Genomic relationships in Thinopyrum

Abstract

Substantial autosyndesis in the two F1 hybrids obtained by crossing Triticum turgidum var. group durum Morris & Sears with Thinopyrum distichum (Thunb.) Löve and Th. junceiforme (Löve & Löve) Löve resulted in mean meiotic configurations of 14,12I; 4,8II; 0,38III and 0,75IV in the pollen mother cells (PMC’s) of the first hybrid, and 14,42I; 4,82II; 0,12III and 0,19IV in those of the second hybrid. These and other observations demonstrated that both the above tetraploid (2n = 28) Thinopyrum species are segmental allopolyploids. The two intrageneric crosses of Th. distichum with Th. elongatum (Host) D.R. Dewey and Th. junceiforme provided the first direct cytological evidence linking the genomes of Th. distichum with the J genome, thus proving that this southern hemisphere species indeed belongs to the same genus as northern hemisphere species such as Th. elongatum and Th. junceiforme. The Je1 genome of Th. elongatum appears to be as closely related to the two genomes of Th. distichum as it is to the genomes of Th. scirpeum (K. Presl) D.R. Dewey and Th. junceiforme, producing mean meiotic configurations of 2,91I; 4,36II; 2,96III and 0,12IV in the PMC’s of their triploid hybrid. On these grounds it is recommended that the two genomes of Th. distichum be designated Jd1 and Jd2. The latter genomes appeared to be less closely related to the J1 and J2 genomes of Th. junceiforme than to Je1. New amphiploids were synthesized by treating the F1 hybrids with colchicine. Fertile partial amphiploids AABBJd1Jd2 were obtained by back-crossing the T. durum/Th. distichum amphiploids to T. durum. By applying the pivotal genome concept at the polyploid level the feasibility of producing new recombined genomes from the Jd1, Jd2 and Je1 genomes was demonstrated. Outosindese in die twee F1-hibriede wat verkry is deur Triticum turgidum L. var. groep durum Morris & Sears met Thinopyrum distichum (Thunb.) Löve en Th. junceiforme (Löve & Löve) Löve te kruis, het gemiddeld 14,12I; 4,8II; 0,38III en 0,75IV in die mikrosporosiete van die eerste hibried tot gevolg gehad, en 14,42I; 4,82II; 0,12III en 0,19IV in dié van die tweede. Hierdie waarnemings dui op segmentallopoliploїdie in beide bogenoemde tetraploïede (2n = 28) Thinopyrum-soorte. Die twee intrageneriese kruisings van Th. distichum met Th. elongatum (Host) D.R. Dewey en Th. junceiforme het die eerste direkte sitologiese getuienis verskaf dat die genome van Th. distichum J-genome is. Sodoende is bevestig dat die inheemse soort, Th. distichum, aan dieselfde genus behoort as soorte soos Th. elongatum en Th. junceiforme wat in die noordelike halfrond voorkom. Die Je1 -genoom van Th. elongatum is bykans net so naverwant aan die twee genome van Th. distichum as aan die genome van Th. scirpeum (K. Presl) D.R. Dewey en Th. junceiforme, aangesien die triploïede hibried van eersgenoemde twee soorte se mikrosporosiete gemiddeld 2,91I; 4,36II; 2,96III en 0,12IV gehad het. Op grond van hierdie bevindings word aanbeveel dat die twee genome van Th. distichum Jd1 en Jd2 genoem word. Laasgenoemde genome blyk nader verwant te wees aan die JVgenoom as aan die J1- en J2-genome van Th. junceiforme. Nuwe amfiploïede is ontwikkel deur die F1-hibriede met kolchisine te behandel. Vrugbare gedeeltelike amfiploïede AABBJd1Jd2 is verkry deur die T. durum/Th. distichum-amfiploïede met T. durum terug te kruis. Die toepassing van die spilgenoomkonsep op die poliploïede vlak het dit moontlik gemaak om nuwe rekombinante genome uit die Jd1 -, Jd2 - en Je1 - genome te ontwikkel.