Overcoming the barrier to interspecific hybridization of Fagopyrum esculentum with Fagopyrum tataricum

Summary Tartary buckwheat (Fagopyrum tataricum) was successfully hybridized with common buckwheat (F. esculentum), both diploid (2n=16), using the latter as male parent during bud pollination. The barrier normally encountered in such hybridization was overcome by enhancing the cross-compatibility of the two species, which was accomplished by synthesizing a unique genotype of common buckwheat. This novel plant was produced by selecting common buckwheat plants that exhibited, at isozyme loci PGM, SKDH and ADH, alleles with similar mobility to those found in tartary and then transferring these alleles to a single plant through six generations of breeding. Ovule culture was used to rescue the 7–10 day old embryos. On the rescue-culture medium 41% of the hybrid embryos formed calli larger than 200 m in diameter. Most ceased to grow before reaching 1500 m, but four out of 263 cultured ovules continued to grow as callus. One of these differentiated and formed callus with buds and shoots from which cloned plants were produced. The remaining embryos either did not grow at all or formed very small calli. When tartary was crossed with the original genotype of common buckwheat, only 22% of the hybrid embryos formed small calli and none differentiated. Hybridity of the calli and the plantlets was determined by RAPD and isozyme analysis, respectively. Flowers produced by the hybrid plants were of the same type (homomorphic) and size as those of tartary, but with white sepals like common buckwheat.Abbreviations CTAB cetyltrimethylammonium bromide - GA₃ gibberellic acid - IAA indoleacetic acid - IBA indolebutyric acid - PVP polyvinylpyrrolidone