Among the natural resources, plant biodiversity is the key to human existence and survival. Horticultural crops contribute to nutritional and livelihood security. Mankind depends on near about 5000 plant species worldwide to meet food and other needs. This number is just a fraction of total world flora of 2.5 lakh species of mosses, ferns, conifers and flowering plants. More than 50,000 plant species are meeting the food (calories) needs of human world wide. There is still greater dependence on a few plant species; 20 to 30 in global context. Horticultural crops encompass fruit crops, vegetables, ornamentals, plantation crops, spices, aromatic and medicinal plants, tuber crops and mushrooms. Temperate, subtropical and tropical horticultural crops are characterized by their adoption to varying ecology and land use patterns.
