Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2005
Publication Date: 4/20/2005
Citation: Don, C., Lookhart, G.L., Naeem, H., Macritchie, F., Hamer, R.J. 2005. The effect of wheat genetic background and growing conditions on the glutenin macro-polymer. Journal of Cereal Science. 42(1): 69-80.
Interpretive Summary: Wheat is one of the most important food crops in the world. Wheat quality is governed by a combination of genetic and environmental factors. The quality of any given cultivar varies due to growing conditions and some cultivars are more susceptible than others. The effects of heat stress on the wheat quality factors was studied by characterizing the gluten macro polymers (GMP) of mature wheat lines that vary only in the high molecular weight glutenin subunits 5+10 and 2+12. Wheat plants were grown under controlled conditions, using various day and night temperature regimes to simulate six different stress levels. Heat stress increased with increasing day temperatures. Heat stress mainly affected the quantity of the GMP's. The quantities of insoluble glutenin fractions, like GMP, play an important role in wheat flour dough mixing properties. We were able to visualise particles in the GMP with a Confocal Scanning Laser Microscope. More large particles were measured with Laser Light Scattering in heat stressed samples than in samples grown under mild conditions and very large glutenin particles (>100um) were found in severly heat stressed samples. The glutenin particle size was shown to affect dough time-to-peak. In severely stressed samples, much larger amounts of SDS soluble proteins and less SDS insoluble proteins were observed.
Technical Abstract: Wheat quality is governed by both genetic and environmental factors. The guality of any given variety varies due to growing conditions and some varieties are more susceptible than others. The effects of heat stress on the gluten macro polymers of mature near-isogenic lines of Lance C and Lance A varying only in HMWGS 5+10 and 2+12, respectively, and Warigal A and Warigal C also varying only in 5+10 and 2+12, respectively, were studied. Wheat plants were grown under controlled conditions, using various temperature regimes -t degrees C day/t degrees C night- to simulate six different stress levels. Treatment 1, control, involved growing the plants for the entire cycle at 20C day / 16C night. Treatment 2 consisted of 30C day /18C night temperatures starting at 16 DAA and continuing for 3 days and then returning to the control conditions. Treatment 3 was 35C day and 20C night starting at 16 DAA and continuing for 3 days and then returning to the control conditions. Treatment 4 was 35C day 20C night starting at 16 DAA and continuing until maturity. Treatment 5 was 40C day and 25C night starting at 16 DAA and continuing until maturity. Heat stress increased going from treatment 1 to 5. SDS insoluble / SDS soluble ratios were least iin Treatment 5, indicating that heat stress mainly affects GMP quantity. Clearly, the quantity of insoluble glutenin fractions like GMP and UPP, played an important role in wheat flour dough mixing properties. A Coulter Scanning Laser Microscope was used to detect GMP particles. The particle size measurements, for all varieties, indicated that more large particles are shown in heat stressed samples than in samples grown under mild conditions and severely heat stressed samples have very large glutenin particles, > 100 um. The presence of much larger amounts of SDS soluble proteins overs SDS insoluble proteins in severly stressed samples was observed.