Biology of Callistethus plagiicollis (Coleoptera: Scarabaeoidea: Rutelinae) and comparative morphology of its larvae.

Larvae of the beetle subfamily Rutelinae are poorly described in the literature. Notably, the morphology of the larvae of Callistethus plagiicollis Fairmaire has not previously been analyzed. Here, we report for the first time that these larvae feed on the tubers and roots of Gastrodia elata Blume, an important traditional Chinese herbal medicine, which causes a reduction in the yield and economic value of G. elata. We employed scanning electron microscopy and light microscopy to investigate the morphology and occurrence regularity of egg, larvae, pupae, and adult specimens of C. plagiicollis collected from the G. elata planting base in Guizhou Province, China, with a focus on the ultrastructure of mature larvae. The results revealed one generation of C. plagiicollis per year in the study area and three instar stages of larvae. Mature larvae were identified by the following characteristics: raster without palidia with a large number of hamate setae, antennal apex containing seven sensilla basiconica, larval haptomerum containing eight sensilla styloconica and four enlarged heli, and seven longitudinally arranged stridulatory teeth on the stipes of the maxilla. The combination of scanning electron and light microscopy effectively revealed the difference between membranous and sclerotized structures, ensuring accurate identification of C. plagiicollis larvae. By determining the feeding characteristics and occurrence regularity of C. plagiicollis, this study has implications for improved pest management in G. elata crops. RESEARCH HIGHLIGHTS: We identified C. plagiicollis as a new pest of G. elata, a traditional Chinese medicine Scanning electron and light microscopy were combined to analyze the morphology of the mature larvae of C. plagiicollis for the first time We determined the feeding characteristics and occurrence regularity of C. plagiicollis, which can be used to develop effective pest management strategies.

A novel sugar beet cyst nematode effector 2D01 targets the Arabidopsis HAESA receptor-like kinase.

Plant-parasitic cyst nematodes use a stylet to deliver effector proteins produced in oesophageal gland cells into root cells to cause disease in plants. These effectors are deployed to modulate plant defence responses and developmental programmes for the formation of a specialized feeding site called a syncytium. The Hg2D01 effector gene, coding for a novel 185-amino-acid secreted protein, was previously shown to be up-regulated in the dorsal gland of parasitic juveniles of the soybean cyst nematode Heterodera glycines, but its function has remained unknown. Genome analyses revealed that Hg2D01 belongs to a highly diversified effector gene family in the genomes of H. glycines and the sugar beet cyst nematode Heterodera schachtii. For functional studies using the model Arabidopsis thaliana-H. schachtii pathosystem, we cloned the orthologous Hs2D01 sequence from H. schachtii. We demonstrate that Hs2D01 is a cytoplasmic effector that interacts with the intracellular kinase domain of HAESA (HAE), a cell surface-associated leucine-rich repeat (LRR) receptor-like kinase (RLK) involved in signalling the activation of cell wall-remodelling enzymes important for cell separation during abscission and lateral root emergence. Furthermore, we show that AtHAE is expressed in the syncytium and, therefore, could serve as a viable host target for Hs2D01. Infective juveniles effectively penetrated the roots of HAE and HAESA-LIKE2 (HSL2) double mutant plants; however, fewer nematodes developed on the roots, consistent with a role for this receptor family in nematode infection. Taken together, our results suggest that the Hs2D01-AtHAE interaction may play an important role in sugar beet cyst nematode parasitism.

Dual activity of Meloidogyne incognita-regulated Musa acuminata Pathogenesis-related-10 (MaPR-10) gene.

Plant immunity to pathogen infections is a dynamic response that involves multiple organelles and defence signalling systems such as hypersensitive response (HR) and systemic acquired resistance (SAR). The latter requires the function of Pathogenesis-related (PR) proteins, a common plant protein family with diverse roles in plant innate immunity. Our previous proteomics study showed that a PR gene (ITC1587_Bchr9_P26466_MUSBA) was differentially regulated during a compatible banana-M. incognita interaction, substantiating the isolation of this gene in the current study. Here, we successfully isolated and characterised Pathogenesis-related-10 (PR10) gene with ß-1,3-glucanase and ribonuclease (RNase) activities from two Musa acuminata cultivars (denoted as MaPR10) namely Berangan and Grand Naine (ITC1256). We found that MaPR10 cloned sequences possess glycine-rich loop domain and shared conserved motifs specific to PR10 gene group, confirming its identity as a member of this group. Interestingly, we also found a catalytic domain sequence for glycoside hydrolase family 16 (EXDXXE), unique only to MaPR10 cloned sequences. Two peptide variants closely related to the reference sequence ITC1587_Bchr9_P26466_MUSBA namely MaPR10-BeB5 and MaPR10-GNA5 were overexpressed and purified to test for their functionality. Here, we confirmed that both protein variants possess ß-1,3-glucanase and ribonuclease (RNase) activities, and inhibit the growth of Aspergillus fumigatus, a human opportunistic pathogen. To our knowledge, this is the first PR10 plant proteins with such properties to be reported thus far.

Potato cyst nematodes Globodera rostochiensis and G. pallida.

TAXONOMY: Phylum Nematoda; class Chromadorea; order Rhabditida; suborder Tylenchina; infraorder Tylenchomorpha; superfamily Tylenchoidea; family Heteroderidae; subfamily Heteroderinae; Genus Globodera. BIOLOGY: Potato cyst nematodes (PCN) are biotrophic, sedentary endoparasitic nematodes. Invasive (second) stage juveniles (J2) hatch from eggs in response to the presence of host root exudates and subsequently locate and invade the host. The nematodes induce the formation of a large, multinucleate syncytium in host roots, formed by fusion of up to 300 root cell protoplasts. The nematodes rely on this single syncytium for the nutrients required to develop through a further three moults to the adult male or female stage. This extended period of biotrophy-between 4 and 6 weeks in total-is almost unparalleled in plant-pathogen interactions. Females remain at the root while adult males revert to the vermiform body plan of the J2 and leave the root to locate and fertilize the female nematodes. The female body forms a cyst that contains the next generation of eggs. HOST RANGE: The host range of PCN is limited to plants of the Solanaceae family. While the most economically important hosts are potato (Solanum tuberosum), tomato (Solanum lycopersicum), and aubergine (Solanum melongena), over 170 species of Solanaceae are thought to be potential hosts for PCN (Sullivan et al., 2007). DISEASE SYMPTOMS: Symptoms are similar to those associated with nutrient deficiency, such as stunted growth, yellowing of leaves and reduced yields. This absence of specific symptoms reduces awareness of the disease among growers. DISEASE CONTROL: Resistance genes (where available in suitable cultivars), application of nematicides, crop rotation. Great effort is put into reducing the spread of PCN through quarantine measures and use of certified seed stocks. USEFUL WEBSITES: Genomic information for PCN is accessible through WormBase ParaSite.

The botanical eurycomanone is a potent growth regulator of the diamondback moth.

Eurycomanone is a quassinoid compound that is derived from Eurycoma longifolia, and it is often used as an indicator to evaluate the active ingredients of Eurycoma longifolia. However, Eurycomanone has rarely been reported to have biological activity toward pests. In this study, we evaluated the antifeedant activity of eurycomanone against the diamondback moth(Plutella xylostella), with a non-selective AFC50(the concentration that corresponds to 50% antifeedant action) value and selective AFC50 of 17.5 mg/L and 14.2 mg/L, respectively, which were 2.1-fold (36.9 mg/L) and 2-fold (28.5 mg/L) lower than that of azadirachtin, respectively. In addition, eurycomanone was used to treat the roots of Brassica chinensis L. at a concentration of 100 µg/g for 72 h. The antifeedant index was found to reach 93% by tracking the leaves. After feeding with 20 µg/g eurycomanone, no pupae or eclosion were observed. To explore this mechanism, we used scanning electron microscopy to discover that eurycomanone could prevent the development of taste receptors on the maxillary palp of diamondback moth larvae. Additional electrophysiological measurements showed that eurycomanone exhibited excitatory action to the central taste neurons of diamondback moth and significantly inhibited the GABAA receptor current. Eurycomanone exhibited significant activity as an antifeedant, inhibited growth and excelled at systemic absorption.

The Plant Sesquiterpene Nootkatone Efficiently Reduces Heterodera schachtii Parasitism by Activating Plant Defense.

Plant parasitic nematodes, including the beet cyst nematode Heterodera schachtii, constitute a devastating problem for crops worldwide. The limited availability of sustainable management options illustrates the need for new eco-friendly control means. Plant metabolites represent an invaluable source of active compounds for the discovery of such novel antagonistic agents. Here, we evaluated the impact of eight plant terpenoids on the H. schachtii parasitism of Arabidopsis thaliana. None of the metabolites affected the plant development (5 or 10 ppm). Nootkatone decreased the number of adult nematodes on A. thaliana to 50%, with the female nematodes being smaller compared to the control. In contrast, three other terpenoids increased the parasitism and/or female size. We discovered that nootkatone considerably decreased the number of nematodes that penetrated A. thaliana roots, but neither affected the nematode viability or attraction to plant roots, nor triggered the production of plant reactive oxygen species or changed the plant's sesquiterpene profile. However, we demonstrated that nootkatone led to a significant upregulation of defense-related genes involved in salicylic and jasmonic acid pathways. Our results indicate that nootkatone is a promising candidate to be developed into a novel plant protection agent acting as a stimulator of plant immunity against parasitic nematodes.

Utilization of Cladophora glomerata extract nanoparticles as eco-nematicide and enhancing the defense responses of tomato plants infected by Meloidogyne javanica.

Tomato (Solanum Lycopersicum L.) is an important vegetable crop that belongs to the family Solanaceae. Root-knot nematodes reflect the highly critical economically damaging genera of phytoparasitic nematodes on tomato plants. In this study, the eco-nematicide activity of freshwater green macroalga Cladophora glomerata aqueous extract and their synthesized silver nanoparticles (Ag-NPs) against root-knot nematodes Meloidogyne javanica was investigated on tomato plants. The formation and chemical structure of Ag-NPs was examined. The aqueous extract from C. glomerata was applied against the root-knot nematodes besides the biosynthesized green silver nanoparticles with 100, 75, 50, and 25% (S, S/2, S/3, S/4) concentrations. To investigate the plant response toward the Green Synthesized Silver Nanoparticles (GSNPs) treatment, expression profiling of Phenylalanine Ammonia-Lyase (PAL), Poly Phenol Oxidase (PPO), and Peroxidase (POX) in tomato were examined using Quantitative Real-Time PCR (Q-PCR). The results indicated that GSNPs from C. glomerata exhibited the highest eco-nematicide activity in the laboratory bioassay on egg hatchability and juveniles (J2S) mortality of M. javanica compared with the chemical commercial nematicide Rugby 60%. Also, results showed a significant reduction in galls number, egg masses, females per root system/plant, and mortality of juveniles. The results of PAL and PPO enzyme expression for the control plants remained relatively stable, while the plant inoculated with nematode M. javanica as well as the activity of genes in scope was increased from 14 to 28 Days after Nematode Inoculation (DANI). These activities were improved in inoculated plants and treated with C. glomerata extract and their green syntheses of Ag-NPs and the other plants treated with Rugby 60% (4 mL/L). The greatest activities of the three enzymes were evident after 14 days after the nematode inoculation. It can be concluded that the green synthesized nanoparticles using C. glomerata could be used as potent nematicides against M. javanica which induces the immune system to defend against nematode infection.

Molecular insights into the compatible and incompatible interactions between sugar beet and the beet cyst nematode.

BACKGROUND: Sugar beet (Beta vulgaris subsp. vulgaris) is an economically important crop that provides nearly one third of the global sugar production. The beet cyst nematode (BCN), Heterodera schachtii, causes major yield losses in sugar beet and other crops worldwide. The most effective and economic approach to control this nematode is growing tolerant or resistant cultivars. To identify candidate genes involved in susceptibility and resistance, the transcriptome of sugar beet and BCN in compatible and incompatible interactions at two time points was studied using mRNA-seq. RESULTS: In the susceptible cultivar, most defense-related genes were induced at 4 dai while suppressed at 10 dai but in the resistant cultivar Nemakill, induction of genes involved in the plant defense response was observed at both time points. In the compatible interaction, alterations in phytohormone-related genes were detected. The effect of exogenous application of Methyl Jasmonate and ET-generator ethephon on susceptible plants was therefore investigated and the results revealed significant reduction in plant susceptibility. Genes putatively involved in the resistance of Nemakill were identified, such as genes involved in phenylpropanoid pathway and genes encoding CYSTM domain-containing proteins, F-box proteins, chitinase, galactono-1,4-lactone dehydrogenase and CASP-like protein. Also, the transcriptome of the BCN was analyzed in infected root samples and several novel potential nematode effector genes were found. CONCLUSIONS: Our data provides detailed insights into the plant and nematode transcriptional changes occurring during compatible and incompatible interactions between sugar beet and BCN. Many important genes playing potential roles in susceptibility or resistance of sugar beet against BCN, as well as some BCN effectors with a potential role as avr proteins were identified. In addition, our findings indicate the effective role of jasmonate and ethylene in enhancing sugar beet defense response against BCN. This research provides new molecular insights into the plant-nematode interactions that can be used to design novel management strategies against BCN.

The mechanism of potato resistance to Globodera rostochiensis: comparison of root transcriptomes of resistant and susceptible Solanum phureja genotypes.

BACKGROUND: Globodera rostochiensis belongs to major potato pathogens with a sophisticated mechanism of interaction with roots of the host plants. Resistance of commercial varieties is commonly based on specific R genes introgressed from natural populations of related wild species and from native potato varieties grown in the Andean highlands. Investigation of molecular resistance mechanisms and screening the natural populations for novel R genes are important for both fundamental knowledge on plant pathogen interactions and breeding for durable resistance. Here we exploited the Solanum phureja accessions collected in South America with contrasting resistance to G. rostochiensis. RESULTS: The infestation of S. phureja with G. rostochiensis juveniles resulted in wounding stress followed by activation of cell division and tissue regeneration processes. Unlike the susceptible S. phureja genotype, the resistant accession reacted by rapid induction of variety of stress response related genes. This chain of molecular events accompanies the hypersensitive response at the juveniles' invasion sites and provides high-level resistance. Transcriptomic analysis also revealed considerable differences between the analyzed S. phureja genotypes and the reference genome. CONCLUSION: The molecular processes in plant roots associated with changes in gene expression patterns in response to G. rostochiensis infestation and establishment of either resistant or susceptible phenotypes are discussed. De novo transcriptome assembling is considered as an important tool for discovery of novel resistance traits in S. phureja accessions.

Phytochemical Study of Safflower Roots (Carthamus tinctorius) on the Induction of Parasitic Plant Germination and Weed Control.

Weeds have been a major threat in agriculture for several generations as they lead to decreases in productivity and cause significant economic losses. Parasitic plants are a specific type of weed causing losses in crops of great relevance. A new strategy has emerged in the fight against parasitic plants, which is called 'suicidal germination' or the 'honey-pot strategy'. Regarding the problem of weed control from an ecological point of view, it is interesting to investigate new natural compounds with allelopathic activity with the aim of developing new natural herbicides that can inhibit the growth of weeds without damaging the environment. Safflower crops have been affected by parasitic plants and weeds and, as a consequence, the secondary metabolites exuded by safflower roots have been studied. The sesquiterpene lactone dehydrocostuslactone was isolated and characterised, and the structurally related costunolide was identified by UHPLC-MS/MS in safflower root exudates. These sesquiterpene lactones have been shown to stimulate germination of Phelipanche ramosa and Orobanche cumana seeds. In addition, these compounds were phytotoxic on three important weeds in agriculture, namely Lolium perenne, Lolium rigidum and Echinochloa crus-galli. The exudation of the strigolactones solanacol and fabacyl acetate have also been confirmed by UHPLC-MS/MS. The study reported here contributes to our knowledge of the ecological role played by some secondary metabolites. Moreover, this knowledge could help identify new models for the development of future agrochemicals based on natural products.

RNAseq Analysis of Rhizomania-Infected Sugar Beet Provides the First Genome Sequence of Beet Necrotic Yellow Vein Virus from the USA and Identifies a Novel Alphanecrovirus and Putative Satellite Viruses.

"Rhizomania" of sugar beet is a soilborne disease complex comprised of beet necrotic yellow vein virus (BNYVV) and its plasmodiophorid vector, Polymyxa betae. Although BNYVV is considered the causal agent of rhizomania, additional viruses frequently accompany BNYVV in diseased roots. In an effort to better understand the virus cohort present in sugar beet roots exhibiting rhizomania disease symptoms, five independent RNA samples prepared from diseased beet seedlings reared in a greenhouse or from field-grown adult sugar beet plants and enriched for virus particles were subjected to RNAseq. In all but a healthy control sample, the technique was successful at identifying BNYVV and provided sequence reads of sufficient quantity and overlap to assemble > 98% of the published genome of the virus. Utilizing the derived consensus sequence of BNYVV, infectious RNA was produced from cDNA clones of RNAs 1 and 2. The approach also enabled the detection of beet soilborne mosaic virus (BSBMV), beet soilborne virus (BSBV), beet black scorch virus (BBSV), and beet virus Q (BVQ), with near-complete genome assembly afforded to BSBMV and BBSV. In one field sample, a novel virus sequence of 3682 nt was assembled with significant sequence similarity and open reading frame (ORF) organization to members within the subgenus Alphanecrovirus (genus Necrovirus; family Tombusviridae). Construction of a DNA clone based on this sequence led to the production of the novel RNA genome in vitro that was capable of inducing local lesion formation on leaves of Chenopodium quinoa. Additionally, two previously unreported satellite viruses were revealed in the study; one possessing weak similarity to satellite maize white line mosaic virus and a second possessing moderate similarity to satellite tobacco necrosis virus C. Taken together, the approach provides an efficient pipeline to characterize variation in the BNYVV genome and to document the presence of other viruses potentially associated with disease severity or the ability to overcome resistance genes used for sugar beet rhizomania disease management.

Metabolomic Fingerprinting of Potato Cultivars Differing in Susceptibility to Spongospora subterranea f. sp. subterranea Root Infection.

Plants defend themselves from pathogens by producing bioactive defense chemicals. The biochemical mechanisms relating to quantitative resistance of potato to root infection by Spongospora subterranea f. sp. subterranea (Sss) are, however, not understood, and are not efficiently utilized in potato breeding programs. Untargeted metabolomics using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was used to elucidate the biochemical mechanisms of susceptibility to Sss root infection. Potato roots and root exudate metabolic profiles of five tolerant cultivars were compared with those of five susceptible cultivars, following Sss inoculation, to identify tolerance-related metabolites. Comparison of the relative metabolite abundance of tolerant versus susceptible cultivars revealed contrasting responses to Sss infection. Metabolites belonging to amino acids, organic acids, fatty acids, phenolics, and sugars, as well as well-known cell wall thickening compounds were putatively identified and were especially abundant in the tolerant cultivars relative to the susceptible cultivars. Metabolites known to activate plant secondary defense metabolism were significantly increased in the tolerant cultivars compared to susceptible cultivars following Sss inoculation. Root-exuded compounds belonging to the chemical class of phenolics were also found in abundance in the tolerant cultivars compared to susceptible cultivars. This study illustrated that Sss infection of potato roots leads to differential expression of metabolites in tolerant and susceptible potato cultivars.

Nematicidal Activity of Stevia rebaudiana (Bertoni) Assisted by Phytochemical Analysis.

To date, there has been great demand for ecofriendly nematicides with beneficial properties to the nematode hosting plants. Great efforts are made towards the chemical characterization of botanical extracts exhibiting nematicidal activity against Meloidogyne spp., but only a small percentage of these data are actually used by the chemical industry in order to develop new formulates. On the other hand, the ready to use farmer produced water extracts based on edible plants could be a sustainable and economic solution for low income countries. Herein, we evaluate the nematicidal potential of Stevia rebaudiana grown in Greece against Meloidogyne incognita and Meloidogyne javanica, two most notorious phytoparasitic nematode species causing great losses in tomato cultivation worldwide. In an effort to recycle the plant's remnants, after leaves selection for commercial use, we use both leaves and wooden stems to test for activity. In vitro tests demonstrate significant paralysis activity of both plant parts' water extracts against the second-stage juvenile (J2) of the parasites; while, in vivo bioassays demonstrated the substantial efficacy of leaves' powder (95% at 1 g kg-1) followed by stems. Interestingly, the incorporation of up to 50 g powder/kg of soil is not phytotoxic, which demonstrates the ability to elevate the applied concentration of the nematicidal stevia powder under high inoculum level. Last but not least, the chemical composition analyses using cutting edge analytical methodologies, demonstrated amongst components molecules of already proven nematicidal activity, was exemplified by several flavonoids and essential oil components. Interestingly, and to our knowledge, for the flavonoids, morin and robinin, the anthocyanidin, keracyanin, and a napthalen-2-ol derivative is their first report in Stevia species.

Root treatment with oxathiapiprolin, benthiavalicarb or their mixture provides prolonged systemic protection against oomycete foliar pathogens.

Oxathiapiprolin is a fungicide effective against downy mildews of cucumber (Pseudoperonospora cubensis) and basil (Peronospora belbahrii) and late blight of tomato (Phytophthora infestans). To avoid fungicide resistance, it is recommended to apply oxathiapiprolin as a mixture with a partner fungicide that have a different mode of action. Here it is shown that a single application of oxathiapiprolin, benthiavalicarb, or their mixture (3+7, w/w) to the root of nursery plants grown in multi-cell trays provided prolonged systemic protection against late blight and downy mildews in growth chambers and in field tests. Soil application of 1mg active ingredient per plant provided durable protection of up to four weeks in tomato against late blight, cucumber against downy mildew and basil against downy mildew. Not only did the mixture of oxathiapiprolin and benthiavalicarb provide excellent systemic control of these diseases but also mutual protection against resistance towards both oxathiapiprolin and benthiavalicarb.

Cell Wall Modifications in Giant Cells Induced by the Plant Parasitic Nematode Meloidogyne incognita in Wild-Type (Col-0) and the fra2 Arabidopsis thaliana Katanin Mutant.

Meloidogyne incognita is a root knot nematode (RKN) species which is among the most notoriously unmanageable crop pests with a wide host range. It inhabits plants and induces unique feeding site structures within host roots, known as giant cells (GCs). The cell walls of the GCs undergo the process of both thickening and loosening to allow expansion and finally support nutrient uptake by the nematode. In this study, a comparative in situ analysis of cell wall polysaccharides in the GCs of wild-type Col-0 and the microtubule-defective fra2 katanin mutant, both infected with M. incognita has been carried out. The fra2 mutant had an increased infection rate. Moreover, fra2 roots exhibited a differential pectin and hemicellulose distribution when compared to Col-0 probably mirroring the fra2 root developmental defects. Features of fra2 GC walls include the presence of high-esterified pectic homogalacturonan and pectic arabinan, possibly to compensate for the reduced levels of callose, which was omnipresent in GCs of Col-0. Katanin severing of microtubules seems important in plant defense against M. incognita, with the nematode, however, to be nonchalant about this "katanin deficiency" and eventually induce the necessary GC cell wall modifications to establish a feeding site.

Identification of unhealthy Panax notoginseng from different geographical origins by means of multi-label classification.

Root-knot nematode is a common plant-parasitic pest with a highly destructive that infects more than 2000 plant species. Panax notoginseng (P. notoginseng) is one of the most susceptible traditional medicine. More importantly, it is difficult to distinguish the powders of P. notoginseng infected with root-knot nematode from those of healthy P. notoginseng due to the color and shape are same after being ground into powder. In this paper, Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) was used to identify P. notoginseng samples. Multiplicative scatter correction (MSC) was applied to preprocess the spectral data. Competitive adaptive reweighted sampling (CARS) and successive projection algorithm (SPA) were employed to select feature variables. Density-based spatial clustering of application with noise (DBSCAN) was adopted to discover groups within the data. Also, we found that the geographical origin is a pivotal factor to consider when identifying unhealthy P. notoginseng. Therefore, we introduced a novel multi-label classification (MLC) method to identify healthy and unhealthy P. notoginseng powders from three different geographical origins. In addition, binary relevance method (BR), classifier chain (CC), ensembles of classifier chains (ECC), and multilayer perceptron classifier (MLPC) were applied to create classification models, ECC exhibits superior performance in particular.

African Nightshade and African Spinach Decrease Root-Knot Nematode and Potato Cyst Nematode Soil Infestation in Kenya.

Plant-parasitic nematodes, particularly root-knot nematodes (RKN: Meloidogyne spp.) and cyst nematodes (CN: Globodera and Heterodera spp.) cause severe yield reduction in most cultivated crops and are of high economic importance. African nightshade (Solanum spp.) and African spinach (Amaranthus spp.) are important African indigenous vegetables (AIV) and are rich sources of nutrition and income. However, their host status to plant-parasitic nematodes remains largely speculative. Therefore, a survey was conducted which revealed that S. villosum exhibited high root galling, whereas on S. scabrum, A. cruentus, and A. dubius root galling was rare or very low. Additionally, soil collected from the rhizosphere of S. villosum and S. scabrum contained few cysts of potato cyst nematodes (PCN), and no developing PCN females were observed on the roots of growing plants. Therefore, we studied the dynamics of RKN and PCN on A. dubius, A. cruentus, S. scabrum, and S. villosum over 2 years in a field experiment. The effects of AIV crop species on RKN and PCN soil infestation were evaluated using susceptible S. lycopersicum or S. tuberosum. After first, second, and third cultivation of A. dubius, A. cruentus, and S. scabrum, RKN infestation of the soil decreased by more than 85%, whereas S. scabrum and S. villosum decreased PCN densities by more than 80%. When cropping susceptible crops, after three seasons of successive cultivation of these AIV, galling index and number of developing PCN females measured on susceptible crops decreased by more than 75%. Wilting and RKN-PCN coinfection incidences also decreased significantly. Here, we present data that support the development of a novel cropping system including African spinach and African nightshade, which reveals a high potential to manage RKN and PCN in an environmentally friendly, effective, and productive way.

Thiophenes from Echinops grijsii as a Preliminary Approach To Control Disease Complex of Root-Knot Nematodes and Soil-Borne Fungi: Isolation, Activities, and Structure-Nonphototoxic Activity Relationship Analysis.

Naturally occurring thiophenes possess excellent nematicidal and fungicidal activities. However, thiophenes often have limited application in soil due to their light-dependent toxicity given the living and reproductive condition of soil-borne pathogens. In this study, six new (1-6) and six known thiophenes (7-12) were isolated from Echinops grijsii. Compounds 1-2, 4-5, 8-9, 11 , and 12 showed stronger nematicidal activity against Meloidogyne incognita than commercial nematicide abamectin. 4-10 were demonstrated as nonphototoxic thiophenes. Among these, 4 and 8 were the most potent thiophenes (LC50 values 2.57 and 0.91 µg/mL in light, 1.80 and 0.86 µg/mL in dark, respectively) against M. incognita. SAR revealed that thiophene skeleton was essential for nematicidal activity, while disubstituted groups were helpful for nonphototoxicity. Although an increased number of acetylenes improved activity, it decreased nonphototoxicity. Acyl groups could suppress the effects of light on activity, with the level of inhibitory effects depending on its number and chain length, while chlorine played important roles in promoting activity. Additionally, compounds 1-2, 4-5, 7, 8, and 10 displayed antifungal activity against six soil-borne fungi in various degrees. The discovery of nonphototoxic thiophenes and elucidation of SAR provide important information for the exploitation and utilization of thiophenes in the integrative management regarding disease complexes caused by the combination of root-knot nematode and soil-borne fungi.

A neglected alliance in battles against parasitic plants: arbuscular mycorrhizal and rhizobial symbioses alleviate damage to a legume host by root hemiparasitic Pedicularis species.

Despite their ubiquitous distribution and significant ecological roles, soil microorganisms have long been neglected in investigations addressing parasitic plant-host interactions. Because nutrient deprivation is a primary cause of host damage by parasitic plants, we hypothesized that beneficial soil microorganisms conferring nutrient benefits to parasitized hosts may play important roles in alleviating damage. We conducted a pot cultivation experiment to test the inoculation effect of an arbuscular mycorrhizal fungus (Glomus mosseae), a rhizobium (Rhizobium leguminosarum) and their interactive effects, on alleviation of damage to a legume host (Trifolium repens) by two root hemiparasitic plants with different nutrient requirements (N-demanding Pedicularis rex and P-demanding P. tricolor). Strong interactive effects between inoculation regimes and hemiparasite identity were observed. The relative benefits of microbial inoculation were related to hemiparasite nutrient requirements. Dual inoculation with the rhizobium strongly enhanced promotional arbuscular mycorrhizal effects on hosts parasitized by P. rex, but reduced the arbuscular mycorrhizal promotion on hosts parasitized by P. tricolor. Our results demonstrate substantial contribution of arbuscular mycorrhizal and rhizobial symbioses to alleviating damage to the legume host by root hemiparasites, and suggest that soil microorganisms are critical factors regulating host-parasite interactions and should be taken into account in future studies.

The Bear Giant-Skipper genome suggests genetic adaptations to living inside yucca roots.

Giant-Skippers (Megathymini) are unusual thick-bodied, moth-like butterflies whose caterpillars feed inside Yucca roots and Agave leaves. Giant-Skippers are attributed to the subfamily Hesperiinae and they are endemic to southern and mostly desert regions of the North American continent. To shed light on the genotypic determinants of their unusual phenotypic traits, we sequenced and annotated a draft genome of the largest Giant-Skipper species, the Bear (Megathymus ursus violae). The Bear skipper genome is the least heterozygous among sequenced Lepidoptera genomes, possibly due to much smaller population size and extensive inbreeding. Their lower heterozygosity helped us to obtain a high-quality genome with an N50 of 4.2 Mbp. The ~ 430 Mb genome encodes about 14000 proteins. Phylogenetic analysis supports placement of Giant-Skippers with Grass-Skippers (Hesperiinae). We find that proteins involved in odorant and taste sensing as well as in oxidative reactions have diverged significantly in Megathymus as compared to Lerema, another Grass-Skipper. In addition, the Giant-Skipper has lost several odorant and gustatory receptors and possesses many fewer (1/3-1/2 of other skippers) anti-oxidative enzymes. Such differences may be related to the unusual life style of Giant-Skippers: they do not feed as adults, and their caterpillars feed inside Yuccas and Agaves, which provide a source of antioxidants such as polyphenols.