Inheritance Of Root And Shoot Traits In Wilting-Resistant Soybean Varieties

To understand the genetic mechanism of drought resistance of soybean and to evaluate the potential utilization of two introduced wilting-resistant germplasm in breeding program, the comparison between the wilting resistant and common varieties was made and the inheritance of root and shoot traits of wilting-resistant soybean varieties was conducted in this thesis. The results were summarized as follows:1. The root dry weight, volume and the tap root length of the wilting-resistant variety of PI47193 8 were higher than those of common varieties of Dare and Fengshouhuang (P<0.01) under irrigated condition and under drought-stressed condition. The above results futher indicated that the bigger root system was one of the main reasons for PI471938 to be resistant to wilting.2. The multi-generation mixed inheritance analysis indicated that the root dry weight in the cross of Dare×PI471938 was controlled by a pair of additive-dominance major genes and additive-dominance-epistasis polygenes, the heritability of the major gene was 10.75%, and the root volume was controlled by two pairs of additive-dominance-epistasis major genes and additive-dominance polygenes, the heritability of the major gene was 54.63%. In the cross of Fengshouhuang × PI471938, the root dry weight was controlled by polygenes, the heritability of the polygenes in F₂ population was 46.68%, the heritability of the polygenes in F₂∶3 population was 53.75%.The root volume was controlled by a pair of additive-dominance major genes and additive-dominance polygenes, the heritability of major gene was 4.4% and the heritability of polygenes was 65.04% in F₂ population, the heritability of the polygenes in F₂∶3 families was 84.79%.3. In the cross of Fengshouhuang × PI416937, the leaf number in F₂ population was controlled by a pair of additive major genes, the stem width was controlled by two pairs of additive-dominance-epistasis major genes, and other agronomic traits including the leaf area, the leaf dry weight, plant height, the main stem node number, the first-class branch number, the pod number, the shoot dry weight were all controlled by polygenes. In the cross of Dare×PI471938, the leaf area and the main stem node number were both controlled by two pairs of coordinate dominance major genes. However, the first-class branch number was controlled by a pair of negative dominace major genes, and the leaf number, the leaf dry weight, plant height, stem width, pod number, and the shoot dry weight were controlled by polygenes in F₂ population.4. Based on the genetic models of wilt-resisting traits, the principle of parent and progeny selection, and the procedure of drought-resistance breeding program were proposed in the discussion section. The results will provide theoretical basis for drought-resistant breeding of soybean.