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Substantial autosyndesis in the two F1hybrids obtained by crossing Triticum turgidumvar. group durumMorris & Sears with Thinopyrum distichum(Thunb.) Löve and Th. junceiforme(Löve & Löve) Löve resulted in mean meiotic configurations of 14,12I; 4,8II; 0,38IIIand 0,75IVin the pollen mother cells (PMC’s) of the first hybrid, and 14,42I; 4,82II; 0,12IIIand 0,19IVin those of the second hybrid. These and other observations demonstrated that both the above tetraploid (2n=28) Thinopyrumspecies are segmental allopolyploids. The two intrageneric crosses of Th. distichumwith Th. elongatum(Host) D.R. Dewey and Th. junceiformeprovided the first direct cytological evidence linking the genomes of Th. distichumwith the J genome, thus proving that this southern hemisphere species indeed belongs to the same genus as northern hemisphere species such as Th. elongatumand Th. junceiforme. The Je1genome of Th. elongatumappears to be as closely related to the two genomes of Th. distichumas 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; 2,96IIIand 0,12IVin the PMC’s of their triploid hybrid. On these grounds it is recommended that the two genomes of Th. distichumbe designated Jd1and Jd2. The latter genomes appeared to be less closely related to the J1and J2genomes of Th. junceiformethan to Je1. New amphiploids were synthesized by treating the F1hybrids with colchicine. Fertile partial amphiploids AABBJd1Jd2were obtained by back-crossing the T. durum/Th. distichumamphiploids to T. durum. By applying the pivotal genome concept at the polyploid level the feasibility of producing new recombined genomes from the Jd1, Jd2and Je1genomes was demonstrated.

Polyploid features in some derivatives of Disahybrids prompted an investigation of their chromosome numbers and those of their hybrid parents, the parental species, and a few close relatives. Disa unifloraBerg. has 2n=36; D. cardinalisLinder, D. racemosaL.f., D. tripetaloides(L.f.) N.E. Br. ssp. aurataand D. venosaSw. have 2n=38, whereas D. sagittalis(L.f.) Sw. and D. uncinataH. Bolus have 2n=40. D. tripetaloidesssp. tripetaloidesfrom Joubertsgat is a natural triploid with 2n=57. Two of the hybrid derivatives, viz. DisaBetty’s Bay ‘Helderberg’ and DisaDiores ‘Colette’ are near tetraploids with 2n=68, whereas three others, viz. DisaFoam ‘Jeanette’, DisaHelmut Meyer ‘Pat’ and DisaUnimeyer ‘Apricot’ are near triploids with 2n=48, 54 and 52 respectively. The hybrids and especially their robust polyploid derivatives are most attractive and are ideal for the cut-flower industry.