EVALUATION OF THE SEED-DRESSING POTENTIALS OF PHYTOCHEMICALS FROM Caricapapaya and Piper guineenseON THE GERMINATION OF COWPEA (Vigna unguiculata L. Walp) SEEDS AND INCIDENCE OF THE SEED-BORNE FUNGI

Cowpea is the most important grain legume in Nigeria. The crop plays a soil fertility restorative role in farming systems. Its protein-rich grains are widely consumed and the haulms are fed livestock. However, its production is constrained by fungal attacks at all stages of its growth, amongst other socio-economic factors. Some of these diseases which affect the crop are seed-borne and seed transmissible. Their control has been by use of synthetic fungicides. But these are associated with discouraging drawbacks on human and eco-health. Alternatively, plant extracts are being screened as sources of novel fungicides. This study evaluated in vitro two concentrations (30% and 50%) of extracts from Caricapapaya (roots, seeds, leaves) and Piper guineense (seeds, leaves) as seed-dressing phytochemicals on the germination of cowpea seeds and the incidence of the seed-borne fungi. The seeds were soaked in each concentration of the crude aqueous extracts for 12 hr, removed and air-dried at room temperature for 8hr. The treated seeds were then plated on solidified PDA in Petri dishes and incubated for 7 days in the inoculation chamber. The dishes were arranged in completely randomized design (CRD), made up of 6 treatments and 5 replicates giving 300 seeds for each concentration. The results showed generally that the germination profile was better (p<0.05) at the 30% rate of application than 50%.  Regardless of dosage of treatment, cowpea seeds dressed in Carica papaya root extracts gave 100% germination while those treated with Piper guineense failed to germinate. This study also affirmed that species of Fusarium,  Colletotrichum, Curvularia, Mucor and Aspergillus were associated with seeds of cowpea variety IAR-48. It indicated that C. papaya root and P. guineense seed extracts significantly (p<0.05) gave a better reduction of these seed-borne fungi. At 30% concentration, the mean incidences were 19.20% and 4.80% while 5.20% and 0.00% were obtained from 50% dosage respectively. Though 50% concentration of the extracts generally gave a higher reduction of the fungal load in the cowpea seeds, in other words a better control of the organisms, the germination of the treated seeds were significantly (p<0.05)  better with 30% concentration. Hence, aqueous root extracts of C. papaya could be used as effective seed-dressing phytochemical in IPM programmes for the control of seed-borne fungi of cowpea for improved productivity. However, P. guineense seed extracts should be tried out in further studies to determine their seed-safe levels or application methods.