The Amphiploids 297 



evolved remains lor lurther study. Answering the question whether 

 this type arose as a segiegate, or directly from a diploid-tetraploid 

 hybridization requires more data.""- ^"" A jjattern for research has 

 been established.'""^ 



Another method for converting the tetraploid species into hexa- 

 ploids has been reported. ^-^ Planting the 28-chromosomal species in 

 the autumn instead of spring, a regular procedure for these hard 

 wheat types, after two, three, or four seasons the durum spring wheats, 

 28-chromosome species, suddenly change into the vulgarc or 42- 

 chromosomal soft wheat sj^ecies. There was no evidence of hybridiza- 

 tion, and no intergrading forms. This method obviously differs from 

 the two explanations given by Japanese and American geneticists for 

 the origin of hexaploid species. 



12.2-2: Other aiuphipJoids among Triticluae. The amphiploids 

 made from interspecific and intergeneric hybridization among Aegi- 

 lops, Triticiim, and Agropyron ha\e increased many iold.''' "•'• i^--^"' «"• "■*■ 

 88, 100. 101, 118. 66. 6s. 86. w^. 98. 110 ^^^^^^ ^\^^. flj-^t fertile Triticinn-Agropyron 



amphiploid was produced with colchicine in 1939.-'^ A wealth of 

 material is at hand to solve the basic problems that determine the 

 progress to be made in using amphiploids.'"' '-" Since all the cases 

 cannot be reviewed, a selection will be made to point out theoretical 

 and practical problems. 



Among Aegilops, the species have evolved by interspecific hybrid- 

 ization and chromosomal doubling.'*' There are diploid, tetraploid, 

 and hexaploid species rejjrcsented by haploid numbers, yi ^7, n ^ 14. 

 ?7 =: 21, respectively. Since Aegilops has contributed to hexaploid 

 wheat, a knowledge of these species is important even though the 

 group has little economic value of its own. 



In 1913 Cook discovered a hybrid in Palestine involving the Emmer 

 Triticurn dicoccoides and some form of Aegilops. Later, Percival 

 jjointed to Aegilops rylindrica as a contributor of the spelt characters 

 in the tetraploid Triticurn. Evidence accumulated suggesting that T. 

 aesiivum L. arose as a segregate out of a cross between T. dicoccoides 

 and A. cyliudrica. The amphiploid [n ^ \A) , Aegilops cylindricd 

 (n ^ 14) , was synthesized by crossing Aegilops caudata (n := 7) X A. 

 sqiKirrosa (n = 7) and doubling the chromosomes with colchicine.'"" 

 Now three sets of data come into focus. First, earlier taxonomic 

 wf)rk brought tetraploid Tritidim and the tetraj)loid Aegilops cylin- 

 (irira together. Second, the tetra]:)loid A. (\li}i(lric(i evolxed Irom two 

 diploid species, one being A. s(jiiarrosa. Ihird, the synthetic amphi- 

 ploid, Triticurn di( <)< ( oides var. spontaneoxnllosmn X Aegilops sr/uar- 

 rosa is similar to natmal Triticurn spelta.-'^'^^ In 1931 a sj)eltlike 

 sterile hybrid between tetraploid Triticuin diioccuni and Aegilops 

 sqiiarrosa was made by McFadden, l)ut for want of a ready method to 



