Studies on genetic elimination of seed lipoxygenase for utilization of soybeans.

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Normal soybean seeds contain three lipoxygenase isozymes, L-1, L-2, and L-3. These isozymes are responsible for the generation of objectionable grassy beany flavors which build a barrier against the wide utilization of soy protein products. By the use of the lipoxygenase lacking mutants, L-1-less, L-2-less and L-3-less soybeans, we have been attempting to breed soybeans with low levels of the objectionable grassy flavors. The objective in this investigation is to clarify whether any defects occur in the important agricultural traits in the lipoxygenase lacking soybeans.New techniques using the carotene bleaching activity of lipoxygenase were developed for the detection of L-1, L-2 and L-3, Respectively. By the use of the new techniques, about ten thousands progeny seeds from L-1-less X L-2-less crosses were analyzed. However, no double mutant seeds lacking both L-1 and L-2 have been identified indicating that the <Lx_1> locus tightly links with the <Lx_2> locus.Three to four backcrosse … More s were made to the recurrent parents 'Suzuyutaka' to obtain the near-isogenic lines lacking L-1, L-2, L-3, L-1・L-3, and L-2・L-3, respectively. By using the near-isogenic lines, the performance on the characters such as productivity and plant growth was evaluated in Morioka and Tsukuba. The results showed that no significant physiological and morphological differences through each stage of germination, early growth, flowering and seed development among the lines and var. Suzuyutaka. Moreover, no difference of seed damages by insect pests, such as pod borer or stink bugs was observed among the lines in both places.In another experiment, it was shown that there was no significant difference in activity levels of leaf and youg pod lipoxygenases that have been thought to play physiologically important roles among the lines and var. Suzuyutaka.These results indicate that it is possible to breed soybean varieties with low levels of the undesirable lipoxygenase actions by the use of the lipoxygenase lacking soybeans. Less