| Correlation between the frequency of trisomics and
seed weight in rye trisomics M. KAMANOI The Institute for Breeding Research, Tokyo Agricultural University Tokyo, Japan In barley trisomics the transmission rates of the extra chromosome were higher in the smaller seeds than in the larger ones (RAMAGE 1955). TSUCHIYA (1960) also obtained the same result in barley trisomics. According to EINSET (1943) there is a correlation between the chromosome length and the transmisson rate in maize trisomics. The trisomic possessing larger chromosome showed a higher frequency of trisomics in their progenies than in shorter chromosome. In Datura there is, however, no relation between the transmission rate and the chromosome length (BLAKESLEE and AVERY 1938). In Matthiola trisomics (FROST 1919) it is probable that the higher frequency of transmission of the extra chromosome is associated with the higher percentage of seed germination. In rye trisomics chromosome length and germination percentage seem not to be correlated with the transmission rate of the extra chromosome. Each trisomic has the different extra chromosome in length. In order to check the correlation between the transmission rate of the extra chromosome and seed weight, the seed of four types out of seven primary trisomics, that is Feeble, Pseudonormal, Semi-stout and Dwarf were classified into two groups by their weight. In both groups of each type, twenty seeds were utilized and sown individually. The germinated plants were examined by chromosome counting. In Feeble the average weight of lighter seeds is 8.7 m gr. and 14.2 m gr. for heavier grains. Those of the other three types are like as Feeble. From the data presented in table it is apparent that there is significant correlation between the transmission rate and seed weight. The frequency of the trisomics from lighter grains was conspicuously higher than from heavier seeds. In Dwarf the lighter seeds produced 90 percent of trisomics, whereas no trisomic plant was found from heavier seeds at all. The results from lighter seeds showed a variation from 46.7 percent in Pseudonormal to 90 percent in Dwarf, while 0 percent in Dwarf to 10.5 percent in both Feeble and Pseudonormal from heavier grains. From a random sample the frequencies of trisomics were 13.9 percent in Feeble, 29.3 in Pseudonormal, 13.6 in Semi-stout and 20.7 in Dwarf, respectively. This tendency of an increased frequency of trisomics from lighter seeds enable the selection of a higher percentage of trisomics than from random sample. |