Elucidating the disease alleviating potential of cyanobacteria, copper nanoparticles and their interactions in Fusarium solani challenged tomato plants

The antimicrobial potential of cyanobacteria and metal nanoparticles has been explored for the control of phytopathogens, however, their interactions or synergy in a combined mode has not been studied. In the present investigation, the biocontrol potential of copper nanoparticles (CuNPs), cyanobacterium Calothrix elenkinii and copper nanoparticles augmented Calothrix elenkinii (CuNPs-Ce) were evaluated. Measures of disease severity indices, microbiological and physiological parameters in Fusarium solani infected tomato plants were evaluated, under greenhouse conditions. Application of C. elenkinii (Ce) and CuNPs alone showed 61–66% disease control efficacy, however, CuNPs-Ce showed higher efficacy of 76%. Similarly, augmentation enhanced the chitosanase activity by 10% and 7%, compared to CuNPs and C. elenkinii alone, respectively in pathogen challenged plants. Among the diseased plants, 1.3–1.6 fold increases in root length, root and shoot fresh weight were recorded in CuNPs-Ce treated plants, compared to control. The rhizosphere soil of diseased plants showed higher dehydrogenase activity, as compared to healthy plants. With the application of C. elenkinii, either alone, or augmented with CuNPs, the total PLFA content in soil increased significantly by 1.4–3.3 folds, compared to the control. However, it reduced in soils treated with chemical control Bavistin, reflecting its negative effects on soil microbial communities. The application of CuNPs or C. elenkinii alone or CuNPs-Ce not only reduced the disease severity, but also improved plant vigour. In future, efforts should focus towards exploiting the synergistic behavior of CuNPs-Ce as multifaceted biocontrol agents to control Fusarium root rot in tomato crop and minimize the dose for deployment effectively.