Hybrid origin of “Bauhinia blakeana” (Leguminosae: Caesalpinioideae), inferred using morphological, reproductive, and molecular data

Abstract

Bauhinia blakeana (Leguminosae subfam. Caesalpinioideae tribe Cercideae), or the Hong Kong Orchid Tree, is of great horticultural value. It is completely sterile and is shown here to be the result of hybridization between the largely sympatric species, B. purpurea and B. variegata. Although the analysis of patterns of morphological variation revealed only a few examples of phenotypic intermediacy, study of intersimple sequence repeat (ISSR) markers enabled unequivocal identification of the parental species due to the presence of additive inheritance of alleles and the absence of any bands that are unique to B. blakeana. Investigation of aspects of the reproductive biology of the taxa furthermore revealed that the parental species are largely xenogamous, have flowering periods that overlap seasonally and temporally, and share common pollinators. Evidence is provided to show that B. blakeana is not naturally stabilized and is only maintained horticulturally by artificial propagation. It is therefore recommended that the hybrid be regarded as a horticultural cultivar rather than a naturally occurring species; a new cultivar name, Bauhinia 'Blakeana', is accordingly validated.

Esfingofilia e sistema de reprodução de Bauhinia curvula Benth. (Leguminosae: Caesalpinioideae) em cerrado no Centro-Oeste brasileiro

“…e B. corymbosa Roxb. e a autocompatibilidade em B. pauletia (Heithaus et al 1974), B. purpurea L. e B. variegata L. (Lau et al 2005). Esterilidade é observada em B. x blakeana, espécie oriunda da hibridização entre B. purpurea e B. variegata (Lau et al 2005).…”

Vegetative propagation of bauhinia x blakeana, an ornamental sterile tree

“…Bauhinia x blakeana Dunn belongs to the Fabaceae family and is a natural hybrid derived from the cross between B. purpurea L. and B. variegata L. This ornamental tree has been much cultivated in gardens, streets and parks of subtropical and temperate regions (LAU et al, 2005), showing easy adaptation (MAK et al, 2008). It is deciduous and produces dark pink fragrant flowers, which are the symbol of its original habitat, the Island of Hong Kong, in China (LAU et al, 2005;MAK et al, 2008).…”

“…It is deciduous and produces dark pink fragrant flowers, which are the symbol of its original habitat, the Island of Hong Kong, in China (LAU et al, 2005;MAK et al, 2008).…”

“…According to Lau et al (2005), this hybrid is completely sterile, as different fertilization methods originated no seeds. The authors also believe that B.…”

“…Therefore, in order to preserve the species, it is essential to artificially propagate it. Cuttings or grafting on rootstocks of same genus species are the most indicated propagation methods (LAU et al, 2005;MAK et al, 2008).…”