A Natural Major Module Confers the Trade-Off between Phenotypic Mean and Plasticity of Grain Chalkiness in Rice

Area of Science:

• Plant genetics
• Crop breeding
• Molecular biology

Background:

• A key challenge in crop breeding is the trade-off between improving a trait's average performance and its adaptability to environmental changes.
• Grain chalkiness, a crucial quality trait in cereals, is highly sensitive to environmental conditions, yet the mechanisms governing its mean-plasticity trade-off are poorly understood.
• Modern breeding practices have led to a decline in the phenotypic plasticity of grain chalkiness.

Purpose of the Study:

• To investigate the genetic and molecular mechanisms underlying the trade-off between the mean and plasticity of grain chalkiness.
• To identify genetic factors and environmental drivers influencing this trade-off.
• To propose a molecular breeding strategy for optimizing both grain chalkiness mean and plasticity.

Main Methods:

• Genome-wide association studies (GWAS) were conducted on ten grain chalkiness traits over five years using a mini-core collection.
• Quantitative trait locus (QTL) analysis was employed to map genetic loci controlling grain chalkiness mean and plasticity.
• Key genes, MPC5 and GCP6, were identified and their regulatory interactions investigated.

Main Results:

• A significant trade-off exists between grain chalkiness mean and plasticity, controlled by distinct genetic architectures.
• High temperature and wide grain width were identified as major environmental factors driving this trade-off.
• The transcription factor GCP6 was found to inhibit MPC5 expression, forming a regulatory module for the mean-plasticity trade-off.
• Minimal marker sets explained a substantial portion (two-thirds) of grain chalkiness variation.

Conclusions:

• The study elucidates the genetic basis of the mean-plasticity trade-off in grain chalkiness.
• Identified genes and regulatory pathways provide targets for improving grain quality and adaptability.
• A proof-of-concept breeding strategy demonstrates the potential for simultaneously optimizing grain chalkiness mean and plasticity.