Effect of disease complex of Meloidogyne incognita and Fusarium solani on fungus root rot incidence, nematode reproduction, and enzyme activities involved in defense mechanisms of grafted cucurbit hybrids

Abstract

This study investigated the interplay between the root-knot nematode, Meloidogyne incognita (Mi), and the fungal pathogen, Fusarium solani (Fs) in grafted cucurbit hybrids (watermelon and sweet melon). Results revealed that Fs root rot incidence was exacerbated when combined with Mi. Nonetheless, the existence of Fs caused a noteworthy decline in Mi reproduction, affecting hosts that were both resistant and susceptible. Additionally, plant growth suffered more from combined infection than from single pathogens, with the susceptible sweet melon showing greater growth reduction. The study further explored the impact of the disease complex on antioxidant defence mechanisms. Leaf tissues from both grafted hybrids displayed elevated levels of lipid peroxidation (MDA) and antioxidant enzyme activities (SOD and APX) upon infection with Fs alone, Mi alone, or both. Interestingly, the susceptible sweet melon exhibited a stronger increase in these defence responses compared to the resistant watermelon. Notably, combined Fs and Mi infection led to the highest levels of MDA, SOD, and APX activity. These findings highlight the complex interplay between Fs and Mi in cucurbit hybrids. While Fs virulence increased with coinfection, Mi reproduction was suppressed. Furthermore, the study suggests that susceptible plants may have a more pronounced activation of antioxidant defence mechanisms when confronted with the combined stress of these pathogens.

Keywords

• cucurbit hybrids
• disease complex
• enzyme activities
• Fusarium solani
• Meloidogyne incognita
• nematode development