Crop adaptation to climate change:An evolutionary perspective

The disciplines of evolutionary biology and plant and animal breeding have been intertwined throughout their development,with responses to artificial selection yielding insights into the action of natural selection and evolutionary biology providing statistical and conceptual guidance for modern breeding.Here we offer an evolutionary perspective on a grand challenge of the 21st century:feeding humanity in the face of climate change.We first highlight promising strategies currently under way to adapt crops to current and future climate change.These include methods to match crop varieties with current and predicted environments and to optimize breeding goals,management practices,and crop microbiomes to enhance yield and sustainable production.We also describe the promise of crop wild relatives and recent technological innovations such as speed breeding,genomic selection,and genome editing for improving environmental resilience of existing crop varieties or for developing new crops.Next,we discuss how methods and theory from evolutionary biology can enhance these existing strategies and suggest novel approaches.We focus initially on methods for reconstructing the evolutionary history of crops and their pests and symbionts,because such historical information provides an overall framework for crop-improvement efforts.We then describe how evolutionary approaches can be used to detect and mitigate the accumulation of deleterious mutations in crop genomes,identify alleles and mutations that underlie adaptation(and maladaptation)to agricultural environments,mitigate evolutionary trade-offs,and improve critical proteins.Continuing feedback between the evolution and crop biology communities will ensure optimal design of strategies for adapting crops to climate change.

Genomics of plant speciation

Studies of plants have been instrumental for revealing how new species originate.For several decades,botanical research has complemented and,in some cases,challenged concepts on speciation developed via the study of other organisms while also revealing additional ways in which species can form.Now,the ability to sequence genomes at an unprecedented pace and scale has allowed biologists to settle decades-long debates and tackle other emerging challenges in speciation research.Here,we review these recent genome-enabled developments in plant speciation.We discuss complications related to identification of reproductive isolation(RI)loci using analyses of the landscape of genomic divergence and highlight the important role that structural variants have in speciation,as increasingly revealed by new sequencing technologies.Further,we review how genomics has advanced what we know of some routes to new species formation,like hybridization or whole-genome duplication,while casting doubt on others,like population bottlenecks and genetic drift.While genomics can fast-track identification of genes and mutations that confer RI,we emphasize that follow-up molecular and field experiments remain critical.Nonetheless,genomics has clarified the outsized role of ancient variants rather than new mutations,particularly early during speciation.We conclude by highlighting promising avenues of future study.These include expanding what we know so far about the role of epigenetic and structural changes during speciation,broadening the scope and taxonomic breadth of plant speciation genomics studies,and synthesizing information from extensive genomic data that have already been generated by the plant speciation community.

Genetically Based Trait Differentiation but Lack of Trade-offs between Stress Tolerance and Performance in Introduced Canada Thistle

Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations.Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions(nutrient stress,shading,simulated herbivory,drought,and mowing),to evaluate whether native and introduced individuals differ in performance or stress tolerance.An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse.Introduced populations tended to be larger in size,but no trade-off of stress tolerance with performance was detected;introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens.We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments,consistent with recent climate adaptation within the introduced range.Our results are consistent with rapid adaptation of introduced populations,but,contrary to predictions,the evolution of invasive traits did not come at the cost of reduced stress tolerance.

Mobilizing Crop Biodiversity

Over the past 70 years,the world has witnessed extraordinary growth in crop productivity,enabled by a suite of technological advances,including higher yielding crop varieties,improved farm management,synthetic agrochemicals,and agricultural mechanization.While this"Green Revolution"intensified crop production,and is credited with reducing famine and malnutrition,its benefits were accompanied by several undesirable collateral effects(Pingali,2012).These include a narrowing of agricultural biodiversity,stemming from increased monoculture and greater reliance on a smaller number of crops and crop varieties for the majority of our calories.This reduction in diversity has created vulnerabilities to pest and disease epidemics,climate variation,and ultimately to human health(Harlan,1972).

Plant Evolutionary Adaptation

In 1973,evolutionary biologist Theodosius Dobzhansky penned a famous essay titled“Nothing in Biology Makes Sense Except in the Light of Evolution”(Dobzhansky,1973).In the essay,he described how many features of biology,such as the adaptive radiations of Drosophila fruit flies and the similarity of embryo development across animal species,are best explained by evolution.Although Dobzhansky’s examples largely came from the animal kingdom,evolution is also the chief unifying theory in plant biology,linking molecular,cell,and whole organism-level phenomena.Plant Communications is intended to represent all of the plant sciences,and evolution can provide connections between the diverse studies published in the journal.This is illustrated by this special issue on Plant Evolutionary Adaptation,in which evolutionary approaches are employed to explain phenomena ranging from the geographic distribution of genomic variation to patterns of plant dispersal to the success of invasive species.Here we provide background for the topics addressed by these studies and highlight their main conclusions,moving from molecular to organismal-level studies.