Differential Morphological, Structural and Biological Characteristics of Cysts in Heterodera Species in Korea
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Morphological (cyst shape, color, and sizes [length (L), maximum width (W), volume and âaâ (L/W)]), structural (vulvar cone slope angle [VCSA], surface wrinkle [VCSW], cyst wall thickness, composition, and texture) and biological characteristics (fecundity, hatching, and emergence [number of second-stage juveniles (J2) from a cyst]) in preceding Heterodera glycines (Hg), currently-recorded H. sojae (Hs) and H. trifolii (Ht) were examined by microscopy. Cysts were lemon-shaped, indicating the genus is Heterodera except for Hs that formed frequently globular cysts with significantly flatter VCSA (102.2°) with smooth VCSW than Hg (50.6°) and Ht (82.0°), but not genus Globodera because of the presence of vulvar cone in Hs. Ht was significantly larger in all morphological characteristics than Hg and Hs, suggesting Ht may be diagnosed differentially by cyst sizes and also host plant preferences. Hs showed smaller âaâ value with more globular shape and stronger structures with more thickened and strengthened collagen-like texture of cyst wall than Hg and Ht. This suggests Hs may be diagnosed differently by structural characteristics from the others, especially Hg with similar cyst sizes. There were no significant differences in emergence (inoculum potential) among cyst nematodes due to the offset of fecundity and hatching rate; however, the inoculum potential of Hs may be not so persistent as Hg and Ht in fields because of its lower fecundity and higher hatching rate (causing rapid inoculum loss) than the others. These characteristics of cysts provide information useful for simple and differential diagnoses and reliable management of cyst nematodes. Keywords: biological characteristics, cysts, Heterodera spp., morphological and structural characteristicsKeywords:
Heterodera
In studies of nematode-suppressive soil and plant-parasitic nematode management, it is often desirable to kill nematodes in the soil but keep the microbial community alive. The effect of temperature treatment on survival of Heterodera glycines , the soybean cyst nematode (SCN), and associated fungi and bacteria was investigated. Extracted eggs and cysts, and cysts in soil were subjected to treatments of temperatures ranging from −80 to 55°C for 1 to 24 h. Nematode survival was determined by hatching in vitro and by infectivity and development in soybean, and fungal survival was determined by plating the eggs or cysts on potato dextrose agar. The nematodes survived well between −20 and 45°C, but could not survive at −80 or 48°C and above, while some nematodes were killed after heat treatment of 46°C. By contrast, fungi survived well in the cysts at −80°C, and also much better than nematodes at the high temperatures. Glasshouse studies demonstrated that both bacteria and fungi survived well in the soil treated with −80°C. Transferring 5% of −80°C-treated soil to autoclaved soil could effectively establish nematode suppressiveness. Our study demonstrated that freezing soil at −80°C can kill SCN but maintain nematode suppressiveness, and the soil treatment can improve the method for nematode-suppressive soil evaluation.
Heterodera
Soybean cyst nematode
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The effects of nutrition on fecundity and yield of nematode in continued culture were evaluated. Results showed that fecundity and yield of nematode were higher in culture medium containing pure insect substance than those not containing it.Declined nematodes could restore to high fecundity after continued culturing in pure insect substance medium for two generations. In order to obtain high yield in mass production of nematode, use a high fecundity nematode strain and a culture medium containing insect substance are essential.
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The family of FMRFamide-related peptides (FaRPs) is widely distributed among invertebrates, where the peptides serve as neuromodulators. Published reports indicate that numerous FaRP sequences exist in free-living and animal parasitic nematodes. Using a FMRFamide ELISA, FaRP immunoreactivity was detected in extracts of the soybean cyst nematode, Heterodera glycines, in both sexes and at all developmental stages. HPLC-ELISA results revealed a number of immunoreactive components in H. glycines preparations, and a comparison with extracts of the free-living nematodes Caenorhabditis elegans and Panagrellus redivivus showed significant qualitative differences in FaRP immunoreactivity between the plant parasite and the two free-living nematodes. Total and specific immunoreactivities varied during H. glycines development, with the highest specific activity in juveniles and males, and the highest total activity in mature females. Total female immunoreactivity was located primarily within the mature eggs. A significant portion, however, was associated with the female body, perhaps with egg laying.
Heterodera
Soybean cyst nematode
FMRFamide
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Soybean cyst nematode infestation continues to be a serious agricultural problem. As part of an interdisciplinary effort to identify a biorational solution to the problem, analogs of glycinoeclepin A, a natural hatching stimulus of the nematode, were prepared and tested. Several of the analogs were discovered to inhibit the hatching of soybean cyst nematode eggs. On the basis of the results of egg hatch tests, the minimum functionality for egg hatch inhibition appears to be a keto diacid. Keywords: Nematode; hatching inhibitor; synthesis
Soybean cyst nematode
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The sex ratio of the Arkansas 1 isolate of Heterodera glycines was determined in experiments in which 'Lee' soybean was inoculated with either one or two larvae. A 3:1 male to female sex ratio was established for this isolate under the test conditions used. No influence of one nematode on the penetration and development to adult of another nematode in the same root was detected in double larval inoculations.
Heterodera
Soybean cyst nematode
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An unnamed fungus, designated ARF, that parasitizes eggs and sedentary stages of cyst nematodes is a potential biological control agent of Heterodera glycines. The objectives of this study were to determine whether ARF isolates differ in their ability to suppress nematode numbers in soil and to compare the efficacy of ARF in heat-treated and native soil. The effectiveness of 11 ARF isolates was compared by introducing homogenized mycelium into heat-treated soil. Soybean seedlings were transplanted into pots containing fungus-infested soil and inoculated with H. glycines. After 30 or 60 days, the number of nematodes and the percentage of parasitized eggs were determined. Three isolates (907, 908, and TN14), which were previously reported to be weak egg parasites in vitro, consistently suppressed nematode numbers by 50% to 100%. Of the isolates previously reported to be aggressive egg parasites, four (903, BG2, MS3, and TN12) reduced nematode numbers by 56% to 69% in at least one experimental trial, but the other four had no effect on nematode numbers. When the efficacy of isolate TN14 was tested in heat-treated and native soil, nematode suppression was greater in the heat-treated soil in only one of two trials. In both soil treatments, nematode numbers were reduced by more than 60%. We conclude that virulence toward nematode eggs in vitro is a poor indicator of effectiveness of an ARF isolate in soil, and that the presence of soil microbes may reduce, but does not completely inhibit, activity of isolate TN14.
Heterodera
Soybean cyst nematode
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Abstract In the spring of 2019, a cyst nematode was discovered from soil samples collected from an alfalfa field in Millard County, Utah. The soil samples were submitted to one of us (SH), who extracted the nematode cysts and sent them to the USDA-ARS, Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), Beltsville, MD for morphological and molecular identification. Cysts and living nematode juveniles (J2) recovered from the cysts were examined morphologically and molecularly for species identification which indicated that the specimens were Heterodera medicaginis. This represents the first record of H. medicaginis in Utah and the second report of this nematode in North America.
Heterodera
Soybean cyst nematode
Mycology
Nematode infection
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Heterodera
Soybean cyst nematode
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To examine if the resistance of soybean to Heterodera glycines would differ at Kariwano and Kikyogahara, four experiments were conducted at these places under the same design, in which two nematode-populations from Kariwano (A) and Kikyogahara (B) were inoculated to the plant of cliffererit resistant varieties cultured in pot. The cyst formation of the nematode were more with the population B than with A most distinctly in the medium resistant varieties, and the damages of plant were greater with the population B than with A in the weaker resistant varieties. The two populations should belong to different physiological strains of the nematode.
Soybean cyst nematode
Heterodera
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Influence of susceptible and resistant soybean varieties to the development of the soybean cyst nematode(Heterodera glycines) was examined. It does not seem likly that there are any differences between varieties in attracting the Second Stage larvae of the nematode. In susceptible varieties, there were large populations and three generations during a ten·week examination period, while the resistant varieties maintained very low populations and had only two generations.
Heterodera
Soybean cyst nematode
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