A study of the genic basis for differences in quantitative characters between two varieties of Triticum Aestivum L
Tai, George Chaio-chih
Four quantitative characters, heading date, plant height, yield and seed number, have been studied in four inbred backcross line experiments. It was demonstrated that among the genes which differentiate the wheat varities Ramona and Baart, there are seven loci which have detectable effects on the four characters. The first four detected loci (loci 1, 2, 3 and 4) were found to be responsible for heading date inheritance. They also expressed pleiotropic effects on plant height, yield, and seed number. Two additional loci (loci 5 and 6) showed effects on plant height. The genes for tall stature were found to be sensitive to temperature and/or moisture for their expressivity. Anoth locus (locus 7) waa observed to cause seed shattering and consequently to reduce yield in the Baart inbred backcross experiment in 1967. This locus may interact with its genetic background. In the Ramona inbred backcross lines, approximately 92, 96, 82 and 57 percent of the total genetic variation for heading date, plant height, yield and seed number respectively were due to the detected loci. The corresponding values were 91, 75, 85 and 80 percent respectively in the Baart inbred backcross lines. Results from diallel cross experiments among lines isogenic for detected loci showed that both dominance and epistasis are involved in heading date inheritance. Only additive genic effects seem to be important in plant height inheritance.