First report of Fusarium brachygibbosum in sunflower in Iraq and the protective role of methyl jasmonate in enhancing antioxidant defense mechanisms

Abstract

Plant pathogenic fungi are constantly evolving and spreading into new host plants, raising the importance of efficient pathogen control methods. The aim of this study was to investigate the role of methyl jasmonic acid (MeJA) in enhancing defense mechanisms of sunflower plants (Helianthus annuus L.) affected by wilting disease. Three fungal pathogens were isolated from infected plants and identified using morphological and molecular characterization. Sunflower genotypes Sakha, Ishaqi, and Aqmar were then inoculated with the pathogens separately and treated exogenously with MeJA at 1, 2, and 3 mM. Parameters of seed germination, plant biomass, fungal pathogenicity, and antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) gene expression and activities were evaluated. Results showed that wilting disease was caused by Macrophomina phaseolina and Rhizoctonia solani, along with first-time reported Fusarium brachygibbosum on sunflowers in the Iraqi region. Pathogenicity assays indicated that F. brachygibbosum exhibited the highest pathogenicity, decreasing significantly all assessed parameters, while R. solani was the least pathogenic. The Sakha genotype was the most resistant to fungal infection, showing the highest growth, reproduction, and defense. Additionally, treatment with MeJA significantly improved seed germination, biomass, and CAT and SOD activity, with 1 mM MeJA significantly upregulating these antioxidant enzymes in the Sakha genotype. These findings underscore the intricate interactions between sunflower genotypes, fungal pathogens, and MeJA treatment, suggesting that strategic MeJA application and the selection of resistant genotypes could enhance crop resilience and improve disease management strategies in agriculture.