A cytogenetic method for stacking gene pairs in common wheat

Area of Science:

• Plant genetics
• Cytogenetics
• Wheat breeding

Background:

• Gene stacking is crucial for crop improvement in wheat (Triticum aestivum L.).
• Robertsonian translocations offer a potential mechanism for non-reciprocal gene transfer and fixation.
• Understanding the cytological and genetic behavior of these translocations is key to their application.

Purpose of the Study:

• To assess the potential of non-reciprocal Robertsonian translocations for gene stacking in wheat.
• To investigate the cytological and genetic behavior of wheat translocations.
• To determine if fusion monosomics can be used to fix gene content in specific chromosome arms.

Main Methods:

• Crossing a double monosomic with a contrasting disomic wheat line.
• Identifying individuals with broken monosomes using DNA markers.
• Analyzing meiotic pairing and chromosome configurations using multi-color genome-specific fluorescence in situ hybridization (mcGISH).
• Conducting genetic analysis of testcrosses and doubled haploids.

Main Results:

• Two instances of double breaks (potential translocations) were identified in ovule progeny.
• Fusion monosomics formed trivalents during meiosis, with preferential alternate (V-shaped) disjunction.
• Quasi-linkage was observed for loci in hemizygous ends of the trivalent.
• Selective advantage favored standard chromosomes over deficiencies in male testcrosses and doubled haploids.

Conclusions:

• Non-reciprocal Robertsonian translocations can be generated in wheat.
• Fusion monosomics facilitate temporary linkage of gene pairs via alternate disjunction.
• Combined effects of alternate disjunction and selection lead to fixation of gene content in progeny.
• This mechanism offers a strategy for targeted joint fixation of gene pairs in wheat.