Cuticular fractures promote postharvest fruit rot in sweet cherries

Preharvest cuticular fractures in sweet cherry fruit have been suggested to facilitate pathogen invasion, and a method to classify the mount of cuticu lar fracturing into five categories (from 1 = no visible fractures to 5 = s evere fracturing) has previously been proposed. Sweet cherry fruit of the f our cultivars Early Burlat, Lapins, Van, and Vista were sorted into these f ive categories of cuticular fracturing and inoculated with conidial suspens ions of either Botrytis cinerea or Monilinia laxa. After incubating the fru it at 20 degreesC and 100% relative humidity for 4 to 7 days, they were ass essed for visible fungal growth. Due to quiescent infections of M. laxa, fr uit treated with B. cinerea developed more brown rot than gray mold. Howeve r, a significant linear relation (P < 0.05) between the amount of cuticular fracturing and fungal infections was obtained in five of seven trials with B. cinerea and in two of four trials with M. laxa, indicating that fungal infections in sweet cherry fruit may be facilitated by cuticular fractures, independent of cultivar and year, a significant linear relation was found between the category of cuticular fracturing and percentage of infected fru it after inoculation with both B. cinerea and M. laxa, and in control fruit (P = 0.0001, 0.0183, and 0.0182, respectively). This is the first report q uantifying an increase in fungal infection with increasing amount of cuticu lar fracturing. The mean difference in fruit rot (%) +/-. standard deviatio n among fruit in fracturing categories 1 and 5, expressed as the linear con trast of amount of fruit rot in category 5 minus amount of fruit rot in cat egory 1, was 37.2 +/- 7.4 (P = 0.0001), 35.4 +/- 11.0(P = 0.0022), 17.0 +/- 6.7 (P = 0.0135), and 29.8 +/- 4.7 (P = 0.0001), after treatments with B. cinerea, M. laxa, water control, and for all data pooled. respectively.