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Balidion, Johnny Frias [1], Cubeta, Marc A. [1].

Influence of culture media and environmental factors on the growth and sporulation of Lasiodiplodia theobromae associated wih dieback symptoms of cacao (Theobroma cacao) in the Philippines.

Lasiodiplodia theobromae has become an emerging threat to the cacao industry and its ability to persist endophytically or become pathogenic when the host is under stress makes it challenging to manage. Phylogenetic analysis of 80 L. theobromae isolates from cacao twigs exhibiting dieback symptoms sampled from 12 cacao-growing provinces in the Philippines with ITS and tef1-α loci revealed high intra-specific variation among isolates. To examine phenotypic variation, we selected 12 isolates based on their phylogenetic relationships to compare morphological characters and mycelial growth at different growth media, temperature, and water activity levels. Optimum temperature for mycelial growth was 30 °C with minimum growth at 15 °C and reduced growth at 35 °C. Spore gemination was greater than 85% at 40 °C and less than 10% at 15 °C across all the isolates. Water activity at -3 MPa reduced mycelial growth and spore germination across all isolates with the lowest values observed at -5 MPa. Optimum mycelial growth was observed in potato dextrose agar but highest pycnidia production was observed in oatmeal agar. Reduced oxygen levels and light conditions does not affect mycelial growth, but light enhances sporulation. Conidia were subovoid with broadly rounded apex initially hyaline and aseptate, eventually becoming dark brown and one-septate at 12 days after pycnidia formation. However, variation in the incubation period for pycnidia production and number of pycnidia produced on oatmeal agar under 12-hr light: dark incubation was observed. After establishing optimum mycelial growth and sporulation conditions, we are currently evaluating the disease-causing ability of these isolates on cacao.

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1 - North Carolina State University, Entomology and Plant Pathology, Center for Integrated Fungal Research, Raleigh, NC, 27606, USA

Lasiodiplodia theobromae
water activity

Presentation Type: Poster
Session: MYP3, Mycology Posters III
Location: /
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: MYP3008
Abstract ID:1017
Candidate for Awards:MSA Best Poster Presentation Award by a Graduate Student

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