Heat Stress during Grain Filling Modifies Kernel Protein Composition in Field‐Grown Maize

Abstract

Episodes of extremely high temperatures (>35°C) may cause a premature cessation of maize kernel growth (i.e., heat stress), depressing crop grain yield. However, little is known about the influence of this constraint on chemical composition of maize kernels, a key trait for end‐use related attributes. Four maize genotypes (flint, popcorn, temperate semi‐dent, and temperate × tropical semi‐dent) with distinctive endosperm types were grown at heated and non‐heated temperature regimes during the early or late stages of the effective grain‐filling period. Heat stress during early stages decreased both protein and starch contents of kernels, but the impact on the former was lower (up to −42%) than on the latter (up to −50%), resulting in increases of kernel protein concentration (up to +14%). The flint and popcorn hybrids, with hard endosperm type, tended to be less vulnerable to such effects due to an enhanced capacity to sustain kernel growth. For all hybrids, heat stress during late stages of kernel growth, reduced similarly protein and starch contents (up to −38%), without affecting kernel protein concentration. Heat stress always altered endosperm protein composition by increasing the relative abundance of glutelins, and β‐ plus γ‐zeins, at the expense of that of α‐zeins. The significant environment × endosperm‐type interaction for kernel chemical compounds should be linked to quality parameters for different maize end‐uses.

Kernel Hardness‐Related Traits in Response to Heat Stress during the Grain‐Filling Period of Maize Crops

“…In this study, heat stress reduced traits related to maize kernel hardness and, concomitantly, increased and decreased the relative abundance of band g-zeins and a-zeins, respectively (results from the same experiments published in Mayer et al, 2016). Gerde et al (2016) stated that band g-zeins and, to a lesser extent, aand d-zeins were positively related with kernel hardness attributes when dealing with environmental (years and soil N supply) and genetic (specific genotypes within kernel type) effects.…”

“…In this regard, it is known (Pomeranz et al, 1986;Duarte et al, 2005;Lee et al, 2007) that the relationships between TKW or kernel size distribution and other physical traits related to hardness are not consistent, and that can also be genotype dependent (Cirilo et al, 2011). Given the fact that this genotype had highly anticipated kernel growth cessation under the heated TR (Mayer et al, 2016), its reduced kernel or bulk density would have been the result of an anticipated maturity of kernels from the tip of the ear, as it was seen before from harvesting kernels at immature stages of development ( Jennings et al, 2002, and references cited therein). 1C).…”

“…Analyzing the timing of heat stress imposition, and as was previously documented for kernel biochemical composition (Mayer et al, , 2016, most of the kernel hardness-related traits seemed to have a greater sensitivity to heat stress at early than at late stages of the effective grainfilling period, which could not be attributed to nonuniform heating across stages (i.e., mean daily maximum air temperatures achieved within heated shelters during Stage 1 and Stage 2 were similar; Mayer et al, 2014). In environments prone to extremely high temperature, moving the sowing date earlier or later in the growing season could be a key strategy for preventing the early grain-filling stages from coinciding with the period of greater risk of heat-stress incidence, and thereby reducing the associated loss in maize hardness.…”

“…To our knowledge, no effort has been made to elucidate the effects of episodes of extremely high temperatures (>35°C) on kernel hardness of field-grown maize crops. Particularly, heat stress during early stages of the grainfilling period can enhance kernel protein concentration and alter protein composition by increasing the relative abundance of glutelins and band g-zeins at the expense of a-zeins (Mayer et al, 2016). Particularly, heat stress during early stages of the grainfilling period can enhance kernel protein concentration and alter protein composition by increasing the relative abundance of glutelins and band g-zeins at the expense of a-zeins (Mayer et al, 2016).…”

“…The incidence of such abiotic constraint, which is expected to become more frequent with global warming (Eyshi Rezaei et al, 2015), can provoke large grain yield losses (i.e., heat stress; Wahid et al, 2007) through kernel abortion (Rattalino Edreira et al, 2011) and/or cessation of kernel growth Rattalino Edreira et al, 2014). Particularly, heat stress during early stages of the grainfilling period can enhance kernel protein concentration and alter protein composition by increasing the relative abundance of glutelins and band g-zeins at the expense of a-zeins (Mayer et al, 2016). Given the positive influence of protein concentration and g-zeins on kernel hardness and its related traits (Fox and Manley, 2009;Gerde et al, 2016, and references cited therein), heat stress could lead to lighter but harder kernels.…”