| dc.description.abstract | Tomato is attacked by several plant parasitic nematodes but root-knot nematodes are the most
important causing considerable losses. Studies were undertaken in the greenhouse to
determine the suppressiveness of a wide range of plant species to root knot (Me/oidogyne spp.)
nematodes. Plants were grown in pots and inoculated with 6000 eggs and lor juveniles. The
treatments were arranged in a completely randomized design with 10 replications. After sixty
days, the experiment was terminated and galling, egg mass indices and juvenile counts
determined on a scale of 1-9 and the modified Baermann funnel technique, respectively. A field
experiment was conducted to verify the greenhouse results in nematode infested microplots.
This was arranged in a randomized complete block design with three replications. After three
months the experiment was terminated and similar data taken.
Among the plants tested, Tagetes patu/a, Gossypium hirsutum, Desmodium unicinetum, Chloris
gayana, Zea mays, A/strameria sp., Capscium allium, Crata/aria juncea, Arachis hypogaea,
Sorghum bicoior, Tithonie diversiflora and Pennisetum purpureum were rated as suppressive
with galling and egg mass indices ranging from 0-3. High galling and egg mass indices of 7.0-
9.0 were recorded on Allium cepa, Statice sp., Brassica o/eracea var. capitata, Helianthus
annuus, Lab/ab purpure us, Coriandum sativum and Vigna subterranea while the rest of the
other plants were rated moderately resistant with galling and egg mass indices ranging from
3.0-6.1. Results of an experiment conducted in the greenhouse to determine the level of root
penetration of resistant plants by Me/oidogyne juveniles showed that penetration was lower in
some plants. Penetration was 95% lower in T. patu/a and 80% lower in crotalaria as compared
to the control (tomato).
Damage by nematodes was significantly (P!:. 0.05) reduced in tomato plants planted following a
crop of sweetcorn alone or in combination with Tagetes patu/a, Grata/aria juncea, sorghum
bicotor and Asparagus sp. in the field. After the first season, nematode population density
continued to decrease in all the treatments while it continued to increase throughout the two
seasons under tomato monoculture. Tomato plants grown in association with Tagetes patu/a,
rhodes grass and sweetcorn had lower galling indices of not more than 1.5 compared to
associations with cotton, crotalaria, sorghum, asparagus, garlic, chrysanthemum, tithonia,
spring onion and sesame where gall indices were higher than 2.0.
This study shows that despite the wide host range of Me/oidogyne species, there is a wide
range of economically important plants from which suitable candidate crops can be chosen and
incorporated into different cropping systems. Some of the plants can be grown for advantages
of soil fertility improvement through nitrogen fixization, to prevent soil erosion, quality forage and
ornamental value. Extensive on-farm studies in different agroecological zones needs to be
carried out and the mechanisms of nematode suppression established. | en |
