MSc

Brinjal or Eggplant (Solanum melongena L.), an important vegetable crop belonging to the family Solanaceae is grown for its fruits. Due to it’s versatality in use in Indian diet, brinjal is described as the ‘King of vegetables’ (Choudhary and Gaur, 2009). Such a potential crop is known to suffer from many diseases including damping off, seedling blight fruit rot etc caused by Phomopsis vexans, Fusarium sp, Rhizoctonia solani, Sclerotium rolfsii, Phytophthora capsici etc. These diseases cause crop loss up to 30-50 % (Masuduzzaman et al., 2008).
In the organic era of cultivation of crops, use of chemical means of disease management is having least significance. In this context, an ecofriendly management strategy for the management of Phomopsis blight and fruit rot in brinjal was taken up.
Brinjal fruits showing the typical symptom of fruit rot were collected from different blocks of College of Agriculture, Vellayani, isolated and identified as Phomopsis vexans. Its’ pathogenicity was proved following Kochs’ Postulates.
Symptomatology studies of the disease under natural and artificial conditions were studied. Under both the situations symptoms appeared almost similar. The symptoms first appeared as pale, sunken, circular to oval areas on the fruit surface. Affected fruits became soft and watery at first; decay penetrated rapidly throughout the fruit, causing a light-brown discoloration of the flesh. Under dry conditions, fruits get shrivelled and became mummified. Black pycnidia arranged in a concentric pattern can generally be seen.
Cultural and morphological study of the pathogen were also done. Cultural and morphological characters of the pathogen was studied on PDA. Both types of conidia - Alpha and Beta conidia are produced by the pathogen. Four different media were tested, viz., Potato Dextrose medium, Czapek’s Dox medium, Host Extract Dextrose medium and Oat Meal medium. Best solid medium for the growth of Phomopsis vexans was PDA whereas the best liquid medium was Czapek’s Dox broth. Growth of the pathogen was also tested in different pH from 5.0 to 9.0 and optimum pH for the growth of the pathogen was found as 8.0. Five different carbon sources were tested, viz., dextrose, lactose, maltose, starch and sucrose. Among these lactose was found as the best carbon source for the growth. The different nitrogen sources tried were ammonium carbonate, ammonium chloride, ammonium nitrate, potassium nitrate and sodium nitrate. Among them sodium nitrate was found to be the best.
During the isolation of antagonists from phyllosphere and rhizosphere of brinjal plants many organisms were obtained. Among them the fungal antagonists selected were Trichoderma sp. and Aspergillus sp. The bacterial isolates selected for the inhibition studies of the pathogen were B1 and fluorescent bacterial isolate (FB – 2). These were further evaluated under laboratory conditions and fluorescent bacterial isolate (FB - 2) was found to show the maximum suppression of the pathogen.
In vitro screening of bio control agents/plant extracts/oil cakes were also tested against the pathogen. The best antagonist obtained under in vitro screening by dual culture technique, was fluorescent bacterial isolate. Leaf extracts at 20 and 30 per cent concentrations from Ocimum sanctum, Azadirachta indica, Lantana camara and Clerodendron oderatum were tested against Phomopsis vexans under in vitro conditions by poisoned food technique and maximum inhibition of the pathogen was obtained in Ocimum sanctum at 20 and 30 per cent concentration. Among the oil cakes viz., coconut oil cake, gingelly oil cake, neem cake and groundnut oil cake tested against the pathogen, highest inhibition was obtained from ground nut oil cake.
The selected treatments from the in vitro tests were subjected to in vivo screening. For this a pot culture experiment in CRD with three replications and nine treatments were laid out in the College of Agriculture, Vellayani. The treatments used were fluorescent bacterial isolate (2 %), Ocimum sanctum leaf extract (20 %), ground nut oil cake (200 g/pot) individually and in combinations with standard fungicidal check carbendazim 0.1 per cent and inoculated control. The variety Swetha was used for the in vivo experiment.
Application of soil amendment with groundnut oil cake (200 g/pot), seedling root dip with talc based formulation of fluorescent bacterial isolate, FB - 2 (2 %) for 20 min. and foliar sprays with a combination of talc based formulation of fluorescent bacteria (2 %) + Ocimum sanctum leaf extract (20 %) was found to be the best for the management of Phomopsis blight and fruit rot disease of brinjal.