| I. Editorial 40 years after the discovery of right chromosome numbers of the genus Triticum H. KIHARA National Institute of Genetics, Misima, Japan It is already 40 years since the right chromosome numbers of wheat were found by two botanists. Their discoveries were made independently and confirmed each other. In Japan, in 1918, Sakamura reported in a short paper1) that the chromosome numbers of Triticum species show a polyploid relationship with 7 as the basic number, namely:
In U.S.A. Sax observed 28 chromosomes in the first nuclear division of the fertilized egg in T. durum. His paper was published also in 1918, whereupon he found polyploidy in this genus and went further into investigations of sterility and chromosome behavior in wheat hybrids2) (cf. the figures on the cover i and explanations on the cover iii). Until 1918, it was generally accepted that all wheat species have the same chromosome number, namely 8 haploid and 16 diploid chromosomes. It was therefore a great surprise to many cytologists and geneticists of the world, when these findings were reported. Particularly attention was drawn to the fact that Schulz's classification of wheat into three groups (1913) based upon morphological characters is in perfect agreement with their chromosome numbers, einkorn having 7, emmer 14 and dinkel 21 in haploid phase. That the Triticum species fell naturally into three groups has been concluded independently by 3 authors already in 1914, namely by Vavilov as a result of studying their resistance to the attacks of fungi, by Zade from serum reactions and by Tschermak from the degree of sterility they show when crossed. |
| 1) Sakamura, T. (1918) : Kurze Mitteilung uber die Chromosomenzahlen und
die Verwandt- schaftsverhaltnisse der Triticum-Arten. Bot. Mag. Tokyo,
32. 2) Sax, K. (1918) : The behavior of the chromosomes in fertilization. Genetics 3. Sax, K. (1921): Sterility in wheat hybrids I. Ibid. 6. Sax, K. (1922): Idem II, III. Ibid. 7. |
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