STUDIES ON THE LEAF SPOT DISEASE OF EGGPLANT
ABSTRACT
Field, greenhouse and laboratory studies were carried out at the Department of Crop Science,
University of Nigeria, Nsukka in order to evaluate the leaf spot disease of eggplant and its
management with some botanicals. Field survey of diseased plants was conducted on
eggplant farm. Solanum aethiopicum L. plants were sampled on every 1 m distance along the
diagonal transects for disease incidence and severity. Pathogen isolation from severely
infected leaves was carried out in the laboratory where the diseased leaves were plated on
fresh Potato Dextrose Agar. Identification of the isolated fungi was carried out with the aid of
identification scheme based on their cultural characteristics. Nursery preparation for raising
eggplants used in the green house was also carried out on a sterilized soil. The five most
abundant pathogens isolated were inoculated separately on the seedlings of eggplant in five
replicates.
The experiment was arranged in a completely randomized design. Phytochemical
contents of the four plant extracts were determined in the laboratory. An in vitro control of the
organism responsible for the leaf spots was carried out using plant extracts at 0.030 g/ml,
0.060 g/ml, and 0.120 g/ml and 0.250 g/ml concentrations. The experimental design was a
9x4 factorial in a completely randomized design (CRD). The data were analyzed using
analysis of variance (ANOVA). Means were later separated using Fisher’s least significant
difference (F-LSD). Helminthosporium infestans Dur. & Mont, Cladophialophora carrionii
Trejos, Aspergillus niger van Tieghem, Rhizopus nigricans Ehrenb and Neurospora africana
Huang & Backus were isolated from the diseased eggplant leaves. H. infestans recorded the
highest percentage frequency (61.11 %) while A.
niger had the lowest percentage frequency
(5.56 %). H. infestans was pathogenic to eggplant seedlings. The Koch postulate test
confirmed H. infestans as the causal organism of the spots symptoms. The qualitative
phytochemical analysis on the test plants revealed the presence of tannin, soluble
carbohydrate, hydrogen cyanide, steroids, flavonoids, alkaloids as well as glucosides in all
the extracts analyzed. The effect of ethanolic extracts of the test plants significantly (Preduced the incidence and severity of the pathogen. Anti-fungal activity of seed extracts of G.
kola on H. infestans was highest at 0.0120 g/ml concentrations. G. kola could be used as
fungicide to manage leaf spot in eggplant because of its availability and eco-friendliness.
Field, greenhouse and laboratory studies were carried out at the Department of Crop Science,
University of Nigeria, Nsukka in order to evaluate the leaf spot disease of eggplant and its
management with some botanicals. Field survey of diseased plants was conducted on
eggplant farm. Solanum aethiopicum L. plants were sampled on every 1 m distance along the
diagonal transects for disease incidence and severity. Pathogen isolation from severely
infected leaves was carried out in the laboratory where the diseased leaves were plated on
fresh Potato Dextrose Agar. Identification of the isolated fungi was carried out with the aid of
identification scheme based on their cultural characteristics. Nursery preparation for raising
eggplants used in the green house was also carried out on a sterilized soil. The five most
abundant pathogens isolated were inoculated separately on the seedlings of eggplant in five
replicates.
The experiment was arranged in a completely randomized design. Phytochemical
contents of the four plant extracts were determined in the laboratory. An in vitro control of the
organism responsible for the leaf spots was carried out using plant extracts at 0.030 g/ml,
0.060 g/ml, and 0.120 g/ml and 0.250 g/ml concentrations. The experimental design was a
9x4 factorial in a completely randomized design (CRD). The data were analyzed using
analysis of variance (ANOVA). Means were later separated using Fisher’s least significant
difference (F-LSD). Helminthosporium infestans Dur. & Mont, Cladophialophora carrionii
Trejos, Aspergillus niger van Tieghem, Rhizopus nigricans Ehrenb and Neurospora africana
Huang & Backus were isolated from the diseased eggplant leaves. H. infestans recorded the
highest percentage frequency (61.11 %) while A.
niger had the lowest percentage frequency
(5.56 %). H. infestans was pathogenic to eggplant seedlings. The Koch postulate test
confirmed H. infestans as the causal organism of the spots symptoms. The qualitative
phytochemical analysis on the test plants revealed the presence of tannin, soluble
carbohydrate, hydrogen cyanide, steroids, flavonoids, alkaloids as well as glucosides in all
the extracts analyzed. The effect of ethanolic extracts of the test plants significantly (Preduced the incidence and severity of the pathogen. Anti-fungal activity of seed extracts of G.
kola on H. infestans was highest at 0.0120 g/ml concentrations. G. kola could be used as
fungicide to manage leaf spot in eggplant because of its availability and eco-friendliness.
