Abstract: I-69(Populus deltoides Bartr. cl. "Lux" (I-69/55)) as a female parent was crossed with three different male parents in 1983. Three hybrid combinations were: I-69×I-63 (P. deltoides Bartr. cl. "Harvard"(I-63/51)), I-69×P. x euram. cv. serotina, and I-69 ×P. nigra(from Xinjiang), numbered as No. 34, No. 37 and No. 32, respectively. After nursery test 21 hybrid clones of I-69 half-sib family were selected out to continue field test in Mian County of Shanxi Province in the fall of 1985. I-69 and local mainly-cultivated P. x euram. clone were used as two controls. After four growth seasons, the results indicated that: the height and DBH of the clones of combination No. 34 was significantly higher than that of combination No. 37, No. 32 and local P. x euram. clone from age 2 to age 5; based on all clones (23) tested and clones (21) of I-69 half-sib family, the estimated value of broad-sense heritability(h²) of height and DBH increased as age increaed, ranging from 0.50 to 0.56 at age 2 and from 0.85 to 0.95 at age 5; however, the estimated value of broad-sense heritability of height and DBH was low for full-sib clones(14) of hybrid combination No. 34. Twenty-three clones tested were divided into three groups using the method of systematic cluster analysis: (1) fast-growing and high resistance to B. horsfieldi(G1), including three clones such as 34-17, 34-135 and 34-314; (2) fast-growing but less resistant(G2), including twelve cottonwood clones such as I-69 and 34-301, etc.; (3) growing slowly and less resistant(G3), including eight eurameicana poplar clones. The difference of resistance rate to B. horsfieldi between G1 and either G2 or G3 is statistically significant. Mainly taking the resistance into account, clones 34-17 and 34-135 (resistance rate 100%) were combined together named Nan-kang No. 1, clone 34-314 (resistance rate 87.5%) was named Nan-kang No. 2.

Key words: Poplar, Resistant Breeding, Batocer horsfieldi(Hope.), Pest resistance rate Height, DBH, Heritability