Integrating biotechnology into tree improvement programs.

Time is a major constraint in the progress of tree improvement programs. Four ways in which time influences the tree improvement process are (i) evolutionary time, (ii) time to harvest, (iii) time to achieve phenotypic stability, and (iv) time to reach reproductive maturity. The ways in which each of these affects the three phases of a tree improvement program (conservation, selection and breeding, and propagation) are identified and discussed. How biotechnological techniques, as well as other enabling technologies, address the time constraint problem is also discussed. The biotechnological approaches include tissue culture, molecular genetics, and genetic engineering; the enabling technologies include early testing and flower induction. Through tissue culture it is possible to increase genetic gain per unit time and increase total genetic gain by using more of the total genetic variation. Development of high-resolution linkage maps, through application of molecular genetics technology, will provide new a...