The chromosome content and genotype of two wheat cell lines and of their somatic fusion product with oat.

Somatic hybridization seeks to genetically combine phylogenetically distant parents. An effective system has been established in bread wheat (Triticum aestivum L.) involving protoplasts from a non-totipotent cell line adapted to in vitro culture (T(1)) in combination with totipotent protoplasts harvested from embryogenic calli (T(2)). Here, we report the karyotype and genotype of T(1) and T(2). Line T(1) carries nine A (A-genome of wheat), seven B (B-genome of wheat) and eight D (D-genome of wheat) genome chromosomes, while T(2) cells have 12 A, 10 B and 12 D genome chromosomes. Rates of chromosome aberration in the B- and D-genomes were more than 25%, higher than in the A-genome. DNA deletion rates were 55.6% in T(1) and 19.4% in T(2), and DNA variation rates were 8.3% in T(1) and 13.9% in T(2). Rate of DNA elimination was B- > D- > A-genome in both T(1) and T(2). The same set of cytological and genetic assays was applied to a derivative of the somatic fusion between protoplasts of T(1), T(2) and oat (Avena sativa L.). The regenerant plants were near euploid with respect to their wheat complement. Six wheat chromosome arms-4AL, 3BS, 4BL, 3DS, 6DL and 7DL-carried small introgressed segments of oat chromatin. A genotypic analysis of the hybrid largely confirmed this cytologically-based diagnosis.