Occurrence of Aneuploidy Across the Range of Coast Redwood (Sequoia sempervirens)

Abstract

1Aneuploidy, a condition characterized by an abnormal number of chromosomes, can have significant consequences for fitness of an organism, often manifesting in reduced fertility and other developmental challenges. In plants, aneuploidy is particularly complex to study, especially in polyploid species such as coast redwood (Sequoia sempervirens), which is a hexaploid conifer (2n=6x=66). This study leverages a novel Markov Chain Monte Carlo (MCMC) method based on sequence depth to investigate the occurrence of aneuploidy across the range of coast redwood. We show that aneuploidy is prevalent in second-growth redwoods, predominantly as additional chromosomes, while tissue culture plants frequently experience chromosome loss. Although our study does not directly assess the fitness of aneuploids, the frequency of chromosomal instability observed in tissue culture plants compared to second-growth and old-growth trees raises questions about their long-term developmental viability and potential to become established trees. These findings have significant implications for redwood conservation and restoration strategies, especially as tissue culture becomes the primary mode of producing nursery stock plants used in reforestation.