Abstract: This research adopted the Huangjingui, Huangqi, Huangguanyin, Tieguanyin and Hongyafoshou as parent plants to make artificial hybridization between cultivars with various sprouting date and to observe the trend of genetic variation in the F₁ leaf-expansion period. Results showed that:① The F₁ leaf-expansion periods occurred a successive variation with the average value of their parent leaf-expansion periods as the central value, the variation range was large and the average value of the F₁ leaf-expansion period was close to the average value of their parents. ② In the combinations of early-sprouting and early-sprouting cultivars, the super-parental phenomenon in both positive and negative directions of genetic variation of shortening or postponing the F₁ leaf-expansion period were observed. In the combination of late-sprouting and early-sprouting cultivars, the F₁ leaf-expansion periods were located between their parents. In the combination of late-sprouting and middle-sprouting cultivars, the F₁ leaf-expansion period were mostly close to the that of middle-sprouting cultivars. ③ The male paternal showed more influence on the leaf-expansion period in F₁ generation. When the leaf-expansion period of male parent was earlier, the F₁ leaf-expansion period was also early in F₁ generation. If the leaf-expansion period of paternal plant were same, the leaf-expansion period in F1 generation was related to the difference of the leaf-expansion period between their parents. When the difference between their parental plants was small, the large variation of leaf-expansion period occurred in the F₁ generation. For these reasons, it is possible to acquire the hybrid with the earlier leaf-expansion period than their parental plants via through the hybridization between early-sprouting and early-sprouting cultivars. Simultaneously, it is possible to forecast the F₁ average leaf-expansion period in the F₁ generation and possible variation range in the F₁ generation according to the paternal leaf-expansion period, the average value and their difference of leaf-expansion periods between the two parents.

Key words: Breeding of tea plants, F₁ generation, Leaf-expansion period, Genetic variation