Conditional QTL Analysis and Fine Mapping for Thousand-Kernel Weight in Common Wheat

Area of Science:

• Plant genetics
• Quantitative genetics
• Crop improvement

Background:

• Thousand-kernel weight (TKW) is a crucial yield component in crops.
• Understanding the genetic basis of TKW and its relationship with kernel size traits is vital for breeding programs.
• Previous studies have identified quantitative trait loci (QTLs) for TKW, but their individual effects and interactions with kernel dimensions require further elucidation.

Purpose of the Study:

• To dissect the genetic architecture of thousand-kernel weight (TKW) by analyzing its relationship with kernel length (KL), kernel width (KW), and kernel diameter ratio (KDR) at the individual QTL level.
• To identify both unconditional and conditional QTLs influencing TKW and related traits.
• To fine-map a major-effect TKW QTL and determine the primary genetic driver of TKW variation.

Main Methods:

• Utilized a recombinant inbred line (RIL) population for unconditional and conditional QTL analysis of TKW.
• Employed a simplified physical map for QTL identification and analysis.
• Conducted fine mapping of a major TKW QTL using near-isogenic lines (NILs).

Main Results:

• Identified 37 unconditional and 34 conditional QTLs for TKW and related traits.
• Detected 6 QTLs with independent effects and 18 QTLs with common influences from multiple kernel traits.
• Discovered 26 pairs of epistatically interacting QTLs and fine-mapped a major TKW QTL (QTkw1B) to a specific interval on chromosome 1B.
• Conditional and NIL-based analyses confirmed kernel length as the main contributor to TKW increase.

Conclusions:

• The combined QTL mapping approach provides a deeper understanding of the genetic interrelationships between TKW and kernel size traits.
• Kernel length plays a significant role in determining thousand-kernel weight.
• The identified QTLs and fine-mapped region offer a theoretical foundation for future candidate gene discovery and marker-assisted breeding for improved TKW.