Characterization of Alternaria alternata isolates from different citrus species grown in Tunisian Cap Bon peninsula

Abstract The prospection of citrus trees affected by Alternaria alternata in Tunisian Cap Bon peninsula for 2 years, 2018 and 2019, showed a variation in the percentage of isolation frequency depending on the region, age of citrus trees and citrus species and varieties. Thirty isolates of A. alternata from citrus species were characterized and studied for their variability. The isolates were subjected to morphological identification using macroscopic and microscopic features and molecular characterization through PCR amplification of their internal transcribed spacer regions. A high morphological and molecular diversity within A. alternata isolates was detected. The molecular sequencing results precisely confirmed that these fungal isolates belong to A. alternata strains. Pathogenicity test showed that A. alternata T1 and T9 isolates were capable of causing disease symptoms only on young leaves of clementine plant (MA3 variety). These findings are useful in the development of sustainable strategies to manage Alternaria in citrus‐growing areas in Tunisia.