Physiological and Agronomic Insights Into Water Use Efficiency Differences Among Mid-Season Indica Rice Varieties

Area of Science:

• Agricultural Science
• Plant Physiology
• Agronomy

Background:

• Freshwater scarcity poses a significant threat to rice (Oryza sativa L.) production, impacting global food security.
• Identifying rice varieties with high water use efficiency (WUE) and grain yield is essential for sustainable agriculture.
• Limited understanding exists regarding the specific agronomic and physiological traits linked to varying WUE in rice.

Purpose of the Study:

• To evaluate agronomic and physiological traits of rice varieties with differing water use efficiency (WUE) levels.
• To identify key traits associated with high yield and WUE in rice under water-limited conditions.
• To provide data-driven guidance for selecting rice varieties suitable for water-scarce environments.

Main Methods:

• A 2-year field study categorized six indica rice varieties into low, medium, and high WUE groups.
• Systematic evaluation of agronomic traits (e.g., grain yield, harvest index, leaf area index) and physiological traits (e.g., photosynthesis, carbohydrate levels, enzyme activity, root characteristics).
• Principal component analysis (PCA) was employed to identify traits strongly correlated with yield and WUE.

Main Results:

• High WUE varieties (HWVs) demonstrated significantly higher grain yield and WUE compared to low and medium WUE varieties.
• HWVs exhibited superior productive tiller percentage, harvest index, leaf area index (LAI), grain-leaf ratio, and flag leaf characteristics.
• Enhanced photosynthetic rates, non-structural carbohydrate (NSC) accumulation, antioxidant enzyme activities, root biomass, root oxidation, and zeatin + zeatin riboside (Z+ZR) content were observed in HWVs.
• PCA identified productive tiller percentage, effective LAI, leaf photosynthesis, root dry weight, and Z+ZR levels as key drivers of yield and WUE.

Conclusions:

• Enhanced shoot and root traits collectively contribute to superior water use efficiency and grain yield in rice.
• Specific traits like productive tillering, efficient photosynthesis, robust root systems, and optimal hormone levels are critical for high WUE varieties.
• This research offers valuable insights for breeding and selecting rice cultivars adapted to water-limited agricultural systems, promoting sustainable production.