| A dominant gene of dwarfism located on chromosome 4D
in Triticum aestivum cv. 'Ai-bian 1' N. IZUMI*, S. SAWADA* and T. SASAKUMA** * Lab. of Forage Crops, Obihiro Univ. Agri. & Vet., Obihiro, Japan. ** Kihara Inst. for Biol. Res., Yokohama, Japan. Reduction of plant height is one of the main subjects in mordern wheat breeding, and dwarf or semi-dwarf genes have been identified in common wheat (reviewed by KONZAK 1975; GALE & LAW 1978; GOTOH 1977). There are three major genes genetically well analysed. Norin 10 has two major recessive semi-dwarfing genes, Rht-1, and Rht-2 (ALLAN et al. 1968; FICK & QUALSET. 1973), which has been used as a donor parent to introduce modern semi dwarf cultivars. These genes were identified to be located on chromosome 4A (GALE and MARCHALL 1976) and on 4D (GALE et al. 1975), respectively. On the other hand, a variety 'Tom Thomb' has a semi-dominant dwarf gene, Rht-3, located on 4A (MORRIS et al. 1975). Plant height is a quantitative character affected considerably by aneuploid condition, which have made it difficult to determine the number of dwarfing gene involved or the type of gene action. To avoid these difficulties, the insensitivity test to gibberellic acid was employed (ALLAN et al. 1959; GALE et al. 1975), which clarified the characteristics of dwarf genes. Recently, a very short stature variety, 'Ai-bian 1' (winter wheat) had been bread at Genetics & Breeding Institute of Shei-Beii Agricultural Academy (San-Shi, China), and the seeds were sent to Dr. H. KIHARA (Kihara Institute, Yokohama, Japan) for research study. The authors would like to express their sincere thanks for their supplying the seeds of 'Ai-bian 1' for the present study. The study was carried out to identify the characteristics of the dwarf gene in 'Ai-bian 1'. Materials and Methods Plant characters of 'Ai-bian 1' were compared with those of 'Chinese Spring' (tall variety) and 'Norin 10' (semi-dwarf). Plant height, spike length, number of tillers, leaf length, internode length, and seed-set were examined with twenty plants for each line. 'Ai-bian 1' was crossed as the male parent with monosomic lines and normal disomics of 'Chinese Spring'. The F1 plants were grown in the greenhouse, and monosomics were selected cytologically. The selected F1 plants were selfed for obtaining F2 progeny. The F2 obtained were sown in pots and vernalized at 5C for 4 weeks. Subsequently, they were transplanted in a randomized block design with three replications in the field during spring, 1981 at the experimental field of Obihiro Univ., Obihiro, Japan. Some F2 families were restricted in the population size and 6D group was not obtained because of dry cultivation condition at transplanting. The measurement were conducted on the individual basis. The population was classified into two groups, short and tall, by using 50 cm as the criterion. Chi-squre test was applied to ascertain whether the segregation of each group fits to 3:1 ratio. |
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