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ThesisItem Open Access Fungal diseases of selected medicinal plants of Kerala(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1991) Sukumara, Varma A; KAU; ; Abi, CheeranThesisItem Open Access Bio-deterioration of important vegetable seeds due to mycoflora II(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1991) Ambika, S; KAU; Jose, P CBio-deterioration of important vegetable seeds due to mycoflora-II" was studied at the Department of Plant Pathology, College of Horticulture, Vellanikkara during the year 1988-89. Three vegetable seeds viz., bhindi (Abelmoschus esculentus (L.) Moench), cowpea Vlqna unquiculata (L.l Walp) and dolichos bean (Dolichos 1ablab L .) were used for the investigations. The objectives of the investigations were 1. To assess the role of seed-borne mycoflora and bio-deterioration of important vegetable seeds (bhindi, cowpea and dolichos bean)2. To study the influence of seasons on the association of seed-borne mycoflora of stored vegetable seeds 3. To assess the effect of relative humidity on the viability of vegetable seeds 4. To study the role of seed mycoflora on the germination of seeds and 5. To find out the effect of fungicides to minimise the fungal bio-deterioration of stored vegetable seeds.ThesisItem Open Access Effect of 2-bromo-2-nitro propaine-1, 3-diol and cowdung extract on growth and virulence of Xanthomonas campestris pv. oryzae(Department of Plant Pathology, College of Agriculture, Vellayani, 1991) Sreekumar, C T; KAU; Sasikumar NairThe present investigation was taken up to assess the efficacy of two alternative control methods, spraying with bactrinol-100 and cowdung extract in controlling bacterial blight of rice. An attempt was also made to elucidate the factor present in cowdung extract responsible for the control of bacterial blight pathogen. The pathogen was isolated from an infected rice field in kuttanad and tested for sensitivity to antibiotics, bactrinol-100 and cowdung extract under vitro conditions. Under in vitro conditions, terramycin 500 ppm was found to be most efficient in checking the growth and virulence of the pathogen followed by 250 ppm terramycin and 500ppm bactrinol-100. Cowdung extract failed to produce a typical growth inhibition zone. Subsequently the pathogen was inoculated in T(N)1- rice plants raised in pots, the disease was induced and the plants were sprayed with antibiotics, bactrinol-100 and cowdung extract. Under pot culture conditions terramycin 500 ppm reduced the disease intensity to the maximum followed by 500 ppm bactrinol-100. Cowdung extract was found to be better than some of the chemical treatments like terramycin 100 ppm, streptocycline 100, 250 and 500 ppm and bactrinol-100 at 100 and 250 ppm. Under field conditions 500 ppm terramycin gave maximum disease control at both the locations after the first and second spray. The grain yield was found to be maximum after spraying with 500 ppm terramycin at both the locations. The increase in thousand grain weight was found to be maximum in plants sprayed with cowdung extract in jyothi variety and in plants sprayed with 500 ppm bactrinol-100 in C-153 rice variety. Maximum reduction in chaffy grains was achieved after spraying with 500 ppm terramycin at both the locations. Straw yield was maximum in plants sprayed with 100 g/1 of cowdung extract in jyothi variety and in plants sprayed with 500 ppm terramycin in c-153 variety. So it is evident that unless appropriate control measures for bacterial blight are taken in time, significant yield losses can occur in rice varieties like jyothi and c-153. Spraying cowdu ng extract may be very useful to control bacterial blight especially when the disease incidence is mild. It can also be given as a prophylactic spray which may reduce the severity of the disease. These hypotheses have to be proved conclusively by further filed trails. The mode of inhibition of x. campestris pv.oryzae appeared to be due to an overgrowth of the pathogen mainly by bacteria and probably by some fungi present in cowdung extract. On working out the economic aspects of controlling bacterial blight it was observed that economic return was maximum after spraying infected plants with 100 g/1 cowdung extract followed by 500 ppm bactrinol-100. So economically it appears, that the use of cowdung extract or bactrinol-100 would be ideal to control bacterial blight of rice.ThesisItem Open Access Etiology and control of blight and fruit rot of brinjal(Department of Plant Pathology, College of Agriculture, Vellayani, 1991) Jenny John; KAU; Suharban, MThe present investigation was undertaken to evolve an economically feasible management practice against the fruit rot and twig blight of brinjal. Infected plant parts of brinjal showing initial stages of infection were collected from different localities and symptomatology of the pathogen was studied in detail. The pathogen was brought into pure culture and sent to C.M.I. International Mycological Institute, U.K. for identification. It was identified to be Phomopsis vexans (Sacc. & Sydow.) Harter. Pathogenicity of the fungus was studied by inoculating the fruits and stems of the host plants and typical symptom similar to natural conditions were observed. Host range of the pathogen was studied by inoculating the different vegetables with the test fungus. Only carrot and tomato was found susceptible to the pathogen. The fungus grew well equally on potato dextrose host extract and oat meal media followed by Czapek’s and Richards’s media. Good sporulation of the fungus was also noticed in potato dextrose and host extract media, fair sporulation in oat meal and Czape’ks media and no sporulation in Richards’s media. In some cases wavy growth of the pathogen was noticed in potato dextrose agar. In liquid media good mycelia growth of the fungus was observed in potato dextrose, host extract and Czapek’s followed by oat meal and Richard’s media. Culture filtrate of the fungus caused drying of the leaves of the young seedling kept dipped in it and on leaves of matured plants it developed dark brown spots and these leaves dried up eventually. Seed treatment with culture filtrate exerted an inhibitory effect on germination of seeds of brinjal, chilli, tomato and greengram, whereas germination percentage was above 90 in seeds kept in sterile water. There was no difference in germination of seeds treated with culture filtrate fresh and that which was boiled for 10 minutes. The germination of seeds greatly reduced in seeds extracted from infected fruits both in blotter and sand method whereas the germination percentage of seeds extracted from healthy fruit was above 90 per cent. The seedlings raised from infected fruit showed damping off symptom after 2 weeks. Laboratory evaluation of different fungicides revealed that all the fungicides could inhibit the growth of the pathogen. Bordeaux mixture gave complete inhibition of growth of fungus at 750 ppm concertation while bavistin had the same effect at 500 ppm concentration. In field evaluation with different fungicides to control Phomopsis fruit rot it was found that spraying with CoC-50 at fortnightly interval was the best fungicide as the per cent infected fruits were minimum, that is 3.9, followed by Bordeaux mixture, dithane M-45, kavach, calixin, bavistin, and cumin L, with per cent infected fruits being 8.95, 10.7, 14.64, 15.35, 17.04, 20.56 respectively. Seeds of brinjal when soaked in spore suspension for 24 hours showed a reduction in germination compared to those seeds soaked in sterile water for the same period. Seed treatment with different fungicides showed that bavistin was the best fungicide in inhibiting the effect of the pathogen on seed germination followed by dithane M-45, and COC -50.
