Ear branching as a means of increasing grain uniformity in wheat

Abstract

Grain growth was compared in two field-grown wheats, Kalyan Sona, a high-yielding, seinidwarf line with few spikelets per ear and many grains per spikelet, and a branched-eared cultivar with many spikelets, each with few grains. The basis of comparison was the spikelet in Kalyan Sona and the branch in the branched material. Within the central spikelets of the main ear in Kalyan Sona, grain growth rates for the greater part of filling were b > a = c > d > e; final weights per grain for these florets were 42, 40, 37,26, and 12 mg respectively. The gradation in growth rate for the eight grains along the branch in the branched-eared cultivar was relatively small with the consequence that all grains were similar in size at maturity (range 39–43 mg); peak growth rates for all positions were at least as high as for grains a, b, and c in Kalyan Sona.

In another cultivar, Triple Dirk, increasing competition for assimilates by reducing the light intensity during grain filling had a differential effect on grains within the spikelet but scarcely on the pattern between spikelets. The relationship between all grains was unaffected by temperature changes.

The results are discussed in relation to competition for assimilates between grains, and the suggestion made that a high number of grains per spikelet may not use the available assimilates most efficiently. Ear branching is proposed as a preferable alternative, as this also provides abundant grain sites to utilize assimilates to the potential of the photosynthetic system, yet ensures grain uniformity per ear, regardless of grain number, by having few grains in each spikelet.