Optimizing ethephon-mediated sucrose allocation to increase kernel number in maize

Area of Science:

• Plant Physiology
• Agricultural Science
• Molecular Biology

Background:

• Delaying ethephon application increases maize kernel number via enhanced assimilate allocation, but mechanisms are unclear.
• Understanding these mechanisms is crucial for optimizing maize yield through plant growth regulator timing.

Purpose of the Study:

• To investigate the physiological and molecular effects of delayed ethephon application on maize kernel development.
• To elucidate how ethephon timing influences dry matter accumulation, partitioning, and carbohydrate metabolism.

Main Methods:

• Ethephon applied at 8- to 15-leaf stages (E8-E15) to maize plants.
• Physiological measurements of internode elongation, dry matter, and kernel set.
• RNA-sequencing (RNA-seq) analysis at silking and 8 days post-silking.

Main Results:

• Delayed ethephon application (E14-E15) significantly shortened internodes and increased whole-plant dry matter.
• Ear dry matter increased, leading to higher kernel number (+8.3%) and grain yield (+7.4%) without affecting spikelet number.
• Elevated sucrose and trehalose-6-phosphate (T6P) in the ear at silking enhanced assimilate import and utilization.

Conclusions:

• Delayed ethephon application optimizes pre-flowering sucrose partitioning to the ear by retarding stem growth.
• Enhanced T6P accumulation and suppressed sucrose-non-fermenting1-related protein kinase (SnRK1) activity improve ear sink capacity.
• Post-flowering sucrose utilization is promoted, leading to increased maize kernel number and yield.