DisplayTitle

Characterization of Basidiomycetes Associated with Wood Rot of Citrus in Southern Italy

First, second, fifth, and eighth authors: Dipartimento di Agraria, Università degli Studi Mediterranea, Località Feo di Vito, 89122 Reggio Calabria, Italy; third and seventh authors: Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi “Aldo Moro”, Via Amendola 165/A, 70126 Bari, Italy; and fourth and sixth authors: Dipartimento di Gestione dei Sistemi Agroalimentari e Ambientali, Università degli Studi, Via Santa Sofia, 100, 95123 Catania, Italy.

The characterization of Basidiomycetes associated with wood rots in commercial citrus orchards in southern Italy revealed that both white and brown rot fungi are implicated in this disease. Fomitiporia mediterranea was the most prevalent species causing a white rot, followed by Fomitopsis sp. which, by contrast, was associated with brown rot wood decay. Furthermore, Phellinus spp. and other nonidentified basidiomycetous fungi showing genetic affinity with the genera Phellinus and Coniophora were occasionally isolated. Artificial inoculations on lemon (Citrus limon) branches showed a faster wood colonization by Fomitopsis sp. compared with F. mediterranea, indicating that the former species as a potentially serious pathogen of citrus trees. The analysis of F. mediterranea internal transcribed spacer (ITS) sequences revealed a high level of genetic variability, with 13 genotypes which were both homozygous (6 genotypes) and heterozygous (7 genotypes). The presence of heterozygous genomes based on ITS sequences has never been reported before for F. mediterranea. This, together with the high frequency of basidiomata on infected wood, unambiguously confirms the outcrossing nature of reproduction in F. mediterranea and the primary role of basidiospores in the dissemination of inoculum. Similarly, high genetic variability was observed analyzing Fomitopsis sp. Because basidiomata of this fungus have not been observed on citrus trees, it can be hypothesized that basidiospores are produced on alternative host plants.