Studies on the tissue culture and potential for the development of a genetic transformation system for avocados (Persea americana Mill.)

The avocado industry needs improved cultivars with better agronomic traits such as increased resistance to pests and diseases. These could be developed with biotechnological approaches to breeding such as the use of genetic engineering. a prerequisite to the use of this technique if the development of an efficient in vitro regeneration system. The objective of this study therefore, was to develop a tissue culture protocol suitable for the propagation and transformation of avocado. To do this, the effects of the preconditioning of mother plants, different explant sources, growth regulator pretreatments of explants and different compositions of the growth medium were examined. The results of these confirmed that avocado is typical of woody plants, as avocado tissues shows a decrease in morphogenetic capacity as they age, and the most juvenile explant, the embryonic shoot axis, showed the highest potential for shoot regeneration. Regrowth of explants after removal of the first flush of shoots resulted in the production of shoot bases in vitro. Shoot bases were most efficiently produced when embryonic axes were dissected transversely to the axis of growth. This study has resulted in the production of an efficient system for the production of multiple shoots from embryonic shoot tissues of avocado through the induction of shoot bases. This tissue culture system could be extended to the use of somatic tissues as a source of explants. If shoot bases can be established from such tissues, this will provide a means by which avocado can be clonally propagated and provides a system by which genetic transformation and other techniques of biotechnology can be applied to the production of new and superior cultivars