Analysis of vegetative storage protein accumulation in soybean cultivars expressing different green stem disorder severity affected by soil moisture change

ABSTRACT Green stem disorder (GSD), characterized by delayed stem senescence during seed maturation, complicates harvesting in soybean production. Although GSD is associated with a sink – source imbalance, a rapid and precise evaluation of GSD has not been established. In sink-limited soybean plants, vegetative storage protein (VSP) accumulates. In this study, pot and field experiments were conducted to reevaluate the relationship between GSD, sink – source imbalance caused by soil moisture change, and VSP accumulation as a possible indicator of GSD in Kyoto, Japan over two years. Drought treatment for four weeks from R1 (beginning flowering), R3 (beginning pod), or R5 (beginning seed) growth stage in pots using the short growth-period cultivar Yukihomare reduced sink size in both years, but reduced relative sink mass (pod weight/shoot weight) and increased GSD severity only in 2017, suggesting that sink-source imbalance, affected by soil moisture, can induce GSD. Soil moisture change from around R3 or R5 to maturity in fields using trench-filled or unfilled water tended to change GSD severity but not VSP accumulation in the uppermost fully expanded leaves from R5 (2018) or 15 days before R5 (2019) to 28 days after R5. GSD and VSP responses, however, differed between the two contrasting cultivars, Tachinagaha and Touhoku 129, suggesting the potential usability of VSP for GSD evaluation. GRAPHICAL ABSTRACT