CHAPTER ONE INTRODUCTION
Background
Pepper belongs to the genus Capsicum and is a member of the Solanaceae family that includes tomato, potato, tobacco and egg plant. The genus originated from Central and South America (Dagnoko et al., 2013). Pepper is the most important spice and vegetable crop in the world (Berhanu et al., 2011). It is considered to be the first spice to be used by man. There is archaeological evidence of pepper and other fossil foods from as early as 6000 years ago (Hill et al., 2013). The genus Capsicum has twenty-five wild and five domesticated species (Bosland and Votava, 2000; (Nkansah et al., 2011). The domesticated species are Capsicum annuum, Capsicum frutescens, Capsicum chinense, Capsicum pubescens and Capsicum baccatum. Among these, Capsicum annuum is the best known domesticated species in the world (Hot, 2010). The non-pungent form (bell pepper) is used by many people as green vegetable and chili peppers used as spice or condiment (Singh et al., 2006).
Hot pepper is one of the most famous and used spices in the world. Thus, it is now an integral part of most cultures of the world. Christopher Columbus is credited for the introduction of hot pepper to Europe in 1492 from America (Hot, 2010). Capsicum chinense is the hottest among the Capsicum species and Habanero and Scotch Bonnet are the hottest varieties of Capsicum chinense (Singh et al., 2006). Ted et al. (2012) reported that pungency is the most notable characteristic of hot peppers. The reason most people eat chili pepper is the heat or pungency associated with the fruit (Paul and Stephanie, 2010). Thus, it is also one of the general parameters considered for export (CEDA 2009). The pungency of hot pepper is due to one of its capsaicinoids (alkaloids) components of which the main one is capsaicin.
Capsicum (sweet and hot) has many benefits. Its potential uses and benefits cover many areas such as food and nutrition, medicine, cosmetics, plant based insecticides (PBI), crime
control/aerosols, and income generation ( Dagnoko et al., 2013). Nutritionally, hot pepper like any other Capsicum species is rich in vitamin A and C, calcium, phosphorus, and potassium. It has been reported that peppers are highly appreciated for their spicy flavor and nutritional value (Miguel et al., 2010). Medically, extract from hot pepper is known to be used for pain relief products (Berke and Shieh, 2001). Hot pepper can also be used for cosmetic production (Rehima, 2006). Ceballos-Muller and Toon, 2010.
Pepper is a common agricultural product produced and consumed in Ghana (Cellabos –Muller and Toon, 2010). It is one of the major vegetable crops exported in Ghana. It is a good income source for small producers and is significantly one of the foreign exchange earning vegetable crops (Bonsu et al., 2003). MiDA (2010) also reported that Chili peppers production in Ghana has been mainly for local consumption. However, export to the European market has been increasing. Ghana is the fifth largest exporter of chili peppers to the European Union and the demand of pepper has been increasing yearly by 17 percent on average since 2000 (MiDA, 2010). Despite this encouraging improvement that hot pepper has added to the export value of vegetables , statistics indicate that vegetable exports from Ghana decreased from 4, 156.2 tons in 2006 to 2, 165.1 tons in 2009 with a corresponding decrease in cash value from $2, 305, 825
(GH¢2, 123, 409) to 1, 308, 218 (GH¢1, 861, 974). There was therefore a 46% decrease in export quantities but with 36% increase in cash value in 2010. The decrease in vegetable production and export (including hot pepper) can mainly be attributed to lack of good planting materials or varieties that meet export standards (Nkansah et al., 2011).
Because the vegetable seed industry in Ghana is not potent, local seed companies import exotic seeds to satisfy local producers. Thus, farmers grow both the local and exotic varieties. There is also limited and current agronomic data on the performance of both local and exotic genotypes. Producers therefore are likely to continue planting varieties with low economic potential (Kwatei et al., 2014). Again, it has been reported that pepper producers in Ghana are
realizing about half the percentage of the attainable yields which indicates low production (MiDA, 2010). This may be assigned to low soil fertility, pests and diseases pressure, unavailability and high cost of irrigation systems, inadequate knowledge of improved technologies and the use of unimproved varieties (MiDA, 2010). It is essential then to assess the potential of the genetic stock of hot pepper varieties in order to have a clear picture of their genetic constitution and heritable proportion of important traits to facilitate selection for production and improvement programs.
Nyadanu et al. (2014), have reported that it is no longer an option but a necessity to breed improved varieties which satisfies the preferences of farmers and consumers in Africa.
Objectives
The main objective of the study was to evaluate variability in agro-morphological and fruit quality traits in hot pepper genotypes to aid selection of genotypes for commercial production as well as pepper improvement programs.
Specific Objectives
The specific objectives of the study were to:
- evaluate some agro-morphological and fruit quality characters of hot pepper genotypes
- determine genetic variation among hot pepper genotypes using phenotypic characters
- estimate heritability and interrelationship of the traits studied
- identify and select superior genotypes based on agro-morphological characters and some fruit quality traits.
CHAPTER TWO
LITERATURE REVIEW
Classification and Taxonomy of Capsicum Species
Pepper (sweet and hot) belongs to the genus Capsicum. The genus is a member of the Solanaceae family which include important crops such as eggplant, tomato, potato, tobacco, and petunia (Bosland, 1996). It is in the sub-family Solanoideae and tribe Capsiceae (Knapp et al., 2004). Capsicum species are diploids and most have 24 chromosomes (n = x = 12) with several wild species having 26 chromosomes (n = x = 13) (Tong and Bosland, 2003). Peppers are perennial woody plants but grown as herbaceous annuals in temperate areas (Jeffrey, 2005). Capsicum originated from Central and South America (Grubben and Mohammed, 2004). Christopher Columbus is credited for the discovery of Capsicum in 1492. It is believed that pepper has the earliest culinary history from far back 7000 BC (Debra, 2003). The genus Capsicum has five domesticated species namely: Capsicum annuum, C. baccatum, C. chinense,
C. frutescens, and C. pubescens (Berke and Shieh, 2001). It is estimated to have twenty five species. This is expected to expand with new species to be discovered (Eshbaugh, 1993). Capsicum annuum is the most cultivated among the five species (Csillery, 2006). The five domesticated species are further grouped into two taxonomic complexes; Capsicum annuum,
C. frutescens and C. chinense in one group (Pickersgill, 1988) while C. baccatum and C. pubescens are also in another complex (Walsh and Hoot, 2001).
- Morphology of Capsicum Species
Domesticated Capsicum species are differentiated by using morphological traits based on colour and flower morphology and seeds (Andrews, 1995). The flower of this genus is bisexual, hypogynous and mostly pentamerous (Bosland and Votava, 2000). In C. annuum, the flower is solitary. However, in other species they are borne in cymule especially in C. chinense and C. frutescens. The flowers are usually white but occasionally tinged with purple, and are borne
in the axils of the leaves or branches (Jeffrey, 2005). They have complete flowers with calyx, corolla, and male and female sex organs. The Capsicum calyx is broadly campanulate, ribbed, and about 2 mm long (Dharamadhaj and Prakash, 1978). The genus usually has five stamens with bluish anthers which are joined to the base of the corolla. The stamens dehisce longitudinally, exposing the pollen. Capsicum species have single style which are often longer than the stamens, especially in hot peppers. Stigma is club-shaped and in the domesticated the number of locules may vary between two and four or more. Variation is not in the number of locules in the same plant (Jeffrey, 2005).
Capsicum fruit is a berry (Knapp, 2002). Extensively, variations exist in fruit shape, size, wall thickness and fleshiness, colour and pungency. These are influenced by genetic and environmental factors (Andrews, 1995). Fruits at the tender stages are usually borne in an erect position. However, in some varieties it turns downward into a pendant position as it grows (Jeffrey, 2005). Pod length varies from less than 1 to 32.5 cm. The pedicel length also varies in different pod types. Fruit colours range from green, yellow, orange red /purple, brown, black, and white. (Chaim et al., 2003). Cultivated fruit reaches the mature green stage in 35-50 days after the flower is pollinated (Bosland and Votava, 2000).
The seeds of Capsicum are attached to the placenta walls. Seeds lack pubescence except for Capsicum pubescens. Seed weight varies according to species, variety, and growing conditions (Jeffrey, 2005).
- Environmental and Growth Conditions oafpsCicum Species
Capsicum species do not do well on dry or compacted soils. Sandy loam with pH range of 5.5-
6.8 is suitable for production. Well drained, efficient and constant supply of moisture are beneficial for production (Jeffrey, 2005). It is prone to frost damage (Watkins and Cantliffe, 1983a). Optimum day and night temperatures for seedlings and young plants range between 24 oC – 29 oC and 10 oC to 16 oC. The best temperature for fruit set ranges between 18 oC and 27
oC (Jeffrey, 2005). Efficient seed germination requires a constant temperature ranging between 15 °C and 30 °C (Randle and Homna, 1980; cf. Dell‘Aquila, 2004). Germination does not occur when seeds are exposed to temperatures below 8 °C or above 40 °C (Choi, 1985). In domesticated species, seed germination does not depend on any strict light requirements (Hernandez-Verdugo et al., 2001b). Peppers grown under greenhouse conditions are taller, and develop fragile tissue than those planted on the field (Gomez-Guillamon and Cuartero, 1987). Capsicum species are usually indeterminate. They have continuous sympodial branching with the individual branch systems functioning as relatively autonomous integrated physiological units (Thomas and Watson, 1988; cf. de Swart et al., 2004). Anthesis in pepper starts from 30- 42 days after planting (Gibbon and Pain, 1985; Khah and Passam, 1992). It is controlled by day length (Aleemullah et al., 2000). High temperature during fruit set has negative influence on productivity while low temperature deforms fruit shape (Rylski and Spigelman, 1982; Rylski, 1972).
- Importance of Capsicum Species
Pepper serves as a condiment in diverse dishes. The fruits are consumed fresh, dried or in processed form (Geleta, 1998; Seleshi, 2011). It has several nutritional benefits. The genus is rich in Vitamins A and C (Bosland and Votava, 2000). Lee and Kader (2000) reported that some pepper varieties contain seven times more vitamin C than orange. The vitamins A, C and beta-carotenoids in pepper are known to be powerful antioxidants (Simonne et al., 1997). Pepper may also contain magnesium, iron, thiamin, riboflavin, and niacin (Debra, 2003). Red form of Capsicum fruits contains lycopene and this is believed to have anti-cancer properties (Simmone et al., 1997).
Capsicum species has many medicinal benefits. Their medicinal use dates back to the days of the Mayas. They used them to treat asthma, coughs, and sore throats (Bosland, 1996). Pepper can also be used for the treatment of fevers and colds (Norman, 1992). Pharmaceutically, the
active compound capsaicin is used as a counter-irritant balm for external application (Carmichael, 1991). It is the active ingredient in Heet and Sloan’s Liniment, two rubdown liniments used for sore muscles (Bosland, 1996). Capsicum influences circulation, relieves gas and colic, aids digestion, and prevent infection in the body (Debra, 2003). Another beneficial use of pepper is in the area of crop protection where extracts from pepper is used as bio- insecticide. Bouchelta et al. (2003, 2005) reported that pepper extracts used on eggs and adults of the tabaci whitefly proved to be potent. Chili extracts applied on thrips, pod borers, and pod suckers on cowpea reduced their population (Oparaeke et al., 2005). Secondary metabolites such as alkaloids, saponins and flavonoid in Capsicum species are a source of toxicity which affect insects (Bouchelta et al., 2005). Oleoresin in pepper is used as spray to act as a non- lethal repellent to both animal and human targets (De, 2003) and serves as a valuable riot control agent and self-defense tool (Sanatombi and Sharma, 2006).
