Wheat quality expert visits ARC-SGI's Cereal Chemistry Laboratory
BAREND WENTZEL, ARC-Small Grain Institute
Dr Carlos Guzman Garcia, head of the Wheat Chemistry and Quality Laboratory at the International Centre for Wheat and Maize Improvement (CIMMYT) in El Batan, Mexico, visited South Africa in January this year. He was invited by the ARC-Small Grain Institute (ARC-SGI) in Bethlehem.
The CIMMYT maintains one of the world’s largest and most diverse wheat and maize seed collections, with approximately 180 specialised researchers from 40 countries, along with 700 support staff, working at five research stations in Mexico and 18 offices in the developing world.
Recent estimates indicate that wheat varieties developed by the CIMMYT and its partners are planted on more than 64 million hectares in developing countries, representing more than 75% of modern wheat varieties planted in those countries. Most South African grown wheat varieties derive from CIMMYT-germplasm.
Dr Guzman Garcia presented talks at the ARC-SGI and the universities of the Free State and Stellenbosch on: Wheat quality improvement at CIMMYT; Quality selections for segregating and advanced wheat material; Rheology, electrophoresis and marker assisted selection.
The CIMMYT has the largest wheat breeding programme in the world and accommodates two cycles per year by means of a shuttle programme. Their main focus is to select for high adaptability, high yield, disease resistance as well as heat and drought tolerance.
Wheat quality forms an integral part of their breeding programme. During 2014 they evaluated 5 000 bread wheat lines and 10 000 durum wheat lines. High throughput methodologies are applied to screen samples. Some methods are modified to minimise sample size and the time required for analysis. Adjusted methods are validated against internationally approved methods.
Quality is a complex trait and can be subdivided into milling quality (high flour yield), processing quality (production of uniform products with minimum cost), end-use quality (according to consumer preference) and nutritional value. Wheat quality is a variable concept, depending on the type of end-product, processing conditions (automated, semi-automated or manual) and consumer preference.
Main factors influencing wheat quality are grain morphology (milling quality), kernel hardness (flour yield and end-use quality), protein content and composition (processing, end-use and nutritional quality) and flour colour (end-use quality). Kernel hardness is regarded as the most important trait since it affects processing and end-use quality and is therefore classified accordingly.
Hard kernels require more time and energy during the milling process while soft kernels require more sifting time and renders lower flour yield. Hard kernels are prone to starch damage resulting in higher water absorption, a desirable trait for bread making, while soft kernels are more suitable for cookies due to lower water absorption levels.
It is more efficient to improve end-use quality by means of improving protein quality than protein content. The CIMMYT selects for protein composition and not protein content since protein content is strongly influenced by the environment and is negatively associated with grain yield.
Wheat breeding lines are classified in six classes according to flour analysis, with the first two classes being of the highest quality:
- Pan-type bread for the mechanised industry
- Leavened bread for the semi-mechanised industry
- Dense and flat bread for manual baking
- Poor, inferior quality
Plant breeders and scientific institutions across the world have open access to germplasm and methodologies developed by the CIMMYT, since it is a non-profit organisation. Plant breeders and students receive training and further their studies on a regular basis at the CIMMYT.
Collaboration between the Cereal Chemistry Laboratory (ARC-SGI) and the CIMMYT (Wheat Chemistry and Quality Laboratory) was established during the visit of Dr Guzman Garcia.
We are grateful to the Winter Cereal Trust for funding Dr Guzman Garcia’s visit.
Publication: May 2015