Comparison of grain yield and 2-acetyl-1-pyrroline (2AP) content in leaves and grain of two Thai fragrant rice cultivars cultivated at greenhouse and open-air conditions

To verify how different growing environments affect the aroma quality and production yield of fragrant rice, two commercial Thai fragrant rice cultivars, Khao Dawk Mali 105 (KDML 105) and Pathum Thani 1 (PTT 1) were grown in a greenhouse and also open air. Between the two growing environments, the temperature difference averaged 6 C. Each rice cultivar was grown in clay loam and sandy loam soils. In addition, a water stress treatment was applied at the beginning of the grain filling stage and onward. Determination of 2-acetyl-1pyrroline (2AP) in both rice leaves and grain was accomplished using automated headspace-gas chromatography with selective nitrogen/phosphorus detection. The results showed that throughout all growth stages the rice leaf 2AP content was different for both rice cultivars depending on the soil type. The KDML 105 cultivar had higher 2AP content in clay loam soil compared to PTT 1. A reverse trend was observed in the sandy loam soil. The grain 2AP content and grain yield of both rice cultivars were lower for those plants grown in the greenhouse condition. The water stress treatment led to higher 2AP content in both the leaves and grain of the two rice cultivars, which averaged 19% higher for rice leaves and 22% higher for rice grain. However, the water stress treatment dramatically decreased grain yield for all growing conditions. The interaction effects of these environmental factors were analysed using a full-factorial design. The interaction between rice cultivar temperature had the strongest effect on the 2AP content, whereas rice cultivar soil type greatly affected rice grain yield.