Population Genetics of Plant Pathogens

Abstract

Population genetics consider the origin, maintenance and spatiotemporal distribution of genetic variation of species under the influences of mutation, gene flow, recombination, drift and selection. Mutation is the primary source of genetic variation and its rates vary significantly among genomes within or among pathogen species. Recombination increases genetic variation and plays a key role in the dissipation of linkage disequilibrium. Gene flow increases the genetic variation of local populations but decreases population differentiation. The principle determinant of gene flow is the dispersal mechanism of plant pathogens. Genetic drift is determined by effective population size. Pathogen populations with large effective sizes tend to have less genetic drift, therefore greater genetic variation and be more stable over time. Natural selection can increase or decrease genetic variation and population differentiation, depending on the type of selection. Directional selection can cause a rapid loss of major resistance agrochemical effectiveness. Key Concepts Genetic variation of plant pathogens results from their coevolutionary interaction with hosts and other ecological factors. Mutation by which new nucleotide sequences are generated is the primary source of genetic variation and pathogen evolution. Stochastic change in the frequencies of neutral alleles by genetic drift in the pathogen populations leads to nonadaptive genetic differentiation while selection for ecological traits results in adaptive genetic differentiation. Pathogen evolution is escalated in modern agroecosystems attributable to monoculture, agricultural intensification and globalisation. Plant diseases cause more damage to the hosts in the newly invaded territories than in their centre of origin as a result of the lack of host–pathogen coevolution. Selection is the primary force responsible for the loss of resistance gene and agrochemical effectiveness. Natural selection on plant pathogens can be manipulated by spatiotemporal deployment of host resistance and application of agrochemicals. Resistance gene rotation can delay pathogen evolution and maximise the life span of resistance genes. Effective field hygiene can reduce both the epidemic severity of plant diseases and the evolutionary rate of plant pathogens.

New microsatellite markers for the population studies ofRacodium therryanum, a causal agent of snow blight in Japan

“…One more way of gene flow is human-related migration. Especially for soilborne fungi, dispersal with contaminated plant material is a remarkable source for long-distance gene flow (Agrios, 2005;Zhan, 2016). This might have happened also in this study, seedlings sampled in the forest sites had been grown and transplanted from the nursery.…”

Microbial genetic resources in food security to face COVID-19 pandemic

“…The main element of the process of coevolution is genetic reciprocity; i.e., when an organism develops a trait as an adaptive response towards a factor that affects its biological aptitude, the biological counterpart will respond by generating another trait or traits which will allow them to adapt to the new trait developed by the first organism, and so on (McDonald, 2004). The generation of these traits or phenotypes is ruled by different evolutionary forces (Zhan, 2016;McDonald, 2004), thus hosts, microorganisms and other organisms related to agricultural systems coevolve, adapting to their surroundings if anthropomorphic action guarantees time as a factor of evolution. Under conditions of biodiversity and ecological balance, for every trait generated, other traits are produced which weaken it and a balance or state of health can be maintained.…”

“…El proceso de coevolución tiene como elemento fundamental la reciprocidad genética; es decir, que cuando un organismo desarrolla un caracter como respuesta adaptativa hacia un factor que afecta su aptitud biológica, la contraparte biológica responderá generando otro carácter(es) que les permitirán adaptarse al nuevo caracter desarrollado por el primer organismo y así suscesivamente (McDonald, 2004). La generación de estos caracteres o fenotipos se rige por diferentes fuerzas evolutivas (Zhan, 2016;McDonald, 2004) Special Issue: Covid-19 and Plant Health, November, 2021…”

The Gene Flow Direction of Geographically Distinct Phytophthora infestans Populations in China Corresponds With the Route of Seed Potato Exchange

“…Gene flow, or migration, refers to the movement of alleles among spatially or temporally separated populations and is a major driving force in the evolution of populations. Gene flow may increase the genetic variation of local pathogen populations but decrease the genetic difference between populations, which can slow or limit population differentiation (Endler, 1973;Zhan, 2016). Population genetics studies have contributed to our understanding of the evolutionary history of plant pathogens, as well as to the development of strategies to prevent their spread in major crops (Mcdonald and Linde, 2002).…”