Pathogenicity of Alternaria alternata on fruits and leaves of ‘Fortune’ mandarin (Citrus clementina × Citrus tangerina)

Abstract Nine isolates of Alternaria causing black rot of ‘Fortune’ mandarin were obtained from a commercial orchard in the Murcia region of south-east Spain. The isolates, according to their morphological and physiological characteristics, were identified as A. alternata. Analysis of DNA sequences of the internal transcribed spacers 1 (ITS1) and 2 (ITS2) of the ribosomal DNA corroborated the morphological identification. In this work, we evaluated the pathogenicity of each of the nine isolates on fruits and leaves as well as fruit susceptibility to the pathogen at different growth stages. Studies were performed on both wounded and unwounded fruits and leaves. Disease development was faster in wounded than in unwounded organs, one and two days after inoculation, respectively. Differences in pathogenicity were observed among the A. alternata isolates, depending on the plant organ. Immature fruits were more susceptible; fruit infection tolerance increased with maturity, for both wounded and unwounded fruits...