Selection of female parents with high fertility and high combining
abilities for cross-breeding Populus tomentosa
Received: 20 October 2016 / Accepted: 11 May 2017
Ó Northeast Forestry University and Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract To select maternal parents with high fertility and
high combining ability during cross breeding of Populus
tomentosa Carr., the ploidy level of 75 female clones was
determined using ﬂow cytometry. In addition, genetic
variations and phenotypic correlations of seed traits and
early growth traits, as well as the general combining ability
(GCA) for seedling height (SH) and basal diameter (BD) of
all diploid half-sib families were examined. A total of 26
natural triploid clones were identiﬁed. For all diploid
families, family effects were signiﬁcant for inﬂorescence
length (IL), thousand kernel weight (TKW), seedling
emergence rate (SER), and for SH and BD. There was a
positive correlation between TKW and other traits,
excluding IL. The seed-bearing coefﬁcient (NS 9 SER)
ranged from zero to 32.4%. Clones 3-10-2, 2-8, 3119,
3206, and 3-10-1 had the best performance of the GCA for
SH and BD. Based on the fertility and GCA for SH and
BD, clone 3-10-2 and clone 3119 could be used as female
parents for controlled cross-breeding of P. tomentosa.
Keywords Fertility ability Á General combining ability Á
Genetic variation Á Half-sib family Á Populus tomentosa
Chinese white poplar, Populus tomentosa Carr. (family
Salicaceae, genus Populus, section Populus), is one of the
most important indigenous tree species in northern China.
Due to its high growth rate, excellent disease resistance,
and good wood quality, it plays an important role in wood
production, landscaping, and ecological protection (Zhu
and Zhang 1997).
Cross-breeding is commonly used by tree breeders of P.
tomentosa (Li and Zhu 1989; Zhu 1990; Zhang et al. 1999)
because it can broaden the genetic base and create richer
genetic variations. However, owing to low seed-bearing
abilities, few hybrid seedlings have been harvested
(Lin and Zhu 1988; Zhang et al. 1992). Thus, backcrossing,
as an alternative breeding strategy, was introduced for
genetic improvement (Lin and Zhu 1988, Li and Zhu
1989). During these backcrosses, diploid hybrids,
P. tomentosa 9 P. bolleana, were typically used as female
parents because of their high fertility and the large number
of hybrid seedlings that could be obtained (Lin and Zhu
1988; Zhang et al. 2006). These hybrids play an important
role in the triploid breeding program for P. tomentosa (Shi
et al. 2012). However, in cross-breeding practices, clones
of P. tomentosa were only used as male parents to provide
The arboretum, located in Guan County, Shandong
Province, began in 1986 and included 1047 clones of P.
tomentosa. Kang (1996) and Zhu et al. (1998) sampled 56
clones with rapid growth rates for chromosome counting,
and ﬁve natural triploid female clones were discovered. In
Project funding: This work was supported by the Special Fund for
Beijing Common Construction Project.
The online version is available at http://www.springerlink.com
Corresponding editor: Hu Yanbo.
& Xiang-yang Kang
National Engineering Laboratory for Tree Breeding, Beijing
Advanced Innovation Center for Tree Breeding by Molecular
Design, Beijing Laboratory of Urban and Rural Ecological
Environment, Beijing Forestry University, Beijing 100083,
J. For. Res.