Photosynthetic contribution of the ear to grain filling in wheat: a comparison of different methodologies for evaluation.

Rut Sanchez-Bragado,Matthew P Reynolds,Gemma Molero,Jose Luis Araus

doi:10.1093/jxb/erw116

Abstract

The culm (particularly the flag leaf) and the ear are believed to play a major role in providing assimilates for grain filling in wheat. However, the results obtained in the past varied depending on the methodology applied. Three different methodologies were compared that aimed to assess the relative contribution of the culm (photosynthetic organs below the ear) and the ear to grain filling. The first two consisted of applications of photosynthesis inhibition treatments, including the use of the herbicide DCMU and organ shading. The third was a non-intrusive method that compared the carbon isotope composition (δ(13)C) of mature kernels with the δ(13)C of the water-soluble fraction of the peduncle, awns and glumes. Several advanced CIMMYT lines were tested under good agronomic conditions. The δ(13)C approach assigned a higher photosynthetic contribution to the ear than to the culm. However, some methodological considerations should be taken into account when applying the δ(13)C approach, particularly the sampling method used, in order to prevent post-harvest respiration. The shading approach assigned a similar contribution to the ear as to the culm. The DCMU approach assigned a greater role to the culm but herbicide application to the culm affected the ear, thus biasing the final grain weight. Moreover DCMU and shading approaches may cause compensatory effects which overestimated the contribution of unaffected organs. This study may help to develop precise phenotyping tools to identify physiological traits such as ear photosynthesis that could contribute towards increasing grain yield.

Highlights

Whereas breeding efforts in recent decades have been focused on improving crop adaptation to disease and abiotic stresses (Araus et al, 2002), interest in raising the yield potential has grown only recently (Reynolds et al, 2012)
The shading approach assigned a similar contribution to the ear as to the culm
The DCMU approach assigned a greater role to the culm but herbicide application to the culm affected the ear, biasing the final grain weight

Summary

Introduction

Whereas breeding efforts in recent decades have been focused on improving crop adaptation to disease and abiotic stresses (Araus et al, 2002), interest in raising the yield potential has grown only recently (Reynolds et al, 2012). The increase in sink strength and harvest index due to dwarfism alleles (Maydup et al, 2012), or the increase in the ‘communalism’ habit of the crop canopy Ear photosynthesis is thought to play an important role in terms of the source of photoassimilates during grain filling, under drought, and under good agronomical conditions (Araus et al, 1993; Tambussi et al, 2005, 2007b; Maydup et al, 2010; Sanchez-Bragado et al, 2014b). In conditions where leaf photosynthesis is limited, assessing the photosynthetic contribution of the ear to grain yield may be relevant

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