Although non-genetic inheritance is thought to play an important role in plant ecology and evolution, evidence for adaptive transgenerational plasticity is scarce. Here, we investigated the consequences of copper excess on offspring defences and fitness under recurring stress in the duckweed Spirodela polyrhiza across multiple asexual generations . Growing large monoclonal populations (greater than 10 000 individuals) for 30 generations under copper excess had negative fitness effects after short and no fitness effect after prolonged growth under recurring stress. These time-dependent growth rates were likely influenced by environment-induced transgenerational responses, as propagating plants as single descendants for 2 to 10 generations under copper excess had positive, negative or neutral effects on offspring fitness depending on the interval between initial and recurring stress (5 to 15 generations). Fitness benefits under recurring stress were independent of flavonoid accumulations, which in turn were associated with altered plant copper concentrations. Copper excess modified offspring fitness under recurring stress in a genotype-specific manner, and increasing the interval between initial and recurring stress reversed these genotype-specific fitness effects. Taken together, these data demonstrate time- and genotype-dependent adaptive and non-adaptive transgenerational responses under recurring stress, which suggests that non-genetic inheritance alters the evolutionary trajectory of clonal plant lineages in fluctuating environments.

Understanding non-target-site resistance (NTSR) to herbicides represents a pressing challenge as NTSR is widespread in many weeds. Using giant duckweed (Spirodela polyrhiza) as a model, we systematically investigated genetic and molecular mechanisms of diquat resistance, which can only be achieved via NTSR. Quantifying the diquat resistance of 138 genotypes, we revealed an 8.5-fold difference in resistance levels between the most resistant and most susceptible genotypes. Further experiments suggested that diquat uptake and antioxidant-related processes jointly contributed to diquat resistance in S. polyrhiza. Using a genome-wide association approach, we identified several candidate genes, including a homolog of dienelactone hydrolase, that are associated with diquat resistance in S. polyrhiza. Together, these results provide new insights into the mechanisms and evolution of NTSR in plants.

The exceptionally high growth rate and high flavonoid content make the giant duckweed Spirodela polyrhiza (L.) Schleid. (Arales: Lemnaceae Martinov) an ideal organism for food production and metabolic engineering. To facilitate this, identification of the genetic basis underlying growth and metabolic traits is essential. Here, we analysed growth and content of 42 metabolites in 137 S. polyrhiza genotypes and characterized the genetics underpinning these traits using a genome‐wide association (GWA) approach. We found that biomass positively correlated with the content of many free amino acids, including L‐glutamine, L‐tryptophan, and L‐serine, but negatively correlated with specialized metabolites, such as flavonoids. GWA analysis showed that several candidate genes involved in processes such as photosynthesis, protein degradation, and organ development were jointly associated with multiple metabolic traits. The results suggest the above genes are suitable targets for simultaneous optimization of duckweed growth and metabolite levels. This study provides insights into the metabolic diversity of S. polyrhiza and its underlying genetic architecture, paving the way for industrial applications of this plant via targeted breeding or genetic engineering.

The exceptionally high growth rate and high contents of flavonoids make the giant duckweed Spirodela polyrhiza (L.) Schleid. (Arales: Lemnaceae) an ideal organism for food production and metabolic engineering. To facilitate this, identification of the genetic basis underlying growth and metabolic traits is essential. Here, we characterized the genetics underpinning the growth and contents of 42 metabolites in S. polyrhiza using a genome-wide association (GWA) approach. We found that biomass positively correlates with contents of many free amino acids, including L-Glutamine, L-Tryptophane and L-Serine, but negatively correlates with many specialized metabolites, such as flavonoids. GWA analysis showed that several candidate genes were simultaneously associated with several metabolic traits, qualifying them as targets for growth manipulation and metabolic engineering. Together, this study provides insights into the metabolic diversity of S. polyrhiza and its underlying genetic architecture, paving the way for industrial applications of this plant via targeted breeding or genetic engineering.