Acceleration of histopathological and biochemical defense patterns in mung bean with biopriming of Amycolatopsis sp. SND-1 against Cercospora leaf spot disease

Abstract

ObjectivesFailure of chemical control methods in conferring protection against Cercospora leaf spot (CLS) disease in mung bean crop led to the investigation of biocontrol agents for effective management of the CLS. The current study was focused on increased defense response (histochemical and biochemical) in mung bean plants by alginate pellet formulation of endophytic Amycolatopsis sp. SND-1 (SND-1) against CLS disease. MethodsThe sodium alginate bioformulation of SND-1 was prepared by standard method using CaCl2 and evaluated for viability and contamination. Greenhouse study of prepared SND-1 formulation was performed on mung bean plants against CLS infection. Further, the acceleration of histochemical depositions (lignin, H2O2 and phenol) by differential staining methods and biochemical defense enzymes like PAL, GLU, and POX, phenolic, flavonoid and chlorophyll contents and cell death analysis were evaluated through microscopic and spectroscopic studies. ResultsThe viability assay of the prepared formulation exhibited a negligible reduction in SND-1 spores (99.5% to 86.55%) throughout the six months of storage period. In-vivo (Greenhouse) study exhibited increased growth parameters in alginate pellet formulation of SND-1challenged with Cercospora pathogen (SND-1+Pathogen) treated mung bean plants in comparison with Control (SDW) and only pathogen infested plants. Consequently, the plants with SND-1+Pathogen treatment showed significant reduction in disease severity up to 56%. Furthermore, the microscopic evaluation of histochemical defense markers depicted increased deposition of lignin (82.43±0.31%), H2O2 (47.97±0.66%), and phenol (76.74±0.79%) and cell death analysis through microscopic observation exhibited lesser dead cells of 31% in SND-1+Pathogen treatment in comparison with other treatments. Defense patterns at biochemical level hinted the elevation in activities of defense enzymes like PAL, GLU and POX at 12 and 24 h post pathogen inoculation (hpi) in SND-1+Pathogen treatment. The formulation treatment with pathogen (SND-1+Pathogen) also substantiated that enhanced total phenolic, flavonoid, and chlorophyll contents at different time intervals. ConclusionsOverall the present investigation showed that Amycolatopsis sp. SND-1 formulation confers the protection in mung bean upon Cercospora infection and it might be an effective eco-friendly approach towards sustainable agriculture.