© 2012 Science From Israel / LPPLtd., Jerusalem Israel Journal of Plant Sciences Vol. 60 2012 pp. 325–334 DOI: 10.1560/IJPS.60.3.325 *Author to whom correspondence should be addressed. E-mail:telzur@bgu.ac.il Intergeneric hybridization within the tribe Hylocereeae, subfamily Cactoideae (Cactaceae) Noemi Tel-Zur, a, * Joseph mouyal, b aroldo CisNeros, a aNd yosef miZrahi b a French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer 84990, Israel b Department of Life Sciences, Ben-Gurion University of the Negev, Be’er Sheva 84105, Israel (Received 10 August 2011; accepted in revised form 12 February 2012) ABSTRACT Controlled hand-cross-pollinations were performed among the genera Hylocereus, Selenicereus, and Epiphyllum and synthetic intergeneric hybrids were obtained. Parental lines and the intergeneric hybrids were studied for their nuclear DNA (2C) content and for their morphological and phenological characteristics. Hybrids between Hylocereus and Selenicereus species produced viable seeds, a inding that showed the lack of post-zygote barriers. Partial to complete sterility was observed in the intergeneric Epiphyllum × Selenicereus hybrids. The dominant relationship be- tween the alleles controlling morphological and phenological traits was elucidated. Among the traits studied, the presence of spines and/or hairy-spines on the fruit peel, the co-dominance of the ripening time, and the dominance of the high number of shoot ribs were the most signiicant characteristics proving hybridization. Further development of species-speciic molecular markers will be valuable for a suitable taxonomic description of these species and for future breeding and genetic studies of these genera with high horticultural potential. Keywords: Epiphyllum, hand-cross-pollination, Hylocereus, Selenicereus, wide hybridization INTRODUCTION Wide hybridization can occur between individuals from two different species of the same genus or from spe- cies belonging to two different genera (Sharma, 1995). However, mating between two different species is pre- vented by mechanisms of reproductive isolation, which include pre- and post-zygote barriers (Rieseberg and Willis, 2007). These barriers reduce the possibility of gene low, thereby maintaining the integrity of each spe- cies and hence facilitating the development of speciic characteristics (Widmer et al., 2009). Successful wide hybridization has resulted in the development of inter- speciic and intergeneric hybrids, and the new plant ma- terial produced is a valuable tool in breeding programs and for the study of the genetic relationships between species and genera. To obtain synthetic interspeciic or intergeneric hybrids, pre- and post-zygote barriers are frequently overcome by the development and use of a variety of technologies such as ovary, ovule, or embryo rescue, pollen storage, somatic hybridization and in vi- tro fertilization (Sharma et al., 1996; Metz et al., 2000; Liu et al., 2005; Kranz and Scholten, 2008). Vine cacti [Cactaceae, subfamily Cactoideae, tribe Hylocereeae (Britton and Rose) Buxbaum] are night blooming epiphytes that are endemic to the Americas (Barthlott and Hunt, 1993). According to the New Cactus Lexicon (Hunt, 2006), the genera Hylocereus (Berger) Britton and Rose, Selenicereus (Berger) Brit-