Bait Plants Research Articles

Evaluation of Rz2 Gene Expression in Sugar Beet Hybrids Infected with Beet Necrotic Yellow Vein Virus.

Sugar beet hybrids are essential in modern agriculture due to their superior yields, disease resistance, and adaptability. This study investigates the role of the Rz2 gene in conferring resistance to beet necrotic yellow vein virus (BNYVV) in 14 sugar beet hybrids cultivated in Kazakhstan, including local and European varieties. The Rz2 gene, encoding a CC-NB-LRR protein, is a known resistance factor against BNYVV. Using RT-qPCR, we assessed Rz2 expression and detected BNYVV in bait plants inoculated with virus-infested soil. Our findings identified two highly resistant varieties: the Kazakh cultivar 'Abulhair' and the French line 22b5006. Additionally, the Kazakh cultivar 'Pamyati Abugalieva' and the French hybrid 'Bunker' exhibited increased resistance, suggesting involvement of other resistance loci. Notably, the Danish hybrid 'Alando', despite resistance to rhizomania, did not effectively resist BNYVV, highlighting possible evasion of its genetic factors by local virus strains. Our results emphasize the importance of Rz2 in resistance breeding programs and advocate for further research on additional resistance genes and the genetic variability of BNYVV in Kazakhstan. This work pioneers the molecular evaluation of BNYVV resistance in sugar beet in Kazakhstan, contributing to sustainable disease management and improved sugar beet production.

Dynamics of Potato Virus Y Infection Pressure and Strain Composition in the San Luis Valley, Colorado.

The San Luis Valley (SLV), Colorado, is the second-largest fresh-potato-growing region in the United States, which accounts for about 95% of the total production in Colorado. Potato virus Y (PVY) is the leading cause of seed potato rejection in the SLV, which has caused a constant decline in seed potato production over the past two decades. To help potato growers control PVY, we monitored the dynamics of PVY infection pressure over the growing seasons of 2022 and 2023 (May through August) using tobacco bait plants exposed to field infection weekly. PVY infection dynamics were slightly different between the two seasons, but July and August had the highest infection in both years. The first PVY infection was detected in the second half of June, which coincides with the emergence of potato crops in the valley. PVY infection increased toward the beginning of August and declined toward the end of the season. Three PVY strains were identified in tobacco bait plants and potato fields, namely PVYO, PVYN-Wi, and PVYNTN. Unlike other producing areas of the United States, PVYO is still the major strain infecting potato crops in Colorado, comprising ∼40% of total PVY strain composition. This could be explained by the prevalence of the potato cultivar Russet Norkotah that lacks any identified N genes, including the Nytbr that controls PVYO, which imposes no negative selection against this strain. The current study demonstrated the usefulness of bait plants to understand PVY epidemiology and develop more targeted control practices of PVY.

Rizobactérias promotoras de crescimento de plantas isoladas de solos cultivados usando plantas Glycine max L. como isca

ABSTRACT: The current production of major crops, such as Glycine max L., has become increasingly adept on the use of bio-inputs, such as application of plant growth-promoting inocula. However, the evaluation of the potential of bacterial isolates from soils with different time histories of agricultural use are still scarce, and methods for isolation and testing of multifunctional microorganisms need to be continuously innovated and improved. Thus, we used G. max bait plants to attract rhizobacteria from soils obtained from three areas with different time histories of soybean cultivation. We evaluated the influence of the management and characteristics of soils on the phosphate-solubilizing bacterial population. We then tested the multifunctional potential of the isolated rhizobacteria for calcium phosphate (CaHPO4) and iron phosphate (FePO4) solubilization, considering their potential as microbial inoculants in the future. The use of bait plants enabled the isolation of 139 phosphate solubilizing rhizobacteria, including four strains with multifunctional potential. The largest number of solubilizing bacteria was obtained from the interaction of bait plants with soil from an area with a history of soybean cultivation for thirty consecutive years. The high concentration of P, Fe, and K found in the soil were associated with this occurrence. In the in vitro tests, the pH values of the culture media had a moderate negative relationship with the amounts of P made available by the isolates, indicating that other processes besides the availability of organic acids, may underlie the solubilizing action of the isolates. The rhizobacteria SAF9 (Brevibacillus sp.), SAF11 (Brevibacillus sp.), BRC11 (Pseudomonas fluorescens), and SAC36 (Bacillus velezensis) stood out as multifunctional and are indicated within a perspective of obtaining bioinoculants to promote plant growth directly, indirectly, or synergistically, contributing to increase the range of bio-inputs for soybean cultivation and more sustainable agricultural practices.

A brief note on the incidence and management of Plasmodiophora rassica

Plasmodiophora brassica is a causal agent of brassica clubroot, and synthetic and bio fungicides showed actions against P. brassica. Under controlled-environment conditions, the mechanism of suppression of P. brassica by bio fungicides was antibiosis and mediated host resistance. To promote the delivery of bio fungicides, various formulations like granular and seed treatment were produced, so neither bio fungicides nor chemical fungicides were sufficiently compelling to reduce the population of resting spore P. brassica. Resistant cultivars substantially decreased clubroot intensity and canola yield losses. P. brassica resistance is the most consistent and economically appropriate management approach, but some studies indicate that clubroot resistance may not be robust. To build and deploy a different source of resistance constantly. The bait plants and soil modifications are not commercially practical. Crop data manipulation, soil fumigation, chemical fungicide application, and bio fungicides have much more ability to control P. brassica. The combinations of strategies that can minimize the pressure of disease in infested areas and enhance the resilience and number of the resistant gene versus P. brassica still need to be identified.

Ongoing evolution of Beet necrotic yellow vein virus towards Rz1‐resistance breaking in Europe

AbstractOver the last three decades, the control of Beet necrotic yellow vein virus (BNYVV) in sugar beet has relied on the cultivation of varieties harbouring the Rz1 resistance gene. The strong selection pressure on BNYVV has favoured the development of resistance‐breaking strains that display mutations at amino acid positions 67–70 (tetrad) in the pathogenicity factor P25 and strains possessing an additional RNA component (RNA5). To evaluate the durability of Rz1 resistance, it is essential to monitor the ongoing virulence development in BNYVV populations. Therefore, we characterized BNYVV populations from different fields in Europe suspected to possess resistance‐breaking properties. The ability to overcome Rz1 resistance could be confirmed for several populations in greenhouse bait plant tests using susceptible and resistant genotypes. These populations were able to accumulate similar virus concentrations in both genotypes. Most of the populations harboured multiple P25 tetrad variants, but there was no obvious effect of the sugar beet genotype on their composition. The strong selection pressure on P25 was reflected by the overall high number of P25 haplotypes with several amino acids under positive selection. Two different RNA5 species closely related to either the French or the Asian RNA5 type were additionally identified in some populations. Finally, high‐throughput sequencing revealed the formation of genetic reassortments between different virus types, but the overall sequence diversity within BNYVV populations was relatively low and not affected by the genotype. Our results highlight the ongoing adaption of BNYVV towards Rz1 resistance, stressing the importance of alternative resistance sources.

Plasmodiophora brassicae in Mexico: From Anecdote to Fact.

For years, the presence of clubroot disease and its causal agent, Plasmodiophora brassicae, in Mexico has been stated as a fact. However, an intensive search of the scientific literature in English and Spanish, as well as gray literature including theses and government reports, did not reveal any information about the actual detection of the pathogen, affected hosts, or areas with clubroot presence, or any information about clubroot (hernia de la col in Mexico). We followed a multistep process to confirm whether P. brassicae was indeed in Mexico. First, we identified agricultural communities with a history of cruciferous crop cultivation. Second, we asked growers if they had seen clubroot on their crops, using pictures of the characteristic root galls. Third, we collected soil from the locations where clubroot was reported and looked for clubroot/P. brassicae in the soil using several cruciferous bait plants. For the first time we confirm the presence of the clubroot pathogen P. brassicae in Mexico, through a bioassay, the presence of resting spores, and a P. brassicae-specific PCR assay. The identification of P. brassicae in Mexico will contribute to our understanding of the genetic diversity of this elusive and devastating plant pathogen in future studies.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Türkiye’de şeker pancarı üretim alanlarında enfeksiyon oluşturan Beet necrotic yellow vein virus izolatlarının p31 geninin moleküler karakterizasyonu

Beet necrotic yellow vein virus (BNYVV), which is known as "the agent of rhizomania disease" and transmitted by Polymyxa betae, is the most destructive and prevalent virus species in sugar beet fields in Turkey and in the world. In this study, seventeen BNYVV-infested soil samples were selected according to their geographic locations. Firstly, BNYVV was propogated as bait plant technique. 
 P31 protein encoded by BNYVV RNA-4 is associated with efficient vector transmission and virulence. In this study, nucleotide sequences of p31 coding region of 12 different isolates were obtained. The BLAST and phylogenetic analysis divided BNYVV isolates into two different p31 groups as Group II and Group III. The Group II consisted of IGR-6, IGR-9 and ERC-52 isolates and found to have high nucleotide identity with Kas2 isolate (99.76%-99.88%). Also, GZP-27, ELZ-44, SMS-61, EDR-125, BRS-148, CNK-150, KAS-281, KYS-524 and ANK-617 which were divided into Group III had the highest similarity (99.88%-100%) with IV isolate (Italy).

Both male- and female-produced pheromones influence Colorado potato beetle movement in the field.

Colorado potato beetle [Leptinotarsa decemlineata (Say); Coleoptera: Chrysomelidae] is a widespread key pest of potatoes and other solanaceous crops of the temperate Northern Hemisphere. Its evolution of multiple pesticide resistance is a continuing threat if chemical control is relied upon for pest management. An integrated approach including semiochemicals and other non-pesticidal tactics is essential to sustainable management. In addition to the known volatile aggregation pheromone produced by male adult beetles that is attractive to both females and males, there is a yet-unidentified female-produced sex pheromone. Using caged 'bait plants' in the field in Maryland, USA, we tested the attraction of male and female beetles to groups of male-only, female-only, larvae, and uninfested bait plants. Results of five field experiments demonstrate that the female-produced sex pheromone is attractive to male beetles, whereas the male-produced pheromone is attractive to both females and males. Male attraction increased with higher densities of females on bait plants, but female attraction did not change with female density on bait plants. This is the first study to demonstrate male attraction to the female sex pheromone in the field, and to our knowledge, the first to demonstrate a beetle species using bidirectional communication between males and females. Use of semiochemicals for monitoring and management of Colorado potato beetle should consider male-, female-, as well as plant-produced volatiles as important tools for pest manipulation in potato integrated pest management. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Transmission of the Invasive Pathogen Phytophthora ramorum from Symptomatic to Healthy Host Plants During a Five-Year Period in California

Reliable data on the transmission of airborne plant pathogens are crucial for the development of epidemiological models and implementation of management strategies. The short-distance vertical transmission of the forest pathogen Phytophthora ramorum from a symptomatic California bay laurel (Umbellularia californica) to healthy containerized rhododendrons (Rhododendron caucasicum × R. ponticum var. album) was monitored for five winters (2016/17 to 2020/21) in a field experiment in Northern California. Transmission events were observed during four winters at a frequency of 1 to 17 per season, but not during the extremely dry winter of 2020/21, and were positively correlated to total rainfall rates. The first leaf symptoms were detected around mid-December and reached the highest numbers in January of most years. Only limited symptom development was observed in the spring, with the last detections in May. The exposure time (the time between the first rainfall after placing a bait plant under the bay laurel and development of symptoms) varied between 3 and over 150 days, with an average between 14 and 21 days. P. ramorum was detected from water samples collected from the canopy of the symptomatic California bay laurel. No horizontal pathogen spread was detected from symptomatic to healthy rhododendrons placed at a distance of 2 to 6 m.

Corrigendum

Ecology LettersVolume 25, Issue 1 p. 252-252 CORRIGENDUMFree Access Corrigendum This article corrects the following: Light availability and light demand of plants shape the arbuscular mycorrhizal fungal communities in their roots Lena Neuenkamp, Martin Zobel, Kadri Koorem, Teele Jairus, John Davison, Maarja Öpik, Martti Vasar, Mari Moora, Marc-André Selosse, Volume 24Issue 3Ecology Letters pages: 426-437 First Published online: December 15, 2020 First published: 27 October 2021 https://doi.org/10.1111/ele.13909AboutSectionsPDF Comments ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL The authors Neuenkamp et al. (2021) would like to correct the following errors found in the paper. Under the Results section the following paragraph ‘Among bait plants root samples, similar numbers of VT occurred exclusively in the roots of shade-intolerant or shade-tolerant plants, and in open or shaded grassland sites (Appendix S8B and C). However, the number of exclusive VT in the roots of plants with different shade-tolerance depended on the light conditions (Figure 1). In light that is, open grassland sites, there were more exclusive VT in the roots of shade-intolerant than shade-tolerant plants (28 VT vs. 20 VT) (Figure 1a), while in shaded grassland sites there were twice as many exclusive VT in the roots of shade-tolerant compared with shade-intolerant plants (34 VT vs. 16 VT) (Figure 1b)’. is corrected as ‘Among bait plants root samples, similar numbers of VT occurred exclusively in the roots of shade-intolerant or shade-tolerant plants, and in open or shaded grassland sites (Appendix S8B and C). However, the number of exclusive VT in the roots of plants with different shade-tolerance depended on the light conditions (Figure 1). In light that is, open grassland sites, there were more exclusive VT in the roots of shade-intolerant than shade-tolerant plants (30 VT vs. 17 VT) (Figure 1a), while in shaded grassland sites there were twice as many exclusive VT in the roots of shade-tolerant compared with shade-intolerant plants (29 VT vs. 15 VT) (Figure 1b)’. REFERENCE Neuenkamp, L., Zobel, M., Koorem, K., Jairus, T., Davison, J., Öpik, M. et al. (2021) Light availability and light demand of plants shape the arbuscular mycorrhizal fungal communities in their roots. Ecology Letters, 24(3), 426– 437. Comments Please enable JavaScript to view the comments powered by Disqus. Volume25, Issue1January 2022Pages 252-252 ReferencesRelatedInformation

Suitability of Hybrid and Landrace Maize Plants Within Conventional and Organic-Polyculture Maize Agroecosystems for Hosting Parasitic Wasps

Abstract Polycultures and conventional monoculture have different effects on insect pests and natural enemies. Little is known about the parasitoid response to landrace and hybrid plants damaged by insect pests within organic-polyculture agroecosystems vs. monoculture ones. The aim of the present study was to compare the suitability of these agroecosystems for hosting parasitic wasps by evaluating the parasitism rate, parasitoid abundance, and species composition on landrace and hybrid maize races within organic-polyculture and conventional maize agroecosystems. This study was performed within the Mesoamerican region where maize was originally domesticated and where the maize insect pest Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) originated. Maize plants of landrace and hybrid varieties were used to attract egg parasitoids of D. maidis within each of the two agroecosystems; conventional maize monoculture and an organic-polyculture of landrace maize, beans, and squash, which also included weed plants. Four treatments were conducted in this field experiment: 1) landrace-within organic agroecosystem, 2) hybrid-within organic agroecosystem, 3) landrace-within conventional agroecosystem, and 4) hybrid-within conventional agroecosystem. A community of parasitic wasps, of which the micro-wasp Paracentrobia sp. (Hymenoptera: Trichogrammatidae) was the most abundant member, was found attacking the D. maidis eggs in both agroecosystems. The parasitism rate and parasitoid abundance were similar among the four treatments. However, the abundance of parasitoids was greater in the conventional maize monoculture. Bait plants (landrace and hybrid maize) within each agroecosystem did not show differences in either parasitoid abundance or parasitism rate.

CRISPR-Based Isothermal Next-Generation Diagnostic Method for Virus Detection in Sugarbeet.

Rhizomania is a disease of sugarbeet caused by beet necrotic yellow vein virus (BNYVV) that significantly affects sugarbeet yield globally. Accurate and sensitive detection methods for BNYVV in plants and field soil are necessary for growers to make informed decisions on variety selection to manage this disease. A recently developed CRISPR-Cas-based detection method has proven highly sensitive and accurate in human virus diagnostics. Here, we report the development of a CRISPR-Cas12a-based method for detecting BNYVV in the roots of sugarbeet. A critical aspect of this technique is the identification of conditions for isothermal amplification of viral fragments. Toward this end, we have developed a reverse transcription (RT) recombinase polymerase amplification (RPA) for detecting BNYVV in sugarbeet roots. The RT-RPA product was visualized, and its sequence was confirmed. Subsequently, we designed and validated the cutting efficiency of guide RNA targeting BNYVV via in vitro activity assay in the presence of Cas12a. The sensitivity of CRISPR-Cas12a trans reporter-based detection for BNYVV was determined using a serially diluted synthetic BNYVV target sequence. Further, we have validated the developed CRISPR-Cas12a assay for detecting BNYVV in the root-tissue of sugarbeet bait plants reared in BNYVV-infested field soil. The results revealed that BNYVV detection is highly sensitive and specific to the infected roots relative to healthy control roots as measured quantitatively through the reporter signal. To our knowledge, this is the first report establishing isothermal RT-RPA- and CRISPR-based methods for virus diagnostic approaches for detecting BNYVV from rhizomania diseased sugarbeet roots.

Ocorrência e caracterização de populações de bactérias nodulíferas fixadoras de N2 oriundas de áreas de assentamento em Marabá, Pará, Brasil

The native edaphic population study may show are servoir of genetic resources for the selection of efficient strains, besides being an indicator of anthropic tests. The aim of this paper was to characterize and evaluate the occurrence of bacteria population that nodulate and fix N2 using cowpea like a bait plant. This research happened in a greenhouse situated at the Federal Institute of Para, Campus Maraba Rural. Some soil samples were collected in the PA 26 de Marco country into eight environments: being three individual areas under banana and cassava cultivation, one under capoeira and forest. The experimental design was completely randomized with three replications and eight treatments, that consist of the study areas. At 35 days after emergencies of the plants, they were collected to determine the number of nodules (NN), dry matter of the area (DMA) and root (DMR). From each treatment in this process, ten nodules were isolated for the morphological and physiological characterization of their colonies. Nodulation occurred in all treatments, with a large variation in NN and DMA production. 53 strains were isolated and most of them presented morphological and physiological characteristics similar to those found in the genera Rhizobium, Sinorhizobium, Allorhizobium e Mesorhizobium.

Diversity of soil-borne fungal species associated to root rot and vine decline of melon in Sardinia (Italy)

Monosporascus root rot and vine decline of melon (MRRVD) is a destructive disease complex mainly occurring in semiarid cultivation areas. In the last decade, in the melon producing area of Sardinia (Italy), yield reductions up to 100% were recorded due to the occurrence of MRRVD. The present study aimed to undertake a two-year survey of fungal pathogens associated with MRRVD grown as a monocrop in two locations in Central Sardinia, Sinis, and Sassu, and to investigate the possible role of soil fungal diversity in the disease development. Melon plants were affected by similar symptoms but colonized by a set of soil-borne fungal pathogens different between surveyed sites and cropping seasons, including Plectosphaerella melonis, P. cucumerina, Fusarium solani, Macrophomina phaseolina and Monosporascus cannonballus. Olpidium bornovanus and O. virulentus were isolated using bait plants and detected by NGS analysis. Bait plants had a general decrease in biomass and yellowing of foliage. The presence of most of the isolated pathogens was also confirmed by the NGS analysis of the soil microbiome. Our results confirm that among the fungal complex implicated in the occurrence of RRVD in Sardinia, O. bornovanus along with O. virulentus likely assume a key role in the development of the disease alone and possibly in association with other pathogens. Differences in the pathogenic fungal spectrum here recorded in symptomatic roots may be associated with agricultural practices, soil physicochemical characteristics, and fungal community composition and function profile.

Pathogenicity of Pythium species to maize

Pythium isolates from diseased and dead bait plants of maize and cress grown in compost or various soils (maize fields, parkland under deciduous trees, grassland) were characterised and tested for pathogenicity to maize (Zea mays L.). In pot tests performed under controlled conditions, pathogenicity of the isolates to maize was apparent by reduction of root and shoot growth, whereas damping-off of maize seedlings was less frequent. Contrarily, pea seedlings were killed by pathogenic Pythium isolates. Pythium isolates from diseased maize seedlings and pathogenic strains from other gramineous plants (P. phragmitis, P. aff.phragmitis, P. catenulatum) were not necessarily more virulent to maize compared to isolates originating from dicotyledonous plants (cress). The most virulent isolates originated from compost and caused a reduction of maize shoot growth of up to 60%. Phylogenetic analysis revealed that they were very closely related to P. ultimum var. ultimum and P. arrhenomanes, respectively. Isolates originating from maize fields, grassland and parkland under deciduous trees, a reference culture of P. arrhenomanes and strains of P. phragmitis, P. aff. phragmitis and P. catenulatum with known pathogenicity on reed were non-pathogenic on maize. Isolates from compost, and from maize fields generally had a higher temperature optimum for mycelial growth (30 °C) and a faster growth rate (1.5–2.0 mm h−1) compared to the isolates from parkland under deciduous trees and grassland soil (20–25 °C, ~1.0 mm h−1), respectively. This study indicates a potential impact of pathogenic Pythium on maize plants even in the absence of visible symptoms.

Tissue-Specific Dynamics in the Endophytic Bacterial Communities in Arctic Pioneer Plant Oxyria digyna.

The rapid developments in the next-generation sequencing methods in the recent years have provided a wealth of information on the community structures and functions of endophytic bacteria. However, the assembly processes of these communities in different plant tissues are still currently poorly understood, especially in wild plants in natural settings. The aim of this study was to compare the composition of endophytic bacterial communities in leaves and roots of arcto-alpine pioneer plant Oxyria digyna, and investigate, how plant tissue (leaf or root) or plant origin affect the community assembly. To address this, we planted micropropagated O. digyna plants with low bacterial load (bait plants) in experimental site with native O. digyna population, in the Low Arctic. The endophytic bacterial community structures in the leaves and roots of the bait plants were analyzed after one growing season and one year in the field, and compared to those of the wild plants growing at the same site. 16S rRNA gene targeted sequencing revealed that endophytic communities in the roots were more diverse than in the leaves, and the diversity in the bait plants increased in the field, and was highest in the wild plants. Both tissue type and plant group had strong impact on the endophytic bacterial community structures. Firmicutes were highly abundant in the leaf communities of both plant types. Proteobacteria and Bacteroidetes were more abundant in the roots, albeit with different relative abundances in different plant groups. The community structures in the bait plants changed in the field over time, and increasingly resembled the wild plant endophytic communities. This was due to the changes in the relative abundances of several bacterial taxa, as well as species acquisition in the field, but with no species turnover. Several OTUs that were acquired by the bait plants in the field and represent phosphate solubilizing and diazotrophic bacterial taxa, suggesting major role in nutrient acquisition of these bacteria for this nonmycorrhizal plant, thriving in the nutrient poor arctic soils.

Elimination of Tobacco rattle virus from viruliferous Paratrichodorus allius in greenhouse pot experiments through cultivation of castle russet.

Corky ringspot (CRS) is a widespread potato tuber necrotic disease caused by Tobacco rattle virus (TRV) infection. In the Pacific Northwest, this virus is transmitted by the stubby root nematode (SRN) within the genus Paratrichodorus. Remediating CRS affected fields is a major challenge that can be mitigated by growing plant varieties that are resistant to TRV infection. Growing alfalfa has been shown to reduce TRV levels in CRS infested fields over time but the development of a potato cultivar with these same capabilities would be of great economic benefit to potato growers. Castle Russet is a new potato clone that does not develop symptoms of CRS disease. To assess its ability to reduce soil virus load, Castle Russet, tobacco var. “Samsun NN”, alfalfa var. “Vernema”, and Russet Burbank potato were grown for a period of 1 to 3 months in soils containing viruliferous SRN populations at two different inoculation pressures (60 nematodes/pot and 1060 nematodes/pot) in greenhouse pot experiments. SRN population size and the presence of TRV were assessed over several months post inoculation. Results indicate that plant host and length of exposure significantly influence SRN population dynamics, whereas the TRV infection status of bait plants was significantly affected by both of these factors as well as inoculation pressure. These results suggest that both alfalfa var. “Vernema” and Castle Russet are resistant to TRV infection and may potentially be used to eliminate the virus from fields affected by CRS.

Taxi drivers: the role of animals in transporting mycorrhizal fungi.

Dispersal of mycorrhizal fungi via animals and the importance for the interacting partners' life history as well as for ecosystems is an understudied topic. In this review, we describe the available evidence and the most important knowledge gaps and finally suggest ways to gain the missing information. So far, 33 articles have been published proving a successful transfer of mycorrhizal propagules by animals. The vast majority of research on invertebrates was focused on arbuscular mycorrhizal (AM) fungi, whereas papers on vertebrates (mainly rodents and artiodactyls) equally addressed ectomycorrhizal (ECM) and AM fungi. Effective dispersal has been mostly shown by the successful inoculation of bait plants and less commonly by spore staining or germination tests. Based on the available data and general knowledge on animal lifestyles, collembolans and oribatid mites may be important in transporting ECM fungal propagules by ectozoochory, whereas earthworms, isopods, and millipedes could mainly transfer AM fungal spores in their gut systems. ECM fungal distribution may be affected by mycophagous dipterans and their hymenopteran parasitoids, while slugs, snails, and beetles could transport both mycorrhizal groups. Vertebrates feeding on fruit bodies were shown to disperse mainly ECM fungi, while AM fungi are transported mostly accidentally by herbivores. The important knowledge gaps include insufficient information on dispersal of fungal propagules other than spores, the role of invertebrates in the dispersal of mycorrhizal fungi, the way in which propagules pass through food webs, and the spatial distances reached by different dispersal mechanisms both horizontally and vertically.

Prevalence and Distribution of Beet Necrotic Yellow Vein Virus Strains in North Dakota and Minnesota.

Beet necrotic yellow vein virus (BNYVV) is the causal agent of rhizomania, a disease of global importance to the sugar beet industry. The most widely implemented resistance gene to rhizomania to date is Rz1, but resistance has been circumvented by resistance-breaking (RB) isolates worldwide. In an effort to gain greater understanding of the distribution of BNYVV and the nature of RB isolates in Minnesota and eastern North Dakota, sugar beet plants were grown in 594 soil samples obtained from production fields and subsequently were analyzed for the presence of BNYVV as well as coding variability in the viral P25 gene, the gene previously implicated in the RB pathotype. Baiting of virus from the soil with sugar beet varieties possessing no known resistance to rhizomania resulted in a disease incidence level of 10.6% in the region examined. Parallel baiting analysis of sugar beet genotypes possessing Rz1, the more recently introgressed Rz2, and with the combination of Rz1 + Rz2 resulted in a disease incidence level of 4.2, 1.0, and 0.8%, respectively. Virus sequences recovered from sugar beet bait plants possessing resistance genes Rz1 and/or Rz2 exhibited reduced genetic diversity in the P25 gene relative to those recovered from the susceptible genotype while confirming the hypervariable nature of the coding for amino acids (AAs) at position 67 and 68 in the P25 protein. In contrast to previous reports, we did not find an association between any one specific AA signature at these positions and the ability to circumvent Rz1-mediated resistance. The data document ongoing virulence development in BNYVV populations to previously resistant varieties and provide a baseline for the analysis of genetic change in the virus population that may accompany the implementation of new resistance genes to manage rhizomania.

CHALCIDOIDEA SPECIES (INSECTA: HYMENOPTERA) ON THE WOODY VINE CAMPSIS RADICANS (L.) SEEM. EX BUREAU

The woody vine Campsis radicans has extrafloral nectaries on the sepal, pedicel and green fruits. Its nectar attracts abundant Hymenoptera and especially representatives of the Chalcidoidea superfamily. During a six-year study (2012-2017) in the period from July to mid-October, 2117, specimens of Chalcidoidea from 13 families were collected. A total of 116 species were determined, of which 63 were new species to the Serbian fauna, and 11 to the fauna of the Balkan Peninsula. Campsis radicans can be considered as a “bait plant” that attracts many groups of Hymenoptera, which is very important for the study of their fauna, and in particular, for almost all the families of the Chalcidoidea superfamily. Campsis radicans is also significant since its extrafloral nectar is food to many Chalcidoidea species in periods when no other food is available. Given that almost all of the identified Chalcidoidea species are natural enemies of other insects (most commonly of phytophagous insects), C. radicans indirectly provides a natural balance in different terrestrial ecosystems.