Surprisingly frequent chromosomal instability in cultivated peanut

Area of Science:

• Genetics
• Plant Biology
• Genomics

Background:

• Cultivated peanut (Arachis hypogaea) has a narrow genetic origin but exhibits wide phenotypic diversity.
• Early generations of polyploidy in peanut show high instability and homoeologous exchange, generating diversity.
• Cultivated peanut is generally considered genetically stable due to selection, contrasting with early-generation instability.

Purpose of the Study:

• To investigate if chromosomal instability persists in modern cultivated peanut.
• To quantify the frequency of spontaneous large-scale chromosomal changes in pure pedigree peanut.
• To understand the role of residual instability in peanut's adaptability and evolution.

Main Methods:

• Advancing lineages from a single peanut plant ('Tifrunner' cultivar) through seven generations in a controlled greenhouse environment.
• Analyzing 233 plants for chromosomal abnormalities, including deletions and aneuploidies (ABBB composition).
• Reinterpreting previously published data from recombinant inbred populations to assess instability frequency.

Main Results:

• Identified three new large-scale chromosomal instability events in 233 plants: a deletion on chromosome B01 and two ABBB compositions.
• The B01 deletion was associated with reduced pod width and seed weight.
• At least 1% of pure pedigree Arachis hypogaea plants exhibit spontaneous large-scale chromosomal changes.

Conclusions:

• Chromosomal instability persists in cultivated peanut at a significant frequency (at least 1%).
• Spontaneous large-scale chromosomal changes contribute to peanut's long-term adaptability and evolution.
• The findings challenge the notion of complete genetic stability in modern cultivated peanut.