Adaptive Diversity of Echinochloa Species to Osmotic Stress

Three Echinochloa species inhabit various crop fields with different soil moisture conditions. Therefore, a growth pouch test was conducted to investigate adaptive diversity of six Echinochloa species, three from Korea and three from USA, to osmotic stress by assessing shoot and root growths. Echinochloa crus-galli var. praticola showed the greatest tolerance to osmotic stress in both root (GR 50 =1316.3 g PEG L −1 ) and shoot (GR 50 =212.2 g PEG L −1 ) growths, while Korean E. oryzicola was most sensitive to osmotic stress in both root (GR 50 =116 g PEG L −1 ) and shoot (GR 50 =126.2 g PEG L −1 ) growths. Root to shoot (R/S) ratio of Echinochloa crus-galli var. praticola increased with increasing osmotic stress, while that of Korean E. oryzicola decreased, suggesting that R/S ratio is closely related to osmotic stress tolerance in Echinochloa species. Our results clearly demonstrate that E. crus-galli var. praticola maintains high R/S ratio even under high osmotic stress, which enables this species to well adapt to dry upland condition. In contrast, while E. oryzicola fails to maintain sufficiently high R/S ratio, resulting in poor adaptability to dry upland condition.