DETECTION, IDENTIFICATION AND MANAGEMENT OF FUNGI ASSOCIATED WITH COWPEA (Vigna unguiculata L. Walp) SEED IN TWO AGROECOLOGICAL ZONES OF GHANA
The research was done to assess the seed health status of cowpea seeds produced by seed companies and producers in two agro-climate zones of Ghana. The two zones considered were Guinea Savannah and Semi-deciduous forest zones. A 5x3 factorial set out in Completely Randomized Design with three replications was the experimental design used.
Six seed samples collected from each agro-climatic zone were visually inspected and categorized into broken/cracked seed coat, discoloured, undamaged, varietal mixture and insect damaged seeds. All the seed samples except Hewale and Kirkhouse benga showed all the categories of damage to varying extents. Highest percentage of damaged seeds were observed in Semi-deciduous forest zone. Seed discolouration was the most common category of damage in all the seed samples. Discoloured seeds ranged from 1.6-9.2%; insect damaged (0.0-11.3%); broken/cracked seed coat (0.1-4.1%); varietal mixture (0.0-6.5%) and undamaged seeds (79.2-96.8%).
Blotter and Agar plate incubation techniques, morphological characterisation and molecular technique were used to detect, isolate and identify fungi associated with the cowpea seed samples. Agar plate method generated the maximum quantity of fungi. Aspergillus flavus, Aspergillus niger, Aspergillus amstelodami, Colletotrichum truncatum, Corynespora casiicola, Macrophomina phaseolina, Botryodiplodia theobromae, Rhizoctonia solani, Rhizopus stolonifer, Penicillium spp., Curvularia lunata, Fusarium incarnatum and Fusarium proliferatum were the fungi associated with the cowpea seed samples. All the fungi except Curvularia lunata, Fusarium proliferatum and Aspergillus amstelodami were present on the seed samples obtained from the Guinea Savannah zone. Seed samples from Guinea Savannah zone had a high percentage fungal prevalence. Macrophomina phaseolina and Aspergillus niger correlated significantly to reduction in seed germination. Four seed treatments [Biological control agent (Trichoderma harzianum), ethanol extract of Garlic (Allium sativum) and Ethiopian pepper (Xylopia aethiopica) and synthetic chemical (20% Imidacloprid and 20% Metalaxyl) were tested in-vitro for their efficacy on identified fungi, germination percentage and seedling vigour of cowpea seeds. The biological control agent (Trichoderma harzianum) was the most effective seed treatment compared to all the other treatments. It reduced the prevalence of all the fungi associated with the seeds. Also, T. harzianum increased germination percentage and seedling vigour by 17% and 874.5 respectively than the untreated seeds. The efficacy of the treatments was reduced as the duration of storage increased but was significantly better than the untreated seeds. Hence, Trichoderma harzianum could be used as seed dressant to increase productivity.