Plant domestication slows pest evolution

Comparative Transcriptome Analysis Reveals the Molecular Basis of Brassica napus in Response to Aphid Stress

Rapeseed is a globally important economic crop that can be severely impacted by aphids. However, our understanding of rapeseed resistance to aphid stress is very limited. In this study, we analyzed the resistance characteristics of the low aphid-susceptible variety APL01 and the highly aphid-susceptible variety Holly in response to aphid stress. APL01 had a more significant inhibitory effect on aphid proliferation compared with Holly during the early stage of inoculation, whereas Holly showed stronger tolerance to aphid stress compared with APL01 during the later stage of inoculation. Through transcriptome, physiological, and gene expression analyses, it was revealed that chitinase activity, catalase activity, calcium signal transduction, and activation of systemic acquired resistance might be involved in aphid resistance in B. napus. The degree of inhibition of photosynthesis in plants under aphid stress directly determines the tolerance of B. napus to aphid stress. Furthermore, four promising candidate genes were screened from eight genes related to rapeseed response to biotic stress through RT-qPCR analysis of gene expression levels. These research findings represent an important step forward in understanding the resistance of rapeseed to aphid stress and provide a solid foundation for the cloning of genes responsible for this resistance.

Solid-State Fermentation: Applications and Future Perspectives for Biostimulant and Biopesticides Production

With the expansion of the green products market and the worldwide policies and strategies directed toward a green revolution and ecological transition, the demand for innovative approaches is always on the rise. Among the sustainable agricultural approaches, microbial-based products are emerging over time as effective and feasible alternatives to agrochemicals. However, the production, formulation, and commercialization of some products can be challenging. Among the main challenges are the industrial production processes that ensure the quality of the product and its cost on the market. In the context of a circular economy, solid-state fermentation (SSF) might represent a smart approach to obtaining valuable products from waste and by-products. SSF enables the growth of various microorganisms on solid surfaces in the absence or near absence of free-flowing water. It is a valuable and practical method and is used in the food, pharmaceutical, energy, and chemical industries. Nevertheless, the application of this technology in the production of formulations useful in agriculture is still limited. This review summarizes the literature dealing with SSF agricultural applications and the future perspective of its use in sustainable agriculture. The survey showed good potential for SSF to produce biostimulants and biopesticides useful in agriculture.

Domestication provides durum wheat with protection from locust herbivory

Lower plant resistance to herbivores following domestication has been suggested as the main cause for higher feeding damage in crops than in wild progenitors. While herbivore compensatory feeding has also been proposed as a possible mechanism for raised damage in crops with low nutritional quality, predictions regarding the effects of plant domestication on nutritional quality for herbivores remain unclear. In particular, data on primary metabolites, even major macronutrients, measured in the organs consumed by herbivores, are scarce. In this study, we used a collection of 10 accessions of wild ancestors and 10 accessions of modern progenies of Triticum turgidum to examine whether feeding damage and selectivity by nymphs of Locusta migratoria primarily depended on five leaf traits related to structural resistance or nutrient profiles. Our results unexpectedly showed that locusts favored wild ancestors over domesticated accessions and that leaf toughness and nitrogen and soluble protein contents increased with the domestication process. Furthermore, the quantitative relationship between soluble protein and digestible carbohydrates was found to poorly meet the specific requirements of the herbivore, in all wheat accessions, both wild and modern. The increase in leaf structural resistance to herbivores in domesticated tetraploid wheat accessions suggested that resource allocation trade-offs between growth and herbivory resistance may have been disrupted by domestication in the vegetative organs of this species. Since domestication did not result in a loss of nutritional quality in the leaves of the tetraploid wheat, our results rather provides evidence for a role of the content of plants in nonnutritive nitrogenous secondary compounds, possibly deterrent or toxic, at least for grasshopper herbivores.

Wheat Rhizosphere Microbiota Respond to Changes in Plant Genotype, Chemical Inputs, and Plant Phenotypic Plasticity

Modern wheat varieties that were selected since the Green Revolution are generally grown with synthetic chemical inputs, and ancient varieties released before1960 without. Thus, when changes occur in rhizosphere microbiota structure, it is not possible to distinguish if they are due to (i) changes in wheat genotypes by breeding, (ii) modifications of the environment via synthetic chemical inputs, or (iii) phenotypic plasticity, the interaction between wheat genotype and the environment. Using a crossed factorial design in the field, we evaluated the effects of either modern or ancient wheat varieties grown with or without chemical inputs (a N fertilizer, a fungicide, and an herbicide) on “microbiome as a phenotype.” We analyzed the rhizosphere microbiota by bacterial and fungal amplicon sequencing, coupled with microscope observations of mycorrhizal associations. We found that plant genotype and phenotypic plasticity had the most influence on rhizosphere microbiota, whereas inputs had only marginal effects. Phenotypic plasticity was particularly important in explaining diversity variations in bacteria and fungi but had no impact on the mycorrhizal association. Our results show an interest in considering the interaction between wheat genotype and the environment in breeding programs, by focusing on genes involved in the phenotypic plasticity of plant-microbe interactions.

Identification and Characterization of Resistance of Three Aphid Species on Contrasting Alfalfa Cultivars

Simple Summary

Aphis craccivora Koch (cowpea aphid, CPA), Acyrthosiphon pisum Harris (pea aphid, PA) and Therioaphis trifolii Buckton (spotted alfalfa aphid, SAA) are the three species of devastating pests on alfalfa in China. A study was conducted in the laboratory for identification and characterization of resistance to these three aphids among 16 of the main alfalfa cultivars planted in China. Resistance was indicated by antibiosis, antixenosis, and measuring feeding behavior using EPG (electrical penetration graph). The results indicated that different alfalfa cultivars have significantly different resistance levels to a particular species of aphid, and the same alfalfa variety also has different resistance to the three aphid species. Specifically, we evaluated the resistance of different alfalfa cultivars to CPA, which can help us for further study on the defense mechanism against CPA and for better management of this pest.

Abstract

Aphids on alfalfa (Medicago sativa) including Aphis craccivora Koch (cowpea aphid, CPA), Acyrthosiphon pisum Harris (pea aphid, PA) and Therioaphis trifolii Buckton (spotted alfalfa aphid, SAA) cause significant yield losses worldwide. In this experiment, the development of these three species of aphids on 16 alfalfa cultivars was compared. The results showed that the plant cultivar had a significant influence on the development of aphids as there are significant differences in the body weight of aphids reared on different alfalfa cultivars. In addition, antibiosis between the alfalfa cultivars Pegasis and Gannong NO.9 and the three species of aphids was evaluated by measuring aphid body weight and fecundity. Antixenosis was measured using choice tests, and feeding behavior was quantified using electrical penetration graphs (EPG). The Pegasis cultivar was observed to have both antibiosis and antixenosis effects with CPA, but was susceptible to PA and SAA compared with the Gannong NO.9 cultivar. CPA had less mean body weight, less fecundity, and shorter feeding time on the Pegasis cultivar, and preferred to settle on Gannong NO.9 cultivar. In contrast, Gannong NO.9 exhibits antibiosis and antixenosis to PA and SAA compared with Pegasis, as shown by lower body weight, lower fecundity and chose to settle less often, but EPG data showed that PA and SAA showed no different significance in feeding behavior between Pegasis and Gannong NO.9.

Influence of wild, local and cultivated tobacco varieties on the oviposition preference and offspring performance of Spodoptera litura

The influences of different plants on herbivores have recently attracted research interest; however, little is known regarding the effects of wild, local and cultivated varieties of the same plant from the same origin on herbivores. This study aimed to examine the effects of different tobacco varieties from the same origin on the oviposition preference and offspring performance of Spodoptera litura. We selected two wild ('Bishan wild tobacco' and 'Badan wild tobacco'), two local ('Liangqiao sun-cured tobacco' and 'Shuangguan sun-cured tobacco') and two cultivated ('Xiangyan No. 5' and 'Cunsanpi') tobacco varieties from Hunan Province, China. We found that female S. litura varied in oviposition preferences across the tobacco varieties. They preferred to lay eggs on the cultivated varieties, followed by the local varieties, with the wild varieties being the least preferred. Furthermore, different tobacco varieties significantly influenced the life history parameters of S. litura. Survival rate, pupal weight, emergence rate and adult dry weight decreased in the following order: cultivated varieties > local varieties > wild varieties. Conversely, the pupal stage and development period decreased in the following order: wild varieties > local varieties > cultivated varieties. Therefore, we conclude that wild tobacco varieties have higher resistance to S. litura than cultivated and local varieties, reflecting the evolutionary advantages of wild tobacco varieties.

Comparative analysis of the rhizomicrobiome of the wild versus cultivated crop: insights from rice and soybean

Plant domestication was a pivotal accomplishment in human history, which led to a reduction in genetic diversity of crop species; however, there was less research focus on how this reduced genetic diversity of crops in affecting rhizosphere microbial communities during crop domestication process. Here, we used high-throughput sequencing to explore the different effects of crops domestication on rhizosphere microbial community structure of rice (Oryza sativa L. and Oryza rufipogon Griff.) and soybean (Glycine max L. and Glycine soja Sieb. et Zucc.). Results indicated that rhizosphere fungal communities are more strongly influenced by crop domestication than bacterial communities. There was a stronger relationship for fungi and bacteria in the cultivated crops than in the wild relatives. Results also showed that the wild varieties had a higher abundance of beneficial symbionts and a lower abundance of pathogens comparing with the cultivated varieties. There was a similar tendency for both rice and soybean in rhizosphere microbial communities by comparing wild crops and their cultivated varieties. In conclusion, crop domestication had a stronger effect on the fungal communities than on the bacterial communities and had improved the microbial relationship in rhizosphere of cultivated crops.

Crop domestication: anthropogenic effects on insect-plant interactions in agroecosystems

Although crop domestication is considered a model system for understanding evolution, the eco-evolutionary effects of domesticated crops on higher trophic levels have rarely been discussed. Changes in size, shape, quality, or timing of plant traits during domestication can influence entire arthropod communities. The plant traits specific to crop plants can be rare in nature. In the face of such novelty, it is important to understand how species and trophic levels vary in their responses. Although the evidence is still limited, crop domestication can influence the ecology, genetics, and evolution of plants, insect herbivores, natural enemies, and pollinators. We call for more study on how eco-evolutionary processes operate under domestication to provide new insight on the sustainability of species interactions within agroecosystems.

Targeting detoxification genes by phloem-mediated RNAi: A new approach for controlling phloem-feeding insect pests

Many phloem-feeding insects are considered severe pests of agriculture and are controlled mainly by chemical insecticides. Continued extensive use of these inputs is environmentally undesirable, and also leads to the development of insecticide resistance. Here, we used a plant-mediated RNA interference (RNAi) approach, to develop a new control strategy for phloem-feeding insects. The approach aims to silence "key" detoxification genes, involved in the insect's ability to neutralize defensive and toxic plant chemistry. We targeted a glutathione S-transferase (GST) gene, BtGSTs5, in the phloem-feeding whitefly Bemisia tabaci, a devastating global agricultural pest. We report three major findings. First, significant down regulation of the BtGSTs5 gene was obtained in the gut of B. tabaci when the insects were fed on Arabidopsis thaliana transgenic plants expressing dsRNA against BtGSTs5 under a phloem-specific promoter. This brings evidence that phloem-feeding insects can be efficiently targeted by plant-mediated RNAi. Second, in-silico and in-vitro analyses indicated that the BtGSTs5 enzyme can accept as substrates, hydrolyzed aliphatic- and indolic-glucosinolates, and produce their corresponding detoxified conjugates. Third, performance assays suggested that the BtGSTs5 gene silencing prolongs the developmental period of B. tabaci nymphs. Taken together, these findings suggest that BtGSTs5 is likely to play an important role in enabling B. tabaci to successfully feed on glucosinolate-producing plants. Targeting the gene by RNAi in Brassicaceae cropping systems, will likely not eliminate the pest populations from the fields but will significantly reduce their success over the growing season, support prominent activity of natural enemies, eventually allowing the establishment of stable and sustainable agroecosystem.

Plant domestication decreases both constitutive and induced chemical defences by direct selection against defensive traits

Studies reporting domestication effects on plant defences have focused on constitutive, but not on induced defences. However, theory predicts a trade-off between constitutive (CD) and induced defences (ID), which intrinsically links both defensive strategies and argues for their joint consideration in plant domestications studies. We measured constitutive and induced glucosinolates in wild cabbage (Brassica oleracea ssp. oleracea) and two domesticated varieties (B. oleracea var. acephala and B. oleracea var. capitata) in which the leaves have been selected to grow larger. We also estimated leaf area (proxy of leaf size) to assess size-defence trade-offs and whether domestication effects on defences are indirect via selection for larger leaves. Both CD and ID were lower in domesticated than in wild cabbage and they were negatively correlated (i.e. traded off) in all of the cabbage lines studied. Reductions in CD were similar in magnitude for leaves and stems, and CD and leaf size were uncorrelated. We conclude that domestication of cabbage has reduced levels not only constitutive defences but also their inducibility, and that reductions in CD may span organs not targeted by breeding. This reduction in defences in domesticated cabbage is presumably the result of direct selection rather than indirect effects via trade-offs between size and defences.

The eco-evolutionary impacts of domestication and agricultural practices on wild species

Agriculture is a dominant evolutionary force that drives the evolution of both domesticated and wild species. However, the various mechanisms of agriculture-induced evolution and their socio-ecological consequences are not often synthetically discussed. Here, we explore how agricultural practices and evolutionary changes in domesticated species cause evolution in wild species. We do so by examining three processes by which agriculture drives evolution. First, differences in the traits of domesticated species, compared with their wild ancestors, alter the selective environment and create opportunities for wild species to specialize. Second, selection caused by agricultural practices, including both those meant to maximize productivity and those meant to control pest species, can lead to pest adaptation. Third, agriculture can cause non-selective changes in patterns of gene flow in wild species. We review evidence for these processes and then discuss their ecological and sociological impacts. We finish by identifying important knowledge gaps and future directions related to the eco-evolutionary impacts of agriculture including their extent, how to prevent the detrimental evolution of wild species, and finally, how to use evolution to minimize the ecological impacts of agriculture.This article is part of the themed issue 'Human influences on evolution, and the ecological and societal consequences'.

Growing larger with domestication: a matter of physiology, morphology or allocation?

Domestication might affect plant size. We investigated whether herbaceous crops are larger than their wild progenitors, and the traits that influence size variation. We grew six crop plants and their wild progenitors under common garden conditions. We measured the aboveground biomass gain by individual plants during the vegetative stage. We then tested whether photosynthesis rate, biomass allocation to leaves, leaf size and specific leaf area (SLA) accounted for variations in whole-plant photosynthesis, and ultimately in aboveground biomass. Despite variations among crops, domestication generally increased the aboveground biomass (average effect +1.38, Cohen's d effect size). Domesticated plants invested less in leaves and more in stems than their wild progenitors. Photosynthesis rates remained similar after domestication. Variations in whole-plant C gains could not be explained by changes in leaf photosynthesis. Leaves were larger after domestication, which provided the main contribution to increases in leaf area per plant and plant-level C gain, and ultimately to larger aboveground biomass. In general, cultivated plants have become larger since domestication. In our six crops, this occurred despite lower investment in leaves, comparable leaf-level photosynthesis and similar biomass costs of leaf area (i.e. SLA) than their wild progenitors. Increased leaf size was the main driver of increases in aboveground size. Thus, we suggest that large seeds, which are also typical of crops, might produce individuals with larger organs (i.e. leaves) via cascading effects throughout ontogeny. Larger leaves would then scale into larger whole plants, which might partly explain the increases in size that accompanied domestication.

Plant domestication and the assembly of bacterial and fungal communities associated with strains of the common sunflower, Helianthus annuus

Root and rhizosphere microbial communities can affect plant health, but it remains undetermined how plant domestication may influence these bacterial and fungal communities. We grew 33 sunflower (Helianthus annuus) strains (n = 5) that varied in their extent of domestication and assessed rhizosphere and root endosphere bacterial and fungal communities. We also assessed fungal communities in the sunflower seeds to investigate the degree to which root and rhizosphere communities were influenced by vertical transmission of the microbiome through seeds. Neither root nor rhizosphere bacterial communities were affected by the extent of sunflower domestication, but domestication did affect the composition of rhizosphere fungal communities. In particular, more modern sunflower strains had lower relative abundances of putative fungal pathogens. Seed-associated fungal communities strongly differed across strains, but several lines of evidence suggest that there is minimal vertical transmission of fungi from seeds to the adult plants. Our results indicate that plant-associated fungal communities are more strongly influenced by host genetic factors and plant breeding than bacterial communities, a finding that could influence strategies for optimizing microbial communities to improve crop yields.

Mechanisms and evolution of plant resistance to aphids

Aphids are important herbivores of both wild and cultivated plants. Plants rely on unique mechanisms of recognition, signalling and defence to cope with the specialized mode of phloem feeding by aphids. Aspects of the molecular mechanisms underlying aphid-plant interactions are beginning to be understood. Recent advances include the identification of aphid salivary proteins involved in host plant manipulation, and plant receptors involved in aphid recognition. However, a complete picture of aphid-plant interactions requires consideration of the ecological outcome of these mechanisms in nature, and the evolutionary processes that shaped them. Here we identify general patterns of resistance, with a special focus on recognition, phytohormonal signalling, secondary metabolites and induction of plant resistance. We discuss how host specialization can enable aphids to co-opt both the phytohormonal responses and defensive compounds of plants for their own benefit at a local scale. In response, systemically induced resistance in plants is common and often involves targeted responses to specific aphid species or even genotypes. As co-evolutionary adaptation between plants and aphids is ongoing, the stealthy nature of aphid feeding makes both the mechanisms and outcomes of these interactions highly distinct from those of other herbivore-plant interactions.