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Author: search.filters.author.Kongtragoul, PornprapaSubject: search.filters.subject.durian diseases

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    Sensitivity of Phytophthora palmivora Causing Durian Diseases to Metalaxyl-M and Dimethomorph in Southern and Eastern Thailand
    (2025-05-14)
    Kongtragoul, Pornprapa
    ;
    Charoensiri, Sasidara
    ;
    Rimchon, Somkiat
    ;
    Knight, Susan
    Metalaxyl-M (Met-M) and dimethomorph (Dim) are two systemic fungicides commonly used in Thailand to treat durian rot diseases caused by Phytophthora palmivora, a pathogen that significantly affects durian production. Fungicides have long been used by Thai durian farmers to control this infection, but managing the disease has become increasingly challenging in recent years. Monitoring fungicide resistance evolution is essential for effective disease management. In 2020 and 2022, eighty-one and sixty isolates, respectively, were collected from naturally infected durians in southern and eastern Thailand. All isolates were identified as P. palmivora through sporangium formation. Furthermore, 23 out of the 141 isolates were confirmed as P. palmivora based on sequencing of the internal transcribed spacer (ITS) and 5.8S regions of rDNA. All isolates were tested for mycelium growth sensitivity to Met-M and Dim. EC50 values were used to classify sensitivity into three categories: sensitive (S) at EC50 < 1 mgL<sup>-1</sup>, moderately resistant (MR) at EC50 between 1 and 100 mgL<sup>-1</sup>, and resistant (R) at EC50 > 100 mgL<sup>-1</sup>. In southern Thailand, 58% of the isolates were Met-M<sup>R</sup>Dim<sup>S</sup>, and 41.25% were Met-M<sup>S</sup>Dim<sup>S</sup>. In eastern Thailand, 36.67% were Met-M<sup>MR</sup>Dim<sup>S</sup>, and 41.67% were Met-M<sup>S</sup>Dim<sup>S</sup>. These findings indicate that the populations of P. palmivora in the durian orchards in southern and eastern Thailand consisted of a mixture of sensitive, moderately resistant, and resistant strains.
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    ZINC OXIDE NANOPARTICLES INHIBIT SOME FUNGAL PATHOGENS INFECTION ON DURIAN SEEDLINGS
    (2024-01-01)
    Kongtragoul, Pornprapa
    ;
    Pantakan, Miss Sansanee
    Durian disease-causing organisms such as fungi can infect durian trees at any stage of development. Chemical fungicides are widely used because they are convenient and simple to use. However, it impacts the health of producers, consumers, and the environment. As a result, recommendations have been developed and established for researching zinc oxide nanoparticles (Zn-ONPs) that can inhibit fungal growth as an alternative for preventing and eliminating such fungi. The purpose of this study is to collect and isolate some fungi that cause durian diseases and their pathogenicity test, as well as to investigate the efficacy of Zn-ONPs ranging in size from 25 to 50 nm in inhibiting germination and fungal infection on durian seedlings. Three isolates of Phytophthora sp. (CL4_F1, CL4_S5, CL4_F10), two isolates of Fusarium sp. (CL6_FL1, CL6_FL2), two isolates of Phomopsis sp. (CH1_PF1, CH1_PF2), and two isolates of Rhizoctonia sp. (CL1_RL1, CL1_RL2) were successfully isolated as durian pathogenic fungi. All isolates were pathogenic on durian seedlings, with a 100% disease incidence. As a result, it was found that increasing the concentration of ZnO-NPs could further inhibit growth in the germination and infection of durian seedlings. All tested isolates had delayed germination by ZnO-NPs at all concentrations. Furthermore, as the severity of the disease decreased, ZnO-NPs could inhibit infection in durian seedlings at higher concentrations.