ABSTRACT
The results showed significant variations in characters within and among genotypes in years. There were significant differences among the genotypes in the expression of plant height in the 2002 assessment. Oshosho genotype had the highest values in plant height corresponding to 37.3cm and 54.9cm in 2002 and 2003, respectively. In the number of branches per plant, the genotype, the year and the genotype x year interaction were all highly significant (P=.01). This trait approximately ranged from 5 – 35; 71 – 163 and 55 – 215 in 2002, 2003 and 2004 seasons, respectively. Canopy diameter and number of leaves per plant had significant variations across the years of evaluation. The yearly mean values for 2002, 2003 and 2004 for canopy diameter ranged from 29cm to 42cm, while the number of leaves per plant ranged from 100 – 213 across the different genotypes. The number of fruits per plant varied significantly in the different years. Also, the year, genotype and genotype x year mean square values were all highly significant. The highest three year mean values of approximately 62 and 54 were obtained in UNS2 and UNS3 for number of fruits per plant. Fresh fruit yield ranged from 0.7 – 7.4t/ha, 3.1 – 10.1 t/ha and 3.3 – 11.1t/ha in the 2002, 2003 and 2004 evaluation seasons, respectively. Shombo had the highest mean yield of 7.74t/ha. Tatase genotype had significantly the highest average fruit weight of 10.5g. Variations were also observed in the expressions of other characters as fruit length and diameter, pericarp thickness, number of seeds per fruit, fruit dry weight and seed weight per fruit. In genetic analysis, broad sense heritability estimates were high for most of the yield components and fruit characters. Fresh fruit yield had broad sense heritability value of 48.4%. High genetic advance of 42.7, 42.0 and 43.9 at 5% selection intensity were obtained for number of leaves per plant, number of nodes per plant and number of fruits per plant, respectively. Phenotypic variances were higher than the corresponding genotypic variances in all the characters. Estimates of correlation coefficients showed significant associations among the traits. Plant height had significant positive correlation of 0.96** and 0.94** with main stem length and fruit length in the total correlation analysis. Plant height had significantly negative correlation of -0.95 and -0.87 with fruit diameter and fruit moisture content. The number of nodes per plant had significant positive correlation with the following traits; number of fruits per plant (0.87**), fresh fruit weight (0.87**) and fresh fruit yield (0.93**), respectively. The number of fruits per plant had significant positive correlation with the other traits namely; canopy diameter, number of nodes per plant and fresh fruit yield. Fruit length had significant negative correlation value of -0.94** with fruit diameter and -0.91** with fruit moisture content. The chemical analysis of the fruits showed that crude protein varied from 6.13% in Nsky–lp to 8.75% in Shombo, Tatase and Nsky –rw. The Ascorbic acid content of the fruits ranged from 83mg/100g in Tarugu to 100mg/100g in Shombo. The total carotenoid content ranged from 6mg/100g to 34mg/100g while β- carotene ranged from 4 to 16mg/100g in Shombo and Dangarawa, respectively. Antinutritional compounds like tanin, phenol, phytate, saponin and oxalate were present. Successful crosses were more readily obtained from Sho x Nsky-rw than from Tat x Nsky–rw. The F1 plants of Sho x Nsky-rw had heterotic effects in both vegetative and fruiting attributes while Tat x Nsky–rw showed hybrid vigour in vegetative attributes only. A high rate of flower abortion was observed among the hybrids of Tat x Nsky–rw. Cytological investigations of the pollen mother cells of the F1 hybrids of Tat x Nsky-rw showed meiotic abnormalities. Prominent among these were a non-disjunction at Anaphase II of meiosis, resulting in three daughter nuclei, that was one ‘diploid’ and two haploid, instead of four haploid nuclei in the microsporophyte. Mitotic chromosome count revealed a somatic chromosome number of 2n = 24 in both Tatase and Nsky–rw. The karyotypic formulars proposed for these two genotypes are 8m + 3sm + 1t for Nsky-rw and 5m + 7sm for Tatase. The size class of the chromosome lengths in both genotypes was ‘medium-small’ as their mean chromosome length were within the range of 2 – 5mm. A satelite chromosome was observed in the somatic cells of Nsky–rw.
TABLE OF CONTENTS
Title page- – – – – – – – – – i
Certification – – – – – – – – – ii
Dedication – – – – – – – – – – iii
Acknowledgement – – – – – – – – iv
Abstract – – – – – – – – – – vi
Table of contents – – – – – – – – viii
Lists of tables – – – – – – – – – ix
Lists of figures – – – – – – – – xii
List of plates – – – – – – – – – – xvi
Introduction – – – – – – – – – 1
Literature review – – – – – – – – 4
Materials and methods – – – – – – – 14
Results and Discussion – – – – – – – 30
- Characterization and Evaluation of the Genotypes – – – 30
A (i) Field Characterization and Evaluation – – – – 30
(ii) Genetic Estimates – – – – – – – – 65
(iii) Correlation Estimate – – – – – – – 71
(iv) Genotype by Trait Biplot – – – – – – – 86
- Nutrient Evaluation – – – – – – – 93
- Discussions on Characterization and Evaluation of the genotypes – 98
2 A. Hybridization Results – – – – – – – 112
Assessment of the hybrids for growth and yield – – – 112
- Discussions on Hybridization of the genotypes – – – 138
3 A. Cytological Studies – – – – – – – 145
- Discussions – – – – – – – – 152
Summary and Conclusion – – – – – – 154
References – – – – – – – – – 161
CHAPTER ONE
INTRODUCTION
Capsicum belongs to the family, Solanaceae (Bosland and Votava, 2000). It is the only source of capsaicin, an alkaloid that is a digestive stimulant and an important ingredient of the daily diet of Nigerians. Capsicum peppers are valuable on account of their richness in ascorbic acid, which is an important Vitamin. The fruit colour is due to the presence of total carotenoid pigments. These consist mainly of capsanthin and capsorubin. The extent of the colouring matter is important for puree, spice and drug industries. Pepper colouring matter is also used to impert colour to food in traditional diets. Most C. annuum genotypes have unique aroma that is highly cherished in traditional diets of many countries. Flavour is a basic characteristic stimulating the desirability of food. Together with colour, texture and nutrition, it forms the cornerstone of contemporary food industries throughout the world (Blenford, 1997; Bosland and Votava, 2000). In Nigeria, peppers occupy the third position among the cultivated vegetables and consumers place a high premium on the aromatic types (Uzo, 1982). It has been reported that due to adverse health implications of most artificial flavourings, there has been an increasing demand for natural flavours (Hoch, 1997). Pepper is a good source of natural flavour.
There are diversities in characters which are not taxonomic per se but which have great significance to the breeder. Within C. annuum complex, several such variations in characters exist. A wide range of variability in morphology, agronomy, ecology, chemical composition and flavour have been observed. Wide variations occur in plant height, canopy spread, number of branches per plant and other agronomic traits such as number of fruits and fruit weight per plant. Variations also exist in fruit forms and quality traits. The fruit types may be distinguished by shape and colour. Often times, they are classified as pungent or non-pungent with variations in pungency level. The various fruit shapes have formed part of the basis for the identification for the different types.
Peppers contain several chemicals including water, volatile oil, capsaicinoids, resins, protein, fibre, vitamins and mineral elements, all at different concentrations in their fruits (Borget, 1993; Bosland and Votava, 2000). Those chemicals have importance for nutritional value, taste, colour and aroma. The vitamin C content of ripe fruits is enough to meet or exceed the adult recommended daily allowance (RDA), of 60mg (NRC, 1989). The carotenoids contribute to pepper colour and its nutritional value; the capsaicinoids are the alkaloids that give hot peppers their characteristic pungency and are also essential components of many drugs used in the treatment of arthritis and other ailments (Bosland and Votava, 2002). In developed countries, as in United Kingdom, market gardens are flourishing as a result of increasing demand for natural flavours and peppers are good sources of the essential oils responsible for natural flavours (Borget, 1993; Blenford, 1997). The aromatic compound in certain exotic pepper genotypes can be detected by taste at concentrations as low as 2 parts per trillion.
The mild flavours from different pepper genotypes are combined by the industrialist in wine production to achieve a characteristics flavour peculiar to their products. Flavour from pepper is widely exploited in puree, drug and food industries. Having a good understanding of the great industrial potential and general importance of peppers, it calls for concern that Nigerian genotypes have not been characterized in any deep detail. Characterization is fundamental to any meaningful breeding programme.
The wide variability in growth, yield and of the diverse fruit forms can be exploited to advantage as selection depends on the amount of variability existing in the germplasm. For rapid progress in selection, studies on the association of yield with component characters are essential in elucidating the degree of relationnship among the relevant traits. There is need to assemble the aromatic peppers of Nigeria and characterize them to determine the extent of variability and relationship between characters among the genotypes. Furthermore, the genetic variability between C. annuum genotypes may offer an opportunity for improving these genotypes through hybridization. Success in such direction might lead to the development of hybrid varieties that would meet the confectionery needs of industries. Thus this research was set up to:
- characterize the Nigerian aromatic pepper genotypes for growth, yield and nutritional and chemical composition.
- produce hybrids and assess their growth and yield potentials
- study the meiotic behaviour among the F1
determine the karyotipic status of some parental genotypes
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