| Segregation ratio and viability of several chlorophyll
mutants in T. monococcum T. FUJII The National Institute of Genetics, Misima, Japan The segregation ratio often showed a wide range of variation in the X2-generation. The mutant homozygotes appeared very often in too small numbers, for instance 14:2 in albina-5002, 12:2 in albina-5005 and 19:4 in xantha-5041. Occurrence of more than 25 per cent of recessive homozygotes, as 1:5 in chlorina-5040, was very rare. But the usual 3:1 ratio could be found in the successive generations of 35 of 45 chlorophyll mutant strains. Among the remaining 10 strains, such as albina-5008, -5012, striata-5057, basi-viridis-5059, the segregation did not fit the 3:1 ratio. Low germination ability of the mutant homozygotes in some strains (striata-5057, basi-viridis-5059) is partly responsible for their deficient numbers. In all investigated cases the mutation from dominant to recessive concerned single genes. But in some strains, such as basi-viridis-5077, viridi-albina-5072, virdo-xantha-5100 etc., albina and striata plants were segregated from the heterozygotes. A peculiar phenomenon was observed in virido-xantha-5100, namely the occurrence of 76 virido-xanthas, 9 albinas and 6 striatas besides 59 normal plants. These strains will be further investigated. Viability was examined in 65 strains of several chlorophyll mutants, such as albina chlorina, basi-viridis, etc. Ability recover the chlorophyll content was mostly observed in bi-colored mutants, to such as basi-viridis and virido-albina and did not occur in uniformly colored ones, such as chlorina, xantha and albina. Neither could the striata mutant recover the chlorophyll content. The recovery occurred only when they were grown in the greenhouse or in the phytotron and was restricted in the field to the warm season. In most of the mutants, except chlorina and striata, occurred a more pronounced dilution of green color in the field during the winter months than at seedling stage and they all died out. But the time rate of chlorophyll content recovery was different by the strain. Also differences within the same mutant type were observed, for instance in the recovery speed and viability. May be different steps in the genetic make-up of chlorophyll production are blocked in the various strains. |