Global warming, environmental changes, water shortage, and sustainable development are the most up-to-date issues, which have challenged mankind. Researchers worldwide are engaged in addressing some of these problems, including reduction in carbon dioxide accumulation, and enrichment of perennial woody species on the terrestrial ecosystem. About 12 million hectares of the world's forests disappear every year. By 2025, the world population will reach 7. 5 billion, and the forest area will be reduced to well below 50 % of the current area. Reforestation is an important to prevent the loss of forest resources including timber, biodiversity and water resources. Therefore, subsequent volume of reforestation over the deforested land should be followed to safeguard the forests and maintain its size, which will require a continuous supply of planting material. Similarly fruit trees, including tropical and subtropical fruit trees, are consumed both as fresh and in the processed form including juices, beverages, and dried fruits. They are an important source of nutrition e. g. rich in vitamins, sugars, aromas and flavour compounds, and raw material for food processing industries. The production, cultivation and maintenance of tree species provide highly sustainable production systems that conserve soils, microenvironment and biodiversity. Fruit trees have longjuvenile periods and large tree size. In many fruit trees e. g. avocado and others controlled crosses are difficult to make due to massive fruit drop.

Global warming, environmental changes, water shortage, and sustainable development are the most up-to-date issues, which have challenged mankind. Researchers worldwide are engaged in addressing some of these problems, including reduction in carbon dioxide accumulation, and enrichment of perennial woody species on the terrestrial ecosystem. About 12 million hectares of the world's forests disappear every year. By 2025, the world population will reach 7. 5 billion, and the forest area will be reduced to well below 50 % of the current area. Reforestation is an important to prevent the loss of forest resources including timber, biodiversity and water resources. Therefore, subsequent volume of reforestation over the deforested land should be followed to safeguard the forests and maintain its size, which will require a continuous supply of planting material. Similarly fruit trees, including tropical and subtropical fruit trees, are consumed both as fresh and in the processed form including juices, beverages, and dried fruits. They are an important source of nutrition e. g. rich in vitamins, sugars, aromas and flavour compounds, and raw material for food processing industries. The production, cultivation and maintenance of tree species provide highly sustainable production systems that conserve soils, microenvironment and biodiversity. Fruit trees have longjuvenile periods and large tree size. In many fruit trees e. g. avocado and others controlled crosses are difficult to make due to massive fruit drop.