Reproductive Isolation of Triticum Boeoticum and Triticum Urartu and the Origin of the Tetraploid Wheats

Abstract

The diploid wheats Triticum boeoticum and T. urartu are sympatric with one another throughout the geographic range of the wild tetraploids. Reciprocal crosses between ecogeographic types within each diploid species gave viable seed, but interspecific crosses consistently gave viable seed only when T. boeoticum was the female parent. Apparently urartu cytoplasm in combination with the boeoticum genome resulted in nonviable seed. The endosperm failed to develop normally despite regular endosperm fertilization. The F1 plants obtained were completely self sterile although they showed regular intergenomic pairing (7II) at meiosis. Presumably the accumulation of cryptic differences between the two closely related genomes under reproductive isolation accounts for this sterility. The same accumulated cryptic differences could largely account for the preferential diploid pairing in the tetrapolid wheats which presumably were derived from such hybrids by chromosome doubling. The behavior of reciprocal crosses between the diploids and tetraploids suggested that T. boeoticum contributed the cytoplasm to both of the wild tetraploid species.

Geographic differentiation of domesticated einkorn wheat and possible Neolithic migration routes

“…To this end, 136 landraces of einkorn with rather wellknown origin were selected. Nine accessions of wild einkorn and three accessions of T. urartu (the donor of the A genome to durum/emmer and bread wheats, not fertile with einkorn but morphologically almost identical to wild einkorn; Johnson and Dhaliwal, 1976;Heun et al, 2008) were included into our analyses as reference points. The resulting 148 accessions were fingerprinted by DArT-seq DNA markers, a sequence-based improvement of the 'diversity array technology' (DArT) allowing whole-genome analyses (Wenzl et al, 2004).…”

Genes encoding plastid acetyl-CoA carboxylase and 3-phosphoglycerate kinase of the Triticum / Aegilops complex and the evolutionary history of polyploid wheat

“…These two diploid einkorn wheats produce sterile hybrids, indicating that they are valid biological species (4). T. urartu exists only in its wild form.…”

Differentiation between homoeologous chromosomes 1A of wheat and 1Am of Triticum monococcum and its recognition by the wheat Ph1 locus.

“…Both approaches are employed here to examine the nature of differentiation, and its recognition by Phl, between a single pair of closely related homoeologous chromosomes, 1A of wheat and lAm of T. monococcum L. (2n = 2x = 14). T. monococcum is closely related to T urartu, the source of the wheat A genome, as indicated by the observation that their chromosomes form seven MI bivalents in their hybrids (28 losomic lAL X T monococcum ssp. aegilopoides G1777 and was five times backcrossed to CS monotelosomic (Mt) IAL (29).…”