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<p>Squash (<i>Cucurbita</i> spp.) is an economically important vegetable crop in Pakistan, yet its productivity is severely impacted by powdery mildew. Despite frequent outbreaks, limited data exist on its causal agents and host range in Pakistan. This study aimed to assess the prevalence, incidence, characterization and host range of associated squash powdery mildew (SPM) pathogens. Surveys conducted during 2020 and 2021 in the Pothwar region revealed 100% disease prevalence with mean incidence of 50.47% and 59.78%, respectively. Disease incidence was positively correlated with humidity and rainfall. Healthy plant assays for culture maintenance and preservation of inoculum at −20 °C were found the most efficient for maintaining the pathogen virulence even after a year whereas, 500 mg powder/L (3.4 × 10<sup>4</sup> spores) was standardized as optimum inoculum load for the onset of utmost disease severity. Microscopic observation of each sample identified two coexisting SPM causal agents i.e. <i>Podosphaera xanthii</i> (<i>Px.</i>) and <i>Golovinomyces cichoracearum</i> (<i>Gc.</i>). Nucleotide sequences of highly virulent isolates from pathogenicity tests confirmed the species identity and phylogenetic analyses revealed genetic similarity with global isolates. All cucurbit crops were susceptible to SPM whereas, the weeds were infected by other powdery mildew species. Interestingly, sunflower (both wild and cultivated) (<i>Helianthus annuus</i>) was found infected with both SPM species which confirms the sunflower as potential alternate host for SPM.</p>

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Morpho-molecular diversity and host range dynamics of squash powdery mildew pathogens prevailing in Pothwar Plateau, Pakistan

  • 期刊论文

  • 发表日期：

    2025年11月4日

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  • Beenish Gul,
  • Farah Naz,
  • Mathews L. Paret,
  • Fanny Iriarte,
  • Zain Haider,
  • Gulshan Irshad,
  • Muhammad Azam Khan

摘要

Squash (Cucurbita spp.) is an economically important vegetable crop in Pakistan, yet its productivity is severely impacted by powdery mildew. Despite frequent outbreaks, limited data exist on its causal agents and host range in Pakistan. This study aimed to assess the prevalence, incidence, characterization and host range of associated squash powdery mildew (SPM) pathogens. Surveys conducted during 2020 and 2021 in the Pothwar region revealed 100% disease prevalence with mean incidence of 50.47% and 59.78%, respectively. Disease incidence was positively correlated with humidity and rainfall. Healthy plant assays for culture maintenance and preservation of inoculum at −20 °C were found the most efficient for maintaining the pathogen virulence even after a year whereas, 500 mg powder/L (3.4 × 104 spores) was standardized as optimum inoculum load for the onset of utmost disease severity. Microscopic observation of each sample identified two coexisting SPM causal agents i.e. Podosphaera xanthii (Px.) and Golovinomyces cichoracearum (Gc.). Nucleotide sequences of highly virulent isolates from pathogenicity tests confirmed the species identity and phylogenetic analyses revealed genetic similarity with global isolates. All cucurbit crops were susceptible to SPM whereas, the weeds were infected by other powdery mildew species. Interestingly, sunflower (both wild and cultivated) (Helianthus annuus) was found infected with both SPM species which confirms the sunflower as potential alternate host for SPM.