PhD

An investigation on biochemical, biological
and nutritional bases of resistance in solanaceous
vegetables against bacterial wi1t incited by Ralstonia
solanacearum (Smith) Yabuuchi et al., has been attempted.
The pathogen R. solanacearumwas isolated from
respecti ve hosts and characterised by various morphological,
cultural, biochemical and physiological tests upto biovar
level.
The three isolates were cross inoculable, and
were sensitive to AmDistryn and Streptocycline. Based on
these studies the tomato and chilli isolates were identified
as Ralstonia solanacearum race I biovar III and that from
brinjal as R. solanacearum race I biovar V.
The study on toxigenic property of the
bacterial isolates revealed that the toxic metabolites were
not host specific.
Out of the 43 varieties / lines screened ,
12 varieties / lines were selected, one each from resistant,
moderately resistant, moderately susceptible and susceptible

categories. The varieties / lines selected were LE 79-5,
BT-IO, LE 470 and Pusa Ruby for tomato; Swetha, Composite-2,
BB-7 and Pusa Purple Long for brinjal and Ujwala, Manjari,
Jwalasakhi and Pusa Jwala for chilli.
The studies on biochemical, biological and
nutritional factors in tomato, brinjal and chilli showed
considerable variation between crops, between varieties/
lines, and between plant parts. However the root being the
primary foci of infection by R. solanacearum the biochemical
reactions in root is considered more important than other
plant parts. Among the biochemical factors, the OD phenol
and specific activity increased due to infection and the
content was higher in the resistant genotype (LE 79-5) both
under heal thy and diseased condition in tomato. In brinj al,
the polyphenol oxidase activity, specific activity and
peroxidase activity increased due to infection and were
higher in resistant genotype (Swetha) both under healthy
and diseased condition. In chilli, total phenol and OD
phenol, increased due to infection and were higher in
resistant plants (Ujwala) under healthy and diseased
condi tions. The soluble sugar content and specific activity
were also higher in resistant plants both under healthy and
diseased condition even though a decrease was observed due
to infection .

In tomato, the resistant genotype showed a
higher content of OD phenol, polyphenol oxidase activity,
specific activity and alkaloids under healthy condition; and
total phenol, OD phenol, soluble protein, specific activity
and peroxidase activity under diseased condition. In
brinjal, the resistant genotype recorded higher content of
total phenol, OD phenol, soluble sugars, amino acids, soluble
protein, polyphenol oxidase activity, specific activity and
peroxidase activity under healthy condition; and polyphenol
oxidase activity, specific activity and peroxidase activity
under diseased condition. In chilli, the resistant genotype
recorded higher total phenol, OD phenol, soluble sugars and
specific acti vi ty under heal thy condition; and total phenol,
OD phenol, soluble sugars, specific activity and peroxidase
activity under diseased condition.
Among the biological factors, the total
microflora (fungi and actinomycetes), Pseudomonads and
parasitic nematodes increased due to infection in resistant
genotype whereas beneficial microbes recorded a decrease in
population in resistant genotype by infection.
In tomato the resistant genotype recorded
higher nematode population under heal thy condi tion and higher
total microflora, virulent Ralstonia and avirulent



Pseudomonas


under diseased condition.


In brinjal the


resistant genotype recorded higher population of fungi,
avirulent Pseudomonas, mycorrhiza and saprophytic nematodes
under heal thy condition, and fungi, virulent Ralstonia,
avirulent Pseudomonas and nematodes under diseased condition.
In chilli, the resistant genotype recorded higher populations
of avirulent Pseudomonas, mycorrhiza and nematodes under
heal thy condition and fungi, avirulent Pseudomonas and
mycorrhiza under diseased condition.
Among the nutritional factors, in tomato the
resistant genotype recorded higher content of potassium and
calcium under heal thy condition and iron, zinc and manganese
under diseased condition. In brinjal the resistant genotype
recorded higher content of nitrogen, calcium, magnesium and
zinc under heal thy condition; and potassium, magnesium, iron
and zinc under diseased condition. In chilli, the resistant
genotype recorded higher content of phosphorus, calcium and
iron under heal thy condition; and nitrogen, potassium
magnesium and zinc under diseased condition.
Thus the study revealed that it was not
possible to arrive at common bases for resistance to
bacterial wilt in tomato, brinjal and chilli taken together.
However it was possible to outline the important parameters
that conditions resistance in individual crops.