Identifying Heat Adaptability QTLs and Candidate Genes for Grain Appearance Quality at the Flowering Stage in Rice

Area of Science:

• Plant Genetics and Breeding
• Crop Science
• Molecular Biology

Background:

• High temperatures during flowering negatively impact rice grain appearance quality.
• Identifying genetic factors controlling grain quality under heat stress is crucial for crop improvement.
• Limited research exists on quantitative trait loci (QTLs) for grain appearance under heat stress.

Purpose of the Study:

• To identify QTLs and candidate genes associated with rice grain appearance quality under heat stress.
• To evaluate the role of specific genes in regulating grain development and heat tolerance.
• To provide genetic resources for enhancing rice grain quality in high-temperature environments.

Main Methods:

• Genome-Wide Association Study (GWAS) on a natural population of 525 rice accessions.
• Analysis of grain length (GL), grain width (GW), and grain chalkiness (GC) under heat stress.
• RNA-sequencing (RNA-seq), qRT-PCR, functional annotation, and mutant analysis of candidate genes.

Main Results:

• Identified 25 QTLs across 10 chromosomes associated with GL, GW, and GC under heat stress.
• Discovered three overlapping QTL hotspots on chromosomes 3, 5, and 11.
• Identified LOC_Os05g06920 (RSH4), LOC_Os05g06970 (peroxidase), and LOC_Os11g28104 (kinase) as high-priority candidate genes.
• Mutant analysis revealed these genes enhance grain appearance and heat tolerance, with some increasing chalkiness under normal conditions.
• Pyramiding superior alleles improved grain quality under high temperatures.

Conclusions:

• LOC_Os05g06920, LOC_Os05g06970, and LOC_Os11g28104 are crucial for rice grain development and heat tolerance.
• These genes play a significant role in maintaining grain appearance quality under heat stress.
• The identified QTLs and genes offer valuable genetic resources for breeding climate-resilient rice varieties.