A SYNTHESIS OF A 42-CHROMOSOME WHEAT

Abstract

THE solution of the jigsaw-like puzzle of the origin of the 42-chromosome wheats of the 'vulgare' or bread-wheat type has been attempted by various methods. A recent endeavour to synthesize a bread -wheat by crossing Triticumturgidum(2n = 28) with Aegilops speltoides (2n = 14) adds a new piece to the puzzle (W. P. Thompson, E. J. Britten and Jean C. Harding, Canad. J. Res., C, 21, 134 ; 1943). It is generally agreed that the monococcum group of wheats (2n = 14) has the chromosome sets AA and the majority of the emmers (2n = 28) the genoms AA and BB, while all the bread-wheats have the constitution AA BB CC, the C sets being derived in some way from some species of the genus Aegilops, one of the species of which, Aegilopscylindrica, seems to have the genoms CO DD. The new species is the result of an attempt to repeat the hypothetical events in the origin of common wheat by first crossing one of the emmer section with a species of Aegilops with 14 chromosomes, and then producing the fertile amphidiploid by doubling the number of chromosomes with the aid of colchicine.