CHARACTERIZATION AND GENETICS OF FLUTED PUMPKIN (Telfairia occidentalis Hook F.) ACCESSIONS IN SOUTH EASTERN NIGERIA
CHAPTER ONE
Introduction
The genus Telfairia, named after the famous Irish naturalist, botanist and plant collector Charles Telfair, is a nutritionally important but scientifically little known member of the family cucurbitaceae and order Telfaireae (the compleat botanica, 2004). The two main species in the genus are Telfairia occidentalis (Hook (F) and Telfairia pedata (Smith ex sim World Agro Forestry Centre, 2004). In Africa Telfairia occidentalis is commonly referred to as fluted pumpkin or fluted gourd. According to Ng (1993), common name that have been used for Telfairia occidentalis outside Africa include gourd, queen’s nut, Zanzibar oil vine. Telfairia occidentalis (Hook. F) is localized to Africa (Robinson and Decker Walters, 1997). According to Akoroda (1990), Telfairia is indigenous to Nigeria and is widely grown in tropical wet coastal areas of West Africa, principally in Benin, Cameroon, Ghana, Nigeria and Sierra Leone. Telfairia occidentalis is a leafy vegetable crop commonly cultivated in the South Eastern part of Nigeria (Odiaka et al.,., 2008). However, it is gradually gaining prominence in the South Western part of the country (Schippers, 2002).
Telfairia belongs to the tribe joliffeae, member of the family cucurbitaceae, sub-family cucurbioidea (Jeffrey, 1980). The crop is a perennial plant which grows vigorously. It is a climber and must be provided with support (stakes) on which the tendril curls or often allowed to sprawl over the ground. It is a long sprawling plant that can grow up to ten (10) meters in length or more, root system ramifying in the top surface of the soil, the stem is angular, glabrous, becoming fibrous when old (Akoroda, 1990). It is a dioecious plant.
The leaves are compound, palamately lobed, usually 3-5 foliate with veins often conveying at the tip of the leaflet, it is arranged spirally, stipules are absent, petiole is 4-11cm long, leaflets with petioles I 0.5-3.5cm long, central are largest up to 15-19cm by 10-12cm, lateral ones asymmetrical, usually denlate in the upper two thirds, sometimes scabrid underneath, 3 veined from near the base. Male inflorescence has an auxiliary raceme up to 3-5cm long. On a peduncle are long pedicellate flower flowing long before the others (Akoroda, 1990). The petioles and leaf blades are covered with multi-cellular hairs which apparently help confer on the plant the drought resistance ability (Asoeqwu, 1988 and Herlots, 1972). The stem of the plant is five ridged and covered, especially when young, with uni-seriate multi-cellular hairs. The stem also has branching tendrils (Herklots, 1972).
The fluted pumpkin is a very important vegetable crop well known for its high nutritional, medicinal and economic value. (Akoroda, 1990; Ehiagbonare, 2008). It ranks among the three most widely consumed vegetables at homes and in restaurants across Nigeria. (Abiose, 1999). The crop services as food for over 35 million people in the world (Akoroda, 1990). It has a creeping growth habit that spreads across the ground to produce an efficient cover to the ground against erosion (Horsfall and Spiff, 2005) and produces large fruits with many large seeds. Telfairia occidentalis is a diploid specie 2n =24 (Ajayi et al., 2004) it is a dioecious plant with male and female flowers borne on different plants. (Okoli and Mgbeogwu, 1983) Purseqlove, 1997). Male plants start flowering earlier (means of 129 days compared with 150 days after planting for female plant) and over a longer period (59 days versus 17 days for females plant). Akoroda and Adejoro, 1990). There are more than 800 open male flowers to single opened female flowers and male flowers open in the evening. About 10 – 15% of given female population do not flower in the first year of planting and abortion of fruit is high (Ajayi et al., 2016). Plant may set up to six fruits but usually one large and one or two medium sized fruits are eventually carried to maturity. To date, attempts at finding markers for accurate sexual identification of seeds or seedlings early during growth have not been successful (Asiegbu, 1985, Emebiri and Nwufo, 1996).
According to Ajayi et al., (2006), the crop is an endangered species and the genetic diversity is valuable in crop breeding programme, as it helps in the identification of diverse parental combinations to create segregating progenies with maximum genetic variability (Barret and Kidwel, 1998) and facilitate introgression of desirable genes from diverse germplasm into available genetic base (Thompson et al., 1998). Genetically diverse and geographically isolated lines may generate a wide range of variation when brought together (Khantun et al., 2010). Knowledge of genetic diversity among existing cultivars of any crop is essential for the long term success in breeding programe and maximizes the exploration of the germplasm resources (Balaj et al., 2002). This is because it provides knowledge of genetic relationship among breeding population and helps in selecting desirable parents for establishing new breeding population.
The success of any crop breeding programme largely depends on the availability of huge genetic variability, genetic advance and character association, direct and indirect effects on yield and its attributes (Nwangburuka et al., 2012). Genetic diversity is important for selection of parents to recover transgressive segregants (Kiran Patio and Ravisankar, 2004). Determination of heritability estimates, using different methods (Obilaria and Fakorede, 1981; Wray and Visscher, 2008) will provide information on the proportion of phenotypic variance that is due to genetic factors for different traits but heritability estimate alone is not a sufficient measure of the level of possible genetic progress that might arise not even when the most outstanding individual are selected in the breeding programme (Nwangburuka et al., 2014). The value of heritability estimates is enhanced when used together with the selection differential or genetic advance (GA) (Ibrahim and Hussien, 2006).
Information on the amount and direction of association between yield and yield related characteristics is important for rapid progress in selection and genetic improvement of a crop (Assish et al., 2008). This will indicate the interrelationship between two or more plant characters and yield, providing suitable means for indirect selection for yield.
1.1 Economic importance of Fluted Pumpkin (Telfairia occidentalis)
Fluted pumpkin (Telfairia ociidentalis Hook F.), a cucurbit leaf and seed vegetable crop native to tropical Africa is well known for its high nutritional, medical and economic value. It ranks among the three most widely eaten vegetables at homes and in restaurants across Nigeria.
Among the important indigenous vegetables, Telfairia occidentalis seems to be widely eaten in Nigeria and cultivated for its edible succulent shoots. With the spread of Igbo’s to other parts of Nigeria, Telfaria is now cultivated in almost all parts of the country (Akoroda, 1990). In the middle belt which is in the Guinea savanna region of Nigeria, it is now being cultivated not only as backyard crop but also as commercial crop during the wet and dry season. Young, succulent shoot and leaves of fluted pumpkin are used singly or in combination with other vegetables such as okra (Abelmoschus esculentus) egusi melon, and dika seed in the preparation of soups for eating starchy foods such as garri and fufu and yam (Dioscorea spp) respectively and tuwo, made from cereals (Ajayi et al., 2006). Leaf extract made from fresh fluted pumpkin leaves is administered as a tonic for the treatment of acute anemia (Schippers, 2000; Akoroda, 1990).
The seeds are used as propagating materials, eaten roasted, boiled or ground to paste as soup thickener. Telfairia leaves are rich in Mg, Fe and fibres (Gupta et al., 1989, Taylor et al., 1983b; Odika et al., 2008) and are used as food supplements. The nutritional value of the fluted pumpkin seeds (53% fat and 27% crude protein) (Taylor et al., 1983) justifies the wide consumption as reported by Odiaka et al., (2008). The nutritionally rich and pleasant tasting leaves and tender shoots are added to soups. These vegetables are sometimes cooked with yam, plantain, banana, cocoyam, rice and beans etc. (Okigbo, 1977). Among the Efiks and Ibibios of southern Nigeria, the leaves of Telfairia occidentalis are used for preparing delicacy like “Edikang Ikong” and Ubo abak soups. The leaves of the plant are very much sought after by sheep and goats hence could be used a fodder (Giami et al., 1999). The seed has an excellent pattern of amino acids (93.7%) which contains higher levels of most essential amino acids (except Iysine) than soya bean with 94.9%. The K and Na availability are higher in Telfairia seed (58.8%) than that of soya bean seed cake (54.9%) (Esuoso et al., 1998; Odiaka et al., 2008). This indicates that Telfairia seed cake may be suitable to fortify foods and the seed oil serves as food oil for making margarine. The high oil content makes it a potential source of raw material for the vegetable oil industries in Nigeria. These justify the apparent increase in it production in Nigeria. The seeds are also used in confectionaries (Herklots, 1972). The seed are also used for polishing coldly made earthen ware pots and the dry shells of the fruit sometimes used for utensils (Giami et al., 1999). The fruit case and pulp of Telfairia which constitute 64% of whole fresh fruit weight can be used as feeding stuff for livestock (Odiaka et al., 2008, Egbekun et al., 1990) and the pectin content of the pulp (1.0%) has been used in the production of marmalade (Egbekun et al., 1998, Oluchukwu and Ossom, 1988)
The cotyledons are processed into seasonings, high-protein cakes, snacks, marmalade, infant weaning foods and flour bread of supplements (Giami et al., 2003). The seeds of the fluted pumpkin are believed to have lactation promoting properties and are therefore in high demand by nursing mothers (Schippers, 2000). The seed is also a source of edible unsaturated oil (Esuoso et al., 2000).
Locally, the roots are known as potent human poison and there are report of their use as fish and human poison (Ezuqwu and Nwodo, 2000; Akoroda 1986, 1990). The root extract though has not found any practical use in pharmacy, could be used as rodenticides because of the high saponin content and cucurbitacin-B which has been reported to cause pulmonary edema (Ezuqwu and Nwodo, 2000). The seed of fluted pumpkin have anti-nutrients, the concentration of which increase with maturity and as a result of this, immature seeds are preferred for food over mature ones (Schippers, 2000). The green leaves are rich source of folic acid, calcium, zinc, potassium, iron, vitamin A, C and K and low in crude fibre (Longe et al., 1983). Due to the richness of the leaves in iron it is used to cure anemia (Martin, 1984).
1.2 Justification of the Study
In many parts of the world and Nigeria in particular, the cultivation of production of Telfairia occidentalis has increased rapidly as a result of its economic values in terms of monetary return to the growers during dry season farming. The consumption of this vegetable, (Telfairia occidentalis) among others thus serves as cheap and important sources of proteins, minerals, vitamins and amino acids (Okafor, 1983). Despite its wide acceptance and spread throughout the Nigeria, utilization and economic return to the grower, there are scanty data or information on genetic identification of existing land races of Telfairia occidentalis. There is also a problem in differentiating existing land races from one another due to wide genetic variations among them. There is also little or no information on the mode of inheritance of some of the yield attributes such as inheritance of seed sized and seed colour among the races or cultivars. Therefore, it was on this basis that this study was carried out to identify, and differentiate existing germplasms and to determine the mode of inheritance of major yield related traits such as seed colour and seed sizes in Telfairia occidentaslis.
1.3 Objectives
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