Carbon status during leaf development in kiwifruit and subsequent resistance of wounded tissue to Botrytis cinerea

Abstract The development of floral shoots of kiwifruit ( Actinidia deliciosa (A. Chev.) C.S. Liang and A.R. Ferguson) was perturbed over 8 weeks prior to fruit set by altering the carbon status of the shoots. A “low carbon” treatment was created by shading individual shoots and reducing photosynthate export from adjacent shoots. A “high carbon” treatment was created by blocking phloem export from another set of floral shoots. Controls were untreated shoots. At the culmination of the 8 week period, the low carbon treatment had significantly depressed specific dry matter, starch and phenolic content of the leaves, whereas the high carbon treatment elevated levels of all these components. An in situ bioassay was then carried out in which leaves from these shoots were wounded, allowed to heal for variable lengths of time—72, 24, or 0 h—and then inoculated with a culture of Botrytis cinerea Pers.:Fr. The incidence and area of Botrytis lesions was recorded over the subsequent 5 days. Lesion incidence in the controls reached a maximum of 55% under conditions of no wound healing prior to inoculation and 5 days incubation, dropping to 0% with 24 h or more healing time. Under the same conditions leaves of the low carbon shoots had 100 and 20% lesion incidence respectively. Lesion growth on wounded leaves of the high carbon shoots was not significantly different from the controls.