Conclusions

Genome symbols of Agropyron species (conventional classification) indigenous to Japan are at present known to be SH for tetraploidy and SHY for hexaploidy. The genomes are common to Elymus (in the narrow sense) species regardless of morphological distinction between genera. In a detailed study oA´rn the cross compatibilities, which was wide-ranging, aided by embryo-rescue, throughout the Triticeae species available at hand in Japan, a tendency was revealed that the genotype the primary factor in the production of the hybrids that finally develop into mature hybrid plants. This genotype, which is the difference reflecting the phylogenetic groups (genera etc.), may play barrier to separate each one from another. We went deep into the investigation of the anomalous phenomena, often observed cytologically. It could be thought that there are genotypes, which produce chromosome inability or another to keep cells under a stable condition; there are genotypes causing chromosome elimination and irregular cytokinesis. The fact that possible amphiploid formation or the other way making limitation to polyploidization higher than a certain level may be an effect of genotype or genotypes concerning to the factors producing these phenomena. Author, therefore, proposed that we must introduce an idea for ploidy formation, which is a genotype conditioning polyploidy that may be called "definitomodis genetic conditions". Details of this and equally the factors, which produce complete sterility despite of high chromosome pairing that occur in some interspecific hybrids requires further deep investigations.

From ecological point of view, three Japanese Agropyron, A. tsukushiense, A. humidorum and A. ciliare, species show unique adaptation and tolerance to the unfavorable summer conditions with long lasting rainy season of Japan, called "Baiu". The species, then, genotypes or genes, determining tolerance conditions, will be fundamental future genetic resources both for theoretical and applied research.

Acknowledgments

The author thanks very much Professor Dr. G. P. Redei,University of Missouri-ColumbiA´ra for kindly critically reading the manuscript and especially for many valuable suggestions. Sincere gratitude is expressed to the late Dr. S. Matsumura for giving me an opportunity to initiate my studies and to have good appreciation for the genus Agropyron, and giving me plant materials more than 50 years ago. I am indebted to the late Dr. E. R. Sears, University of Missouri, who gave me very freely knowledge and ideas on cytogenetics. Also I am grateful to the late Dr. J. Ohwi for giving me instructions and suggestions on grass taxonomy. Thanks are due to Dr. K. Nishikawa, Professor emeritus of Gifu University and former managing director of the Kihara Memorial Yokohama Foundation for the Advancement of Life Science for encouraging me to write this review.