Breeding of high protein soybeans from a species cross between soybeans glycine max and wild soybeans glycine soja necessity of repeated backcrossing method

Kaizuma, N.; Kiuch, Y.; Ono, F.

Journal of the Faculty of Agriculture Iwate University 15(1): 11-28

1980


Accession: 004859397

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Abstract
Several investigations were performed to consider breeding methodology for developing soybean cultivars with high protein percentage from a species cross between soybeans (G. max) and wild soybeans (G. soja). Three populations, i.e., F2 plants derived from a single cross between Hakuho (G. max) and B 3-2-2 (G. soja), B1F2 plants derived from a backcross, Hakuho .times. F1 (Hakuho .times. B 3-2-2), and F3 lines originated from the selected F2 plants with high protein percentage, were grown in 1977 and 1978. The genetic variations in protein percentage and some other morphological characters were investigated. Morphology of the protein bodies and spherosomes in cotyledon cells was observed using EM in some seeds of Hakuho, B 3-2-2 and their F2 plants. The individuals or lines with protein percentage as high as or higher than that of wild soybeans were segregated from all the populations of F2, B1F2 and F3 lines. Morphology of the protein body and spherosome in F2 plants with a high protein percentage resembled very much that of wild soybeans. The number of the genes conferring protein percentage may be relatively small and the F2 and B1F2 plants with the same genotype on protein percentage as that of wild soybeans could be easily reconstituted by genic recombination. Variation in plant height in F2 populations was characterized by very frequent segregation of the plants with much elongated stem over that of wild soybeans. A considerable number of the plants with almost the same stem length as that of soybeans was found in B1F2 population. Non-viney and erect stem types were not detected. The average of the basal stem diameter in F2 populations was much less than the mid-parent value. B1F2 populations equaled that of mid-parent, and the plants with almost the same basal stem diameter as that of soybeans were segragated in B1F2 population. The variation in 100 seed-weight in F2 population had a characteristically narrow range, compared the interparental difference. The average of 100 seed-weight in B1F2 populations considerably increased toward the soybean parent value. Segregation of the plants with nearly the same 100 seed-weight as that of soybeans was not indicated. Various seed coat colors and patterns appeared in F2 and B1F2 populations. A considerable number of B1F2 plants with the same uniformly yellow-colored seed coat as that of soybeans was segregated. Flowering initiation date was studied in the B1F2 population. Very wide variation from early to late was revealed although soybeans and wild soybeans showed almost the same flowering initiation date. No significant phenotypic correlations between protein percentage and some other characters, i.e., plant height, basal stem diameter, 100 seed-weight and flowering initiation date were detected in F2 and B1F2 populations. No relation was indicated between protein percentage and seed coat color. F2 and B1F2 plants with the protein percentage as high as or higher than that of wild soybeans could be easily selected out, but the individuals with the same properties as to plant height, basal stem diameter and 100 seed-weight as those of soybeans were hard to obtain. Multiple backcrossing may be indispensable for developing a morphologically soybean-type variety with high protein percentage from a species cross between soybeans and wild soybeans. Care should be taken so that the individuals with the protein percentage as high as that of wild soybeans might not be lost from any backcrossed populations. A selfed F2 population should be developed after every backcrossing is completed and plants with a protein percentage as high as that of wild soybeans should be selected out before the succeeding backcrossing is performed.