First report of Neopestalotiopsis rosae causing leaf spot on strawberry ( Fragaria x ananassa ) in Benguet, Philippines

Across the 16 strawberry farms (16,000 sqm average) in the six municipalities of Benguet, up to 70% disease incidence were observed since 2022. Symptoms include enlarged brown necrotic spots and black spots (acervuli) formed at the center. Samples were obtained and then used to confirm disease through Koch’s postulate. Symptomatic leaves were surface sterilized and inoculated in quarter-strength potato dextrose agar (qPDA) and incubated for 3-5 days (Baggio et al. 2021). Three representative isolates that exhibited a fuzzy white colony with undulated growth and yellow underside along acervuli production, were purified (PES 1, PES 6, and PES 9). Plate culture morphology is Conidia are 5-celled fusoid with 4 septations as concolorous or versicolorous. The basal and apical cells can have 1-4 filaments, with average length of 22.01 µm. These characteristics are identical with Neopestalotiopsis sp. (Baggio et al. 2021). To determine pathogenicity, detached strawberry leaves of ‘Sweet Charlie’ variety were surface sterilized and inoculated each with spore suspensions (1x104 spores/ml) of the isolates, placed in a clear plastic tub and then stored in the dark at room temperature. Symptoms manifest at 3-4 days after inoculation similar to those observed in the field. A representative culture was deposited to Philippine National Collection of Microorganisms (BIOTECH 3458). Molecular confirmation was conducted by obtaining the genomic DNA using Qiagen™ DNEasy Plant Mini Kit following the manufacturer’s protocol. The ITS (White et al. 1990) and beta-tubulin (Glass and Donaldson 1995) were amplified. Sequences were deposited in GenBank with the following accession numbers: ITS - PV441286-PV4412888; BTUB - PV483391-PV483393. Phylogenetic analysis revealed all the local isolates clustered with the reference N. rosae. This is the first report of N. rosae causing leaf spot in strawberry in the Philippines. Detection of this pathogen in Benguet provides a valuable resource in preventing further disease spread and effective disease management.