QTL identification for yield components using single segment substitution lines dissected by rice CSSL-Z799

Area of Science:

• Plant genetics and breeding
• Crop improvement
• Quantitative trait loci (QTL) analysis

Background:

• Rice (Oryza sativa L.) is a vital cereal crop requiring continuous yield enhancement.
• Improving complex quantitative traits like yield components is challenging due to polygenic inheritance.
• Chromosome Segment Substitution Lines (CSSLs) are valuable tools for gene discovery and precision breeding in rice.

Purpose of the Study:

• To identify quantitative trait loci (QTL) controlling yield-related traits in rice using CSSLs.
• To elucidate the cellular mechanisms underlying enhanced grain length.
• To provide a foundation for gene cloning and marker-assisted breeding in rice.

Main Methods:

• Development of a CSSL (Z799) with substituted segments from a restorer line (R225) into a recipient background (Nipponbare).
• Phenotypic evaluation of CSSLs for yield-related traits.
• Quantitative trait loci (QTL) mapping using both F2 and CSSL populations.
• Microscopic analysis of lemma cells to investigate cellular mechanisms.

Main Results:

• A CSSL population (S1-S5) identified a total of 35 QTL, surpassing the 27 QTL found in an F2 population.
• Five distinct QTL (qGL1, qGL3, qGL12-1, qGL12-2, qGL12-3) significantly increased rice grain length without affecting grain width.
• Two mechanisms were identified: four QTL enhanced grain length via increased cell division, while one QTL promoted cell expansion.

Conclusions:

• The study successfully identified multiple QTL associated with enhanced grain length in rice.
• Distinct cellular mechanisms (cell division vs. cell expansion) contribute to grain length.
• The developed CSSLs offer a powerful platform for dissecting genetic complexity and advancing rice breeding programs.