Variation in the host-parasite relationship of a crop disease

1968 ◽  
Vol 71 (1) ◽  
pp. 19-36 ◽  
Author(s):  
M. H. Arnold ◽  
S. J. Brown
Keyword(s):  
Genetic Variation ◽  
Environmental Conditions ◽  
Phage Type ◽  
Resistance Breeding ◽  
Wide Range ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Main Components ◽  
Host Parasite ◽  
Relationship Of

SummaryVariations in the host–parasite relationship of bacterial blight of cotton, caused by Xanthomonas malvacearum, E. F. Smith (Dowson), axe elucidated in terms of the three main components of variation, namely, genetic variation in the host, genetic variation in the parasite and variations in environment.Although the relative resistance shown by host varieties differed both with the culture of the pathogen used for inoculation and with the environmental conditions, over-riding patterns of host resistance could be detected, showing that certain varieties maintained their resistance over a wide range of conditions.It was found that phage type in X. malvacearum was not related to virulence. Moreover, none of the cultures of the pathogen which had been isolated from different sources, could be shown to be identical when inoculated into a range of host varieties under a range of environmental conditions. It was concluded that the pathogen showed continuous variation in virulence and that it would be difficult and of little value to attempt to define races.Some success was achieved in relating observed variations in the host–parasite relationship to easily measured components of the environment, by using multiple regression analyses. It is suggested that this might provide a means of characterizing the complex variations observed and that the host–parasite relationship could be regarded as a dynamic system, in which disease expression is a function of the interactions of environmental factors and two polygenic systems, that of the host and that of the parasite.Intrapopulation variances were also studied in the host varieties. A population which showed little variation for resistance under one set of conditions might show considerable variation in a different environment or when inoculated with a different culture. It is suggested that selection for resistance under conditions which favour the expression of variation can lead, by repeated selection and inbreeding, to the production of resistant populations which retain their resistance under conditions in which the parental stocks showed no worthwhile resistance. These conclusions are discussed in relation to problems in resistance breeding and genetics.

Certain aspects of the host-parasite relationship of Nematospiroides dubius (Baylis). I. Resistance of male and female mice to experimental infections

Parasitology ◽  
1961 ◽  
Vol 51 (1-2) ◽  
pp. 173-179 ◽  
Author(s):  
Colin Dobson
Keyword(s):  
Relative Length ◽  
Industrial Research ◽  
Male Mice ◽  
Male And Female ◽  
Female Mice ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Nematospiroides Dubius ◽  
Host Parasite ◽  
Relationship Of

1. It has been shown that there is a difference between the resistance of male and female mice to infection with Nematospiroides dubius.2. More parasites were harboured, during both the larval and adult parasitic phases, by male mice.3. These worms were found to occupy a similar relative length of the intestine between the stomach and the caecum in male and female mice infected for either 5 or 10 days.4. The relative length of the intestine infected on the fifth day was significantly greater than that infected on the tenth day.This investigation was carried out during the tenure of a Research Studentship from the Department of Scientific and Industrial Research. I should like to thank Professor I. Chester Jones, in whose department the work was done, for the facilities provided and Dr E. T. B. Francis for his helpful and critical supervision.

The age and sex of the host as factors affecting the host–parasite relationship of the third-stage larva of Amplicaecum robertsi Sprent & Mines, 1960, in the laboratory mouse

Parasitology ◽  
1966 ◽  
Vol 56 (3) ◽  
pp. 399-406 ◽  
Author(s):  
Colin Dobson
Keyword(s):  
Laboratory Mouse ◽  
Suckling Mouse ◽  
Factors Affecting ◽  
Third Stage ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
The One ◽  
Host Parasite ◽  
Relationship Of ◽  
Old Mice

There was no difference between the worm burdens or the lengths of the worms recovered from sexually immature male and female mice infected with Amplicaecum robertsi.In mice older than 70 days there were fewer larvae recovered from the female than the male host. The larvae were also longer in the male than in the female mouse.The suckling mouse harboured fewer larvae than the weanling; the susceptibility of the mouse continued to increase with increasing age until the one-hundredth day in the males and the seventy-fifth day in the females. In animals older than this an age resistance was apparent. It is suggested that the much lower susceptibility of the suckling mouse is due to the small gut and villi size reducing the establishment of the larvae.Worm growth also varied with host age, the longest larvae being recovered from the suckling mice and successively smaller worms from each older age group up to the seventy-fifth day, beyond which there was no significant change in worm growth with age of the host. There was no difference between the worm burdens and the lengths of the worms recovered from 90-day-old mice. The injection of testosterone had little or no effect on the host–parasite relationship of gonad-ectomized animals. Larvae from gonadectomized mice were significantly shorter than those from the intact hosts.

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