Theor Appl Genet (2002) 104:652–660 © Springer-Verlag 2002 Abstract Hybridisation between the annual diploid sun- flower (Helianthus annuus) and the perennial diploid spe- cies Helianthus mollis and Helianthus orgyalis was ob- tained by means of a normal crossing procedure or em- bryo rescue. Hybridisation success was low. All plants examined cytologically appeared to be diploid. However, the phenotypes of these diploids were not intermediate between the parents and, despite great variation, they re- sembled the female parent-type predominantly. Thirty five percent of plants issued from sunflower pollinated with perennial Helianthus had a phenotype resembling the female sunflower parent. On average, only 5% of the minimum number of expected RAPD and RFLP bands from male parents were recovered in plants produced from mature seeds after pollination of sunflower by H. mollis. More hybrids were found among plants ob- tained from embryo rescue, with an average of 25% of the male parent bands recovered per plant. Analysis of in- dividual plants indicated the occurrence of various levels of hybridisation. There was a significant positive correla- tion between the number of phenotype traits related to hybrid status and the number of bands derived from the male parent. A single hybrid plant might possibly repres- ent the product of a ‘normal’ hybridisation event. The mechanisms behind these unusual events and the conse- quences for the breeder are discussed. Keywords Helianthus · Sunflower · Interspecific hybrid Introduction Sunflower (Helianthus annuus L.) is an important oil crop with a narrow genetic background. Introgressed plants from wild forms and foreign species are used successfully by breeders (Korell et al. 1996a, b). Wide crosses between different species of Helianthus, espe- cially between annual and perennial species, are difficult to carry out, and successful hybridisation is usually ob- tained through the use of in vitro embryo rescue methods (Korell et al. 1996a). In this genus, all annual species and the majority of perennial species have the same number of chromosomes (2n=34). However, their geno- mes are different. We characterised at least three differ- ent genomes in addition to the common C-genome back- ground in the genus through a diversity study using RAPDs. Sunflower and all annual species carry the two genomes H and C and belong to the section Helianthus. Helianthus mollis Lam., Helianthus orgyalis DC and many perennial species carry the C, P and A genomes, and belong to the section Atrorubentes. Other perennial species carry only the C and P genomes, and belong to the Ciliares section (Sossey-Alaoui et al. 1998). Helian- thus appears as a segmental allopolyploid or palaeopoly- ploid genus (Wendel 2000). This genomic classification agrees with the classification of Schilling and Heiser (1981) based on phenotype. Attempts to obtain wide interspecific hybridisation in the genus Helianthus have met with some success, espe- cially with the help of embryo-rescue techniques (Georgieva-Todorova 1984; Christov 1991; Jan 1996; Sukno et al. 1998). Kraüter et al. (1991) obtained numer- ous hybrids between sunflower and perennial Helianthus via embryo rescue. Unexpectedly, the pollen viability of some hybrids was high. In annual×perennial crosses, it appeared that parental chromosomes were present as ad- ditions, and that amphiploidisation was necessary for good-fertility levels to be recovered. Natali et al. (1998) have reported on crosses between H. annuus and Jerusa- lem artichoke (Helianthus tuberosus) using somewhat different methods and techniques. Their chromosome studies suggest the addition of parental haploid numbers. However, these hybrids were found to be genetically polymorphic, with DNA alterations. Similarly, extensive genome changes were observed in newly synthesised Communicated by H.C. Becker N. Faure · H. Serieys · A. Bervillé · E. Cazaux · F. Kaan ( ✉ ) INRA UMR, 1097 Diversité et Génome des Plantes Cultivées, UR 1023, Génétique et Amélioration des Plantes, bâtiment 33, 2 place Pierre Viala, F-34060 Montpellier cedex 1, France e-mail: kaan@ensam.inra.fr Fax: +33-4-67-04-54-15 N. Faure · H. Serieys · A. Bervillé · E. Cazaux F. Kaan Occurrence of partial hybrids in wide crosses between sunflower (Helianthus annuus) and perennial species H. mollis and H. orgyalis Received: 23 March 2001 / Accepted: 28 June 2001