Host Plant Resistance Research Articles

Superadditivity between control methods in pest management

AbstractPest Management (PM) has its 1959 origin in Integrated Control, a combination of a reduced dose of insecticide with biological control. At the time, it was not recognised that the interaction between these two control methods was more than additive. This ‘superadditivity’ can also be achieved with the full dose of insecticide, for example, by localising its application in space. There is also likely to be superadditivity in the interaction between partial plant resistance and biological control. Pests on resistant hosts are usually smaller and the same mortality can often be obtained with just two‐thirds or one‐half of the dose of insecticide needed on susceptible plants, giving superadditivity between partial plant resistance and chemical control. These positive interactions between biological control, chemical control and partial host plant resistance form a ‘Pest Management Triad’, though legislation and risk‐aversion may limit the practicability of protocols based on the Triad.

Editorial: Mechanisms of plant host resistance against viruses

Editorial: Mechanisms of plant host resistance against viruses

Identification of Soybean Mosaic Virus Resistant Soybean Genotypes using Gene-Linked Markers

Soybean is widely consumed legumes both in the form of food and feed. In the present scenario, the quality and quantity of soybean production is largely affected by different biotic factors, Soybean Mosaic Virus being one of the major biotic stress. Plant host resistance is an effective major to develop durable resistance from viral diseases, therefore understanding the molecular mechanism and identifying the resistant genotypes can contribute to resistance breeding in soybean. In 2020, ninety genotypes collected from Grain Legume Research Program, local collection and National Agricultural Genetic Resource Center were screened for the presence of resistant genes using gene linked molecular markers. Among them, three genotypes were identified with Soybean Mosaic Virus resistant loci, Rsv1 amplified by linked marker Satt114, four genotypes were identified with resistant loci, Rsv3 with linked marker Sat_424, and eight genotypes were identified with resistant loci, Rsv4 amplified by linked marker Satt558. Thus, showing expression of dominant resistance to some SMV strains. Interestingly, two genotypes (Co 175 and TGx1990-55) possessed both Rsv1 and Rsv3 loci thus showing potential of resisting broad spectrum SMV resistance to all SMV strains. Therefore, this study has identified potential genotypes that can be used as parental materials for resistant gene pyramiding in soybean breeding for SMV resistance

Trap cropping for insect pests in the Canadian Prairies: a review and a case study

AbstractThe Canadian Prairies are one of the major agricultural regions of the world in terms of cereal, oilseed and pulse crop production. With few exceptions, major insect pests like grasshoppers, flea beetles, Lygus bugs, wireworms and pea leaf weevils are controlled with insecticides. Wheat stem sawfly is managed through host plant resistance and endemic natural enemies, whereas cereal leaf beetle is managed through classical biological control. Large farms and short growing seasons in the region present logistical challenges to adopt time intensive pest management systems such as trap crops. Therefore, there is no adoption of trap crops even though some research has demonstrated their potential. In this article we present a brief overview of the pest status and management, and we summarize research on trap crops in the Prairies Ecozone and adjacent ecoregions. We conclude the review with some innovative research ideas to make trap cropping a more appealing pest management system in our quest to reduce dependency on chemical insecticides and increase the environmental resilience of Canadian agroecosystems.

Evaluating tomato lines resistance to Late Blight and molecular genetic screening with the use of molecular markers

Relevance. Tomato late blight caused by Phytophthora infestans can cause almost 100% yield loss in open ground in cool and humid conditions. At the same time, the genetic characteristics of P. infestans allow it to overcome the genetic resistance of host plants over time, which requires breeders to look for new genes for resistance to late blight and to obtain new varieties that have several resistance genes at once.Material and methods. 12 tomato lines, or a total of 335 plants, were obtained from the N.N. Timofeev breeding station collection and planted in an artificially infected background. For molecular genetic screening, 12 plants from the Kr6 line were used. The markers linked to the late blight resistance genes Ph-3, R1, and R3a were utilized.Results. On an artificial infectious background, phenotypic evaluation of tomato resistance to late blight showed 1 line of plants free of pathogen damage, 5 lines of plants fully afflicted by late blight, and 6 lines with only partial plant damage. According to molecular genetic investigation the resistant plants were heterozygotes for the Ph-3 gene. Furthermore, the R1 gene was present in most of the plants under study; but, without the Ph-3 gene, this gene did not provide plant resistance against late blight.Conclusions. The results of this research led to the selection of tomato plants for further breeding that were resistant to late blight. It was shown that markers linked to the Ph-3 and R1 genes might be used for marker-mediated selection. Furthermore, it has been established that tomato plants are more effectively protected against P. infestans when several resistance genes are present.

Influence of endophytic fungi treatments on aluminum contents in Vernicia montana seedlings and soils under different concentrations of aluminum stress

Although leveraging the interaction with endophytic fungi is an efficient and environment-friendly strategy for plants to enhance growth and resistance, how different endophyte species influence host plants’ resilience in adverse conditions remain comparatively unclear. In order to explore the effect of endophytic fungi on the aluminum resistance of woody host plants, Vernicia montana seedlings were subjected to different aluminum concentrations (T0, T1, T2, T3, T4) in this study. The aluminum contents in roots, leaves and rhizospheric soil of V. montana seedlings were determined after applying endophyte suspensions of Pestalotiopsis (NP), Alternaria (LA), Penicillium (QP), Coniothyrium (DC) and Thermophilic (ST) spp. The results showed that aluminum stress treatment, endophytic fungi treatment and their interaction had significant effects on aluminum content in leaves, aluminum content in roots, aluminum content in rhizospheric soil, and the transport and retention rate of aluminum ions in soil-root-leaf. With the increase of aluminum concentrations, the aluminum content in leaves of V. montana increased in the endophyte treatments of LA and ST, decreased in CK, NP and DC, or had marginal variation in QP treatment. Compared with T0, four endophyte treatments of LA, QP, DC and ST significantly reduced root aluminum content under T4 concentration (P < 0.05), contrary to the results of NP treatment. Endophyte treatments significantly increased root aluminum content of V. montana under T1 concentration (P < 0.05). The foliar Al content in fungi-inoculated seedlings was significantly lower than that of the non-inoculated ones under T0 and T3 levels (P < 0.05), the LRR is less than 1, while the opposite trend was observed under T2 and T4 treatments. The aluminum transport coefficient TFsoil-root and TFroot-leaf increased in different proportions under the same aluminum concentration. The findings indicate that the application of endophytic fungi change the aluminum contents and transport from rhizospheric soil, roots to leaves. The specific effects of endophytic fungi vary with the degree of aluminum stress and the fungi genus. The study proves that inoculation of endophytic fungi can improve the aluminum tolerance of host plants, and thereby play an important role in promoting the sustainable development of forestry.

Susceptibility of Capsicum varieties to Thaumatotibia leucotreta (Lepidoptera: Tortricidae) infestation for production optimization.

Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is a major threat to the production and marketing of pepper (Capsicum spp.) in Ghana. To reduce the damage of the pest on pepper farming, it is important to find appropriate control methods, which may include the use of resistant host plants. This study investigated the relative susceptibility of 6 pepper varieties commonly cultivated in Ghana: Legon 18, Bird's eye, Scotch bonnet, Cayenne, KA2, and sweet pepper (Yolo wonder+ variety). Choice and no-choice ovipositional preference tests were conducted and the population growth rate of T. leucotreta was determined by establishing life table parameters including the net reproductive rates (R0), the mean generation time (G), intrinsic rate of natural increase (rm), the population doubling time (T), and the finite rate of increase (λ). In the no-choice test, females exhibited oviposition preference for sweet pepper (12.08 eggs/fruit), while Bird's eye was the least preferred (5.00 eggs/fruit). The same results were observed in the choice test. However, the population growth rate of T. leucotreta was highest on the Scotch bonnet and Cayenne, with rm of 0.124 and 0.127, respectively, while the Bird's eye and sweet pepper recorded the least rm of 0.116. Thus, the tested varieties had varying levels of susceptibility to T. leucotreta infestation. Bird's eye was the least susceptible variety, while Cayenne and Scotch bonnet were the most susceptible varieties. These findings could direct farmers on the choices of pepper varieties for cultivation and proffer potential opportunities to breed new varieties resistant to T. leucotreta infestation.

The response of microbiome assembly within different niches across four stages to the cultivation of glyphosate-tolerant and conventional soybean varieties.

Plants are inherently connected with the microbiome, which plays a crucial role in regulating various host plant biological processes, including immunity, nutrient acquisition, and resistance against abiotic and biotic stresses. Many factors affect the interaction between plants and microbiome. In this study, microbiome samples were collected from five niches (bulk soil, rhizoplane, root endosphere, phylloplane, and leaf endosphere) across four developmental stages (seedling, flowering, podding, and maturity) of various soybean varieties. Composition and structure of bacterial and fungal communities were analyzed using 16S rRNA gene and ITS (Internally Transcribed Spacer) region amplicon sequencing. It was observed that both niches and developmental stages significantly impact on the assembly and composition of soybean microbiome. However, variety, presence of a transgene, and glyphosate application had minimal effects on microbial communities. The dominant microbiome varied across the five niches, with most containing beneficial microbial communities capable of promoting plant growth or increasing disease resistance. Types and abundance of the dominant microbes affected network stability, potentially resulting in functional changes in different ecological niches. This study provides theoretical evidence for microbial protection of plants against diseases and demonstrates that systematic analysis of the composition and diversity of soybean microbiomes can contribute to the development of biological control technologies.

Influences of Salt Stress on Cotton Metabolism and Its Consequential Effects on the Development and Fecundity of Aphis gossypii Glover.

The degree of global soil salinization is gradually deepening, which will inevitably affect agricultural ecology. It has been found that salt stress induces the resistance of host plants to phytophagous pests. However, little is known about the effects of salt-stressed cotton plants on the fitness of cotton aphids (Aphis gossypii Glover). In this study, we investigated the differences between cotton metabolomes under mild (75 mM NaCl) and moderate (150 mM NaCl) salinity conditions and their effects on the fitness of cotton aphids. The results showed that 49 metabolites exhibited significant upregulation, while 86 metabolites were downregulated, with the increasing NaCl concentration. The duration of nymphal aphids under 150 mM NaCl significantly extended to 6.31 days when compared with the control (0 mM NaCl, 4.10 days). Meanwhile, the longevity of adult aphids decreased significantly under 75 and 150 mM NaCl, with an average of 10.38 days (0 mM NaCl) reduced to 8.55 and 4.89 days, respectively. Additionally, the total reproduction number of single females decreased from 31.31 (0 mM NaCl) to 21.13 (75 mM NaCl) and 10.75 (150 mM NaCl), whereas the survival rate of aphids decreased from 81.25% (0 mM NaCl) to 56.25% (75 mM NaCl) and 34.38% (150 mM NaCl) on the 12th day. These results support the hypothesis that plants growing under salt stress are better defended against herbivores. Furthermore, 49 differential metabolites were found to be negatively correlated with the longevity and fecundity of adult aphids, while 86 different metabolites showed the opposite trend. These results provide insights into the occurrence and control of cotton aphids amidst the escalating issue of secondary salinization.

Integrating Antixenosis Against Helicoverpa armigera (Lepidoptera: Noctuidae) and Micronutrition in Kabuli Chickpea (Cicer arietinum L.) Genotypes

ABSTRACTThe leguminous chickpea is a good source of protein, but its yield potential is frequently constrained by biotic stresses, primarily Helicoverpa armigera, a major havoc for cultivation of the crop. To develop host plant resistance for minimizing the losses due to the pod borer, five kabuli parents with desired traits for pod borer tolerance were crossed in diallel mating design to produce 10 crosses which were analysed for traits related to pod borer and nutrition. Based on correlation studies, trichome density was found positively correlated with phenol content, but both the traits were negatively associated with number of damaged seeds. Therefore, the tolerant genotypes were identified on the basis of phenol content, trichome density, number of damaged seeds and field rating. Among parents ICC 12197 was found superior in terms of yield and borer tolerance features with an intermediate pest resistance susceptible rating in addition to higher Fe content. However, significant sca effects for higher phenol content and seed yield in ICC 11764 × ICC 14190 were recorded with reduced number of damaged seeds in addition to higher Fe and Zn content. It was observed that the specific combination involved good and poor combiners for each trait. The same cross also showed significant standard heterosis in desirable direction for phenol content, trichome density, number of damaged seeds and seed yield. Additionally, the ratio of σ2 GCA to σ2 SCA revealed nonadditive gene action in controlling the expression of phenol content, trichome density, number of damaged seeds and Fe and Zn content. Thus, breeder may focus efforts on desirable cross utilizing selection in further segregating generations for higher phenol content, trichome density and Fe and Zn content in addition to yield‐related traits while lesser number of damaged seeds per plant to concentrate for development of pod borer resilient high yielding kabuli genotypes to combat micronutrient deficiency.

Exploiting Induced Plant Resistance for Sustainable Pest Management: Mechanisms, Elicitors, and Applications: A Review

Plants and phytophagous (plant-eating) arthropods have coevolved over millions of years, leading to the development of both constitutive and inducible defense mechanisms in plants. Despite this long history of coexistence, it remains unclear how to precisely regulate each host-arthropod interaction to achieve an equilibrium that maximizes crop yield. The defensive chemicals produced by plants can significantly affect herbivores’ feeding behaviour, growth, and survival. These chemicals may be generated constitutively (continuously) or induced in response to herbivore damage. Induced resistance, a strategy where plants enhance their defences after being attacked, holds potential for reducing the number of insecticides needed in pest management. Chemical elicitors, which trigger the production of secondary metabolites that confer resistance to insects, can be used to manipulate host plant resistance, specifically by inducing resistance. By understanding the mechanisms underlying induced resistance, it is possible to predict which herbivores will be impacted by these responses. Applying induced response elicitors to crop plants can strengthen their natural defences against herbivore damage. Additionally, it is possible to genetically modify plants so that they constitutively produce defense chemicals, providing continuous protection in areas where herbivory is a constant threat. As part of integrated pest management, induced resistance can be used to develop crop cultivars that readily trigger an inducible response in the event of a mild infestation, contributing to sustainable agricultural practices and reducing reliance on chemical pesticides.

Exploration of stable host-plant resistant sources to sterility mosaic disease of pigeonpea (Cajanus cajan L. Huth)

Sterility mosaic disease (SMD) presents a major challenge in pigeonpea cultivation throughout the Indian subcontinent. Chemical control methods, such as acaricides, are neither economically viable nor sustainable, making host plant resistance the preferred approach for managing this disease. In this study, we evaluated 45 pigeonpea germplasm accessions and breeding lines for SMD resistance over two consecutive Kharif seasons (2021-22 and 2022-23). Of the 45 genotypes tested, 8 exhibited low disease incidence (0-10%) (LRG-471, ICPL 151, ICPB 2089, ICPB 2047, ICPB 2092, ICPB 2211, ICPL 85063, and ICPL 14003) and were classified as resistant. Additionally, 23 genotypes showed disease incidence between 10.1-20.0% and were categorized as moderately resistant. These resistant genotypes offer promising new sources of SMD resistance and should be considered for inclusion in future pigeonpea breeding programs aimed at improving resistance. This research provides valuable phenotypic insights and identifies stable resistant sources essential for advancing SMD resistance breeding efforts.

Formononetin derivatives containing benzyl piperidine: A brand new, highly efficient inhibitor targeting Xanthomonas spp

IntroductionPlant bacterial diseases take an incalculable toll on global food security. The indiscriminate use of chemical synthetic pesticide not only facilitates pathogen resistance of pathogenic bacteria, but also poses a major threat to human health and environmental protection. Therefore, it is of great economic value and scientific significance to develop a new antibacterial drug with environmental friendliness and unique mechanism of action. ObjectivesTo design and synthesize formononetin derivatives based on natural products, evaluate their in vitro and in vivo antibacterial activities and elucidate the mechanisms involved. MethodsThe synthesis was carried out by classical active group splicing method. The antibacterial activities were evaluated using turbidimetry and pot experiments. The antibacterial mechanism was further investigated using scanning electron microscopy (SEM), virulence factors, defense enzymes activities, proteomics and metabolomics. Results40 formononetin derivatives containing benzyl piperidine were designed and synthesized. The antibacterial results demonstrated that H32 exhibited the most potent inhibitory effect against Xanthomonas oryzae pv. Oryzae (Xoo) with the EC50 of 0.07 μg/mL, while H6 displayed the highest inhibitory activity against Xanthomonas axonopodis pv. Citri (Xac) with the EC50 of 0.24 μg/mL. Furthermore, the control efficacy of H32 against rice bacterial leaf blight (BLB) and H6 against citrus canker (CC) was validated through pot experiments. SEM, virulence factors and host enzyme activities assay indicated that H32 could not only reduce the virulence of Xoo, but also activate the activities of defense enzymes and improve the disease resistance of host plants. The proteomics and metabolomics analysis demonstrated that H32 could inhibit the synthesis of branched-chain amino acids, make Xoo cells in a starvation state, inhibit its proliferation, weaken its virulence and reduce its colonization and infection of host cells. ConclusionFormononetin derivatives containing benzyl piperidine could be used as potentially effective inhibitors against Xanthomonas spp.

Effects of methyl jasmonate seed treatments on adult oviposition preference and larval performance of seed corn maggot (Delia platura) in corn (Zea mays).

Eliciting host plant resistance using plant hormones such as jasmonates has the potential to protect seeds and seedlings against insect pests; however, several hurdles exist for adapting it for pest management. This includes determining a dose that promotes resistance without limiting plant growth, an application method that growers could use, and ensuring the plants are responsive in the abiotic conditions when the pest occurs. In laboratory and field assays, we tested if treating corn seeds with multiple concentrations of methyl jasmonate would reduce the preference of ovipositing seed corn maggot adults and the performance of larvae feeding on seeds. We found that corn seeds soaked in aqueous 0.2 mM methyl jasmonate solution showed marginally lower seedling growth, but the adult oviposition preference was ~60% lower on these seeds compared to control water-soaked seeds. Seeds that were treated with methyl jasmonate using a conventional polymer-based seed coating showed no effect on seedling growth but reduced adult oviposition preference. In no-choice bioassays with adult flies, we found reduced oviposition on seeds soaked with aqueous methyl jasmonate compared to controls. Larval survival to pupation was also lower in methyl jasmonate-treated seeds. Lastly, the methyl jasmonate-induced resistance also occurred at the lower temperatures typical of the spring soil conditions when this fly is most damaging. Methyl jasmonate seed treatment in aqueous solution or using conventional polymer-based technology, has the potential to deter adult oviposition and reduce maggot performance in spring temperature conditions with minor effects on seed germination and growth. © 2024 Society of Chemical Industry.

Biology, Distribution and Management of Fall Army Worm &lt;i&gt;Spodoptera frugiperda&lt;/i&gt; (J E Smith) in Ethiopia

Fall army worm Spodoptera frugiperda (J E Smith) is a destructive insect pest that is native to tropical and subtropical regions of the Americas and later reported in Africa in 2016. The pest was first detected in Ethiopia in March 2017 and is likely to spread in the country. It is one of the most devastating pests in terms of crop loss and economic impact in developing countries like Ethiopia. It is a voracious pest that can cause significant yield loss. The most preferable host of S. frugiperda is maize and it causes serious damage by feeding on the ears of maize. Prevention of introduction, control, or eradication of S. frugiperda with appropriate measures is important. The IPM is one of the most preferred as complete elimination is not possible. There is a need to develop flexible, coordinated, and effective IPM approach combining various control measures including host plant resistance, mechanical, botanical, biological methods, cultural methods, and suitable doses of pesticides. This study generates information towards these ends.

Morphological Parameters of Sesame in Relation to Susceptibility to Major Sucking Insect Pests

Based on previous field screening data 15 genotypes were selected (based on the number of insect pests population/ plant) to study the role of morphological parameters of sesame. Trichome density, length and width were estimated under microscope with the help of software. The 15 selected genotypes of sesame were studied for finding trichome’s role in host plant resistance against major sucking pests; whitefly Bemisia tabaci), leafhopper (Orocius albicinctus) and mirid bug (Nesidiocoris tenuis) of sesame and the correlation studies revealed that the density of non-glandular trichome showed significant positive correlation with the population of Orocius albicinctus (r= 0.868), Nesidiocoris tenuis (r=0.549) and Bemisia tabaci (r= 0.824) while length and width of non-glandular trichomes and density of glandular trichomes showed non-significant (±) impact on the incidence of tested sucking insect pests.

Short-term responses of spider mites inform mechanisms of maize resistance to a generalist herbivore

Plants are attacked by diverse herbivorous pests with different host specializations. While host plant resistance influences pest pressure, how resistance impacts the behaviors of generalist and specialist herbivores, and the relationship to resistance, is less well known. Here, we investigated the short-term (< 1 h) behavioral changes of a generalist herbivore, the two-spotted spider mite (TSM), and a specialist herbivore, the Banks grass mite (BGM), after introduction to no-choice Tanglefoot leaf-arenas (2 × 2 cm) of three maize inbred lines (B73, B75, and B96). The widely-used inbred line B73 is susceptible to spider mites, while B75 and B96 are known to be mite resistant, especially to TSM. Video tracking was used to record TSM and BGM walking, probing, feeding, resting, web-building and travel distance on arenas of each line. Mite oviposition was also recorded after 72 h. B75, a resistant line, decreased the feeding behavior (i.e., time) of both mite species compared to B73 (susceptible control) and B96. Moreover, TSM appeared to be sensitive to both resistant lines (B75 and B96) with reduced oviposition, and increased resting and web-building times compared to susceptible B73. In contrast, the specialist BGM showed no difference in oviposition, resting and web-building time across all maize inbred lines. Our findings of quite broad and short-term responses of TSM to B75 and B96 are consistent with a role for constitutive or rapidly induced plant defenses in maize in conferring TSM resistance. Other mechanisms of plant resistance may be needed, however, for defense against specialists like BGM.

Managing Insect Pests in Millets: Harnessing Host Plant Resistance in Integrated Pest Management

Managing Insect Pests in Millets: Harnessing Host Plant Resistance in Integrated Pest Management

Plant infection by the necrotrophic fungus Botrytis requires actin-dependent generation of high invasive turgor pressure.

The devastating pathogen Botrytis cinerea infects a broad spectrum of host plants, causing great socio-economic losses. The necrotrophic fungus rapidly kills plant cells, nourishing their wall and cellular contents. To this end, necrotrophs secrete a cocktail of cell wall degrading enzymes, phytotoxic proteins and metabolites. Additionally, many fungi produce specialized invasion organs that generate high invasive pressures to force their way into the plant cell. However, for most necrotrophs, including Botrytis, the biomechanics of penetration and its contribution to virulence are poorly understood. Here, we use a combination of quantitative micromechanical imaging and CRISPR-Cas-guided mutagenesis to show that Botrytis uses substantial invasive pressure, in combination with strong surface adherence, for penetration. We found that the fungus establishes a unique mechanical geometry of penetration that develops over time during penetration events, and which is actin cytoskeleton dependent. Furthermore, interference of force generation by blocking actin polymerization was found to decrease Botrytis virulence, indicating that also for necrotrophs, mechanical pressure is important in host colonization. Our results demonstrate for the first time mechanistically how a necrotrophic fungus such as Botrytis employs this 'brute force' approach, in addition to the secretion of lytic proteins and phytotoxic metabolites, to overcome plant host resistance.

English

Oilseed cultivation is the major source of energy that fulfills the cooking oil requirements of large masses across the globe. Mustard is one of the important members of the brassica family, which is attacked by an aphid, Lipaphis erysimi. This research investigated the field population fluctuations of L. erysimi on different mustard varieties for two growing years. L. erysimi population reached to peak (171.3 nymphs and 141.6 adults) in the Mustard-early variety in early March. Based on Mustard Resistance Index (MRI), the Mardan-Local variety is highly resistant having an Aphid Population Score (APS) and Leaf Damage (LD) of 1 with a pooled annual mean of 1.85 aphids. The varietal preference test results indicated that the highest L. erysimi (8.0 adults) were attracted to the Mustard-early variety while the least (2.80 adults) were attracted to Mardan-local. In the In-vitro bioassay, Lefenuron and Pyriproxyfen caused 100 and 70.4% mortality, respectively. In the field, synchronized experiment, Imidochloprid (control positive) and Lefenuron showed the highest mortalities (100%), respectively. The Pyriproxefen and Runner (Methoxyfenoxid) treated plots had caused 77 and 70.3% mortalities, respectively. The present research is the first attempt to investigate the synchronized effects of Host Plant Resistance and Insect Growth Regulators for the L. erysimi management in Mustard. It is concluded that Mardan-Local variety alongside lefenuron application provides an effective IPM for L. erysimi. These outcomes will help the farmers better understand and manage aphids; it will help the researcher to explore further management tools of Aphids in oilseed crops.