Journal of Plant Pathology Archive

Abstract:

During 2012, several postharvest fruit rots were observed on three lots of lychees (Litchi chinensis Sonn.) cv. Bengali-Mauritius coming from South Africa and commercialized in Italy, with an average incidence of 17%. Fruit blotch resulted in brown discoloration of the rind at the stem-end, rapidly expanding to the whole fruit. Tissues were excised from surface-sterilized fruit, cultured on PDA at 24°C in the dark. Colonies appeared coarse, at first whitish then brown, and produced dark pycnidia (Ø: 0.5 mm), which exuded two types of conidia. α-conidia (2.9-6.7 × 1.6-2.6 μm) were hyaline, unicellular, ellipsoidal to fusiform, biguttulate. β-conidia (9.0-16.0 × 0.9-1.2 μm) were hyaline, unicellular, filiform, curvular. Conidiophores were branched, septate and hyaline. Conidiogenous cells were phialidic, sub-cylindrical, hyaline and enteroblastic. Sclerotia were not produced. α-conidia were significantly shorter than P. litchi-chinensis or Diaporthe litchicola (Tan et al., 2013). The morphology corresponded to the description of Chi (2000) for Phomopsis longanae Chi & Jiang. Fungal DNA was amplified using universal primers ITS1/ITS4 and the amplicon (Accession No. JX417145; 512 bp) showed 98% sequence similarity to Phomopsis sp. and only 90% similarity with D. litchicola. Pathogenicity tests were performed on three isolates of P. longanae, whose conidial suspensions (105 conidia/ml) were placed on artificial wounds of ripe lychee cv. Bengali- Mauritius. Ten days after inoculation, fruit rot was observed and P. longanae was reisolated. Previously, P. longanae was reported on lychee in southern China (Lin and Chi, 1992). To our knowledge, this is the first report of P. longanae causing a postharvest fruit rot of lychee in Italy. The pathogen should be carefully monitored to avoid its establishment on the recently established production of lychee in southern Italy.