Published in Scientific Bulletin. Series F. Biotechnologies, Vol. XX
Written by Daniel CRISTINA, Matilda CIUCA, Petruta Calina CORNEA
Wheat is one of the world’s most important food sources, alongside with rice and maize, directly providing about 50% of human food calories. By 2020, it is estimated that the global demand for wheat will increase by a further 40%, due to the increasing world population. Therefore, higher yield is one of the most important goals in wheat breeding. Larger grains not only directly relate to grain yield but also have favorable effects on seedling vigour and early growth, thereby promoting and stabilizing yielding ability. Large grain size has been an important trait and it is usually measured in plant breeding practice by one thousand grain weight (TGW), mainly determined by grain width (GW), grain length (GL) and grain thickness (GT), but also by grain shape and density. Milling and baking quality is also influenced by grain size and shape. Geometrical models indicated that changes in grain shape and size could result in increases in flour yield of up to 5%. Test weight (volumetric weight), a trait largely used in commercial transactions with wheat, also depends on grain size and shape - larger grains, deviating from spherical shape having lower test weight. Grain size in wheat is a complex character and any information on its genetic control is useful for increasing breeding efficiency. Identifying molecular markers linked to quantitative trait loci (QTLs) controlling seed size would facilitate selection in early generations and may contribute to improved yield and end-use quality in wheat by accumulating such loci into elite backgrounds. Grain size in wheat is a quantitative trait controlled by quantitative trait loci (QTL), and numerous QTLs for grain size have been reported. Previous research showed important QTLs on all chromosomes, but most significant QTLs were identified on chromosomes 1B, 1D, 2A, 2B, 2D, 3A, 3B, 3D, 4B, 4D, 5A, 5B, 5D, 6A, 6B, 6D, 7A, 7B, 7D. Grain size is negatively correlated with grain number, mainly due to competition for available assimilates. Alleviating this correlation should be facilitated by a more detailed knowledge of grain size genetic control. In this mini-review we will focus on the latest information about the QTLs and genes involved in genetic control of wheat grain size and weight, and the best molecular markers associated with these traits.
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