Investigating the Morphological Characteristics, and Host Range of three Pathotypes of Choanephoracucurbitarum using Fifteen Commonly Grown Vegetable Crops

The cultivation of vegetable crops is often challenging to farmers as a result of disease conditions caused by plant pathogens including fungi, bacteria, viruses, nematodes. Choanephora cucurbitarum is a notable fungus responsible for fruit rot, flower rot and leaf blight on a variety of plants. This study was conducted to morphologically characterize three pathotypes of Choanephora cucurbitarum and assess their host range on selected commonly cultivated vegetable crops. To obtain pathotypes of C. cucurbitarum, sections (3 mm2) of infected leaves of Abelmoschus esculentus, Amaranthus hybridus and Solanum melongena were aseptically taken, surface sterilized using 70 % ethanol, and rinsed with distilled water. Sterile sections were incubated in PDA at 27±1 oC. Established cultures were sub-cultured to obtain pure cultures. The Susceptibility of the vegetable crops to the isolated pathotypes (A1, O2 and E3) was tested by using a spore suspension (1 x 106 spores per ml of distilled water) of pathotypes pure culture to inoculate healthy seeds of test plants. Morphological characteristics of the pathotypes were studied by viewing prepared slides of C. cucurbitarum pure culture, using Olympus microscope under 40x and 100x magnifications. Results show that out of fifteen species of vegetables employed in the host range test, only eight species germinated, while only five out of these were established. Morphological characteristics of the three isolates of C. cucurbitarum revealed that the isolate from Amaranthus leaf (A1) had a monosporous Sporangiophore that was long and slender. Isolates from okra (O2) had mycelium that was hyaline, unbranched and without septations. While isolates from eggplant (E3) had a cottony colony, with scanty white mycelium. Host range test confirmed the vegetables (Vigna unguiculata, Cucumis sativus, S. melongena, A. esculentus, A. hybridus) were susceptible to the pathotypes of C. cucurbitarum. Farmers are encouraged to practice good hygiene measures, such as cleaning and disinfecting tools, equipment to prevent the spread of the pathogen.