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Culture contamination
Culture contamination is a problem to in vitro propagation due to rapid proliferation of pathogens (Enjalric, Carron & Lardet, 1998). With the exception of cryptic contaminants, many are visible at primary initiation. Generally, axenic cultures are preferred at any stage, and hence contaminated cultures are often discarded (George, 1993). Contaminants cause death of explants by exuding toxins or overgrowing the explants. Consequently, contaminants out compete and many adversely affect the growth of explants. Many plants are associated with symbiotic microbes that are contaminants in the growth media
Endogenous or endophytic microbes are often difficult to decontaminate although some are beneficial for the growth of explants (Herman, 1990). According to Cassells (1991), culture asepsis is important in any micro-propagation protocol.
Studies on U. kirkiana micro-propagation have been carried out (Maliro, 1997; Chishimba et al., 2000; Nkanaunena, 2002), but without success where explants have been excised from adult stock plants partly due to high contamination. In vitro propagation protocols of U. kirkiana plants were only developed using seedlings (juvenile plant materials) as stock plants (Maliro, 1997; Chishimba et al., 2000; Nkanaunena, 2002). However, as indicated above, it is not possible to ascertain the gender and future characters of U. kirkiana plantlets regenerated from the seedlings. There have been no scientific results available for micro-propagation of P. capensis tree species and successful protocols are yet to be developed.
P. capensis trees are monoecious (Fivaz & Robbertse, 1993), and hence determining the gender of the seedlings or embryos is not as critical as for U. kirkiana tree species. Consequently, use of seeds or embryos as planting materials for P. capensis will not affect the gender of the trees.
GENERAL INTRODUCTION
CHAPTER 1: LITERATURE REVIEW
1.1 Uapaca kirkiana fruit trees
1.1.1 Botany and ecological distribution
1.1.2 Importance and commercial potential
1.1.3 Production and cultivation
1.2 Jacket plum (Pappea capensis) tree species
1.2.1 Botany and ecological distribution
1.2.2 Importance and commercial potentia
1.2.3 Production and cultivation
1.3 Tree domestication process
1.4 Propagation methods
1.3.1 Sexual propagation
1.3.2 Vegetative propagation
1.3.3 Culture contamination
1.5 Mycorrhizae
1.6 Effects of phenolics on graft compatibility
1.6.1 Methods of separation for phenolic compounds
1.7 Summary
CHAPTER 2: IN VITRO PROPAGATION OF MATURE UAPACA KIRKIANA Müell Arg. TREES
2.1 Abstract
2.2 Introduction
2.3 Materials and methods
2.4 Results and discussion
2.5 Conclusion
CHAPTER 3: HISTOLOGICAL EVALUATION OF EARLY GRAFT COMPATIBILITY OF SCION/STOCK COMBINATIONS IN UAPACA KIRKIANA Müell Arg. TREE PROVENANCES
3.1. Abstract
3.2 Introduction
3.3 Materials and methods
3.4 Results and discussion
3.5 Conclusion
CHAPTER 4: EARLY RECOGNITION OF GRAFT COMPATIBILITY IN UAPACA Müell Arg. FRUIT TREES
4.1 Abstract
4.2 Introduction
4.3 Materials and methods
4.4 Results and discussion
4.5 Conclusion
CHAPTER 5: DIAGNOSIS OF PHENOLIC COMPOUNDS IMPLICATED IN GRAFT INCOMPATIBILITY IN UAPACA KIRKIANA Müell Arg. FRUIT TREES
5.1 Abstract
5.2 Introduction
5.3 Materials and methods ..
5.4 Results and discussion
5.5 Conclusion
CHAPTER 6: PRE-TREATMENT METHODS FOR IMPROVING JACKET PLUM (PAPPEA CAPENSIS) SEED GERMINATION
CHAPTER 7: IN VITRO PROPAGATION OF JACKET PLUM (PAPPEA CAPENSIS) TREE SPECIES
CHAPTER 8: JACKET PLUM (PAPPEA CAPENSIS) PLANT REGENERATION THROUGH INDIRECT SOMATIC EMBRYOGENESIS
