利用正向逐步迴歸分析鳥梨實生後裔株高與枝幹生育特性之關係

Study on the Relationship between Plant Height and Shoot Characters of Bird Pear by Forward Stepwise Regression Analysis

將卓蘭、大湖及三灣三地區之鳥梨實生後裔之主要植株性狀與株高進行正向逐步迴歸分析，以瞭解各性狀對株高之貢獻度與相關性。1994年卓蘭系植株生長性狀對株高之貢獻度依次為節數、節間長度、幹截面積、幹徑及分枝數；大湖與三灣系同為幹徑、節數、節間長度、幹截面積及分枝數。1995年卓蘭系植株生長性狀對株高之貢獻度依次為幹徑、節數、節間長度、幹截面積、分枝數及枝刺數；大湖與三灣系前五個因子同為節數、節間長度、幹截面積、幹徑及分枝數，大湖系則有第六因子為枝刺數。1996年三個系統之植株生長性狀對株高之貢獻度前兩個因子均為節數與節間長度，第三因子起，在卓蘭系依次為幹截面積、枝刺數、皮木比、皮幹比、分枝數及皮層厚；大湖依次為枝刺數、幹截面積、幹徑、皮層厚、皮木比及皮幹比；三灣系為幹截面積、幹徑、皮層厚、皮幹比及皮木比。這些性狀對第三年株高的累計絕對係數（accumulated R^2）在三個系統均超過98%，且達0.01%的顯著水準。由以上結果顯示，節數、節間長度與幹的性狀，對當年株高的影響力最大；在多刺的卓蘭系統中，枝刺與株高的關係較密切，而分枝數則影響較小。

Forward stepwise regression analysis was used to understanding the relationship between plant height to plant characters of Bird pear. In 1994, the contribution order of plant characters to plant height were nodes (N), internode length (IL), trunk cross section area (TCSA), trunk diameter (TD), and number of blanches (B) of the plant collected from Chou-lan (Chou-lan line), and in Da-hu and San-wan line were TD, N, IL, TCSA, and B. In 1995, the order of Chou-lan line were TD, N, IL, TCSA, B and number of thorns (TH), for both of Da-hu and San-wan line the former 5 characters were N, IL, TCSA, TD and B. In 1996, nodes and internode length contributed the most of accumulated R^2 to plant height. The accumulated R^2 of all of the characters were more than 98% with 0.01% significantly related to plant height. The results showed that, nodes and internode length were the most important characters to current years plant height. In thorny group, for example Chou-lan line, thorn showed close relation to plant height, while blanches had less relation to plant height.