Increasing maturity reduces wound response and lignification processes against Penicillium expansum (pathogen) and Penicillium digitatum (non-host pathogen) infection in apples

Penicillium expansum is the main postharvest pathogen of pome fruit and is a necrotrophic fungus that requires wounds to infect the fruit. Therefore, injuries caused during harvest and postharvest handling provide an optimal locus for infection. In this study, the effect of wound response in apples harvested at three different maturity stages and stored at two different temperatures (20 and 0 degrees C) infected with P. expansum (pathogen) and Penicillium digitatum (non-host pathogen) was evaluated. The effect of wounding and pathogen inoculation on lignin content was also quantified. At 20 degrees C, less decay incidence and severity were observed when time between wounding-and inoculation increased, and these differences were more important in fruit from immature and commercial harvests. However, at 0 degrees C, wound response was too slow to prevent P. expansum infection. Lignin content was highest in fruit from the immature harvest. Our results indicated that maturity and storage temperature play an important role in apple wound response. This is the first report demonstrating that P. digitatum, a non-host pathogen, was able to develop rots in over-mature apples. (C) 2013 Elsevier B.V. All rights reserved.