Page 392 - e-Book

Infected plants have been reported to appear more susceptible to wilting than healthier

plants. Irrespective of the weight of the root tissues as compared to a healthy plant, the
absorption of nutrients by galled root is appreciably reduced. Thereby resulting in reduced

top growth, as absorbed in the present investigation. Therefore, taking the suggestion Raut
and Sethi (1980) into consideration, assessing the top weight is a better parameter rather than

assessing the root weight and assessing the pathological effect.

Nematode removes plant nutrients, alter nutrient flow pattern in plant tissue and retard

growth (Hunter, 1958), of which may contribute to reduced plant yield. The formation of
galls may create a drain on the plants’ resources in shoot tissue, resulting in suppression of

shoot growth. It was noted earlier that the amount of plant resource diverted would be related
to high nematode population densities (Wallace, 1969.) Hence the reduced root and shoot of

S. melongena as discernible in the present study alright be due to more gall in the root

containing more larvae in the root gall.

A reduction in the root/shoot ratio due to nematode infection was evident in the IUT
plants. Such reduction in root/shoot ratio due to reduced root growth and increased shoot

growth. It was discernible that reduced the root growth due to nematode infection indirectly
included water stress in plant tops. Which thereby reduced root/shoot ratio (O’Bannon and

Reynold, 1965).

Involvement of plant metabolism during pathogenesis is well documented by Giebel

(1982), Tayal and Agarwal (1982) and Sharma et al. (1996) it is now accepted that various
metabolites in the syncytial region of galls are involved in the combat mechanisms of the

pathogenic mechanism.

The major source of energy for the invading pathogens is the stores carbohydrates
which are converted into utilizable form by the action of hydrolytic enzymes secreted by the

nematode. Hence the sugar content of the infected root and shoot tissues showed depletion in

the present study and similar results were reported by many workers (Kannan and Balaji,
1988; Vaitheeswaran and Mohamed Ibrahimand et al., 2008). The reduction in sugar content

might be also due to possible consumption by nematodes for its sustenance and part

mobilization from the metabolic pool for the synthesis of lipid, protein (Broyer, 1959
Steewerd et al., 1966), Phenols (Virtain and Stahman, 1981) through the shikimic acid

pathway (Cowlling and Horsfall, 1980).

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