Organic formulation modulating crop health, yield and managing anthracnose-twister and Stemphylium blight of onion.

In India, onion productivity during the Kharif season (June-October) is considerably lower than in the Rabi season (December-April), largely due to the high incidence of anthracnose-twister and Stemphylium blight. To promote sustainable disease management, four organic formulations (DOGROF-1 to DOGROF-4) were developed using locally available natural bio-resources and evaluated under field conditions for three years (2021-2023) at ICAR-Directorate of Onion and Garlic Research, Pune, using the popular onion varieties Bhima Super (Kharif) and Bhima Shakti (Rabi). Foliar application of DOGROF-3 significantly improved plant height, pseudostem girth, and leaf number, resulting in yield increases of 34.23% in Kharif and 29.17% in Rabi. It also reduced anthracnose-twister and Stemphylium blight severity by 49.62% and 48.09%, respectively. DOGROF-3 also exhibited a higher incremental cost-benefit ratio (ICBR) with values of 1:33.65 (Kharif) and 1:34.04 (Rabi), highlighting its economic feasibility. Microbial profiling revealed DOGROF-3 harbored the highest populations of beneficial bacteria (3×108 cfu/mL), fungi (4 × 105 cfu/mL) and actinomycetes (8 × 105 cfu/mL). LC-MS analysis led to the putative identification of 30 bioactive compounds, including hexylglutathione conjugates, indoleacrylic acid, gibberellins, caffeyl alcohol, isorhamnetin-3-O-rhamnoside, and candicidin D. Literature reports indicate that several of these metabolites are associated with plant growth promotion and antifungal activity, suggesting their possible role in disease suppression and improved plant performance. The nutrient profiling of bioformulations indicated that, although DOGROF-3 contained comparatively lower macronutrients (N- 0.09%, P- 0.97%, K-3.42%), it was markedly enriched in essential micronutrients, particularly zinc (20.25 ppm), manganese (8.62 ppm) and copper (7.18 ppm), which are known to be associated with enhanced enzyme activity, photosynthetic performance, and nutrient-use efficiency. These findings suggest DOGROF-3 offers an eco-friendly, and economically viable alternative to chemical fungicides, supporting sustainable crop health and disease management in onion production.