Abstract:

The objective of this study was to investigate whether a moderate soil-drying or an alternate wetting and moderate-drying irrigation during the grain filling period could improve the grain quality and increase yield in rice. Two rice cultivars, Wuyujing 3 (japonica) and Yangdao 6 (indica), were grown in pots and cement tanks. Three soil moisture treatments and three irrigation patterns, well-watered (WW, well-watered) and conventional irrigation (CI, continuous flooding), moderate soil-drying (MD, soil water potential at – 10 ~ – 30 kPa) and alternate wetting and moderate-drying irrigation (W-MD, re-watered when soil water potential reached at – 25 kPa), and severe soil-drying (SD, soil water potential at – 40 ~ – 60 kPa) and alternate wetting and severe-drying irrigation (W-SD, re-watered when soil water potential reached at – 50 kPa), were imposed during grain-filing. Compared with WW or CI, MD or W-MD significantly increased grain weight, peak viscosity, and breakdown values, and re-duced chalkiness and setback values. The results were reversed for SD or W-SD treatments. Activities of sucrose synthase (SuS), adenine diphosphoglucose pyrophosphorylase (AGP), starch synthase (StS), and starch branching enzyme (SBE) in grains in mid-dle and late grain-filling stages were significantly enhanced, whereas ethylene revolution rate of grains decreased, under MD or W-MD. The SD or W-SD had the opposite effects. The results indicate that both MD and W-MD can improve rice quality, resulting from the physiological mechanism of enhancing activities of SuS, AGP, StS, and SBE and decreasing ethylene production in grains.

Key words:

Rice, Soil moisture, Rice quality, Key enzymes in starch synthesis, Ethylene