Rice seed vigor and seedling establishment in anaerobic soil

Abstract

The rice (Oryza sativa L.) crop is established under hypoxia when sown into flooded or water-saturated soil. This study was conducted to clarify the interrelationship between seed vigor and seedling growth in anaerobic soil and to identify seedling characteristics that predict establishment in the field. Different levels of seed vigor were obtained with different cultivars, times of harvest, and accelerated aging treatments. Seeds of cultivars tolerant of anaerobic soil (ASD1, JC178, Taothabi, and Kuhei 2) and of intolerant cultivars (IR36 and IR50) were produced by harvesting 25, 30, 35, and 40 d after heading. Another set of seeds was aged at 43°C and 100% relative humidity for 0, 3, 6, and 9 d. The characteristics measured were germination and germination rate in petri dishes, coleoptile and mesocotyl lengths in N2 gas in flasks, and seedling establishment, vigor index (which indicates the speed of emergence), height, leaf development, mesocotyl length, and shoot weight in flooded soil in trays and in water- saturated soil in the field. The harvest time did not affect seedling establishment in the field. Aging reduced seedling establishment significantly in the cultivars tested except ASD1, which was tolerant to aging. Seedling establishment in the field was closely correlated with the vigor index in the field (simple linear correlation coefficient r = 0.8 to 1.0), establishment and vigor index in the tray (r = 0.5 to 0.9), and coleoptile length in N2 gas (r = 0.4 to 0.9), suggesting that these characteristics would be useful in the prediction of seedling establishment in anaerobic soil.