Incidence of wounding in commercially-harvested 'd'Anjou' and 'Bosc' pear fruit, healing of wounds to decrease decay caused by Botrytis cinerea, Mucor piriformis, Penicillium expansum, and Penicillium solitum at -1 degrees C, 20 degrees C, and 28 degrees C, and formation of compounds potentially involved in resistance were determined. Use of a blue food coloring to make wounds on fruit more visible on packinghouse lines was evaluated. Over 4 years, an average of 2.9% of 'd'Anjou' pear fruit were wounded during harvest and handling. In 'Bosc: pears, average incidence of wounding was 4.3% where fruit was harvested by workers paid by the hour, and 13.9% where workers were paid by the number of bins harvested. Susceptibility of wounds to infection by hi. piriformis, P. expansum, and B. cinerea at -1 degrees C decreased rapidly during the first 2 weeks, 4 weeks, and 8 weeks, respectively. The percent of wounds that stained well with food coloring was similar to the decay susceptibility curve for P. expansum at -1 degrees C. Susceptibility of wounds to decay in fruit held at 20 degrees C decreased almost linearly from 0 to 2 days. After 2 days at 20 degrees C, 78% of the wounds absorbed stain, a significantly higher percent than were susceptible to decay. Prestorage heat treatment of fruit to 28 degrees C for 24 h prior to inoculation decreased susceptibility of wounds to infection by both P. expansum and P. solitum. In commercial packinghouses, use of a 10% solution of blue food coloring to enhance visibility of wounds in pear fruit resulted in removal of 40% of punctured fruit compared with 22% removal without staining. Histochemical tests of cell walls near wounds showed an accumulation of callose, suberin, tannins and pectic substances, as well as gums and starch, within 4 days after wounding. Lignin was not detected in wound tissue. (C) 1998 Elsevier Science B.V. All rights reserved.
