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Subject: Plant Pathology × Author: KAU × End date: 1997 × Start date: 1997 × Type: Thesis ×
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    ThesisItemOpen Access
    Biocontrol of water hyacinth using fungal pathogens
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Susha Thara, S; KAU; Naseema, A
    Detailed study was conducted on the host range of the already identified fungal pathogens of water hyacinth viz. Colletotrichum gloeosporioides, Fusarium eguiseti and F.pallidoroseum on thirty cultivated plants including vegetables, pulses and oil seeds, field crops, fruits and forest crops and ornamental plants and forty one common weed plants which are seen in and around water ways infested with water hyacinth. It was observed that C. gloeosporioides could infect amaranthus, bhindi, chilli, Euphorbia hirta, Hydrocotyl asiatica and Phyllanthus niruri. Of the thirty cultivated plants and forty one weed plants tested F. eguiseti was seen to be pathogenic to amaranthus, Amaranthus viridis, Commelina . bengalensis, C. jacobi and Monochoria vaginalis. F. pallidoroseum could produce symptoms on napier grass, Axonopus sp., boerhaavia diffusa, C.benghalensis, C.jacobi, Echinochloa colonum, Euphorbia hirta, Justicia diffusa, J.prostrata, M.vaginalis and Oldenlandia umbrellata and Scorpia dulcis. For the effective destruction of the weed, lxl011 spores per ml concentration of Q. gloeosporioides, E. eguiseti and F. pallidoroseum were found to be more effective than lxl09 and lxl010 spores per ml concentration. Cell free metabolites of the pathogenic fungi were found to produce symptoms on water hyacinth plant. Metabolite produced by E. pallidoroseum caused considerable damage than by E.equiseti and C. gloeosporioides. When pathogens were applied singly and in combination on water hyacinth it was observed that the combined application of F. pallidoroseum and F. equiseti followed by F. pallidoroseum alone gave maximum intensity of infection. Eventhough C. gloeospoirioides gave least intensity of infection it can be used as a co-pathogen with E. eguiseti. Metabolite of the pathogens individually and in combination when applied on healthy water hyacinth plants, maximum damage was caused by F.pallidoroseum alone and the combination of metabolite of three fungi viz. C. gloeosporioides,F equiseti and F. pallidoroseum. Least damage was caused by metabolite of C. gloeosporioides. An experiment was conducted to find out suitable carrier materials for the mass multiplication and storage of pathogen. It was observed that for C. gloeosporioides maximum sporulation was in water hyacinth leaf followed by guinea grass straw and rice bran. But the spore viability was maximum for rice straw, and on coir pith. Maximum infection was caused by fungus grown on guinea grass straw and rice straw. In the case of E. equiseti spore counts was higher in guinea grass straw followed by coir pith. The spore germination was maximum in rice bran and coir pith. Maximum infection was produced by the fungi on guinea grass straw, coir pith and waterhyacinth leaf. E. pallidoroseum produce maximum number of spores on rice bran followed by guinea grass straw. It was observed that the germination percentage of spores were maximum on coir pith. Out of the six carrier materials used the fungus produced maximum infection when grown on rice bran and guinea grass straw. In the study for testing the storage life of metabolities, it was observed that the efficiency to produce symptom was reduced on storage in the case of C. gloeosporioides and E. pallidoroseum whereas for E. eguiseti on storage the effeciency of the metabolite to cause damage increased. Metabolite stored on refrigerated condition performed poorly for all the three fungi. Different methods of application of the three fungi were tried. Of the five treatments, placement of bits and dusting the inoculum along with the carrier materials produced maximum infection. In the experiment conducted to characterize the toxin presented in the cell free metabolite of pathogenic fungi, observed the presence of Fusaric acid in the metabolite of Fusarium spp.
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    ThesisItemOpen Access
    Effect of management practices on the incidence and intensity of grey blight disease of coconut
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Anupama, N; KAU; Padmakumari, G
    From a detailed survey on the occurrence of leaf blight disease of coconut in Thiruvananthapuram (Coconut Research Station, Balaramapuram and Instructional Farm, Vellayani) and Alappuzha Districts (Rice Research Station, Kayarnkulam) it was revealed that Pestalotiopsis palmarum (Cooke) Stey was the major pathogen causing grey leaf blight of coconut in both the areas. Curvularia sp. were also found to be contribute to this disease. Of the various media tested, best growth of P. palmarum was seen in potato dextrose agar and broth. Among the various carbon sources tested dextrose, starch and inositol were equally effective for the growth of P. palmarum and for Curvularia sp., Sucrose, dextrose and starch were the best carbon sources. A temperature of 25°C and 35°C was found to be optimum for the growth of P. palmarum and Curvularia sp respectively. Arecanut, cinnamon, clove, guava, mango, nutmeg and sapota intercropped with coconut in the three locations were found to be host of the pathogen P. palmarum. In vitro evaluation of fungicides revealed that Bordeaux mixture (1000 ppm) and Bavistin (2000 ppm) were superior in inhibiting the growth of P. palmarum on the other hand Bordeaux mixture (1000 ppm) and Dithane M-45 (1000 ppm) effectively inhibited the growth of Curvularia sp. Monitoring of the disease intensity over a period of 12 months has shown that grey leaf blight intensity was high in palms planted at closer spacing and which received no fertilizers. The disease intensity was minimum in palms with wider spacing and with higher level of fertiliser (N2P2K2). In general higher level of fertilizers and wider spacing may be considered as a management practice for controlling the incidence and intensity of the grey blight diseases in coconut palm in South Kerala.
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    ThesisItemOpen Access
    Azotobacter and azospirillum inoculants for nitrogen economy in vegetable cultivation
    (Department of Plant Pathology, College of Agriculture,Vellayani, 1997) Arunkumar, S; KAU; Sasikumar, Nair
    The study on Azotobacter and Azospirillum inoculants for nitrogen economy in vegetable cultivation was conducted at College of Agriculture, Vellayani, Thiruvananthapuram during 1994-1996. Two sets of experiments consisting of pot and field trials were conducted for this purpose. Pot culture experiments with amaranthus showed that, plant height, root biomass, leaf area index and yield were significantly high in the treatment combination of Azospirillum inoculation along with FYM and 75 percent fertilizer nitrogen (N3FYM+AS). Flowering time was also significantly delayed in this treatment. Among Azotobacter treatments also plant height, leaf area index and yield were significantly high in the treatment receiving 75 percent nitrogen along with FYM and Azotobacter inoculation (N3FYM+AB). In brinjal while Azospirillum inoculation along with 75 percent nitrogen and FYM (N3FYM+AS) could significantly increase yield and increase plant height and root biomass production, there were no significant difference among Azotobacter treatments on yield. In chilli also Azospirillum treatment coupled with vermicompost and 100 percent nitrogen (N4 VEC+AS) was significantly increasing number of branches, number of fruits and yield. Whereas there were no significant differences among Azotobacter treatments on yield of chilli. When the individual effect of organic manure and biofertilizer application for all the three crops were studied, no significant differences were obtained between two biofertilizer treatments except for some delay in flowering time in amaranthus due to Azospirillum inoculation. But FYM application had favorable effects in most of the plant growth and yield parameters of all the three crops. The selected treatments from pot culture experiments were evaluated under field conditions for all the three crops. Maximum yield for amaranthus was obtained in Azotobacter treatment with FYM and 75 percent fertilizer nitrogen (N3FYM+AB), which also had a significant increase in plant height. For brinjal, the Azotobacter treatment recervmg FYM and 75 percent nitrogen (N3FYM+AB) produced maximum plant height, number of branches, number of fruits and yield. But keeping quality of fruits was significantly high in Azotobacter treatment with full dose of vennicompost and 75 percent fertilizer nitrogen (N3 VECF+AB). For chilli, Azospirillum treatment receiving full dose of vermicompost and 100 percent nitrogen (N4VECF+AS) produced maximum yield which also has got maximum plant height. Keeping quality of fruits was also significantly high in this treatment. The population of bacteria, fungi, actinomycetes, Azospirillum and Azotobacter were significantly high in most of the treatments receiving either Azospirillum or Azotobacter inoculants and organic manure supplements.
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    ThesisItemOpen Access
    Integrated management of sheath rot of rice (Oryza sativa L.)
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Blessy Jose; KAU; Lulu Das
    Sheath rot disease of rice, caused by Sarocladium oryzae Gams and Hawksworth, is one of the most important diseases of rice in Kerala. The present investigation was to work out an efficient ecofriendly integrated control measure utilising biocontrol agents and plant products in combination with the minimum dose of fungicides against this disease. The antagonists found effective against Sarocladium oryzae are Trichoderma sp., Aspergillus sp. and Penicillium sp. Among these, Trichoderma sp. was found to decrease the disease intensity and increase the yield, the most. tried, best. Among the various methods of application of antagonists seed treatment and root dip method were found to be the In the pot culture trial conducted to find out the mode of action of antagonists under various systems of application, none of the treatments proved superior to others. Leaf extract of Ocimum sanctum (10 per cent) had maximum inhibition of the radial growth of the fungus. Minimum dry weight was seen with the bulb extract (10 per cent) of Allium sativum and extract (10 per cent) of Ocimum sanctum. Carbendazim at 0.025 per cent concentration brought about 100 per cent inhibition of radial growth and mycelial weight of S. oryzae. Total inhibition of radial growth of the fun~u9 WBB achieved by the application of 0.25 per cent Ediphenphos and total inhibition of the mycelial growth was achieved by the application of Ediphenphos at 0.075 per cent concentration. For mass multiplication of antagonists, bits of jack seeds proved to be the best substrate for Trichoderma ap. as evidenced by fungal growth. Tapioca rind and wheat grains was the best suited Aspergillus ap. Wheat bran:sand (1:10 w/w) proved to be the best medium for Penicillium sp. For Pestalotiopsis Sp., wheat bran: sand mixture at a proportion of 1:3 and 1:10 were found equally good. The integrated management practices revealed that none of the treatments were superior over others when yield and disease intensity were considered. However, least disease intensity was noticed with the application of Trichoderma sp. as seed treatment, followed by foliar spray of Ediphenphos and leaf extract (10 per cent) of Ocimum sanctum. Highest yield was obtained in the treatment combination of Trichoderma sp, applied as seed treatment followed by the foliar application of Carbendazim and the bulb extract (10 per cent) of Allium sativum.
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    ThesisItemOpen Access
    Management of rhizome rot and root-knot of ginger (Zingiber officinale R.) using V A mycorrhizal fungi and antigonists
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Joseph, P J; KAU; Sivaprasad, P
    Management of rhizome rot, the most destructive disease of ginger incited by Pythium aphanidermatum (Edson)Fitz. using native arbuscular mycorrhizal fungi (AMF) and antagonists was attempted. The extensive survey in the ginger growing belts of the state revealed a definite negative relationship between AMF development and disease incidence. Based on preliminary evaluation with six AMF species, Glomus constrictum was selected as most efficient for disease suppresion, growth enhancement and yield and used as reference culture for the subsequent studies. The population of Heloidogyne incognita, a pre disposing factor for the disease, was reduced in the presence of all the six AMF species particularly with G. fasciculatum. Characterization studies of native AMF associated with ginger indicated that Glomus spp. were more frequent and G. fasciculatum was the most predominent species. Influence of soil types on the AMF occurrence in ginger was evident. Out of the fourteen native AMF developed from ginger rhizosphere, Mi-l and Mi-4, identified as Glomus species, were the most efficient isolates for rhizome rot suppression yield increase and growth enhancement in ginger. Eleven native antagonistic fungi, selected from in vitro evaluation, were screened in the green house and Ai-12, identified as Trichoderma viride, was the most effective isolate for suppression of rhizome rot, growth enhancement and yield of ginger. Ai-13 isolate, identified as Aspergillus fumigatus, was also effective for disease suppression. The isolates, Mi-l, Mi-4, Ai-12 and Ai-13 were tested for their combined effect in the green house. Dual inoculation of Ai-12 with Mi-l and Mi-4 resulted in remarkable synergistic interaction in reducing the disease and enhancing biomass and yield. Both single and dual inoculations of Ai-12, Mi-l and Mi-4 significantly reduced the disease and enhanced plant growth and yield in the field also. Isolate Ai-13 inhibited AMF development and increased disease in the green house and field. Application of AMF inoculum on ginger rhizome after starch coating was very effective for rapid and early colonization of AMF. Out of the various plant protection chemicals tested, thiram and carbofuran least affected the AMF and antagonist development. An effective management strategy of rhizome rot of ginger is evolved in the present study by combining appropriate native AMF (Mi-l and Mi-2) and antagonistic fungi (Ai-12) for inoculation of seed rhizomes at planting time. The present study forms the first report of detailed documentation of native AMF associated with ginger and extensive study on the utilisation of AMF. antagonists and their combined effect for the management of rhizome rot.
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    ThesisItemOpen Access
    Evaluation of non symbiotic nitrogen fixation by bradyrhizobium in cowpea
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1997) Asha, S; KAU; Rajendran Pillai, M V
    A study was conducetd at the College of Horticulture, Vellanikkara during the year 1993-95 on the evaluation of non-symbiotic nitrogen fixation by Bradyrhizobium in cowpea. Twelve isolates collected from different agroclimatic regions of Kerala, two exotic isolates and one KA U isolate were used for the study. First, a pot culture experiment was conducted to screen the above 15 isolates for their efficiency in non symbiotic nitrogen fixation. Two media and two methods of application were also tried. A second pot culture experiment was also conducted to find out the most suitable method of application of the best performer in terms of foliar nitrogen fixation. The results of the screening experiment showed that no particular isolate was effective in improving any of the parameters observed. However,out of the ten characters studied, isolate liS (KAU isolate) ranked best in improving five characters namely, plant height, number of leaves, dry weight of nodule, fresh weight of plants and nitrogen content. Thus 115 was selected as the promising isolate for the second experiment. Isolate 114 (CB-7 56), which showed next better performance in improving number of leaves, dry weight of nodules and fresh weight of plants was also selected. Moreover, it was one of the known exotic isolates supporting non-symbiotic nitrogenase activity. The results of the second experiment clearly established the superiority of seed (soil) inoculation (AI) of Bradyrhizobium over different methods of foliar application. However, foliar applications also showed improved performance over control plants in improving the different parameters observed. Spraying the bacteria grown in broth shake culture (A3) was found effective in improving the number of leaves, dry weight of roots, chlorophyll content and nitrogen content of plant. The study show that, eventhough less efficient, the foliar application of Bradyrhizobium can also be resorted to in improving the performance of cowpea plants in situations where seed (soil) inoculation is not possible.