Field Efficacy of Priming Agents to Enhance Physiological Parameters of Sunflower Under Stress From Charcoal Rot (M. Phaseolina)

Abstract Charcoal rot (Macrophomina phaseolina (Tassi) Goid.) can cause significant yield losses in sunflower (Helianthus annuus L.) throughout the world. Fungicide treatments are often used to manage this pathogen, but due to costs and environmental impacts, alternative methods need to be explored. Priming is an adaptive strategy which enables plant defense systems to react more effectively to pathogen attack. The priming phase in plants can be achieved by stimuli from chemicals, beneficial microbes, arthropods, and abiotic stress which can induce defense systems in plants. The present study was conducted to evaluate the effect of different priming agents such as salicylic acid (SA), abscisic acid (AA), gibberellic acid (GA), and jasmonic acid (JA), as either seed or foliar treatments, on charcoal rot on the sunflower. The experiments were conducted under field conditions in two consecutive years (2017-2018). Ten seed of one susceptible (17577) and two moderately resistant (HA-259 and B-224) sunflower cultivars were treated with 2, 4 and 6 mM concentrations of the individual priming agents.. The plants were artificially inoculated with M. phaseolina before sowing by infesting soil, and sixty days after sowing. A number of yield parameters were quantified [head diameter (cm), 100-seed weight (g), achene per head (number), plant height (cm), stem girth (cm), shoot weight (g), root wet and dry weight (g) and chlorophyll content (mg/g)]. Among the priming agents evaluated, AA exhibited a significant impact on all yield parameters at a higher concentration (6 mM) in both susceptible and moderately resistant cultivars, followed by SA, GA, and JA. The results also revealed that seed treatment priming was more effective than foliar priming. There were statistical differences in yield parameters between both years of the study. The AA seed priming treatment showed the most promise for managing charcoal rot of sunflower. The outcome of this study will help to explore an environmentally sound and economically feasible approach for the management of charcoal rot to get sustainability in edible oil production.