First Report of Fomitiporia punctata Infecting Kiwifruit

During 2000 and 2001, a wood discoloration and decay of 10- to 12-year-old kiwifruit vines (Actinidia deliciosa (Chev.) Liang & Ferguson) was observed in vineyards in all major kiwifruit-growing areas of Greece. Leaves became chlorotic or necrotic, dry, and abscised prematurely. Fruits dropped before reaching full maturity. Necrosis of shoots and twigs progressed from the shoot tips toward the trunk. If the infected twigs were pruned early, the vine occasionally produced new shoots. Cross sections of infected trunks and shoots revealed a light-colored soft rot in the center, surrounded by brown, hard, necrotic wood resembling the esca disease of grapevine, caused by Fomitiporia punctata. From the white rotted areas, a fungus was isolated that formed a dense aerial mycelium with cream-yellow to light-brown colonies on potato dextrose agar (PDA). The fungus was identified as F. punctata (Fr.) Murrill by M. Fischer, Weinbauinstitut, Freiburg-Germany, (personal communication). Pathogenicity tests were performed by artificially inoculating 2-year-old healthy kiwifruit (cv. Hayward) plants. The inoculum consisted of a 7-mm diameter mycelial plug taken from the margin of a 10-day-old culture of F. punctata growing on PDA. A portion of the bark was partially raised from the trunk, and the inoculum was inserted under the bark. The bark was tied with adhesive tape to keep the inoculum in place and sealed with Vaseline to prevent dehydration. Ten plants were inoculated while 10 were used as nonincoculated controls. Wilting of lower leaves was first observed 15 days after inoculation. In longitudinal sections, a brown discoloration on the stem wood was observed 46 days after inoculation in all inoculated vines, while control plants remained healthy. However, the same fungus was isolated from only one infected plant. Low frequency in reisolating F. punctata is often mentioned in the literature (3). Although esca on kiwifruit has been reported in Italy, the fungus initially was identified as Phellinus conchatus and subsequently as F. punctata (1,2). To our knowledge, this is the first published report of F. punctata causing wood decay of kiwifruit. References: (1) F. Calzarano et al. Inf. Fitopatol. 49:12, 1999. (2) S. Di Marco et al. N. Z. J. Crop Hortic. Sci. 28:69, 2000. (3) L. Sparapano et al. Phytopathol. Mediterr. 39:46, 2000.