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Genotype-by-Environment Interaction in Grain Sorghum I. Effects of Temperature on Radiation Use Efficiency

Queensland Dep. of Primary Industries, GPO Box 46, Brisbane, Qld. 4001, Australia
Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506

^* Corresponding author.

Better understanding of genotype-by-environment interaction for radiation use efficiency could facilitate use of crop models to interface physiological research with crop improvement. We grew sorghum [Sorghum bicolor (L.) Moench] hybrids RS610 and ATx623/RTx430 at 17 and 25 °C in glasshouses, monitored dry matter by sequential harvesting, and measured intercepted photosynthetically active radiation (PAR) to determine if a genotype-by-temperature interaction exists. Total dry matter can be considered the product of intercepted PAR and radiation use efficiency. Above-ground dry matter can be determined from total dry matter and partitioning between tops and roots. We used this framework to analyze treatment effects and found a significant temperature-by-hybrid interaction for total dry matter. The ATx623/RTx430 produced 22% more total dry matter at 25 °C than at 17 °C. Total dry matter produced by RS610 at either temperature did not differ significantly from that produced by ATx623/RTx430 at 17 °C. This interaction was caused by a similar effect on radiation use efficiency, which was 4.89 g MJ^–1 for ATx623/RTx430 at 25 °C and 3.76 g MJ^–1 for the other three treatments. We examined canopy structure and known effects on the photosynthesis-respiration balance, but could not determine the physiological basis of the interaction. Hybrids differed significantly in ratio of root to total dry matter. ATx623/RTx430 partitioned more dry matter to roots (0.25) than RS610 (0.22). This effect on partitioning highlighted the potential error in comparing radiation use efficiencies among genotypes using calculations based only on above-ground dry matter.

Received for publication December 17, 1987.