Understanding grain yield responses to source–sink ratios during grain filling in wheat and barley under contrasting environments

Abstract

a b s t r a c tA better understanding of the effects of different source-sink ratio during the grain filling period on grain growth may be relevant in order to further increase cereal grain yield. The main objective of the present work was to determine the effect of different manipulations of the source-sink ratios in wheat and barley grown at four different environmental conditions on responsiveness of sinks (grain growth and yield) and sources (spike photosynthesis and water soluble carbohydrates in the stems). Four treatments were imposed 7 days after anthesis in two contrasting locations with low-and highinputs conditions in wheat (cv. Soissons) and barley (cv. Sunrise): they were a control, a treatment removing all the spikelets from the upper half of the spikes (T S ), and shadings decreasing incident radiation by 75% on the whole canopy (S W ) or only on the leaves (having the top area of the meshes individual holes for each spike to be exposed to solar radiation, S L ). As expected grain yield was closely related to grain number per m 2 . Average grain weight was reduced by shading treatments far more markedly in S w than in S L . Interestingly, significant amounts of water soluble carbohydrates in the stems remained at maturity in S L and S w treatments and spike photosynthesis in S L was consistently higher than in the unshaded controls in both species. These results may be an indication that wheat and barley are not source-limited during grain filling and that only when subjected to an extremely severe stress, grain size would be reduced due to lack of enough assimilates available to fill them.

Dry matter and water dynamics of wheat grains in response to source reduction at different phases of grain filling

“…This is consistent with that shown by Serrago et al (2013) where the mobilization of reserves from stems was an important source of assimilates for growing grains in wheat and barley. Indeed, increases in WSC supply to grain yield and TGW have been reported for wheat cultivars released in the UK from 1972 to 1995 (Foulkes et al, 2002;Shearman et al, 2005).…”

“…This aspect is clearly relevant considering that wheat could be affected by source shortage at different moments during grain filling, thereby forcing the crop to use reserves, which could be insufficient to fill the grains, particularly under high yield conditions (Calderini et al, 2006;Sandaña et al, 2009;Serrago et al, 2013). Therefore, the sensitivity of wheat to source reductions Entire bars show the crop season from emergence to physiological maturity in the control treatment.…”

“…Several studies have assessed the effect of different source-sink ratios on wheat yield and grain weight (Fischer and Laing, 1976;Fischer, 1985;Savin and Slafer, 1991;Slafer and Savin, 1994;Borrás et al, 2004;Sandaña et al, 2009;Serrago et al, 2013); but less information is available about the mechanisms involved in the sourcesink response. Given that grain water content has been found to be a key trait in determining wheat grain weight (Egli, 1990;Saini and Westgate, 2000;Pepler et al, 2006, Hasan et al, 2011, and considering the close balance between water and DM in growing grains (Schnyder and Baum, 1992;Calderini et al, 2000;Saini and Westgate, 2000;Pepler et al, 2006), studying grain water content in response to the source-sink reduction during grain filling could provide useful information on grain growth and its responsiveness to source constraints of wheat as has been shown in maize (Borrás et al, 2003;Borrás and Westgate, 2006).…”

Growth analysis of winter wheat cultivars as affected by nitrogen fertilization / Wachstumsanalyse von Winterweizensorten in Abhängigkeit von Stickstoffdüngung

“…This is in agreement with the results showing a significant relationship between growth rate and yield in maize (Tollenaar et al, 1992) and wheat (Serrago et al, 2013). The effect of N fertilization and cultivar on the yield was significant in all the years (Sugár et al, 2016 -1 ) alone or in combination, based on the stepwise method of multiple regression analysis (n = 36) Tabelle 3.…”

Source limitations due to leaf rust (caused by Puccinia triticina) during grain filling in wheat

“…The general relationship between potential grain size, maximum grain water content and grain growth rate is widely known in wheat crops growing without restrictions during grain filling (Brocklehurst 1977;Sofield et al 1977;Schnyder and Baum 1992). In wheat, variations in grain weight are generally linked to variations in GGR more than to changes in GFD (Miralles and Slafer 1995;Serrago et al 2013), as in healthy crops, grain weight is not normally limited by source. However, as previously stated, diseased crops can be exposed to severe source restrictions to grain growth (Serrago et al 2009;Carretero et al 2010).…”