Allantophomopsis lycopodina - a new aerial pathogen of Lingonberry (Vaccinium vitis-idaea)

Lingonberry (family Ericaceae) is grown for its tart berries which are used in making jams and preserves. In November 2000, field grown lingonberry plants of the cultivar 'Korralle' were found to have dark brown, spreading leaf lesions of various sizes with no marginal chlorosis, branch tip dieback and overall decline. 'Erike Krone' and 'Erike Sagen' plants had similar leaf lesions and necrotic pedicels, leading to shrivelling and blackening of the berries. Isolations from affected leaves and pedicels onto potato dextrose agar (PDA) consistently yielded a fungus identified on the basis of morphological characters as Allantophomopsis lycopodina (Carris, 1990).

Inoculations were undertaken to evaluate the role of A. lycopodina in the pathology of lingonberry. Young healthy 'Red Pearle' lingonberry plants in 9-cm pots were inoculated with mycelial fragments produced in PD broth after four weeks and fragmented in a blender with deionized water. Three test plants were first brought to wilting point prior to inoculation (stressed plants); three additional test plants were not water stressed. The six plants were sprayed with a total volume of 20 ml of suspended mycelial fragments. One wilted and one turgid plant were treated with deionized water as negative controls. All plants were covered with plastic for 72 hr post treatment and placed in a glass house. The remaining inoculum was diluted and plated; inoculum concentration was determined to be 1 x 10⁵ colony forming units per ml. Symptoms were apparent six days post inoculation. All three stressed plants showed numerous leaves with spreading purple-brown lesions, similar to those observed on symptomatic field plants. A few leaf lesions were present on the three non-stressed plants. None of the control plants showed any foliar symptoms. Five symptomatic leaves from each of the stressed and non-stressed plants, and five asymptomatic leaves from each of the two control plants were collected for isolation. Allantophomopsis lycopodina was recovered from each of the stressed plants, whereas it was recovered from only one of 15 leaves from the unstressed plants; the fungus was not recovered from the control plants.

^{This is the first report of leaf disease of lingonberry due to Allantophomopsis lycopodina. The fungus does not appear to be an aggressive pathogen, as unstressed plants developed fewer symptomatic leaves than stressed plants.}