Production and genetic analysis of partial hybrids from intertribal sexual crosses between Brassica napus and Isatis indigotica and progenies

With the dye and medicinal plant Isatis indigotica (2n = 14) as pollen parent, intertribal sexual hybrids with Brassica napus (2n = 38, AACC) were obtained and characterized. Among a lot of F1 plants produced, only five hybrids (H1-H5) were distinguished morphologically from female B. napus parents by showing low fertility and some characters of I. indigotica, and also by having different chromosome numbers. H1-H4 had similar but variable chromosome numbers in their somatic and meiotic cells (2n = 25-30), and H5 had 2n = 19, the same number as the haploid of B. napus. GISH analysis of the cells from H1 and H5 detected one I. indigotica chromosome and one or two chromosome terminal fragments. New B. napus types with phenotypic and genomic alterations were produced by H1 after pollination by B. napus and selfing for several generations, and by H5 after selfing. A progeny plant (2n = 20) was derived from H1 after pollination by I. indigotica twice and had a phenotype similar to a certain type of B. rapa, showing that hybrid H1 likely retained all chromosomes of the A genome and lost some of the C genome in parental B. napus. The reasons for the formation of the partial hybrids with unexpected chromosomal complements and for the chromosome elimination are discussed. Key words: Brassica napus, Isatis indigotica, intertribal hybrid, genomic in situ hybridization (GISH), amplified fragment length polymorphism (AFLP), chromosome elimination. En employant la plante medicinale et tinctoriale Isatis indigotica (2n = 14) comme parent male, des hybrides sexuels inter-tribus avec le Brassica napus (2n = 38, AACC) ont ete obtenus et caracterises. Parmi un ensemble de plantes [F.sub.1] obtenues, seuls cinq hybrides (H1-H5) se demarquaient sur le plan morphologique du parent femelle B. napus en affichant une faible fecondite et des caracteres de l'I. indigotica en plus de s'en distinguer pour ce qui est du nombre de chromosomes. H1-H4 affichaient un nombre semblable bien que variable de chromosomes chez leurs cellules somatiques et meiotiques (2n = 25-30), tandis que H5 possedait 2n = 19 chromosomes, soit le nombre present chez un individu haploide du B. napus. Une analyse GISH des cellules des hybrides H1 et H5 a detecte un chromosome entier de l'I. indigotica ainsi qu'un ou deux fragments chromosomiques terminaux. De nouveaux types du B. napus presentant des alterations phenotypiques et genomiques ont ete obtenus suite au croisement de H1 avec le B. napus original (comme parent male) suivi des plusieurs generations d'autofecondation ou encore suite a l'autofecondation de H5. Un descendant de l'hybride H1 a 2n = 20 a ete obtenu suite a deux cycles de croisement avec l'I. indigotica (comme parent male) et il presentait un phenotype rappelant un certain type du B. rapa, ce qui suggerait que l'hybride H1 aurait vraisemblablement conserve tous les chromosomes du genome A et perdu certains des chromosomes du genome C du B. napus parental. Les auteurs discutent des raisons pouvant expliquer la formation d'hybrides partiels ayant des jeux chromosomiques inattendus et l'elimination chromosomique. Mots-cles : Brassica napus, Isatis indigotica, hybride inter-tribus, hybridation genomique in situ (GISH), polymorphisme de longueur des fragments amplifies (AFLP), elimination chromosomique. [Traduit par la Redaction]
Introduction Most aspects of chromosome behavior are considered to be under genetic control, as are most morphological characteristics (Rees 1961). For example, genetic control has been demonstrated for asynapsis (Beadle [...]