Spray-Induced Gene Silencing (SIGS) of Dual-Target Genes (AaGH10 and AaSOD) Enhances Control of Alternaria alternata White Leaf Spot in Chinese Chive.

Chinese chive (Allium tuberosum) suffers severe yield and quality losses from white leaf spot disease caused by Alternaria alternata. Spray-induced gene silencing (SIGS) presents a sustainable alternative to traditional chemical fungicides. To maximize the biocontrol efficacy of this approach, we designed dsRNAs targeting two candidate virulence-associated genes of Alternaria alternata: AaGH10, encoding a cell wall-degrading enzyme critical for host penetration, and AaSOD, an antioxidant enzyme crucial for reactive oxygen species (ROS) scavenging. We comprehensively evaluated the antifungal efficacy by assessing mycelial growth inhibition, spore germination, and lesion development through in vitro and in vivo assays. The results demonstrated that both single and combinatorial treatments effectively inhibited fungal growth and spore germination, thereby reducing disease incidence on detached leaves and intact greenhouse plants. The application of the dual-target dsRNA formulation achieved an 86.7% control efficacy on detached leaves. Furthermore, it significantly alleviated in vivo disease severity, decreasing the average number of necrotic lesions from 15.6 to 1.3 per leaf. These results demonstrate that the dual-target combination exerts an enhanced protective effect compared with individual interventions. This specific dual-target dsRNA formulation establishes a robust foundation for the control of Chinese chive white leaf spot disease.