Browsing by Author "Lopez, Mark Kevin S."

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    Entomopathogenicity of fungal isolates from bat guano deposits in Palale Cave, Tayabas, Quezon Province, Philippines against rice green leafhopper (Nephotettix nigropictus stål)
    (Studies in Fungi, 2026) Lopez, Mark Kevin S.; Sabino, Noel G.; Lantican, Nacita B.; De Leon, Marian P.
    Nephotettix nigropictus Stål transmits rice pathogens such as yellow dwarf mycoplasma-like organisms, rice dwarf viruses, rice transitory yellowing viruses, and rice tungro viruses; hence, it requires effective control measures. Biological control strategies, such as the use of entomopathogenic fungi, are ecofriendly, targeted, and safer alternatives to chemically synthesized insecticides. This study aimed to investigate the entomopathogenic activities of several fungal isolates from bat guano deposits in Palale Cave, Tayabas, Quezon, Philippines, against the third-instar larvae of N. nigropictus. The fungi were characterized and identified using phenotypic (cultural and morphological features) and genotypic (ITS marker) methods. Entomopathogenicity was assessed through the mean percentage mortality of N. nigropictus third instar larvae exposed to conidia of Talaromyces sp., Trichoderma sp., Aspergillus sp., and Actinomortierella sp. Microscopic observation showed that prolific mycelial growth covered the third instar larvae, and the Koch postulate approach confirmed that the selected fungi are the infecting mycelia. Scanning electron microscopy confirmed the presence of the fungal mycelia covering the head and abdominal region of the larvae. Histopathological analysis using modified Grocott silver nitrate staining showed internal colonization and dominance of the fungal mycelial tissue on the ovipositor region and the compound eyes. In the abdomen of the larvae, fungal mycelial penetration was also observed between tergites and sternites. The promising findings of this study can provide avenues for the development of bioinsecticide agents against N. nigropictus and potentially other insect pests, such as armyworms, stem borers, and thrips that affect crops, particularly rice, the most important staple crop in the Philippines.
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    Evaluation of tolerance and uptake of Cd and Mn for microfungi Aspergillus flavus, Aspergillus oryzae, and Aspergillus terreus isolated from landfill soil collected from Bangar, La Union Philippines
    (Environment and Natural Resources Journal, 2024) Arellano, Jan Aizel E.; Argame, Irish Benja M.; Castillo, Francis Ruel G.; Salazar, Christian Geen E.; Lopez, Mark Kevin S.
    Excessive deposition of heavy metals into the environment due to anthropogenic activities necessitates an eco-friendly clean-up strategy. Among microorganisms, limited studies have been made on the mycoremediation potential of microfungi. This paper evaluated three landfill microfungal isolates of Aspergillus species for tolerance and uptake to Cd and Mn. Culture media optimization was also performed for the evaluation of the tolerance index and heavy metal analysis of soil samples from the landfill site. Among the nine heavy metals analyzed, Mn and Fe were detected in relatively high amounts, while Cd, Ni, and Cu were detected in a moderate range. Luxuriant mycelial growth of A. oryzae (MK120548.1) and A. flavus (MH864264.1) was observed in potato dextrose agar while A. terreus (MH047280.1) grew best in potato sucrose agar. In terms of tolerance index, A. oryzae (MK120548.1) and A. flavus (MH864264.1) demonstrated high tolerance to Cd up to 10 mg/kg. A. oryzae (MK120548.1) showed high tolerance to Mn up to 1,000 mg/kg while A. flavus (MH864264.1) exhibited a very high 10,000 mg/kg tolerance. In terms of metal uptake, A. oryzae (MK120548.1) showed the highest metal uptake of up to 654 mg/kg of Cd, while A. terreus (MH047280.1) exhibited the highest metal uptake of 997 mg/kg of Mn. With these findings, A. oryzae (MK120548.1), A. flavus (MH864264.1), and A. terreus (MH047280.1) have considerable mycoremediation potential. Bioremediation studies in conjunction with plants can be explored to further assess the potential of these Aspergillus species.
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    Microbiology (BIOL 109)
    (Don Mariano Marcos Memorial State University - North La Union Campus, 2020) Lopez, Mark Kevin S.
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    Mycochemical Composition, Antioxidant Properties, and Cytotoxic Activity of Xylaria papulis Lloyd (Xylariaceae) Mycelia Grown in Static and Shaking Indigenous Liquid Culture Conditions.
    (Research and Innovation Department,Khon Kaen University, Thailand, 2026-05) Lopez, Mark Kevin S.; Kalaw, Sofronio P.; Dulay, Rich Milton R.; De Leon, Angeles M.; Reyes, Renato G.
    The search for promising and sustainable sources of secondary metabolites with potential biofunctional activities is important for the possible sources of drugs to treat human diseases. Hence, this study qualitatively assessed the mycochemical composition and investigated the biofunctional activities (antioxidant activity and cytotoxic activity) of Xylaria papulis Lloyd mycelia grown in static and shaking indigenous liquid culture medium. Mycochemical screening revealed the presence of several classes of secondary metabolites, such as phenolics, terpenoids, fatty acid derivatives, alkaloids, and sugar derivatives, in mycelial mat (shaking) and in culture spent (static). Mycelial mat (static) and culture spent (shaking) also contain the same classes of secondary metabolites, with the former including essential oils. Mycelial extracts have greater antioxidant property (≤ 43.19±1.63% RSA) and total phenolics (≤ 47.75±2.31 mg/GAE) compared to the culture spent. Culture spent from shaking condition exhibited cytotoxicity (LC50 = 94.39µg/mL) against brine shrimp larvae. These findings indicate that X. papulis (Lloyd) grown in liquid culture medium can be a sustainable source of diverse secondary metabolites with antioxidant properties and cytotoxic activity. Further, cytotoxicity studies against cancer cell lines can also be investigated for future studies.
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    Optimization of mycelial growth of Xylaria papulis Lloyd (Xylariaceae) in indigenous liquid culture conditions, science city of Muñoz, Nueva Ecija, Philippines
    (Studies in Fungi, 2022-12-28) Lopez, Mark Kevin S.; Kalaw, Sofronio P.; Dulay, Rich Milton R.; De Leon, Angeles M.; Reyes, Renato G.
    The search for potential and inexhaustible sources of bioactive compounds with great functional activities is imperative for potential drug leads in treating various human diseases. In this regard, this study investigated the optimum liquid medium and physical culture conditions for the mycelial growth of X. papulis Lloyd for nutraceutical studies. The greatest mycelial biomass was achieved in PSB liquid medium among the indigenous media evaluated, such as potato sucrose broth (PSB), corn meal broth (CMB), rice bran broth (RBB), and coconut water (CW). In terms of pH, X. papulis Lloyd was observed to grow in a wide range of pH (5.0−8.5), but the best mycelial growth was observed at pH 6.5. Room temperature of 28 °C, lighted (137 lux), and static conditions were the other optimum physical culture conditions for mycelial growth of X. papulis Lloyd.
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    Systematics (BIOL 103)
    (Don Mariano Marcos Memorial State University - North La Union Campus, 2020) Lopez, Mark Kevin S.