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.
INTRODUCTION
Non-wood forest products (NWFPs), are essential parts of forestry products. NWFPs provide a safety net for rural dwellers in many third world countries especially Nigeria, where these products serve as food security, income and medicine, ie ensuring that food is available all year round, at affordable price and of good quality. Poverty according to United Nation (UN, 2002) and National Planning Commission (NPC, 2004), has led over 90% of rural dwellers in Nigeria to depend entirely on harvests of forestry products for their livelihood and economic survival.
Plukenetia conophorum Müell Arg a NWFPs, is a simple dry fruit in the family of Euphobiaceae. It is commonly called African walnut, “ukpa” in southeastern Nigeria and “Asala” in the south-west. It has an African origin (Nwosu, 1979). Okigbo (1977) described P. conophorum as a semi-wild plant found naturally in the wild and may be extensively encountered in rural dwellings and in farmlands where they are protected. Oduwaiye (1991) also confirmed that it is commonly found in the rainforest region of Nigeria where the edible seeds are extensively eaten throughout the southern states of the country. The seeds are available in the months of June – September when other fruits are scarce, and people cherish eating the succulent seeds (Egharevba et al., 2005).
Gillespie (1993) reported that P. conophorum is a twining vine, and rarely sprawling perennial herbs, found in tropical wet forest to seasonally dry forest or scrub. Also, Irvine (1990) documented that the plant, which is a perennial, is also a climber requiring support of woody sticks to climb, grow and survive. The plant starts flowering between 1 and half to 2 years after planting.
The importance of Plukenetia conophorum as an indigenous fruit climber is enormous as it is a multipurpose crop. In West Africa, especially in Nigeria, Sierra Leone and Central Africa, Cameroon, the seeds provide income to the rural people thereby improving their economy (Egharevba et al., 2005). Seeds are reported to be eaten boiled in Cameroon, cooked in the Democratic Republic of Congo and grilled in Gabon (Rependa-Walker and Sillans, 1961). In Nigeria, seeds are cooked, and (or) made into snacks for consumption.
Ethnomedicinal use includes macerations of leaves and roots for treating asthma and hypertension (Okafor and Okorie 1990). Plants are both cultivated in village farms and encouraged to persist in a semi-wild state on farmland for their edible seeds and for the oil extracted from the seeds (Okigbo, 1977 and Egharevba et al., 2005). Recent biochemical research has shown the seeds to have high protein and oil content (Akpuaka and Nwankwor, 2000; Odoemelam, 2003; Oboh and Ekperigin, 2004). Akintayo and Bayer (2002) reported that Plukenetia conophorum yielded 25.65% crude protein, at 8% moisture content, while oil yield of seeds was 49.58%. The very high saponification and iodine values of Plukenetia conophorum oil suggest its utilization in alkyd resin, shoe polish, liquid soap and shampoo. As investigated by Okafor (1991) and Udeala et al. (1984), the fruits yield 47.72% crude protein and 50% fats and oil (Conophor oil) which are of domestic and industrial importance for soap making, vanish and paints. The plants also provide a humid microclimate within the forest as its branches spread on the canopy level of forest trees thereby ameliorating climate change.
The existence of this useful multipurpose under-exploited forest nut plant has been threatened by large scale deforestation, urban development, and uncontrolled bush burning and low knowledge of its nutritional value in some places. United Nations (UN, 2002), observed that a great percentage of Nigeria’s forest products are threatened. Therefore, in order to maintain sustainable conservation and continued availability of “ukpa”, there is the need to develop propagation methods for the plant as this will enhance accessional selection from different places. Domestication helps to conserve and sustain availability of any biological plant resource. Therefore, the objectives of this study include, to:
• determine the proximate qualities and mineral composition of the accessions.
• determine germination pattern of accessions of Plukenetia conophorum using botanical seeds,
• determine rooting and shooting potentials of the stem cuttings of African walnut,
• evaluate early growth of accessions raised in different potting media under field condition.
• evaluate responses of an accession to manure rates, and
This material content is developed to serve as a GUIDE for students to conduct academic research
HORTICULTURAL CHARACTERIZATION OF FIVE ACCESSIONS OF AFRICAN WALNUT (PLUKENETIA CONOPHORUM MÛELL ARG)
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