Bacillus sp. extract used to fabricate ZnO nanoparticles for their antagonist effect against phytopathogens

In order to achieve the food demand of a growing population, agricultural productivity needs to be increased by employing safe strategies. In the present study we have evaluated ZnONPs that were synthesized from the culture supernatant of Bacillus subtilis. Bio mimetically synthesized ZnONPs showed a surface resonance peak of 355 nm corresponding to NPs formation. Further, NPs were examined for their size, shape and element confirmation by DLS, AFM, SEM, TEM and EDAX, which confirmed the synthesized NPs were nearly spherical in size with average diameter of 32 nm by TEM. Surface charge of + 34.3 mV was observed for NPs with a low poly-dispersity index of 0.21. In vitro efficacy studies against fungi Colletotrichum capsici, Sclerotium rolfsii, Alternaria solani and Fusarium oxysporum f. sp. cicero showed up to 99% mycelial growth inhibition at 0.125% ZnONPs. Further, in-vitro disk-diffusion assay showed inhibition zones of 23 ± 0.4 mm and 12.67 ± 0.24 mm for Xanthomonas axonopodis pv. punicae (Xap) and Xanthomonas oryzae pv. oryzae (Xoo) bacterial cultures. Plant toxicity study was observed that ≤ 0.14% NPs concentration was safe under greenhouse conditions. Overall, the present study emphasizes the potential effect of ZnONPs against agricultural pathogens which play an important role in agriculture production.

Synthesis and application of chitosan-copper nanoparticles on damping off causing plant pathogenic fungi

Damping-off disease in seeds and young seedlings in agricultural crops is a major fungal disease that limits the agriculture production. Frequent use of synthetic fungicides against damping-off diseases is known to hamper the environmental balance. Thus, an alternative approach needs to be explored for the management of such economically important fungal diseases. In the present study, simple, economically feasible chitosan-coupled copper nanoparticles (Ch-CuNPs) were synthesized and demonstrated antifungal activity against damping-off disease causing phytopathogens, Rhizoctonia solani and Pythium aphanidermatum. Physico-chemical studies confirmed the size, shape, surface charge, element confirmation and mono-dispersed nature of Ch-CuNPs. In vitro efficacy studies revealed up to 98% mycelial growth inhibition at 0.1% Ch-CuNPs. An extracellular conductivity study of the mycelium showed cellular content leakage within 12 h of treatment. Further, plant toxicity study against chili, cowpea and tomato plants; showed that ≤0.2% NPs were safe under greenhouse conditions. NPs also exhibited growth-promoting activity with chili seeds, by overcoming the limited germination rate of susceptible seeds. Overall, the present study emphasizes the benefits of synthesized Ch-CuNPs on agricultural crops as fungicide and growth-promoter, as well as a safe alternative to pesticides in order to avoid hazardous effect on the environment.