Fomitiporia mediterranea Infecting Citrus Trees in Greece

Abstract

In recent years a serious disease of citrus (the orange cv. Washington navel, lemon and the common mandarin grafted on sour orange rootstocks) has been observed in southern Greek orchards. Affected trees decline, their leaves become yellow and fall early, and shoots and twigs die as the damage expands towards the trunk. Crosssections of the trunks and large branches reveal a light-colored rot in the center, which is surrounded by brown hard necrotic wood. Symptoms start from pruned areas and spread to the rootstock wood, and then resemble esca of grapevine. From the white rotted areas, a fungus was isolated on PDA that formed cream-yellow to light-brown colonies with dense aerial mycelium. Fungal fruit-bodies formed abundantly on the trunks of diseased trees. The fungus was identified as Fomitiporia mediterranea by both traditional and molecular methods. Pathogenicity tests were performed by artificially inoculating orange, mandarin, lemon and sour orange trees with the fungus. Control holes were filled with two PDA plugs. Branches inoculated with the isolates from infected citrus showed wood discoloration that extended up to 20 cm above and 20 cm below the infection hole. The fungus was re-isolated from the discolored parts of the wood. Inoculations with isolates from grapevine and kiwi produced wood discoloration only 3– 4 mm around the holes.