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plants were previously infected with attenuated Tomato Mosaic Virus (ToMV: Tobamovirus
group) strain L 11 A and inoculated with F13 (7.5x10 4 cfu/ml soil) one day before nematode
inoculation (10 J 2 /ml soil) to plants. Similarly, numbers of Mi galls on pepper plants were
less than the control by ca. 70% when the pepper was previously infected with attenuated
Pepper Mild Mottle Virus (Tobamovirus group) strain No. 16 and inoculated with F13 (1x10 5
cfu/ml soil) two days after nematode inoculation (3.1 J 2 /ml soil). In a vinyl house microplot
experiment, average root-knot index (Zeck, 1971) was as low as 1 in plots where tomato
seedlings previously infected with the attenuated ToMV strain L 11 A were transplanted then
two days later given a F13 soil treatment (1.2x10 10 cfu/plant), while the root-knot indices in
plots of only attenuated ToMV or only F13 were 6.5 and 4.5, respectively. The fruit yield of
tomato (ca. 12 kg/plant) from the plot of attenuated virus and F13 was as high as from the
control plot treated with D-D fumigant, while the yields were ca. 8.5 kg/plant at the
inoculated plots receiving only attenuated virus or only F13.
New Approach to Plant Parasitic Nematodes and Fusarium Wilt
Association on Some Field and Vegetable Crops
Mousa, E.M.
Department of Agricultural Botany, Faculty of Agriculture, Menoufiya Universoty, Shebin El-Kom, Egypt
Plant parasitic nematodes often play a major role in disease interactions. This is not
surprising when the habits of these pathogens are considered, including relationships
established with host plants, mode of parasitism, and other facets of their life cycles. Also,
fungi of various types constitute a significant portion of the soil microflora. Some of them are
recognized plant pathogens; others are not normally pathogenic under prevailing conditions.
At any rate, important disease complexes involving certain fungi and nematodes have been
investigated.
Our studies focus on the association between plant parasitic nematodes and soil-borne fungi,
particularly that between root-knot nematodes and Fusarium, wilt .We have come to the
conclusion, that the interaction between root-knot nematode increased the incidence of
Fusarium wilt and the severity of wilt on the hosts investigated. We found that M. incognita
increases the incidence of Fusarium wilt on both wilt resistant cotton cultivars and wilt
susceptible cultivars and invasion by juveniles of root-knot nematodes enabled races of
Fusarium oxysporum f, sp. Lycopersici to attack tomato varieties normally resistant.
Fusarium wilt-root-knot nematode complexes were subjected histological analyses to help in
understanding the relative contributions of each complex component, and may give insight
into basic aspects of the interaction.
On soybean, cotton and tomato giant cells and xylem elements of both Fusarium – resistant
and susceptible plants were haveily invaded by F. oxysporum . Giant cells, although
extensively colonized, were highly sensitive to fungal attack, and became apparently devoid
of contents soon after early invasion by the fungus. Abundant fungal growth in tissues was
observed. This clearing of giant cells was accompanied by gradual debilitation of fungus
hyphae occupying the tissues. Occasional invasion of the female nematode and the egg mass
by the fungus were clearly observed. These investigation stressed that fungal colonization
was not resticed to the galled area of a nematode-infected plant . Vigorous hyphae extended
up into the xylem above the soil line, considerably removed from the site of nematode
activity, even in wilt-resistant plants.
5 th International Congress of Nematology, 2008 259