Comparison between diploid and tetraploid forms of Fagopyrum homotropicum in intraspecific and interspecific crossability and cytological characteristics

Yingjie Wang¹, Rachael Scarth² and Clayton Campbell¹

¹ Kade Research Ltd. Morden, Manitoba, Canada R6M 1E9. ² Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

Yingjie Wang, Rachael Scarth and Clayton Campbell. 2002. Comparison between diploid and tetraploid forms of Fagopyrum homotropicum in intraspecific and interspecific crossability and cytological characteristics. Fagopyrum 19: 23-29

Abstract: Fagopyrum homotropicum is an phylogenetically intermediate species between the two cultivated species, F. esculentum and F. tataricum. It is of interest to distinguish between the diploid (2n = 2x = 16) and tetraploid (2n = 4x = 32) forms within F. homotropicum and to describe the relationships between F. homotropicum and the two cultivated species. Hybrids were developed from both intraspecific crosses within F. homotropicum and interspecific crosses between F. homotropicum and the two cultivated species. Accessions that had the same ploidy level within F. homotropicum were easily crossed but, with one exception, seed abortion occurred. F. homotropicum showed cross compatibility with both F. esculentum and F. tataricum. The hybrids between F. esculentum and F. homotropicum 2x were fertile, suggesting that the genetic backgrounds were similar between the two species. In the intraspecific and interspecific crosses, hybrids between the 2x and 4x forms of F. homotropicum were sterile with 24 chromosomes; it was concluded that eight chromosomes were from the 2x form and 16 chromosomes were from the 4x form. The F. homotropicum 2x was more compatible with F. tataricum than F. homotropicum 4x, but F. homotropicum 4x was more compatible with F. esculentum than F. homotropicum 2x. Both unilateral and bilateral compatibility exist between F. homotropicum and F. esculentum. The allotetraploid origin of F. homotropicum 2n = 4x =32 was confirmed, based on the evidence of normal pollen viability and high seed productivity, stable chromosome number, normal chromosome pairing at meiosis, and the karyotype with two distinct groups of eight somatic chromosomes.

Key words: hybridization, crossability, F. homotropicum, allotetraploid, chromosomes