Characterization and fAFLP genotyping of Penicillium strains from postharvest samples and packinghouse environments

We examined 41 isolates of Penicillium spp. recovered from rotten fruits (including oranges, grapefruits, pears, lemons, strawberries, apples, loquats, prickly pears) and from air and surfaces of markets and packinghouses. Penicillium isolates were identified as P. expansum, P. italicum, P. digitatum, P. olsonii, P. chrysogenum or P. citrinum. Isolates were tested for sensitivity to commonly used postharvest fungicides, and pathogenicity on different potentially susceptible fruit hosts. Genetic characterization was performed with ITS4 and ITS5 primers that specifically identified Penicillium isolates by amplification of a 600-bp fragment, with PEF and PER primers used to identify P. expansum isolates by amplification of a 404-bp fragment, and with fluorescent amplified fragment length polymorphism analysis (fAFLP). Cluster analysis of fAFLP data divided the isolates into five well-separated P. italicum, P. digitatum, P. citrinum, P. chrysogenum and P. olsonii clusters, whereas P. expansum isolates were divided in three distinct clusters. Within all the eight clusters, isolates were well differentiated. Results obtained with fAFLP analysis confirmed the reliability of the method to characterize and identify strains at intraspecific level.