CHARACTERIZATION OF PENTACLETHRA MACROPHYLLA BENTH. THROUGH PROTEIN ELECTROPHORESIS

ABSTRACT

Sodium Dodecyl Sulphate –  Polyacrylamide Gel Electrophoresis (SDS –  PAGE) is  a technique commonly used for the separation of proteins according to their molecular weight, based on their differential rates of migration through a sieving matrix (a gel) under the influence of an applied electrical field. SDS – PAGE was used in assessing the genetic diversity among twelve accessions of African oil bean (Pentaclethra macrophylla) germplasms obtained from NACGRAB (Ibadan) and five villages around Nsukka vicinity. Protein banding patterns were scored for presence and absence and analysed for genetic similarities and dissimilarities among the accessions. A total of 11 different bands were found in the accessions from NACGRAB and total of 9 bands were found in accessions from Nsukka zone. The highest number of bands (10) were found in Accessions A1 and A2 (Nac1 and Nac2) while the lowest (5) band was found in Accession A7 (Nac7). The

banding  pattern  revealed  that  some  of  the  bands  present  in  the  accessions  from NACGRAB were absent in the accessions from Nsukka zone. A dendrogram constructed on the basis of genetic distance matrix by the Unweighted Pair Group Method with Arithmetic Mean Algorithm (UPGMA), using the NTSYS-pc software resolved the germplasm into three distinct clusters and six groups. Cluster one and two had six and five members respectively while cluster three had only one member. Cluster 1 was made up of three groups (1, 2 and 3), cluster 2 was made up of two groups (4 and 5) while cluster 3 was made up of only one group (group 6). Accessions from NACGRAB except Nac7 formed groups 1, 2 and 3 while accessions from Nsukka zone were found in groups 4 and

5. Group 6 was observed to be entirely different from other groups having only one germplasm (Nac7) with the highest genetic diversity as member and therefore considered as an outgroup. The present study has helped in resolving the genetic relatedness among the twelve accessions of P. macrophylla germplasm. The information will be suitable for future breeding for the improvement of the species.

CHAPTER ONE

INTRODUCTION

More than 7,000 plant species have been used as food for humans, but recent decades have seen a small number of crops come to dominate agriculture, to the exclusion of many others. Yet, a large number of crops that are now overlooked have the potential to play a much more important role in sustaining livelihoods and enhancing environmental health (Hawtin, 2007).

In Nigeria, because of population growth, there is an increasing demand for plant products with aesthetic and organoleptic appeal in the diet. Seeds of legumes may account for up to 80% of dietary protein and may be the only source of protein for some groups. Their cooked forms are eaten as meals and are commonly used in fermented form as condiments to enhance the flavours of foods. Legume condiments have been observed to be capable of serving as tasty complements to sauces and soups and can substitute for fish and meat (Achi, 2005). Some oil seeds, e.g. walnut, groundnut etc., are used directly as food while some such as melon, locust bean, castor oil bean etc., are cooked and used in preparation of soup and condiments. Most of them can be processed to obtain fat, oil cake and meal, which could be used for preparation of livestock feeds. Several plants that yield fruit of nutritional and dietary importance have been identified within the forest and savannah regions. One of such important but lesser known legume protein source is the African oil bean seed (Pentaclethra macrophylla) (Akindahunsi, 2004).

There exists a wide variety of oil crops in various parts of the country such as the highly utilized ones like soybean, oil palm, groundnut etc. These are used for the production of various products ranging from food to oil and industrially in the production

of soaps etc. There are also under-utilized ones like walnut, locust bean, castor oil bean, African oil bean (Pentaclethra macrophylla), etc., which are mostly utilized only in the areas where they grow and for limited purposes such as seasoning or snacks (Akindahunsi,

2004).

Although African oil bean seed is a popular indigenous plant in many countries in the tropics, it is referred to as an underutilized species because of its small total economic value in commercial production and trade compared with other crops and agricultural commodities. It is listed among other crops as an underutilized plant ((Akindahunsi, 2004; Enujiugha and Akanbi, 2005; Jaenicke and Höschle-Zeledon, 2006).

According to International Plant Genetic Resources Institute (IPGRI) (2002), neglected crops are those grown primarily in their centres of origin by traditional farmers where they are still important for the subsistence of local communities. While these crops continue to be maintained by sociocultural preferences and the ways they are used, they remain  inadequately documented and  neglected by formal research and conservation. Underutilized crops are those that were once grown more widely or intensively but are falling into disuse for a variety of agronomic, genetic, economic and cultural reasons. Farmers and consumers are using these crops less because they are in some ways not competitive with other species in the same agricultural environment. The decline of these crops may erode the genetic base and prevent distinctive and valuable traits being used in crop adaptation and improvement.   Neglected and underutilized species are often considered ‘minor crops’ because they are less important than staple crops and agricultural commodities in terms of global production and market value (IPGRI, 2002).

Pentaclethra macrophylla Benth. is a multipurpose tree from Africa with potential for agro forestry in the tropics. It is the sole member of the genus occurring naturally in

the humid lowlands of West Africa (Aju and Okwulehie, 2005). It is a large woody plant abundant in the rain forest areas of West and Central Africa. Its discovery in Nigeria was believed to be around 1937, and it was found in the Southern part of Nigeria. It belongs to the family Fabaceae and sub-family Mimosoideae. It is recognized by peasant farmers in the Southeast of Nigeria as an important tree due to  its soil improvement properties (Akindahunsi, 2004). Ibos in Nigeria call it “osisi ugba” or “osisi ukpaka”, the Congolese call it “Congo acacia” and in Cameroon it is called “duala kambola”.

The tree grows to about 21 m in height and about 6 m in girth. The bark is greyish to  dark  reddish brown.  The  compound leaves  possess  a  stout  angular petiole.  Main flowering season is between March and April with smaller flushes in June and November. Fruits  are  available  at  most  periods  of the  year  because  the  large  woody pods  are persistent. The fruits split open explosively with valves curling up. The seeds are irregular and oval; the pods are flat, black and hard. It is composed of oil, protein and small amounts of carbohydrate (Ladipo and Boland, 1995).

Common uses of P. macrophylla include food, salt substitute, edible oil, seed craft, dye, fencing and palings, charcoal, carving bows, medicine (convulsion, itching, lactogenicity,  wound,  diarrhoea,  seed  wood and  ornamental (Enujiugha  and  Agbede,

2000; Asoegwu et al., 2006). The seed is a source of edible oil, it can be used for candle making and soaps. It has been reported that the seeds, when crushed and eaten with red ants could induce abortion (Alinnor and Oze, 2011). A solid – state fermentation of the seeds of African oil bean tree (P. macrophylla) is a popular food delicacy in Nigeria especially among the Ibo ethnic group where it serves as snack, side dish or as a food condiment. It is an essential food item for various traditional ceremonies where it is mixed with slices of boiled stockfish (ugba na okpoloko), garnished with boiled vegetables and

consumed by all socio-economic classes. The seed shells are decorative and are often used to construct beads, which are worn as necklaces, rosaries, and sometimes as local dancing apparels (Abbiw, 1990). Pentaclethra macrophylla has been identified as a minor food supplement; it has also been investigated and found out that this oilseed contains 23-28% protein. It also contains the twenty (20) essential amino acids and essential fatty acids that make up over 10% of the fatty acids in the oil (Enujiugha and Agbede, 2000).

Farmers protect this species on farms because of its open crown form that allows substantial light and does not inhibit crop plants grown under its canopy. This accounts for the tree’s use in combination with food crops on farms and particularly in home gardens in Southeast Nigeria. African oil bean seed is used for the preparation of many delicious African delicacies such as African salad, soups and sausages for eating with different staples. It was reported that there is no serious pest or disease problem known but stem borers  have  been  recorded on  some  old  trees,  and  that  mild  defoliation of  juvenile seedlings is not uncommon. The species is reported to be termite resistant (Ladipo and Boland, 1995).

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