Karyotype analysis of the plant-parasitic nematode Heterodera glycines by electron microscopy: II the tetraploid and an aneuploid hybrid
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ABSTRACT In the plant-parasite nematode Heterodera glycines, 2 forms, in addition to the diploid (9 bivalents), have been isolated and analysed: a tetrapioid (18 bivalents) and an aneuploid (14 bivalents, hybrid between the diploid and the tetrapioid). Observations on the formation of their karyotypes indicates normal and non-homologous pairing. Eighteen normal synaptonemal complexes (SC) are present in pachytene nuclei of the tetrapioid. Two of the SCs are enclosed in a large heterochromatin mass that is displaced to one side of the nucleus. Such a mass has not been observed in the diploid or the aneuploid. Another 2 normal SCs of the tetrapioid have each a ‘modified SC region’ (MSC) within which the SC appears disorganized. The aneuploid has 14 SCs that are unattached at either end. Only 25% of the karyotype length is normal in the appearance of the SCs. The rest can be traced by the presence of disorganized SC material and condensed chromatin. Four MSCs are present in the hybrid nuclei. The possible role of the MSCs in the sex determination system is discussed.Keywords:
Heterodera
Soybean cyst nematode
Thirteen soybean plant introduction (PI) lines, selected for their apparent susceptibility to Heterodera glycines, were compared with cultivar Lee 74 as hosts of H. glycines races 1, 2, 3, and 4. Race 3 produced the highest average number of females of the four races. Compared to Lee 74, more (P = 0.05) females of H. glycines race 1 were extracted from eI 274420, PI 274423, and PI 317333; PI 86457 had more females of H. glycines race 2; and PI 86443, PI 86457, PI 261467, PI 274420, PI 274421, and PI 274423 had more females of H. glycines race 3. Similar numbers of females of H. glycines race 4 developed on all of the soybean lines and Lee 74. PI 274421, PI 274420, or PI 196159 could provide a more or equally susceptible host for H. glycines races 1, 2, 3, and 4 than Lee 74. One of these three lines could be substituted for Lee as the standard susceptible cultivar in the race determination test.
Soybean cyst nematode
Heterodera
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Physiological variation among populations of Heterodera glycines Ichinohe, the soybean cyst nematode, has been a problem for soybean [ Glycine max (L.) Merr.] growers and scientists. These populations have been classified into 16 races, but the system still leaves ambiguity, especially in the characterization of resistance. Two schemes are proposed: one to classify the nematoder aces and the other to designate the soybean response to the nematode. The existing race system by Riggs and Schmitt still serves as a basis for differentiating populations of H. glycines , but with soybean PI 437654 added as an additional nematode response parameter. A practical system using a popular resistant cultivar as the type for resistance is proposed for advisory purposes. Soybean reactions to parasitism by the nematode are denoted by four levels of resistance: resistant, moderately resistant, moderately susceptible, and susceptible.
Soybean cyst nematode
Heterodera
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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 ( Heterodera glycines Ichinohe) is the most damaging pathogen of soybean [ Glycine max (L.) Merr.] in the United States. Observations in fields suggest that high H. glycines population densities are associated with high soil pH, but H. glycines and soil pH have not been linked to soybean yield. The objective of our study was to assess the relationship between soil pH and H. glycines population densities and subsequent effect on yield. Experiments were conducted in Wisconsin from 1997 to 2000 and in Iowa from 1996 to 1998. Results were consistent among the experiments and showed a positive correlation between soil pH and H. glycines population densities and a negative correlation between yield and both soil pH and H. glycines population densities in both states. In the Wisconsin experiment, yield of both H. glycines –resistant and H. glycines –susceptible cultivars decreased as pH increased, but the decrease was less with H. glycines –resistant cultivars. Overall, results indicate that H. glycines population densities and the impact of nematode population densities on soybean yield are related to soil pH; however, the mechanism of these interactions is unknown.
Heterodera
Soybean cyst nematode
Population density
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Four of five geographical isolates of Heterodera glycines from Indiana classified as Race 3 using standard differentials showed many differences when classified using another group of differentials comprised of five soybean breeding lines and cultivars. Two isolates from northern Indiana produced cysts on more of the differentials tested than did three isolates from southern Indiana, suggesting that potential resistant lines should be tested on a range of H. glycines populations originating from the areas for which cultivars are being developed.
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Soybean cyst nematode
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Yields of four soybean cultivars were measured for 4 years in a field infested with Heterodera glycines race 3 and in a field infested with H. glycines race 14. Cultivars included Hutcheson (susceptible to both races), Deltapine 415 (resistant to race 3 and susceptible to race 14), Asgrow 5979 (resistant to both races), and Harwig (resistant to both races as well as most other known races of H. glycines). Although no above-ground symptoms of nematode infection were visible, mean yield was 16-32% greater for Asgrow 5979 than for Hutcheson. Yield for Dehpiue 415 was similar to that of Asgrow 5979 in the field infested with race 3 and similar to that of Hutcheson in the race 14-infested field. Hartwig produced lower yields than Asgrow 5979 in both fields. Yield differences, particularly between Asgrow 5979 and Hutcheson, were attributed primarily to nematodes because both cultivars have been shown to produce similar yields in the absence of H. glycines. This study illustrates the importance of knowing which race of the nematode is prevalent in a field and demonstrates that the nematode can cause significant yield loss in the absence of visible symptoms of infection.
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Heterodera
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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.
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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.
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Soybean cyst nematode
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Soybean cyst nematode, Heterodera glycines Ichinohe, is the most destructive pest of soybean (Glycine max) worldwide, including China. H. glycines virulence phenotypes can be described in two ways. One is the race determination test that uses four soybean lines to categorize H. glycines into 16 “races” (3). The HG type designation is similar, but avoids the implications of the term “race” and includes seven soybean lines rather than four (2). In China, previous data revealed the occurrence of nine H. glycines races including races 1 through 7, 9, and 14, whereas HG types have not been recorded (1). The objective of this study was to reassess virulence phenotypes of H. glycines in China by means of HG types. In 2011 and 2012, 10 SCN populations from the primary soybean production regions of China were identified as six races (races 1, 2, 3, 4, 5, 6, and 14) with the race test scheme (3) and were cultured on a H. glycines-susceptible soybean cultivar. In 2013, seven indicator soybean lines (PI 548402, PI 88788, PI 90763, PI 437654, PI 209332, PI 89772, and PI 548316) plus the susceptible standard soybean “Lee74” were used to determine the HG types of these populations following standardized procedures (2) with some modification in a growth chamber set at 28°C under 16-h days. After 30 days, females were extracted from roots and collected, and a female index was calculated for each indicator line (2,3). The average number of females on Lee74 was more than 100 in all the tests. Eight HG types were identified in the populations tested: HG type 0 (race 3), HG type 7 (race 3 or 6), HG type 2.7 (race 1 or 5), HG type 5.7 (race 3), HG type 1.3.7 (race 14), HG type 2.5.7 (race 1), HG type 1.2.5.7 (race 2), and HG type 1.2.3.5.7 (race 4). To our knowledge, this is the first report of H. glycines HG types in China, which will contribute to development of management strategies implementing the use of resistant cultivars. This work was supported by the Special Fund for Agro-scientific Research in the Public Interest 200903040-03 and the China Agriculture Research System CARS-04. References: (1) W. G. Lu et al. Agr. Sci. China 5:615, 2006. (2) T. L. Niblack et al. J. Nematol. 34:279, 2002. (3) R. D. Riggs and D. P. Schmitt. J. Nematol. 20:392, 1988.
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Heterodera
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