scholarly journals The influence of host nutrition and intensity of infection on the sex ratio and development of Meloidogyne incognita in sterile agar cultures of excised cucumber roots

1967 ◽  
Vol 11 (1) ◽  
pp. 31
Parasitology ◽  
1997 ◽  
Vol 114 (3) ◽  
pp. 231-236 ◽  
Author(s):  
A. M. DUNN ◽  
M. J. HATCHER

This is a report of the prevalence, transmission and intensity of infection of a microsporidian sex ratio distorter in natural populations of its crustacean host Gammarus duebeni. Prevalence in the adult host population reflects differences in the intensity of infection in transovarially infected embryos and in adult gonadal tissue. The efficiency of transovarial parasite transmission to young also differs between populations, but this alone is insufficient to explain observed patterns of prevalence. Infection intensity may be important in determining future infection of target tissue in the adult and subsequent transmission to future host generations. We consider patterns of parasite infection in terms of selection on transmission and virulence.


2011 ◽  
Vol 86 (1) ◽  
pp. 41-45 ◽  
Author(s):  
M. Golestaninasab ◽  
M. Malek ◽  
B. Jalali ◽  
I. Mobedi

AbstractIn the present study, 81 specimens of Capoeta capoeta gracilis (Keyserling, 1861) were collected from the Shiroud River, the Caspian drainage basin, Iran in June and October 2007. The fish were examined for infection with the nematode Rhabdochona fortunatowi (Dinnik, 1933). Nematodes were counted and sexed, then the sex ratio and intestinal site preference of the R. fortunatowi individuals and the intersexual interactions of the parasites were investigated. Significant differences were observed in the prevalence and intensity of infection in relation to host size and sampling season, but not host sex. Parasite burden (mean intensity) was higher in October than in June and the results revealed a decrease in female-to-male sex ratio (FMR) in the fish in October compared to the ones in June. In other words, as the mean intensity of infection of R. fortunatowi increases, the proportion of male worms increases, too. The female-biased sex ratio in June was replaced by a male-biased one in October. Nematode distribution rose to a significant peak in the mid-region of the fish intestine relative to the anterior and posterior parts. Some changes in the distribution of male and female worms in different parts of the host intestine were also observed during June and October. Density-dependent selection and intersexual competition seem to be the main factors driving such a shift in the sex ratio and its variation in different parts of the host intestine.


Plant Disease ◽  
2020 ◽  
Vol 104 (11) ◽  
pp. 2979-2985
Author(s):  
Susan L. F. Meyer ◽  
Margaret H. MacDonald ◽  
Nathan D. Reetz ◽  
Mihail R. Kantor ◽  
Lynn K. Carta ◽  
...  

Chia (Salvia hispanica L.) seeds are used for food, drinks, oil, and animal feed, and all plant parts are employed in traditional medicine. The growing demand for the seed has created a need for improved disease management. Plant-parasitic nematodes have been found on other Salvia spp., but none have been reported from S. hispanica. Chia has also not been tested for production of compounds active against these nematodes. Therefore, aqueous extracts from shoots and roots of six chia lines, Brad’s Organic, Cono, E2, G3, G5, and W13.1, were tested in laboratory assays. Some concentrations of all extracts were nematotoxic, killing about one-third of Meloidogyne incognita (Kofoid & White) Chitwood second-stage juveniles (J2s) in shoot extracts and up to nearly half of J2s in root extracts. Hatch was generally not affected by the extracts. In greenhouse trials, all six chia lines were hosts of M. incognita. Chia line G3 had approximately two times or more eggs per gram of root than Brad’s Organic or Cono. When cucumber seedlings were transplanted into soil amended with chopped chia shoots (2.3 or 2.5% weight of fresh shoots/weight of dry soil), galling and egg production on cucumber roots were not suppressed. To our knowledge, this is the first report that chia is a host to M. incognita (or any phytoparasitic nematode) and that chia shoots and roots produce compounds active against a nematode.


2011 ◽  
Vol 86 (4) ◽  
pp. 401-405 ◽  
Author(s):  
S. D'Ávila ◽  
E.C.A. Bessa ◽  
S. Souza-Lima ◽  
M.L.A. Rodrigues

AbstractIn the present study populations of the avian nematode species Baruscapillaria obsignata are described from Columba livia. Male and female individuals were obtained from 27 birds, fixed in alcohol/formalin/acetic acid (AFA) and preserved in 70% ethanol. Nematodes were identified and then counted under a stereoscopic microscope. Baruscapillaria obsignata were much more frequent in the anterior third of the small intestine, and females were more abundant than males in all infra populations. The prevalence was 55.6%, mean intensity was 11.8 (median 11.0; range 1–31) and abundance 6.56. In the present study, we observed an aggregated distribution of parasite infrapopulations, as demonstrated by the value of the exponent of the negative binomial distribution, K = 0.2773; by the discrepancy index, D = 0.656 and by the variance/mean ratio, 12.44. The female/male sex ratios found in all infrapopulations were always greater than 1, showing a bias in favour of female abundance. This tendency was especially marked in infrapopulations containing fewer individuals. The sizes of infrapopulations ranged from 5 to 31 individuals. The mean sex ratio observed was 2.69 ± 3.28 (median 1.83; range 0–11). In infrapopulations with 5–15 individuals, the sex ratios observed varied from 2.6 to 11, while in those with 17–31 individuals, the sex ratios were lower, ranging from 1.7 to 2.4. There was a negative correlation between the intensity of infection and the sex ratio of infrapopulations. Results are discussed in terms of possible factors influencing the processes that lead to niche restriction and biased sex ratios in parasite infrapopulations.


1980 ◽  
Vol 58 (2) ◽  
pp. 298-303 ◽  
Author(s):  
Eero Helle ◽  
E. Tellervo Valtonen

The occurrence, location, sex ratio, growth, and development of Corynosoma strumosum and Corynosoma semerme were studied in 29 Baltic ringed seals, Pusa hispida botnica, in October–November 1977. The prevalence of infection was 96.5% for both species, the intensity of infection being 68(1 to 324) per infected seal in C. strumosum and 140 (1 to 1230) in C. semerme. Of the C. strumosum, 99% were in the small intestine; the remainder, together with 97% of the C. semerme, were distributed from the caecum to the rectum. The numbers of C. strumosum increased along the small intestine, and although the sex ratio remained constant, young females were more numerous in the anterior part of the intestine and gravid females more numerous distally. Factors affecting the numbers and proportions of the Corynosoma species are discussed with reference to their development and the progress of infection in the intestine of the ringed seal.


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