Karyotype Analysis and Chromosome Designations for Secale Cereale L. "Dakold"

Introduction Secale ccreale L., common rye, has drawn the attention of cytologists for a considerable length of time due to its econonlic importance. This species has been incorporated in a number of breeding programs, both at interspecific and inter~eneric levels. 0 Cytological studies on this species have been mainly concerned with the nature and behaviour of meiotic chron~osomes (Longley and Sando, 1930; Thompson, 193 1 ; Darlington, 193 3 ; Levan, 1942). Detailed study of the meiotic chrornoson~es and chron~omere analysis at pachytene has also been a t tem~ted and on the basis of these data. chron~oson~e maDs of all the seven airs kf chromosomes have been presented (Lima-de-Faria. '1952). Discovery I I , of accessory chronlosomes in this species makes this material very interesting to cytologists and a great deal of worlt has been done on this aspect (Alliintzing, 1949, 1954; Lima-de-Faria, 1948, 1952; Hikansson, 1957). Unfortunately, data on the detailed ltaryotype of this species are very meagre. Some of the cytologists have tried to worlt out the morphology of the somatic chroinosoines (Shmargon, 1938; Levan, 1942; Oinuma, 195 3; Riley and Chapman, 1958). Though the somatic chro~nosomes of rye are quite large in size and possess good stainability, their detailed nlorphology is very difficult to reveal. Except for the one pair of chromosomes with very proilounced secondary constrictions, other chron~osome pairs are rather difficult to distinwish.. With the introduction of addition-and substitution of s~ecif ic rve U I i chromosomes to other cereals, a critical identification of all the seven pairs of cl~rornosoines is an absolute necessity because the phenotypic characters do not always indicate an identifiable effect for each specific chromosome. These considerations led the authors to undertalte a thorougl~ analysis of the ltaryotype of rye. It was thought that if the individual rye chromosomes could be identified from their size. n~or~holocrv and arm index. the data would be of immense value in a DroDer idkntifi;ationu;f addition and sbstitution lines. I I The present report deals with a critical ltaryotype analysis of S. cereale Dakold, a variety used extensively in this laboratory in various breeding projects. Materials and Methods S. ce~eale Dakold, common rye, is a hardy winter type. Seed stoclts utilized in this study came from a foundation stock designated as Daltold 23 which is being maintained bv the Field Husbandry Department, University of Sasltatchewan, Sasltatoon, aska at chew an. Excellent fixation of the somatic chromosomes presented considerable difficulty. Several pre-fixative treatments were tried but it was found that pre-treGment in tap water for 24 hours at 0' to 2OC was most satisfactory.