Involvement of ethylene in the etiology of tomato plants (Lycopersicon
esculentum) infected with the root-knot nematode (Meloidogyne incognita)
was investigated. Endogenous root concentrations of ethylene were not
significantly different in uninfected resistant var. Anahu and susceptible
var. Vendor plants. Exposure of resistant plants to high doses of infectious
nematode larvae did not affect root ethylene concentrations during the
subsequent 30 day period. The possibility that ethylene may be involved in
the mechanism of resistance is therefore not supported by these experiments.
In no experiments did ethylene concentrations in roots of susceptible plants
increase significantly subsequent to ~ incognita infestation. This result
is not consistent with the hypothesis in the literature which suggests that
increased ethylene production accompanies gall formation.
Growth of susceptible tomato plants was affected by ~ incognita
infestation such that root weights increased (due to galling), stem heights
decreased and top weights increased. The possibility that alterations in
stem growth resulted from increased production of 'stress' ethylene is discussed.
Growth of resistant plants was unaffected by exposure to high doses
of ~ incognita and galls were never detected on the roots of these plants.
Root ethane concentrations generally varied in parallel with root
ethylene concentrations although ethane concentrations were without exception
greater. In 4 of 6 experiments conducted ethane/ethylene ratios increased
significantly with time. These results are discussed in the light of
published data on the relationship between ethane and ethylene synthesis.
The term infested is used throughout this thesis in reference to
plants whose root systems had been exposed to nematodes and does not
distinguish between the susceptible and resistant response
