Characterization of the Pathogen Causing Early Blight Disease on Potato

Early blight of potato caused by Solanum tuberosum L., is one of the most significant foliar diseases in Algeria, ranking second only to late blight in terms of economic impact. This study aimed to characterize Alternaria isolates associated with early blight based on their cultural, morphological, physiological, and pathological features. The analysis revealed considerable variation among isolates, allowing the identification of two distinct species: Alternaria solani (six isolates) and Alternaria alternata (seven isolates). Pathogenicity tests indicated that neither of the two tested potato cultivars, Arizona and Rudolph, exhibited resistance to early blight. In contrast, biocontrol assays yielded promising results, demonstrating substantial inhibition of mycelial growth, ranging from 40% to 84%, and a marked reduction in disease severity on both cultivars. These findings highlight the potential of biological control strategies as an alternative to chemical fungicides. However, further validation under field conditions is necessary to confirm their effectiveness in natural environmental and agronomic settings.