Phenotyping wheat photosynthesis using ‘Leaf Hyperspectral Reflectance’

Wheat is an important cereal crop contributing to global food security. Growing human population requires continuous increase in production. While increases in wheat yield gained by modifying harvest index have been fully exploited by plant breeders, improving photosynthesis has the potential to increase wheat yield. Due to a lack of efficient phenotyping methods for photosynthetic traits, it has been hard to explore photosynthetic variation and its genetic regulation. This has prevented the use of photosynthetic traits for crop improvement in wheat. We used ‘leaf hyperspectral reflectance’, a high-throughput phenotyping method, to predict multiple leaf photosynthetic traits in two wheat populations (Seri/Babax, and PSTails) grown at the International Maize and Wheat Improvement Centre (CIMMYT, Mexico). Leaf reflectance spectra were measured on wheat plants at four different growth stages (tillering, booting, anthesis+7 days and grain-filling) from which nitrogen content per unit leaf area (Narea), leaf dry mass per unit leaf area, Rubisco capacity per unit area or nitrogen (Vcmax25, Vcmax25/Narea, respectively) and electron transport rate (J) were calculated. We observed significant variation for different photosynthetic traits among the genotypes of Seri/Babax and PSTails when measured at different growth stages, but rankings between genotypes were not consistent across different growth stages. The average predicted values for Vcmax25, J, and Vcmax25/Narea differed among different growth stages. For Seri/Babax and PSTails, predicted values for Vcmax25/Narea were highest at the tillering stage and lowest at the anthesis+7 stage. Further experiments are being conducted in both Australia and Mexico