Lisa Han MSc, Yakimowski Lab Estimating the stability and heritability of resistance fueling copy number variation in glyphosate-resistant Amaranthus palmeri Copy number variation (CNV), especially when present in extrachromosomal fashion, provides unparalleled opportunity for speciation and adaptation. As observed in agricultural weed species, Amaranthus palmeri, CNV of the herbicide glyphosate’s target gene, EPSPS, has resulted in emergence of glyphosate-tolerant and resistant populations across the globe. The amplification of EPSPS copies in forms of extrachromosomal circular DNA (eccDNA) poses unique challenges when assessing the heritability of EPSPS CNV as its origin and the tethering mechanisms are still mostly unknown. I used 30 F0 pairs and 900 F1 individuals from glyphosate-resistant populations to examine the heritability of EPSPS CNV in relation to parental EPSPS CNV. The results display a shifting pattern in progeny CNV with increasing parental mean EPSPS copy number. Over 70% of progeny resulting from parental crosses of low-med CNV displayed an increase in EPSPS CNV in a single generation while the opposite pattern was observed in progeny resulting from high EPSPS CNV mean parental crosses. This result indicates a substantial decline in heritability after a threshold point of 48.8 mean parental EPSPS CNV. The weaker heritability of eccDNA gene copy number variation at high CNV suggests weak evolutionary potential of highly glyphosate resistant CNV individuals and may constrain the evolution of population EPSPS CNV mean.
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