Effect of incorporation of leaf biomass of Coronopus didymus on management of basal rot disease of onion and its physiology

Abstract

Fusarium oxysporum f. sp. cepae is a soil-borne fungal pathogen that causes basal rot disease of onion (Allium cepa L.) resulting in significant yield losses of the crop. The present study was conducted to assess the disease management potential of Coronopus didymus (L.) Sm., and its effect on onion plant physiology. In laboratory bioassays, different concentrations ranging from 1% to 7% of methanolic extracts of leaves, stems and roots of C. didymus reduced fungal biomass by 60-84%, 51-85% and 73-87%, respectively. In a pot trial, dry leaf biomass of C. didymus was mixed in the soil at 1%, 2% and 3% in combination with F. oxysporum f. sp. cepae and their effect on disease development, plant growth and various physiological parameters was studied in comparison with a negative control (without any addition of pathogen or plant material) and a positive control inoculated only with the fungus. The highest disease incidence (47%) was recorded in positive control. Application of 2% and 3% dry leaf biomass of C. didymus as soil amendment significantly reduced disease incidence to 13% and 3%, respectively. Similarly, plant mortality was reduced to 0% due to 2% as well 3% dry leaf biomass treatments. The highest chlorophyll, sugar and protein content were recorded in treatment where F. oxysporum f. sp. cepae was inoculated with 1% dry leaf biomass incorporation. On the other hand, the highest phenolic content and peroxidase activity were recorded due to combined application of the pathogen and 3% dry biomass incorporation. Present study concludes that soil amendment with 2% leaf dry biomass of C. didymus can effectively manage the basal rot of onion without any adverse effect on plant growth.