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Subject: Plant Pathology × End date: 1994 × Start date: 1994 ×
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    ThesisItemOpen Access
    Screening Of Fungal Pathogens For Biocontrol Of Water Hyacinth (Eichhornia Crassipes (MART.)Solms)
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1994) Santhy Kammath S; Naseema A
    A survey was conducted in and around Trivandrum district viz., in veli, Ambalathara and Akulam to obtain the fungal pathogens of water hyacinth for its biocontrol. Colletotrichum gloeosporioides (Penzig) Penzig and Sacc Curvularia lunata (Wakker) Boedjin, Fusarium equiseti (Corda) sacc., Fusarium semitectum Berk and Rav, Fusarium solani (Mart) sacc., R. solani Kuhn and sterile fungus were found infecting the plants. The seasonal occurrence of the fungi isolated was studied and it was found that Fusarium spp. were present throughout the period of study. C. gloeosporioides and R. solani were present in the rainy season only. The pathogenicity of all the above fungi to the water hyacinth plants was established by artificial inoculation. Host range studies revealed that R. solani had a wide host range, which included amaranthus, cowpea, rice Monochoria vaginalis and panicum repens. The host range of C. gloeosporioides included chilli, Commelina benghalensis, Hydrocotyl asiatica and Ludwigia parviflora Fusarium spp. were found to infect Monochoria vaginalis only. Among the fungal pathogens isolated from water hyacinth, F. semitectum caused highest intensity of infection of 51.10 per cent followed by F. equiseti and F. solani (48.88 per cent) C. gloeosporioides and R. solani caused 44.44 and 45.76 per cent intensity of infection respectively. Curvularia lunata caused the lowest intensity of infection of 20 per cent. An experiment was conducted to fix the concentration of inoculam required for effective destruction of water hyacinth. The spore concentration of 10 9 spores/ml was the most effective one in the case of F. equiseti, F. semitectum and F. solani For C. gloeosporioides spore concentration of 2 x 109 sporce/ml was the most effective one. Different carrier materials were tried for mass multiplication and storage of the promising fungal pathogens of water hyacinth. The different carrier materials tested were coir pith, paddy straw, peat moss, rice bran and wheat bran. Wheat bran was found to be the most suitable media for F. equiseti, F. semitectum and F. solani. In wheat bran, the spore count and viability of the spores of these fungi were maximum. For C. gloeosporioides, in rice bran maximum spore count was obtained whereas, in the case of viability of the spores, rice bran and wheat bran were on par. In peat moss none of the fungi grew. In the field tests conducted to try different methods of application of the fungi viz., C. gloeosporioides, F. equiseti, F. semitectum and F. solani, applying bilts of inoculum of the fungi and spraying of the inoculum of the fungi were found to be the best methods. Whereas, dusting of the inoculum produced very poor symptoms. The field performance of the fungi in different carrier materials showed that rice bran and wheat bran inoculum caused good symptom development on water hyacinth plants whereas, coir pith inoculum caused poor symptom development. All the three Fusarium spp. viz., F. equiseti, F. semitectum and F. solani were found to produce toxin. Which could cause similar symptoms on the water hyacinth leaves as those produced by inoculating the culture bits.
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    ThesisItemOpen Access
    Investigations on mosaic disease of bitter gourd
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1994) Purushothaman, S M; Kau; Rajagopalan, B
    Bitter gourd mosaic virus disease commonly occurring in Kerala was investigated. The symptoms appeared as typical mosaic mottling with dark green and light green patches. Diseased plants were severely stunted and produced only a few flowers and fruits. Transmission studies showed that the virus could be transmitted through mechanical means, grafting and by aphid vectors. The virus was found to be transmitted by the aphids aphis gossypii Glov., Aphis malvae Koch., Myzus persicae Sclz. And aphis craccivora Koch. Among the four species of aphids, A. gossypii and A. malvae were found to be the most efficient vectors. Investigations on the physical properties of the virus revealed that the virus had a thermal inactivation point between 50 and 600C, dilution end point between 1:1000 and 1:10000, longevity in vitro between 12 and 24 h at room temperature (28 - 300C) and 48 and 72 h at 100c. The minimum acquisition feeding and inoculation feeding period of the vector A. malvae were found to be 30s and I min respectively. But the percentage of transmission was maximum when an acquisition feeding period of 30 min and inoculation feeding period of 2 h were given. Influence of starvation before acquisition and inoculation feeding period proved that pre – acquisition starvation for 2 h produced maximum infection but post- acquisition starvation decreased the per cent infection. The vector could retain the virus for I h only. A single aphid could transmit the virus to healthy test plants, but maximum percentage of transmission was obtained with 10 aphids. Host range studies showed that the virus was restricted to the members of the family Araceae, Chenopodiaceae, Cucurbitaceae, Musaceae, Polygonaceae and Solanaceae. Datura metal acted as a symptomless carrier of bitter gourd mosaic virus. Serological studies showed that bitter gourd mosaic virus is related to cucumber mosaic virus, pumpkin mosaic virus and snake gourd mosaic virus. Varietal screening showed that all the varieties and collections were susceptible to biter gourd mosaic virus infection, but the variety Arka Harit and the collections 87 green long 1 C 68234, 61 white medium 1C 45358 and 177 green medium 1C 68324 were least susceptible. Studies on estimation of loss revealed that early infection of bitter gourd plants by the virus significantly reduced the number of leaves, leaf area, intermodal length, thickness of vines, length of vines, number of branches, number of flowers, number of fruits and other fruit characters viz., length of fruits, girth of fruits, weight of fruits and total yield of fruits.
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    ThesisItemOpen Access
    Improvement on the techniques for the cultivation and preservation of tropical species of mushrooms
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1994) Balakrishnan, B; KAU; Chandrasekharan Nair, M
    Intensive collections made from certain selected areas of Kerala yielded a total of eight species of Pleurotus, one species each of Volvariella and Tricholoma, namely V. esculenta and T. lobayense respectively from the native flora. Various species collected were identified and based on the preliminary observations made on their adaptability for large scale cultivation, among the Pleurotus two species have been selected for detailed study along with the other standard cultures procured from various mushroom research centres of the country. The native isolate of T. lobayense in the present study is the first record of the species from Kerala. Detailed studies have been done on various aspects of cultivation of pleurotus spp. With a view to improve the already known technologies so as to suit the conditions of Kerala. The two native species of pleurotus selected have been domesticated and compared with other standard cultures on their performance. Based on the observations made in the seasonal influence, yield and market qualities the species most suited for large scale cultivation in Kerala have been identified. Alternative local substrates for cultivation of oyster mushrooms have been identified and their processing technology standardized. Effective nutritional supplements for increased yield, method for speedy induction of sporocarp, after care method for the once harvested beds for further flushes, effective method for cultivation etc. have been worked out for large scale cultivation of Pleurotus spp. In Kerala. Commonly available low cost substrates in spawn production have been identified and their technologies standardized. Influence of light on spawn growth, influence of storing environment on growth and shelf life of spawn etc. have been studied. Technology for preparation of an instant liquid spawn developed and also a modified method for speedy and low cost production of spawn using polypropylene cover as the container has been standardized. The effect of coconut milk in blending culture media for enhanced growth of various Pleurotus spp. and the effect of coconut milk in their biomass production have been proved. In the strain improvement programme, a substrate influenced mutant of Pleurotus sajor-caju for better yield, a resistant/tolerant strain against the most destructive weed mould Trichoderma viride and an interstock hybrid with desirable traits have been developed. Type of pests and their control etc. have been worked out. The effect of chemical pasteurization of the substrates on checking the weed mould infestation during spawn run and the use of lime powder for spot treatment of beds in the management of T. viride have been proved. Post harvest technology for preservation of both raw and dehydrated forms of mushrooms has been standardized. The native strains of other tropical mushrooms locally collected namely V. esculenta and T. lobayense have been identified based on the detailed description of the same. The performance of the native strain, V. esculenta under cultivation has been compared with that of the standard species, V. volvacea and a technique for cultivation of T. lobayense has been standardized for first time in this part of the country.
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    ThesisItemOpen Access
    Effect of selected medicinal plant extracts on the incidence of pumkin mosaic
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1994) Vimi, Louis; KAU; Balakrishnan, S
    The inhibitory effect of certain medicinal plant extracts on the incidence of pumpkin mosaic was studied using ten day old pumpkin seedlings as the test host. Preliminary screening of 30 species of medicinal plant extracts against pumpkin mosaic virus (PMV) revealed that eight plants possessed 80 or more percent inhibition of the infection. Of these five plants, namely, Basella alba, Glycyrrhiza glabra, Phyllanthus fraternus, Plumbago rosea and Thespesia populnea which showed very high virus inhibitory property were subjected to detailed studies. When the selected medicinal plant extracts were tested at five and ten per cent concentrations, two plants, B. alba and P. rosea showed more inhibition at lower concentration. P. fraternus and T. populnea were more effective at higher concentration. G. glabra showed equal effectiveness at both the concentrations. When the extracts of medicinal plants were mixed with partially purified virus preparation, B. alba, G. glabra and T. populnea showed more inhibition, than when used crude virus preparation. All the five medicinal plant extracts showed more inhibition by pre-inoculation application, than by post inoculation application. Pre – inoculation application of medicinal plant extracts at different time intervals revealed that inhibitory properties of B. alba and G. glabra decreased gradually, whereas, that of P. fraternus and T. populnea reached a maximum after a time gap. Inhibitory property of P. rosea did not show any gradual trend. Among the five selected medicinal plants, B. alba possessed a high degree of systemic effect (88.09%) followed by G. glabra (78.57%). The extracts of P. fraternus and P. rosea showed maximum reduction in percentage transmission of PMV by the vector (Aphis gossypii) when applied before acquisition and before inoculation feeding respectively. All the medicinal plant extracts showed more inhibition of infection in the case of mechanical transmission than in vector transmission. Spread of pumpkin mosaic in the field is not random and the data revealed that it is more or less concentrated around the initially infected plants.
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    ThesisItemOpen Access
    Management of bacterial wilt of ginger incited by Pseudomonas solanacearum (Smith) smith
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1994) Alli Rani, G; KAU; James Mathew
    Bacterial wilt is one of the most destructive disease of ginger in Kerala. The pathogen was isolated from wilted ginger plant and its pathogenicity established. The isolate of bacterium was characterized and identified as Pseudomonas solanacearum (Smith) Smith based on its morphological, cultural, biochemical and physiological characters coupled with its pathogenicity. Invitro inhibitory effect of antibiotics, fungicides, botanicals and others against p. solanacearum was tested. Ambistryn- S and chloromycetin 1000 ppm exhibited maximum inhibition of bacterium. Of the two fungicides tested Bordeaux mixture one per cent gave maximum inhibition of the bacterium. Among the botanicals and others tested, water extract of ocimum spp. And garlic at 50 g/1 exhibited maximum inhibition of the bacterium. Field experiment on the management of bacterial wilt of ginger revealed that none of the treatments gave an absolute control of the disease. However, plots treated with Ambistryn- S and Bordeaux mixture had minimum wilt incidence than the other treatments. The changes in the total rhizosphere microflora and the pathogen P. solanacearum as a result of treatments in field codition were assessed. Ambistryn- S, Bordeaux mixture and chloromycetin had effectively reduced the population of P. solanacearum. Ambistryn- S, Bordeaux mixture, Streptocycline and chloromycetin had reduced the bacterial population. The maximum reduction of fungal population was observed in Bordeaux mixture and Ambistryn-S treated plots. Actinomycetes population was minimum in plots treated with garlic. Results of the study on the in vitro effect of treatments on the soil microflora and the pathogen P. solanacearum revealed that Ambistryn-S and Bordeaux mixture had effectively reduced the P. solanacearum. There was a maximum reduction of bacterial population was recorded in soil treated with Ambistryn-S, Streptocycline, Bordeaux mixture, Chloromycetin and Terramycin. The soil treated with Bordeaux mixture and calixin had minimum count of fungal population. Ambistryn-S, streptocycline and water extract of Ocimum spp. Treated soils had minimum count of actinomycetes. The result of the pot culture study on the management of bacterial wilt of ginger revealed that plants treated with Bordeaux mixture, Ambistryn-S, Terramycin and Chloromycetin had minimum wilt incidence. Correlation studies were made between environmental factors and wilt incidence. There was a positive correlation between maximum air and soil temperature and wilt incidence. The colonization of VA-mycorrhiza was greater in roots of healthy plants than the roots of infected plants. The incidence of phyllosticta leaf spot was minimum in plants treated with Bordeaux mixture, Ambistryn-S, Calixin and Chloromycetin both in pot culture and field experiments. The effect of treatments on plant height, number of tillers and yield were also recorded. Bordeaux mixture and Ambistryn-S treated plants had maximum plant height, more number of tillers and better yield than the other treatments. Thus the present study revealed that one per cent Bordeaux mixture can be used as a prophylactic measure to reduce the incidence of bacterial wilt of ginger. The use of water extracts of botanicals for the control of the disease needs further detailed investigations.