Tel-Zur Noemi, Abbo Shahal, Bar-Zvi Dudy, Mizrahi Yosef
Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 84105, Israel.
Ann Bot. 2004 Oct;94(4):527-34. doi: 10.1093/aob/mch183. Epub 2004 Aug 25.
Hylocereus and Selenicereus are native to tropical and sub-tropical America. Based on its taxonomic status and crossability relations it was postulated that H. megalanthus (syn. S. megalanthus) is an allotetraploid (2n = 4x = 44) derived from natural hybridization between two closely related diploid taxa. The present work aimed at elucidating the genetic relationships between species of the two genera.
Crosses were performed and the putative hybrids were analysed by chromosome counts and morphological traits. The ploidy level of hybrids was confirmed by fluorescent in situ hybridization (FISH) of rDNA sites. Genomic in situ hybridization (GISH) was used in an attempt to identify the putative diploid genome donors of H. megalanthus and an artificial interploid hybrid.
Reciprocal crosses among four diploid Hylocereus species (H. costaricensis, H. monacanthus (syn. H. polyrhizus), H. undatus and Hylocereus sp.) yielded viable diploid hybrids, with regular chromosome pairing. Reciprocal crosses between these Hylocereus spp. and H. megalanthus yielded viable triploid, pentaploid, hexaploid and aneuploid hybrids. Morphological and phenological traits confirm the hybrid origin. In situ detection of rDNA sites was in accord with the ploidy status of the species and hybrid studied. GISH results indicated that overall sequence composition of H. megalanthus is similar to that of H. ocamponis and S. grandiflorus. High sequence similarity was also found between the parental genomes of H. monacanthus and H. megalanthus in one triploid hybrid.
The ease of obtaining partially fertile F1 hybrids and the relative sequence similarity (in GISH study) suggest close genetic relationships among the taxa analysed.
量天尺属和蛇鞭柱属原产于热带和亚热带美洲。基于其分类地位和杂交亲和性关系，推测大花量天尺（同义词：大花蛇鞭柱）是由两个近缘二倍体类群自然杂交产生的异源四倍体（2n = 4x = 44）。本研究旨在阐明这两个属的物种之间的遗传关系。
进行杂交，并通过染色体计数和形态特征对假定的杂种进行分析。通过rDNA位点的荧光原位杂交（FISH）确认杂种的倍性水平。使用基因组原位杂交（GISH）试图鉴定大花量天尺和一个人工倍间杂种的假定二倍体基因组供体。
四个二倍体量天尺属物种（哥斯达黎加量天尺、单刺量天尺（同义词：多根量天尺）、火龙果和量天尺属某物种）之间的正反交产生了可育的二倍体杂种，染色体配对正常。这些量天尺属物种与大花量天尺之间的正反交产生了可育的三倍体、五倍体、六倍体和非整倍体杂种。形态和物候特征证实了杂种起源。rDNA位点的原位检测与所研究的物种和杂种的倍性状态一致。GISH结果表明，大花量天尺的总体序列组成与奥坎波量天尺和大花蛇鞭柱相似。在一个三倍体杂种中，单刺量天尺和大花量天尺的亲本基因组之间也发现了高度的序列相似性。
易于获得部分可育的F1杂种以及相对的序列相似性（在GISH研究中）表明所分析的类群之间存在密切的遗传关系。
