Horticultural Characterization of five Accessions of African Walnut (Plukenetia conophorum Mûell Arg)

Abstract

Plukenetia conophorum Muell Arg commonly called African walnut is cultivated principally for the nuts which are cooked and consumed as snacks. The plant serves many nutritional and medicinal purposes yet its availability is on the decline. To preserve and ensure continued availability of P. conophorum, there is the need to develop propagation protocols for the plant. Five accessions were collected from Mbu, Nsukka, Orba and two locations in Edem-ani all in Enugu State, Southeastern, Nigeria. The objectives of the research were to: evaluate germination and emergence of the crop using botanical seeds; assay nutritional qualities of nuts of selected accessions; determine the influence of graded levels of poultry droppings on the growth of the crop; evaluate rooting and shooting potentials of stem cuttings and field growth performance evaluation of collected accessions. Specific experiments were conducted to achieve each of the objectives listed above. Results showed that sinker seeds had significantly (P<0.05) lower days to first emergence but higher coefficient velocity of emergence than the floaters. Edem-ani 1 and Nsukka accessions had significantly (P<0.05) higher coefficient velocity of emergence. The 2009 sowing showed significantly (P<0.05) higher coefficient velocity of germination than the 2010 planting of seeds treated with NaOCl. The 10% NaOCl solution treated seeds had significantly (P<0.05) lower days to first germination and cumulative dormancy period but higher coefficient velocity of germination. The nursery medium of sawdust + poultry manure + topsoil had significantly (P<0.05) lower days to 100% germination but higher coefficient velocity of germination. Edem-ani accessions showed significantly (P<0.05) lower days to 100% germination and higher coefficient velocity of germination. The nutritional quality assessment revealed that accessions from Mbu, Nsukka and Orba had significantly (P<0.05) higher crude protein, while Edem-ani 2 had significantly (P<0.05) higher fibre. Orba accession had significantly (P<0.05) higher carbohydrate content. The potassium content of Orba accession and the sodium and phosphorus concentration in Edem-ani 1 were significantly (P<0.05) higher than others. The manure rate studies showed that 0t/ha and 10t/ha had significantly lower number of branches and higher length of leaves in 2009 and 2010, respectively than 5 and 15t/ha treated plants. The vegetative propagation of an accession by stem cutting was achieved in semi-hardwood and softwood cuttings in water, coconut water and control pre-sowing treatments. Field growth performance evaluation showed that seedlings raised in saw-dust medium had significantly higher values for most of growth parameters measured whereas those of the accessions were similar except for Orba accession that had significantly higher values for plant girth and number of leaves. The total dry matter, dry matter distribution, dry matter content and moisture content of above ground plant parts showed non-significant difference.