Physiological Properties and Molecular Regulation in Different Edamame Cultivars under Drought Stress

Edamame (Glycine max (L.) Merr.) is an important economic crop worldwide and is a good source of protein and nutrients. Kaohsiung No. 9 (KH9), Kaohsiung No. 11 (KH11), and Xiang-Ji (XJ) are three major edamame cultivars planted in Taiwan. Edamame has high water requirements in all development stages. Insufficient irrigation causes aborted blossoms, small pods, and shriveled beans, thus greatly reducing the yield. We examined the three aforementioned cultivars in drought conditions during the blooming period. The results revealed that drought stress decreased the yield in all three cultivars; however, XJ and KH11 showed better drought resistant ability than KH9 did. The reduction of the qualification rate and the dry weight of qualified pods by drought stress in XJ, KH9 and KH11 was 23%, 33%, 21% and 32%, 62%, and 44%, respectively. The quantitative reverse-transcription polymerase chain reaction results indicated that genes involved in the abscisic acid (ABA) biosynthesis, ABA-dependent, and ABA-independent pathways were upregulated by drought stress in KH11, which may explain why KH11 produced higher yields than KH9 after drought treatment. We determined that drought-related signaling transduction differed among these edamame cultivars, resulting in different drought tolerance.