorded in the plantlets inoculated with Cedecea devisae which was 63.07% more compared to control. Moreover, the concentration of andrographolide in different parts of Kalmegh plants followed the trend-leaves>stem>inflorescence>flowers>seeds>seed husk>root. Except soil pH, other analysed soil parameters of the post harvest soil were significantly improved. Significant enhancement of the soil dehydrogenase, alkaline and acid phosphatase enzymes activity was 14.8% to 54.0%, 57.0% to 234%, and 51.6% to 276% greater, respectively over control. Principal component analysis revealed a strong positive interrelationship between vegetative attributes, soil enzyme activity, biomass yield and andrographolide content. We can suggest from our study that, bioinoculants especially free living nitrogen fixers (Cedecea davisae) along with recommended doses of NPK can effectively control the problem of yellowing (chlorosis) in Kalmegh plants during rainy season.