Interspecific hybridization between diploid Fagopyrum esculentum and tetraploid F. homotropicum

Yingjie Wang¹, Rachael Scarth², and Clayton G. Campbell¹

¹ Kade Research Ltd., Morden, MB. Canada ² Department of Plant Science, University of Manitoba, Winnipeg, Manitoba

Wang, Y., Scarth, R. and Campbell C. 2005. Interspecific hybridization between diploid Fagopyrum esculentum and tetraploid F. homotropicum. Can. J. Plant. Sci. 85: 41-48.

Abstract: The wild diploid species Fagopyrum homotropicum (2x=2n=16) has been used for buckwheat improvement, but, prior to this study, the tetraploid form (2n=4x=32) had not been hybridized with the cultivated species F. esculentum. The object of this study was to hybridize F. esculentum with tetraploid F. homotropicum to increase the genetic variability. Forty-one interspecific F1 hybrids were obtained through ovule rescue in vitro, with hybridity confirmed using morphological characters, chromosome numbers (2n=3x=24) and DNA analysis. The F1 plants were mainly sterile. However, seven seeds were set spontaneously on two hybrid plants, and a large number of seeds were obtained after colchicine treatment. The F2 plants were divided into two groups based on chromosome numbers and morphology. The first group was hexaploid plants (2n=6x=48) or hypohexaploid (2n=44-46), partially fertile with “gigas” features including increased height, dark green leaves, and large seeds with thick hulls. The second group of plants was diploid (2n=2x=16) (0ne plant had 17 chromosomes), with normal growth and fertility, and a combination of characters from both parents, indicating that genetic recombination had occurred during chromosome elimination. The diploid group was superior to the hexaploid group for use in buckwheat breeding programs due to the desirable characters and the ease of crossing. This is the first report of interspecific hybridization using different ploidy levels in the Fagopyrum genus.

Key words: Buckwheat (F. esculentum; F. homotropicum), interspecific hybridization, breeding, tetraploid, diploid, hexaploid, fertility