Effect of thinning on cultivar differences of green stem disorder in soybean

Ryo Yamazaki,Tomoyuki Katsube-Tanaka,Yohei Kawasaki,Katsuyuki Katayama,Tatsuhiko Shiraiwa

doi:10.1080/1343943x.2018.1557531

Abstract

ABSTRACT Green stem disorder (GSD) in soybean (Glycine max (L.) Merrill) negatively affects harvest efficiency and seed appearances. Breeding GSD-insensitive cultivars is expected to be an effective countermeasure to GSD. However, it is difficult to stably detect cultivar differences in GSD under conventional field conditions because the occurrences of GSD largely vary by location and year. The thinning effect, which had been reported to promote GSD, may help accurate phenotyping for occurrences of GSD in breeding. To verify this possibility, the thinning treatment was applied to four cultivars, the GSD severity values of which were evaluated in an independent study by another group. As a result, the cultivar differences in GSD severity were generally comparable between the present and previous studies. However, the difference was more evident, with the thinning treatment exhibiting the GSD score of 2.8 of ‘Hatsusayaka’ compared with the GSD score of 3.6 of ‘Sachiyutaka’, while the scores of those cultivars were similar without the thinning treatment. A positive correlation between GSD severity and N concentration in the main stem could be seen but the increasing rate of GSD score with the N concentration in the main stem differed between cultivars. Thus, although more cultivars need to be tested to prove, the thinning treatment could be useful as a phenotyping technique in the breeding of GSD-insensitive cultivars.

Highlights

Green stem disorder (GSD) in soybean is defined as the symptom in which stems and leaves stay green and retain some moisture even when pods normally become matured (Harbach et al, 2016; Hobbs et al, 2006)
In the previous study (Yamazaki et al, 2018), thinning did not affect the developmental progression of the reproductive stage, which was evaluated based on pod maturation, suggesting that GSD promoted by thinning was characterized by the delayed maturation of the leaves and stems
‘Tamahomare’, the thinning treatment showed severe GSD symptoms compared to the dense or sparse treatment, which were the same as those shown by ‘Sachiyutaka’ and ‘Hatsusayaka’, that was the result of only 1 year (Table 5). These results suggest that the phenomenon that thinning promotes GSD occurrences is not limited to ‘Sachiyutaka’ but is seen generally in soybean cultivars

Summary

Introduction

Green stem disorder (GSD) in soybean is defined as the symptom in which stems and leaves stay green and retain some moisture even when pods normally become matured (Harbach et al, 2016; Hobbs et al, 2006). It has been reported that there are differences in GSD occurrences between cultivars (Fujii et al, 2015; Furuya & Umezaki, 1993; Hill et al, 2006; Isobe et al, 2015; Matsumoto et al, 1986; Mochizuki et al, 2005; Pierce et al, 1984; Yamada et al, 2014). Comparisons of the GSD severity between many cultivars or lines are needed. It is difficult to accurately detect the differences in GSD severity between cultivars or lines because the occurrences of GSD largely vary by field location and cultivation year (Fujii et al, 2015; Hill et al, 2006). It is generally difficult for breeders to find differences in potential GSD sensitivity between cultivars or lines when GSD occurrences are somehow suppressed

Methods

Results

Conclusion