Abstract
Thousand grain weight is one of the components determining wheat grain yield. It represents the average value of individual grain weights which depends on position within the ear and on positon within the spikelet. Our objective was to quantify the influences of individual floret anthesis date, of carpel weight at anthesis and of rate and duration of grain filling, on variation in individual final grain weight. Two bread wheat cultivars were grown in a greenhouse and their ears were sampled from anthesis through to harvest. Each ear was divided into three parts—basal, central and apical—where the two proximal grains were dissected from each of two spikelets. We analysed (i) the flowering time shift within the ear and within the spikelet; and (ii) the growth kinetics during grain filling in relation to position along the ear. For both cultivars, florets located in the central part of the ear were the first to reach anthesis followed by those in the apical part and then the basal part. Within a spikelet, the floret located nearest the rachis flowered first followed by the more distal ones. We found no significant systematic effect of flowering time-shift on final grain weight. Nevertheless, grains in the central part were heavier than the basal ones (9.75% smaller) and than the apical ones (18.25% smaller). These differences were explained mainly by differences in mean grain filling rates. Analysis of growth kinetics enabled an improved explanation of the variability of individual grain weight along the ear.
Highlights
Grain yield of bread wheat (Triticum aestivum L.) can be decomposed into two main components: (i) the number of grains per square meter, which is determined before anthesis and (ii) the thousand grain weight (TGW), which is determined during grain filling
We identified statistically significant differences between the three different ear parts–the heaviest grains were in the central part, lighter grains were in the basal part and lighter grains still were in the apical part (Table 2)
We show that individual grain weights are greatest in the central part of the ear, less in the apical part and intermediate in the basal part
Summary
Grain yield of bread wheat (Triticum aestivum L.) can be decomposed into two main components: (i) the number of grains per square meter, which is determined before anthesis and (ii) the thousand grain weight (TGW), which is determined during grain filling. Grain number per square meter has been identified as the main driver of yield variability [1, 2], there is an urgent need to better understand the sources of variation in TGW because climate change may well lead to increases in abiotic stress during grain filling The TGW is generally calculated at the scale of a plot and represents the mean of many individual grain weights. Wide variability exists in individual grain weight, and this variability has implications for commercial value [5].
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