Limited Water Stress Triggers Adaptive Leaf Trait Response in Australian Commercial Rice Without Compromising Grain Yield and Quality

Water scarcity poses significant challenge for the Australian rice industry, driving the need for varieties with improved water use efficiency (WUE). This study evaluated 18 Australian elite japonica, two indica rice lines, and the West African japonica cultivar Moroberekan to assess stomatal and non-stomatal leaf traits contributing to WUE. Plants were cultivated under controlled glasshouse conditions with two water treatments: ponded (PW) and limited water (LW) maintained at 60-65% field capacity throughout the vegetative stage. Under LW, plants exhibited decreased photosynthetic efficiency, stomatal conductance, and stomatal density but increased cuticular and epicuticular wax (CEW) deposition, which helped conserve water. The rice cultivar Sherpa exhibited reduced sensitivity to regulation of gas exchange, stomatal adjustments and photosynthetic efficiency, and the greatest CEW deposition among the japonica varieties, indicating potential for improved WUE. Thousand grain weight showed no significant differences between the two water treatments. Brown rice yield and milling recovery were also unaffected. Spectral analysis of dehulled seeds suggested that LW stress increased protein content but had no effect on lipids and starch. These findings demonstrate that LW during the vegetative stage can induce water-conserving traits without compromising yield or grain quality; providing valuable insights for developing water-efficient rice varieties.