Woody plants constitute an artificial and heterogeneous group of plants that share some common phenotypic characteristics but otherwise have no strong evolutionary relationships, nor do they share a common habitat. They are a primary source of fiber and timber, and also include many edible fruit species. Their unique phenotypic behavior includes a perennial habit associated with extensive secondary growth. Additional characteristics of woody plants include: developmental juvenility and maturity with respect to growth habit, flowering time, and morphogenetic response in tissue cultures;...

Genetic variability is an important parameter for plant breeders in any con ventional crop improvement programme. Very often the desired variation is un available in the right combination, or simply does not exist at all. However, plant breeders have successfully recombined the desired genes from cultivated crop gerrnplasm and related wild species by sexual hybridization, and have been able to develop new cultivars with desirable agronomie traits, such as high yield, disease, pest, and drought resistance. So far, conventional breeding methods have managed to feed the world's ever-growing...