MYCOPATH, Vol 20, No 1 (2022)

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Screening of selected plant products as alternatives to agar in mycological studies

Chinyerum Gloria Ikechi-Nwogu, Eunice Oluchi Nwachukwu

Abstract


 

This study was carried out to examine the use of selected plant products as alternative to agar for mycological studies because agar is expensive and not readily available. Extracts from Aloe vera leaves (aloe), Terminalia ivorensis bark (black afara), Hevea brasiliensis (rubber tree), Abelmoschus esculentus pod (lady finger), seeds of Detarium macrocarpum (sweet detar), Brachystegia eurycoma (naga), Mucuna sloanei (hamburger bean) and Telfairia occidentalis (fluted pumpkin), grains of Triticum sp. (wheat), Zea mays (maize) and Oryza sativa (rice), tubers of Colocasia esculenta (cocoyam), Manihot esculenta (cassava), Dioscorea bulbifera (aerial yam), Ipomoea batatas (sweet potatoes), Dioscorea rotundata  (white yam) and Dioscorea dumetorum (three-leaved yam) were screened as alternative to agar for cost reduction. These plant extracts combined with potato and dextrose in varying concentrations (5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 g 100 mL-1), were tested for their gelling potentials. The different concentrations of all the plant products were tested at different periods (1 s to 1 h), under different temperature (20–90 oC). The media did not solidify except potato dextrose cassava starch (PDCS) which solidified at 50 g 100 mL in 30 min and at 29 oC. Seven frequently occurring fungi (Aspergillus niger, Aspergillus flavus, Botrydioplodia theobromae, Fusarium poae, Penicillium chrysogenum, Rhizopus oryzae and Trichoderma harzianum) were cultured on PDCS and PDA (potato dextrose agar) for comparison to evaluate their abilities in supporting fungal growth.  The radial growth and mycelial biomass of the test fungi were recorded and subjected to ANOVA. Mycelial biomass values (g) for each test organism for PDCS and PDA were: 3.77 ± 0.64 and 3.94 ± 0.53 for A. flavus; 4.09 ± 1.51 and 2.14 ± 0.41 for A. niger; 8.08 ± 0.19 and 4.97 ± 1.74 for B. theobromae; 1.04 ± 0.32 and 1.97 ± 0.25 for F. poae; 6.42 ± 0.14 and 5.40 ± 0.16 for P. chrysogenum; 7.10 ± 0.86 and 5.88 ± 0.14 for R. oryzae and 5.08 ± 1.02 and 4.30 ± 2.64 for T. harzianum. The mycelia biomass of A. flavus and T. harzianum on PDCS, are not significantly different at P≤0.05 from those on PDA. While those of A. niger, B. theobromae, F. poae, P. chrysogenum and R. oryzae on PDCS were significantly higher than those on PDA. All the tested fungi exhibited normal growth and sporulation on PDCS when compared with PDA (control), but with better growth on PDCS at P≤0.05.

 


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