FIRST REPORT OF TALAROMYCES ALBOBIVERTICILLIUS CAUSING POSTHARVEST FRUIT ROT ON POMEGRANATE IN ITALY

Abstract

In 2016, circular brownish lesions and stamens both covered by greenish sporification, were observed on two month-stored Punica granatum L. fruits (cvs Wonderful One and Acco). Soft rotting originating from wounds on the rind, without nesting or connection with stamen colonization, was recorded on 18% of infected fruit. Surface-sterilized rotted portions were plated on potato dextrose agar (PDA), containing streptomycin and ampicillin (250 mg/l each), incubated at 24oC in the dark and sub-cultured on Malt Extract Agar (MEA). Colonies were velvety, 26.5±1.5 mm in size after 7 day-incubation. The 3-8 acerose phialides (10.5±2.5×2.5±0.5 µm) were slender aculeate or lanceolate, highlighting the symmetrical, biverticillate conidiophores; interlaced hyphae constituted the layers of the typical soft ascomatal wall; mature asci were chain-like. Pinkish-white conidia, from globose to sub-globose, measured 3±1×2±0.5 µm. The divergent metulae (10.5±2.5×3±1.5 µm, each) varied between 3 and 8. Stipes were 300±100×3.25±0.75 µm with smooth surface. These traits, together with the production of intense red soluble pigments, identified the fungus as Talaromyces albobiverticillius Samson et al. (Yilmaz et al., 2014). For confirmation, fungal DNA was amplified using primers Bt2a/Bt2b (Glass and Donaldson, 1995). The amplicon (GenBank accession No. KY563698) showed 99% identity with other T. albobiverticillius sequences. For pathogenicity tests, surface-sterilized fruit of cvs Wonderful One and Acco were wounded, inoculated with a mycelial plug and incubated as above. Sterile plugs were used as controls. Typical symptoms developed only on infected fruits. The re-isolated fungus corresponded to T. albobiverticillius, fulfilling Koch’s postulates. To our knowledge, this is the first report of T. albobiverticillius causing postharvest rot of pomegranate. This fungus is a Penicillium sensu latu (Samson et al., 2011) which may be mistaken for a Penicillium sensu strictu.