Choanephora cucurbitarum

Fungal Disease

Choanephora cucurbitarum

Fungal Disease

Introduction

Choanephora cucurbitarum, commonly known as Choanephora fruit rot, is a fungal disease primarily affecting cucurbits and other vegetables. This opportunistic fungus thrives in warm and humid conditions, causing significant damage to fruits, flowers, stems, and leaves.

Environmental Conditions

• Optimal Temperature: 25°C with 100% relative humidity.

• High Sporulation: At 31°C, large sporangia production is stimulated but conidia formation is reduced.

• Preferred Conditions: Damaged plant tissues and poorly adapted crops in hot, humid climates.

Appearance

• Similar to diseases caused by other Mucorales genera such as Mucor and Rhizopus.

• Host tissues exhibit a hairy appearance due to tall sporangiophores bearing brown sporangiola at their tips.

Geographic Distribution

• Found in tropical to subtropical zones, including:

  • Asia: China, India, Indonesia, Korea, Pakistan

  • Africa: Benin, Congo, Ghana, Kenya, Nigeria, Egypt

  • Americas: USA, Brazil, Colombia, Peru, Venezuela

  • Oceania: Australia, French Polynesia, New Caledonia

Host Range

• Cucurbits: Watermelon, zucchini, squash, pumpkin, vegetable sponge (Luffa cylindrica)

• Other Vegetables: Chili, eggplant, radish, cauliflower, beans, peas, spinach, potatoes

• Other Plants: Yam, sweet potato, okra, amaranth, cowpea, hibiscus, fig, cotton, papaya, sorghum

Symptoms

• Flowers:

  • Colonization of senescent petals, causing rot and darkening.

  • Abortion of young fruits.

• Fruits:

  • Wet, soft lesions starting from senescent floral parts or wounds.

  • Rapid progression to soft rot with a translucent dark appearance.

  • Complete liquefaction within days.

• Stems:

  • Moist, dark green to brown lesions, especially in the cortex.

  • Wilting and drying out of leaves.

• Leaves:

  • Moist alterations evolving into rot.

• Young Shoots:

  • Rot and destruction.

Sporulation and Dissemination

• Thrives on rotten fruit with heavy sporulation.

• Spores are dispersed by wind, rain, sprinkler irrigation, and soil splash.

• Insects may act as vectors.

Notable Cases

• Hokkaido, Japan:

  • Causes flower stalk rot in sugar beet.

  • Dark brown, soft-rotted lesions on flower stalks.

Comparisons

• Similar to Botrytis cinerea in tropical regions.

• Often confused with Rhizopus stolonifer, which causes similar fruit rot symptoms.

Conclusion

Choanephora cucurbitarum is a widespread, polyphagous opportunistic fungus causing considerable damage under favorable humid conditions. Proper identification and management are crucial to preventing significant crop losses in tropical and subtropical regions.