J Syst Evol ›› 2014, Vol. 52 ›› Issue (4): 477-486.DOI: 10.1111/jse.12079

• Research Articles • Previous Articles     Next Articles

New insights into the hybrid origin of Malus toringoides and its close relatives based on a single-copy nuclear gene SbeI and three chloroplast fragments

1,2Liang TANG 1,2Ju LI 1,2Si TAN 1,2Ming-Xia LI 1,2Xiang MA 1,2Zhi-Qin ZHOU*   

  1. 1(Key Laboratory of Horticulture Science for Southern Mountain Regions, Ministry of Education, Chongqing, China)
    2(College of Horticulture and Landscape Architecture, Southwest University, Chongqing, China)
  • Received:2013-07-17 Published:2014-03-20

Abstract: Malus toringoides Hughes and its close relatives, M. maerkangensis M. H. Cheng et al., M. setok Vassilcz., and M. xiaojinensis M. H. Cheng & N. G. Jiang were supposed to derive from hybridizations. However, molecular data are still inadequate to corroborate the hybrid origin hypotheses. In this study, we sequenced a single-copy nuclear gene SbeI and three chloroplast fragments and carried out phylogenetic analyses to investigate the evolutionary origins of the above four putative hybrid taxa. The hybrid nature of M. toringoides is confirmed by the detection of two distinct types of SbeI sequences from it. The chloroplast and SbeI gene phylogenies show that the maternal progenitor of M. toringoides is closely related to M. sikkimensis N. P. Balakr. and M. spectabilis Borkh., and the paternal progenitor is most likely M. transitoria C. K. Schneid. The hypothesis that M. kansuensis (Batalin) C. K. Schneid. is one of the parents of M. toringoides is not supported. Malus maerkangensis and M. xiaojinensis might have originated through hybridization between M. toringoides and M. kansuensis, whereas M. setok is genetically closely related to M. toringoides. The three close relatives of M. toringoides were designated as three novel species by some researchers, however, as they were all apomictic with limited distribution areas and they originated from hybridization and polyploidization, we recommend that their species status should be re-evaluated.

Key words: close relatives, hybrid origin, hybridization, Malus toringoides, single-copy nuclear gene.