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Fig. 2. Durum wheat x Th. bessarabicum hybrid, and its chromosome pairing in the presence and absence of Ph1. (A) Spikes of parental species—durum wheat (left), Th. bessarabicum (right)—and their intergeneric hybrid (center). (B) PMC of the triploid intergeneric hybrid (2n = 3x = 21; ABJ genomes) with Ph1 showing 21 I. Note complete absence of pairing because of the presence of Ph1. (C) PMC of the intergeneric hybrid durum Langdon (LDN) disomic substitution 5D (5B) x Th. bessarabicum, showing 2 III [one V-shaped (arrow) and one frying pan–shaped (arrowhead)] + 4 II + 7 I. Note extensive homoeologous pairing, a welcome feature from the breeding standpoint. Some pairing takes place between the wheat and grass chromosomes (see Fig. 2D). (D) Same hybrid as in (C) with meiotic chromosomes after fluorescent genomic in situ hybridization when the durum wheat A-genome (colored green) was probed with Triticum urartu DNA labeled with FITC, the J-genome was probed with Th. bessarabicum DNA labeled with Rhodamine (colored red), and the remaining chromosomes counterstained with DAPI (colored blue) belong to the B-genome with one D-genome chromosome from 5D. Note wheat–grass pairing (A-J pairing).
