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Wheat quality expert visits ARC-SGI’s

Cereal Chemistry Laboratory

D

r 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 shut-

tle 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, process-

ing conditions (automated, semi-automated or manual) and con-

sumer preference.

Main factors influencing wheat quality are grain morphology (mill-

ing 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 improv-

ing 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 associa-

ted 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

Cookies

Poor, inferior quality

Discard

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.

BAREND WENTZEL,

ARC-Small Grain Institute

Barend Wentzel (ARC-SGI), Dr Carlos Guzman Garcia (CIMMYT, Mexico)

and Dr Cobus le Roux (general manager, ARC-Field Crops division).

Mei 2015

80

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