Seed- Fill Duration and Yield of Grain Crops

Abstract

Abstract Time, as expressed through seed-fill duration, is an important component of the productivity of grain crops. Seed-fill duration is influenced by environmental conditions and there is genetic variation in most crops. Seed-fill duration is regulated by the leaf's ability to supply assimilate to the developing seed (i.e., leaf senescence) and by the ability of the seed to use this assimilate for continued growth. Seed-fill duration in many crops increases as temperature decreases below 30°C. Water stress during seed filling accelerates leaf senescence and shortens the seed-filling period. The response of seed-fill duration to alterations in source–sink ratios is inconsistent and probably depends on whether the supply of assimilate to the seed is affected and if the seed can respond to changes. In some cases increases in harvest index are a result of lengthening the seed-filling period. Environmental variation in seed-fill duration is frequently associated with yield in most crops. Direct selection for long seed-filling periods may increase yield and, conversely, selection for higher yield in many crops resulted in longer seed-filling periods. Seed-fill duration can have a relatively low heritability and is somewhat difficult to measure, and it has not been widely used by plant breeders in cultivar improvement programs. However, given the intractable nature of crop growth rate, lengthening the seed-filling period may be the most promising avenue to higher yields, but new approaches to manipulate it will probably have to be devised.