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Quantifying pre- and post-anthesis heat waves on grain number and grain weight of contrasting wheat cultivars

The study titled “Quantifying pre- and post-anthesis heat waves on grain number and grain weight of contrasting wheat cultivars” investigates the impact of heat stress on wheat productivity. As temperatures rise, wheat faces challenges in maintaining grain yield. Heat stress adversely affects two critical components: grain number per m² (GN) and average grain weight (AGW). However, it remains unclear whether the sensitivity of these components differs and whether their relevance for unstressed yield determination varies across different wheat cultivars.

The key aspects of the study are:

1. Objective and Research Question:
   • This study aims to explore the plasticity of GN and AGW in response to heat waves during pre-anthesis and post-anthesis stages.
   • We investigate whether the sensitivity of these components varies based on the relevance of each component for determining yield in specific wheat cultivars.
2. Materials and Methods:
   • Field experiments were conducted in two locations in Catalonia, Spain.
   • Two contrasting wheat genotypes, Pistolo and Sublim, were selected for their differences in AGW and GN.
   • Heat stress treatments were applied using portable tents with transparent polyethylene films:
     • Pre-anthesis heat stress (pre-AN HT): Applied during booting.
     • Post-anthesis heat stress (post-AN HT): Imposed 15 days after anthesis.
   • The pre- and post-AN HT treatments also involved altering source-sink ratios by removing spikelets on one side of the spike (de-graining) and removing alternate leaves (defoliation).
3. Findings:
   • AGW Differences: Pistolo consistently had fewer but heavier grains than Sublim. These differences were constitutive and not due to resource scarcity.
   • Heat Stress Impact: Both pre-AN HT and post-AN HT led to yield penalties, but pre-AN HT had a greater impact.
   • GN Reduction Mechanism: Pre-AN HT reduced GN mainly through grain abortion, not floret primordia mortality.
   • AGW Reduction Mechanism: Post-AN HT directly reduced potential grain weight (PGW) rather than altering source strength.
   • Cultivar Trends: Cultivars producing more grains constitutively showed less sensitivity of GN to pre-AN HT, while those with heavier grains were less sensitive to post-AN HT.

In summary, understanding the plasticity of GN and AGW under heat stress can inform strategies for improving wheat productivity in a changing climate.

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