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<p>The sour passion fruit (<i>Passiflora edulis</i> Sims) is a very profitable crop, and yield losses due to severe scab epidemics have been a major concern for growers. Scab, caused by fungi from the complex <i>Cladosporium cladosporioides</i>, is very difficult to control. This study aimed to study the events of penetration, colonization, and sporulation of <i>C. passiflorae</i> on the leaves of sour passion fruit plants using light and scanning electron microscopies. The circular lesions of water-soaked appearance and gray color on leaves occurred at 72 hours post-inoculation (hpi). As the lesions expanded, they coalesced and exhibited a brown color surrounded by brown haloes at 96 hpi. At 108 hpi, intense fungal sporulation of gray color was noticed in the necrotic lesions. Conidia started to germinate on the abaxial leaf surface at 24 hpi. The germ tubes were formed in one of the conidial cells from 24 to 48 hpi. The germ tubes grew only over the abaxial leaf surface. Occasionally, the germ tubes grew toward the stomata without evidence of appressoria formation. At 72 hpi, germ tubes penetrated mainly through the stomata and fungal hyphae were noticed in the abaxial epidermal cells and at the substomatal chamber. Fungal hyphae colonized the mesophyll, at first only the cells of the spongy parenchyma. At 84 hpi, the mesophyll cells of the palisade parenchyma were massively colonized by hyphae of <i>C. passiflorae</i>. After colonizing the mesophyll cells, fungal hyphae grew toward epidermal cells in the adaxial leaf surface from which conidiophores emerged. Fungal hyphae massively colonized the leaf tissues at 108 hpi resulting in greater disintegration. Intense formation of conidiophores on the abaxial leaf surface, mainly close to the veins, was observed at 108 hpi and conidia were abundantly produced. Together, these results will undoubtedly contribute to developing more efficient control strategies of scab especially directing the spraying of fungicides to the abaxial leaf surface.</p>

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Infection process of Cladosporium passiflorae on the leaves of sour passion fruit

  • 期刊论文

  • 发表日期：

    2025年2月26日

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  • Verônica Vieira Brás,
  • Leandro Castro Silva,
  • Henara Valéria Miranda Castro,
  • Ana Carolina Souza,
  • Fabrício Ávila Rodrigues

摘要

The sour passion fruit (Passiflora edulis Sims) is a very profitable crop, and yield losses due to severe scab epidemics have been a major concern for growers. Scab, caused by fungi from the complex Cladosporium cladosporioides, is very difficult to control. This study aimed to study the events of penetration, colonization, and sporulation of C. passiflorae on the leaves of sour passion fruit plants using light and scanning electron microscopies. The circular lesions of water-soaked appearance and gray color on leaves occurred at 72 hours post-inoculation (hpi). As the lesions expanded, they coalesced and exhibited a brown color surrounded by brown haloes at 96 hpi. At 108 hpi, intense fungal sporulation of gray color was noticed in the necrotic lesions. Conidia started to germinate on the abaxial leaf surface at 24 hpi. The germ tubes were formed in one of the conidial cells from 24 to 48 hpi. The germ tubes grew only over the abaxial leaf surface. Occasionally, the germ tubes grew toward the stomata without evidence of appressoria formation. At 72 hpi, germ tubes penetrated mainly through the stomata and fungal hyphae were noticed in the abaxial epidermal cells and at the substomatal chamber. Fungal hyphae colonized the mesophyll, at first only the cells of the spongy parenchyma. At 84 hpi, the mesophyll cells of the palisade parenchyma were massively colonized by hyphae of C. passiflorae. After colonizing the mesophyll cells, fungal hyphae grew toward epidermal cells in the adaxial leaf surface from which conidiophores emerged. Fungal hyphae massively colonized the leaf tissues at 108 hpi resulting in greater disintegration. Intense formation of conidiophores on the abaxial leaf surface, mainly close to the veins, was observed at 108 hpi and conidia were abundantly produced. Together, these results will undoubtedly contribute to developing more efficient control strategies of scab especially directing the spraying of fungicides to the abaxial leaf surface.