A major QTL controlling deep rooting on rice chromosome 4

Area of Science:

• Plant genetics
• Agronomy
• Crop science

Background:

• Drought is a major abiotic stress limiting rainfed rice production.
• Improving root system architecture, specifically deep rooting, is crucial for drought tolerance in rice.
• Shallow-rooting rice cultivars are particularly vulnerable to drought stress.

Purpose of the Study:

• To identify quantitative trait loci (QTLs) associated with the ratio of deep rooting (RDR) in rice.
• To analyze genetic factors controlling deep rooting in three mapping populations.
• To enhance drought tolerance in shallow-rooting rice varieties through genetic improvement.

Main Methods:

• Analysis of three F₂ mapping populations derived from crosses between shallow-rooting and deep-rooting rice varieties.
• Quantitative trait loci (QTL) mapping to identify genomic regions associated with deep rooting.
• Phenotypic variance analysis to determine the impact of identified QTLs.

Main Results:

• Five RDR QTLs were detected on chromosomes 2, 4, and 6.
• QTLs on chromosome 4 were consistently located across all three populations.
• These chromosome 4 QTLs explained a significant portion (32.0%–56.6%) of the total RDR phenotypic variance.

Conclusions:

• A key genetic region controlling root growth angle in rice is located on chromosome 4.
• The identified QTLs provide valuable targets for breeding deep-rooting rice cultivars.
• Genetic improvement of root system architecture can enhance rice resilience to drought stress.