fs3.1: a major fruit shape QTL conserved in Capsicum

Area of Science:

• Plant genetics
• Crop science
• Quantitative trait locus (QTL) analysis

Background:

• Fruit shape is a key trait in pepper (Capsicum annuum) breeding.
• The quantitative trait locus (QTL) fs3.1 was previously identified as a major determinant of fruit shape.

Purpose of the Study:

• To verify the effect of fs3.1 in different genetic backgrounds within Capsicum annuum.
• To investigate the conservation and effect of the fs3.1 region in other Capsicum species and related genera.
• To elucidate the developmental mechanism by which fs3.1 influences fruit shape.

Main Methods:

• Verification of fs3.1 effects in backcross inbred lines (BILs) of Capsicum annuum.
• Construction of advanced backcross populations and F2 introgression lines from crosses with Capsicum frutescens and Capsicum chinense.
• Testing of tomato (Lycopersicon spp.) introgression lines containing the homologous region.
• Measurement of ovary and fruit dimensions during development in near-isogenic lines.

Main Results:

• fs3.1 consistently affected fruit shape, width, and pericarp thickness in Capsicum annuum.
• QTLs for fruit shape and width were detected in crosses with C. frutescens and C. chinense, indicating conservation of the fs3.1 region.
• No significant fruit shape QTL was detected in tomato introgression lines.
• fs3.1 primarily increased longitudinal growth in early fruit development in C. annuum, but influenced width in interspecific crosses.

Conclusions:

• The fs3.1 region is a conserved QTL affecting pepper fruit shape across different Capsicum species.
• The developmental effect of fs3.1 on fruit dimensions is modulated by the genetic background.
• Understanding fs3.1's role provides insights for targeted breeding of desirable pepper fruit shapes.