Juveniles Of Soybean Cyst Nematode Research Articles

콩씨스트선충(Heterodera glycines)과 반짝이콩씨스트선충(H. sojae)의 온도별 부화와 살선충 물질에 대한 알과 유충의 약제 반응 비교

콩씨스트선충(Heterodera glycines)과 반짝이콩씨스트선충(H. sojae)의 온도별 부화와 살선충 물질에 대한 알과 유충의 약제 반응 비교

Electropermeabilization-based fluorescence in situ hybridization of whole-mount plant parasitic nematode specimens

A fluorescence in situ hybridization (FISH) protocol was developed for nematodes in which nucleic acid probes are introduced within the organism via electroporation. This modification of existing FISH protocols removes numerous chemical wash steps, and thus, reduces protocol time and specimen loss while improving hybridization sensitivity. The presented work is optimized for juveniles of soybean cyst nematode (SCN; Heterodera glycines) and has been used to identify both host and associated-microbial (viral) targets. Moreover, through the use of two different long wavelength fluorophores, two probes can be colocalized within one individual. This protocol may be adapted to identify targets-of-interest within other life stages and nematode species.This protocol improves:•Hands-on protocol time (by approximately 1.5 h).•Specimen loss (fewer aspiration steps).•Hybridization (allows colocalization with two nucleic acid probes and increases sensitivity).

1,10-Phenanthroline and its derivatives are novel hatching stimulants for soybean cyst nematodes

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a plant-parasitic nematode and one of the most serious soybean pests. Herein, we present the heterocyclic compound 1,10-phenanthroline (Phen) and its derivatives as novel hatching stimulants for SCN. Phen treatment promoted hatching of second-stage juveniles of SCNs in a concentration-dependent manner. In addition, the hatching of SCNs following treatment with Phen occurred more rapidly than that following treatment with the known hatching stimulant, glycinoeclepin A (GEA). Furthermore, the co-application of Phen and GEA enhanced SCN hatching rate compared with that of Phen or GEA alone. A structure–activity relationship study for Phen derivatives suggested that 2,2′-bipyridine is the essential structure of the SCN-hatching stimulants. These results suggest that Phen and its derivatives activate different hatching pathways of SCNs from GEA.

Comparative genomics and transcriptomics analyses reveal divergent lifestyle features of nematode endoparasitic fungus Hirsutella minnesotensis.

Hirsutella minnesotensis [Ophiocordycipitaceae (Hypocreales, Ascomycota)] is a dominant endoparasitic fungus by using conidia that adhere to and penetrate the secondary stage juveniles of soybean cyst nematode. Its genome was de novo sequenced and compared with five entomopathogenic fungi in the Hypocreales and three nematode-trapping fungi in the Orbiliales (Ascomycota). The genome of H. minnesotensis is 51.4 Mb and encodes 12,702 genes enriched with transposable elements up to 32%. Phylogenomic analysis revealed that H. minnesotensis was diverged from entomopathogenic fungi in Hypocreales. Genome of H. minnesotensis is similar to those of entomopathogenic fungi to have fewer genes encoding lectins for adhesion and glycoside hydrolases for cellulose degradation, but is different from those of nematode-trapping fungi to possess more genes for protein degradation, signal transduction, and secondary metabolism. Those results indicate that H. minnesotensis has evolved different mechanism for nematode endoparasitism compared with nematode-trapping fungi. Transcriptomics analyses for the time-scale parasitism revealed the upregulations of lectins, secreted proteases and the genes for biosynthesis of secondary metabolites that could be putatively involved in host surface adhesion, cuticle degradation, and host manipulation. Genome and transcriptome analyses provided comprehensive understanding of the evolution and lifestyle of nematode endoparasitism.

IMMEDIATE RESPONSES OF CYST NEMATODE, SOIL-BORNE PATHOGENS AND SOYBEAN YIELD TO ONE-SEASON CROP DISTURBANCE AFTER CONTINUOUS SOYBEAN IN NORTHEAST CHINA

Habitat disturbance affects numerous ecosystem components and processes, but its effect on continuous soybean system is less available. Soybean was seeded following six preceding crops, including grain soybean (Glycine max L. Merill.), wheat (Triticum aestivum L.), sugar beet (Beta vulgaris L.), tobacco (Nicotiana tabacum L.), corn (Zea mays L.) and hemp (Cannabis Satia L.), on a Mollisol farmland that had previously been cropped to continuous soybean for seven years in Northeast China. Soybean after hemp reduced the number of second-stage juveniles of soybean cyst nematode (J2) by 29.8% compared to continuous soybean, while soybean after corn had the lowest J2 number. The number of soilborne pathogens of Fusarium, Rhizoctonia and Pythium after corn and hemp and root rot disease severity index after all crop disturbance, except sugar beet, were significantly lower than continuous soybean. Soybean yield after hemp disturbance was improved by 10.8%, while sugar beet disturbance had the greatest negative impact on soybean yield. No differences were found among crop disturbance for protein and oil content in soybean seed. Crop disturbance changed the habitat already developed in the continuous soybean system. Adoption of hemp disturbance has the potential to be an alternative approach in managing continuous soybean production system in Northeast China.

Soil Suppressiveness Against the Disease Complex of the Soybean Cyst Nematode and Sudden Death Syndrome of Soybean

The ecology of the complex of soybean cyst nematode (SCN) and sudden death syndrome (SDS) of soybean was investigated under soybean monoculture in two field experiments from 2003 to 2007. Initially, susceptible soybean 'Spencer' was planted while inoculating Fusarium virguliforme into nonfumigated or preseason-fumigated plots (methyl bromide, MB, at 450 kg/ha), and SCN and SDS were monitored. In one field, SCN population densities declined in nonfumigated but increased in fumigated plots. After years of limited SDS in 2003 and 2004, SDS developed later in nonfumigated than fumigated plots. In 2006 in the greenhouse, nondisturbed or disturbed soil cores (10-cm diameter, 30-cm depth) from field plots received two two-level factors: (i) nonfumigated or fumigated (1,070 kg/ha MB); and (ii) noninoculated or inoculated with 9,000 second-stage juveniles of SCN. At harvest, nonfumigated cores from nonfumigated plots had fewer nematodes and less SDS regardless of disturbance or inoculation than the corresponding fumigated cores and any cores from fumigated plots. In the second field, SCN became detectable after 2003 during the monoculture in nonfumigated plots and lagged in fumigated plots; both treatments had low levels of SDS. Exploiting the suppressiveness of the first field could allow for biological control of SDS and SCN in soybean production.

Influence of Winter Annual Weed Removal Timings on Soybean Cyst Nematode Population Density and Plant Biomass

Soybean cyst nematode (SCN) is one of the most yield limiting pathogens in U.S. soybean production. Henbit and purple deadnettle are winter annual weeds shown to facilitate SCN reproduction after crop harvest in the eastern Corn Belt. These weeds, along with volunteer soybean that germinates in autumn after harvest, are common to postharvest soybean production fields and provide an opportunity for SCN reproduction and population increase outside of the typical soybean production season. The objective of this experiment was to determine if autumn removal of these weeds and volunteer soybean can influence the winter weed seedbank, plant biomass, and SCN population densities. Microplots were established with or without Lamium spp. and volunteer soybean, and four winter weed removal timings (none, October, December, and May). Dry weights of autumn Lamium spp. were reduced 50% in October when grown in competition with volunteer soybean. SCN juveniles were found in henbit roots at higher densities in October (42 per gram of root) than December (5 per gram of root) and were also found in the roots of volunteer soybean (14 per gram of root) in October. SCN egg population densities were 50% lower in August after the summer fallow period. The results of this experiment suggest that autumn removal of winter annual weeds and volunteer soybean did not reduce SCN populations.

Purple Deadnettle (Lamium purpureum) and Soybean Cyst Nematode Response to Cold Temperature Regimes

An experiment was conducted in growth chambers to determine the influence of cold temperature regimes, designed to simulate winter temperature conditions and spring recovery, on the interaction between purple deadnettle and soybean cyst nematode (SCN). The study was a factorial arrangement of treatments with five levels of temperature (20, 15, 10, 5, or 0 C), two levels of exposure time to the temperature (10 or 20 d), and two levels of recovery time at 20 C following exposure (0 or 20 d). In general, purple deadnettle shoot and root growth increased with temperature and time. The ability of purple deadnettle to recover from cold temperatures declined as the length of time that the plant was subjected to the cold temperature increased. SCN juveniles per gram of root at the conclusion of the temperature treatment declined as the temperature increased from 0 to 15 C, likely a result of continued purple deadnettle root growth and the inhibition of SCN hatch, growth, or development at those temperatures. SCN female, cyst, and egg production per gram of root generally increased with temperature and occurred under all temperature regimes. The results of this research indicate that, after hatching, SCN juveniles can survive a period of cold temperature inside the roots of a winter annual and continue development when transferred to warmer temperatures. Therefore, in a field environment, where fall or spring alone may not be sufficient for SCN to complete a reproductive cycle on a winter annual weed, the nematode may be able to reproduce by combining the fall and spring developmental periods.

Development of Soybean Cyst Nematode on Henbit (Lamium amplexicaule) and Purple Deadnettle (Lamium purpureum)

A survey of seven production fields in Indiana, Illinois, and Ohio was conducted to assess henbit and purple deadnettle growth and soybean cyst nematode (SCN) development and reproduction on these weeds. Autumn and spring growth of purple deadnettle and henbit was influenced by location within each state. In general, winter annual weeds were larger in size and reached maturity earlier in the spring at the southern sample sites than those in the north. All growth stages of SCN were found to be associated with henbit and purple deadnettle at both autumn and spring sample timings. SCN juveniles were generally found infecting roots at highest abundance in the spring. SCN cyst and egg production also were widespread and occurred to a much higher degree during the autumn than the spring developmental period. The results of this survey indicate that management tactics designed to minimize the potential for SCN reproduction on winter annual weeds would probably be most effective if conducted in the autumn, when the majority of SCN reproduction occurred. However, spring populations of winter annual weeds that harbor SCN juveniles might facilitate additional SCN reproduction and population increase if the weeds are not controlled in a timely manner prior to planting.

Detection of the nematophagous fungus Hirsutella rhossiliensis in soil by real-time PCR and parasitism bioassay

Hirsutella rhossiliensis, a nematophagous fungus, has shown potential in biocontrol of plant-parasitic nematodes. Monitoring the population dynamics of a biocontrol agent in soil requires comprehensive techniques and is essential to understand how it works. Bioassay based on the fungal parasitism on the juveniles of soybean cyst nematode, Heterodera glycines, can be used to evaluate the activity of the fungus but fails to quantify fungal biomass in soil. A real-time polymerase chain reaction (PCR) assay was developed to quantify the fungal population density in soil. The assay detected as little as 100 fg of fungal genomic DNA and 40 conidia g−1 soil, respectively. The parasitism bioassay and the real-time PCR assay were carried out to investigate the presence, abundance and activity of H. rhossiliensis in soil after application of different inoculum levels. Both of the percentage of assay nematodes parasitized by H. rhossiliensis based on the parasitism bioassay and the DNA yield of the fungus quantified by real-time PCR increased significantly with the increase of the inoculum levels. The DNA yield of the fungus was positively correlated with the percentage of assay nematodes parasitized by H. rhossiliensis. The combination of the two is useful for monitoring fungal biomass and activity in soil.

Biological manifestation of resistance to soybean cyst nematode development in ‘Hartwig’ soybean

‘Hartwig’ soybean [ Glycine max (L.) Merr.] is the first cultivar reported to be resistant to all known races of soybean cyst nematode (SCN), Heterodera glycines Ichinohe; however, the nature of resistance in this cultivar is not known. Resistance to SCN in Hartwig and its donor parent, PI 437654, was studied from observations of the developmental stages of the nematode in the plant roots and compared with the development in susceptible ‘Essex’. Soybean seedlings (emerging roots) were exposed to a wild population of SCN for 8 h and transferred to hydroponics. Adult males and females were extracted and the number of immature juveniles in the roots was recorded from stained roots. A greater number of juveniles of SCN penetrated the roots of Hartwig than roots of PI 437654 or Essex. Several immature juveniles were observed in the roots of Hartwig and PI 437654; however, no mature females developed on either of these two lines. There were no immature juveniles in Essex. Many adult males developed in Hartwig and PI 437654. Complete resistance to female development operated in both Hartwig and PI 437654, whereas partial resistance to male development was observed in PI 437654. Hartwig soybean seems to attract more SCN juveniles, resulting in greater initial penetration than occurs in PI 437654 or Essex.