| I. Research Notes Mode of production and properties of a Triticale-strain with 70 chromosomes By Arne MUNTZING Institute of Genetics, Lund, Sweden For several years the present writer has been working with strains of Triticale (2n=56), representing a summation of the chromosome complements of Triticum vulgare (2n=42) and Secale cereale (2n=14). The best ones of these Triticale-strains have a rather satisfactory yield and other favourable properties though none of them is yet sufficiently good to be in practical use. As tetraploid strains of rye have been found to be quite vigorous and productive and two of them have already been released to the farmers, it seemed desirable to produce Triticale-types with 70 chromosomes, representing a combination of wheat and tetraploid rye (42+28=70). At first, however, this work was quite unsuccessful, owing to the fact that the primary cross, wheat x tetraploid rye, in spite of repeated attempts, gave a completely negative result. This may be caused by a lower rate of growth of the pollen tubes of tetraploid rye as compared with the pollen tubes of diploid rye. However, the desired result was obtained by crossing different strains of Triticale (2n=56) with diploid rye. In spite of the large difference in chromosome number this cross succeeds fairly easily and gives viable seeds. It is also possible to cross Triticale and tetraploid rye. After colchicine treatment of plants representing the first-mentioned hybrid combination a strain with 70 chromosomes was obtained. This strain really represents a combination of ordinary vulgare-wheat and tetraploid rye, but of the two rye genomes in the primary hybrid one came through the female parent, the other one through the pollen. From a practical point of view the 70-chromosome Triticale-strain is a complete failure, vigour and especially fertility being quite poor. Moreover, the cytological stability is very unsatisfactory, and the strain shows a marked tendency to revert to lower chromosome numbers. Thus, meiosis must be highly irregular. If further strains, representing the same genomatic combination, behave in a similar way, this indicates that four rye genomes cannot co-operate successfully with the genomes of hexaploid wheat. Triticale-types with 42 chromosomes (tetraploid wheat + diploid rye), at least under Swedish conditions, also have much poorer fertility than 56-chromosome Triticale-strains with 6 wheat and 2 rye genomes. These facts seem to indicate that the ratio of wheat to rye genomes may be important for the fertility of the Triticale-types. If the wheat genomes are numerous in relation to the rye genomes, the Triticale-types are fairly fertile, but if the relative proportion of rye genomes is increased this will on an average have deleterious consequences. |