Different grain-filling rates explain grain-weight differences along the wheat ear

Area of Science:

• Agricultural Science
• Plant Physiology
• Crop Science

Background:

• Thousand grain weight is a key determinant of wheat grain yield.
• Individual grain weight is influenced by its position within the ear and spikelet.
• Understanding factors affecting grain weight variation is crucial for improving crop yields.

Purpose of the Study:

• To quantify the impact of floret anthesis date, carpel weight, and grain filling kinetics on individual final grain weight in wheat.
• To analyze how position along the ear and within the spikelet affects these parameters.
• To elucidate the relationship between flowering time, grain filling, and final grain weight variation.

Main Methods:

• Two bread wheat cultivars were grown under greenhouse conditions.
• Ears were sampled from anthesis to harvest, divided into basal, central, and apical sections.
• Individual grains were dissected, and their flowering time, carpel weight, and growth kinetics during grain filling were analyzed.

Main Results:

• Florets in the central ear section anthesed first, followed by apical, then basal.
• Within spikelets, proximal florets anthesed before distal ones.
• No significant systematic effect of flowering time shift on final grain weight was observed.
• Grains from the central ear section were significantly heavier than basal and apical grains.
• Differences in grain weight were primarily attributed to variations in mean grain filling rates.

Conclusions:

• Grain filling rate, rather than anthesis timing, is the primary driver of individual grain weight variation along the wheat ear.
• Positional effects along the ear significantly influence grain weight, mainly through differential grain filling rates.
• Analysis of growth kinetics provides a better understanding of individual grain weight variability in wheat.