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Subject: Plant Pathology × Author: KAU × End date: 2012 × Start date: 2012 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Characterization and management of ganoderma lucidum inciting basal stem rot of coconut
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2012) Yunus, C; KAU; Beena, S
    The present study on “ Characterization and management of Ganoderma lucidum inciting basal stem rot of coconut ” was undertaken in the Department of Plant Pathology, College of Horticulture, Vellanikkara during 2010-2012 with an aim to isolate the pathogen associated with the disease and to study the cultural, morphological and pathogenic characters of different isolates of the pathogen, symptomatology of the disease, host range and effective management of the pathogen using bio-control agents, phytoextracts and selected fungicides. Purposive sampling surveys were conducted and the occurrence of basal stem rot disease of coconut was observed through out Kerala. The isolation of pathogen from basidiocarps yielded eight isolates of Ganoderma sp. which produced fruiting body in saw dust- rice bran substrate. The pathogenicity of these isolates was tested and observed yellowing, drying and drooping of leaves of coconut seedlings inoculated with all isolates except the isolate GT- from Trivandrum. Basidiocarp formation was noticed only in one seedling inoculated with the isolate GV from Vellayani and reisolation of pathogen was done from this basidiocarp. Symptomatology of the disease under natural and artificial conditions was studied. Under field condition the typical symptom of BSR disease viz., yellowing and drooping of leaves, stem bleeding and basidiocarp formaton were observed in all surveyed areas but all the typical symptoms of disease were not observed under artificial condition. The cultural characters of all the isolates of pathogen were studied on four media viz., Potato dextrose agar, Czapek’s (DOX) agar, Richard’s agar and Soil extract agar media. All isolates produced white mycelial growth on all media but variations in texture, mycelial type, and colour change of mycelium, exudates production and formation of aberrant fruiting body were observed. PDA was found to be the best medium for the growth of pathogen in which all isolates recorded highest growth rate. The pathogen preferred a temperature range of 30-350C and neutral to acid pH of 5-7 for the growth. Slight variation in growth rate was observed under light and darkness. Basidiocarps showed variations in the morphological characters and were stipitate in all isolates except GC from Chirakkacode and GVe from Vettikkal, semicircular to conical shaped, yellowish red to reddish brown with smooth to waved margin, creamy white to brown pore surface, 4.4 – 12.0 x 2.6- 17.0 cm size, 1-10 mm pore length, 139- 254 x 122 – 190 μm pore diameter and 2-10 mm flesh thickness. Basidiospores were brown, ovate to ellipsoidal, truncated apex, double walled with inter wall pillars separating two walls. The size of these basidiospores showed variation in the range of 4.8-13 x 4.5-7.0μm with a spore index of 1.15-1.7. It was trimitic, with generative hyphae hyaline, thin walled, branched, septate and clamped. Reddish brown pigmented skeletal hyphae and colourless binding hyphae were noticed. Based on these observations the eight isolates of the pathogen were identified as Ganoderma lucidum (Leys) Karst. Regarding the in vitro management of the pathogen, two isolates of T. virens and one isolate of T. viride were isolated from rhizophere soil and were proved equally effective with the reference culture, T. viride and T. harzianum in inhibiting the growth of pathogen. Mycoparasitism and production of non volatile metabolites were found to be the mechanisms exhibited by the selected Trichoderma spp. The bacterial antagonists obtained from rhizosphere soil and the reference culture P. fluorescens recorded less than 50 percent inhibition on the growth except in cases of few isolates of the pathogen. It was observed that the selected bacterial antagonists were not much effective in inhibiting the pathogen compared to fungal antagonists. Among the phytoextracts, Azadirachta indica at 20 per cent concentration was found the most effective and recorded more than 50 percent inhibition on the growth of pathogen over control. It was followed by Musa sp. at 10 per cent concentration. The in vitro evaluation of fungicides showed that flusilazole, hexaconazole and iprobenphos at 0.2 per cent concentration were the most effective and recorded cent per cent inhibition on the growth of all isolates of pathogen. The study on the host range of G. lucidium revealed that the seedlings of arecanut, breadfruit, acacia and jack fruit showed yellowing and drooping of leaves and finally wilting of all the seedlings were observed
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    ThesisItemOpen Access
    Exploitation of spent mushroom substrate as mulch for the management of rhizome rot complex disease of ginger
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2012) Remya, J S; KAU; Sheela Paul, T
    Spent mushroom substrate (SMS) is the composted organic material remained after the harvest of a crop of mushroom and it is rich in plant nutrients including minerals and was used as manure in different crops including ginger. Recent findings illustrate that substrate after one cycle cultivation of mushroom can be used for disease management. So far no attempt has been made on the use of spent mushroom substrate from oyster mushroom, against rhizome rot complex disease of ginger. Under these circumstances, a study was conducted to know the effectiveness of oyster mushroom SMS to control the rhizome rot complex disease of ginger. Bacterial wilt and soft rot are the two common rhizome rot diseases of ginger. Ginger plants showing typical wilt symptoms and soft rot symptoms were collected from the farmer’s field. The fungal pathogen Pythium aphanidermatum and the bacterial pathogen, Ralstonia solanacearum were isolated from the rhizomes showing typical symptoms, and pure cultures were maintained. Since Pleurotus florida and P. sajor-caju are the most suitable mushroom species in Kerala, they were selected for the production of spent mushroom substrate. The substrate used were agricultural waste materials like paddy straw, saw dust and neopeat. The enumeration of microorganisms at different stages of mushroom growth were made and the fungi commonly observed were Aspergillus sp. (FA-2 and FA-3) and Trichoderma sp. (FA-1). Maximum number of microbial population was noticed in paddy straw, whereas it was minimum in neopeat. From four different stages of mushroom growth, five different types of bacteria, BA-1, BA-2, BA-3, BA-4 and BA-5 were observed. An in vitro evaluation study was conducted to find out the efficiency of isolated organisms against the pathogens P. aphanidermatum and R. solanacearum. Among the bacterial isolates tested against P. aphanidermatum, BA-4 and BA-5 were effective, whereas against R. solanacearum, only BA-5 was found effective. All the three fungal isolates, FA-1, FA-2 and FA-3 gave 100 per cent inhibition against both the pathogens. But FA-1 was the most effective one. These five antagonists were selected for the compatibility studies by dual culture technique. The selected fungal antagonist FA-1 was identified as Trichoderma viride by studying cultural and morphological characters. The bacterial isolates BA-4 and BA-5 were identified as Pseudomonas aeruginosa and Klebsiella pneumoniae respectively. The effect of spent mushroom substrate for the management of rhizome rot complex disease of ginger was assessed under pot culture conditions. Two separate experiments were conducted for the management of P. aphanidermatum and R. solanacearum. All the treatments were applied at three times- at the time of planting, 60 DAP and 120 DAP. Among the various treatments for the management of both the pathogens associated with rhizome rot complex disease, T. viride from SMS and paddy straw SMS of P. sajor-caju as mulch were found to be the best giving cent per cent disease control. In control treatment, cent per cent disease incidence was noticed. In the experiment for the management of P. aphanidermatum, hundred per cent germination was noticed in the treatment, T. viride from SMS + Reference culture T. viride. Among the treatments with SMS as mulch, paddy straw SMS of P. sajor-caju showed better germination percentage. But in the experiment for the management of R. solanacearum, the treatment Klebsiella pneumoniae showed 100 per cent germination followed by the treatment T. viride from SMS. The growth parameters like number of tillers, number of leaves per tiller and height of tillers were highest in the treatment T. viride from SMS, at two, three, four and five months of planting, in the experiment for the management of P. aphanidermatum. But in the experiment for the management of R. solanacearum, the treatment paddy straw SMS of P. sajor-caju as mulch showed highest number of tillers. Number of leaves per tiller was highest in the treatment K. pneumoniae + reference culture P. fluorescens, in the first three months and the treatment with paddy straw SMS of P. sajor-caju as mulch for the next two months. Height of tillers was observed maximum in the treatments applied with T. viride from SMS. The same trend was noticed in the case of yield also. In the experiment for the management of P. aphanidermatum, highest yield was observed in the treatment T. viride from SMS. But in the experiment for the management of R. solanacearum, the treatment paddy straw SMS of P. sajor-caju as mulch produced highest yield. SMS is rich in microflora with antagonistic effect against pathogenic microorganisms associated with ginger plants. From the pot culture experiment it was clear that for the management of R. solanacearum and plant growth promotion, best treatment is paddy straw SMS of P. sajor-caju as mulch. High cellulolytic capacity of P. sajor-caju favour the maximum degradation of the substrate, thereby provides a niche for the multiplication of favourable microorganisms with antagonistic effect. Whereas, best treatment for the management of P. aphanidermatum and plant growth enhancement is T. viride from SMS. It was found to be better than reference culture T. viride. In addition the beneficial microorganisms may be having plant growth promoting activity which contributes to increased yield in the various treatments. So from the present study, it can be concluded that the use of paddy straw SMS of P. sajor-caju as mulch, along with the application of T. viride from SMS can be considered as an effective management practice against the rhizome rot complex disease of ginger. Depending on the location and climatic condition in which the mushroom crop is raised, the microorganisms harbouring in SMS will vary and they can be used for disease management in various crops.
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    ThesisItemOpen Access
    Cataloguing and management of major diseases of monopodial orchids
    (Department of Plant Pathology, College of Horticulture,Vellanikkara, 2012) Meera, T M; KAU; Vimi, Louis
    Disease is one of the major production constraints in orchid cultivation. Hence an investigation has been undertaken to study the symptomatology, etiology and management of various diseases of important monopododial orchids viz., Phalaenopsis, Vanda (Basket Vanda), Mokara and Arachnis. A survey was conducted in different locations of Thrissur District viz., orchidarium of AICRP on Floriculture Improvement, Department of Pomolgy and Floriculture, COH, Vellanikkara, nurseries at Cheroor, Thrissur, Perinjanam, Madakkathara and Kanimangalam. Different fungal and bacterial diseases were observed and isolation of pathogen yielded eleven fungal pathogens and two bacterial pathogens. The pathogenicity of these organisms was proved by artificial inoculation.Symptomatology of various diseases was studied in detail under natural and artificial conditions. Fusarium sp. caused wilt symptom in Phalaenopsis and caused leaf spot in Arachnis. Sclerotium sp. caused collar rot in Phalaenopsis and dry rotting in Basket Vanda, Anthracnose pathogen, Colletotrichum sp. produced different symptoms in Phalaenopsis, Mokara and Arachnis. In Phalaenopsis, the symptom was irregular sunken spot, in Mokara leaf blighting and in Arachnis, round sunken spot. Heart rot was the symptom of Phytophthora infection in Basket Vanda. Botryodiplodia leaf spot of Basket Vanda was characterized by greyish white coloured spot with black margin and pycnidia at the centre. Alternaria leaf spot of Mokara, was round to oval shaped with a vertical splitting through the centre of the spot. Soft rot of Phalaenopsis by Erwinia sp. and bacterial wilt of Basket Vanda by Burkholderia sp. were the bacterial diseases observed during the survey. Water soaking and rotting of leaves were the symptoms of soft rot while yellowing, wilting and leaf detachment were the symptoms of bacterial wilt.Cultural characters and morphological characters of fungal pathogens were studied and they were identified at species level. Cultural, morphological and gram reaction of bacterial pathogens were studied and they were identified at species level by molecular techniques.For the management of fungal pathogens, an in vitro evaluation was conducted with fungicides and liquid formulation of Pseudomonas fluorescens. Most of the fungicides revealed cent per cent inhibition on the growth where as P. fluorescens showed 53 - 86 per cent inhibition. For the management of bacterial pathogens, an in vitro evaluation was conducted with cowdung, liquid formulation of P. fluorescens, cowdung + P. fluorescens and Streptocycline and differences were observed in their inhibitory properties. Seasonal influence on the incidence of diseases of monopodial orchids was studied for one year. Influence of temperature, humidity and rainfall was prominent in the incidence of Fusarium wilt, collar rot and soft rot of Phalaenopsis whereas not very prominent in the incidence and severity of Botryodiplodia, Alternaria and Fusarium leaf spot diseases of Basket Vanda, Mokara and Arachnis respectively . Incidence of Fusarium wilt was more in the month of November, collar rot in the month of December whereas bacterial soft rot was prominent in rainy months.
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    ThesisItemOpen Access
    Serodiagnosis and standardization of techniques for production of virus free planting materials of Cassava variety,Vellayani Hraswa
    (College of Agriculture, Vellayani, 2012) Asha, B Nair; KAU; Umamaheswaran, K
    Cassava (Manihot esculenta Crantz), the staple or subsidiary food for about one fifth of the world’s population, is an important source of dietary calories. Among the diseases and pests of cassava, cassava mosaic disease (CMD) is a serious factor limiting the productivity of cassava and the variety, Vellayani Hraswa is found to be highly susceptible to the disease. CMD is caused by viruses belonging to the genus Begomovirus of the family Geminiviridae. Since the crop is vegetatively propagated, the CMD is carried from one crop cycle to the next, through the use of infected cuttings used as planting material. Studies were conducted for the diagnosis of cassava mosaic geminivirus and production of disease free planting material of cassava variety, Vellayani Hraswa causing the mosaic disease of cassava in Kerala. The characteristic symptoms observed include chlorotic areas on the leaf and bright mosaic pattern of yellow or pale green patches. In severely affected plants, leaf distortion and twisting, reduction in size of leaf lamina and stunting of plant growth were observed. Host range studies were conducted and the virus was found to infect only Datura stramonium belonging to the Solanaceae family. The sap transmission of the virus using 0.1 M sodium phosphate buffer (pH 7.0) was found not successful from cassava to cassava. Chlorotic lesions were produced on the local lesion host, Datura which later turned necrotic. Insect transmission studies revealed that only whiteflies (Bemisia tabaci) were able to transmit the virus whereas the spiralling whiteflies (Aleurodicus dispersus) and mealy bugs (Ferrisia virgata) associated with cassava could not transmit the virus. Graft transmission of the virus was also found successful. The pathophysiological studies revealed that the total carbohydrate and phenol contents in graft inoculated plants were significantly higher compared to the uninoculated cassava plants. The content of chlorophyll a, b and total chlorophyll were lower in inoculated cassava plants. There was a decrease in total protein content in inoculated plants compared to the healthy plants but was found to be increasing at different stages of inoculation. The activity of the defense related enzymes were higher in case of inoculated plants than that of the control plants. Protein profile study of virus infected cassava plants using SDS- PAGE showed an extra novel protein with approximate molecular weight of 40 KDa corresponding to the coat protein of the virus. Isozyme analysis of polyphenol oxidase produced three isoforms in both healthy and inoculated plants with relative mobility (Rm) values of 0.68, 0.75 and 1. Two isoforms with Rm values 0.63 and 0.74 were observed in case of peroxidase isozyme analysis in inoculated plants whereas only one in healthy plants. The activities of the isoforms were more in the inoculated plants. Serological and molecular characterization of the virus was also done. The virus was partially purified from the infected leaves and antiserum with a titre of 1: 512 was produced. Serological characterization of the virus using ELISA showed the close relationship of ACMV and ICMV with the disease. Presence of the virus in the whitefly vector B. tabaci was confirmed through DAC- ELISA. Detection of the virus was also done using Dot Immunobinding Assay (DIBA). A field level diagnostic kit using DIBA was developed. Multiplex PCR using ICMV and SLCMV specific primers produced an amplicon of size 600 bp corresponding to the DNA- A fragment of SLCMV. Sequencing of the PCR product obtained 584 bp long nucleotide sequences. The cluster dendrogram constructed by multiple alignment of sequences showed three major clusters and the isolated viral sequence shared the same cluster with SLCMV isolates collected from Kerala. The meristem from the infected cassava plants were regenerated into complete plantlets within 30 days in a suitable MS media supplemented with benzyladenine (0.5 ml l-1), naphthalene acetic acid (0.1 ml l-1) and gibberellic acid (0.1 ml l-1) of millimolar concentration. Root induction was better in the basal MS media and was tested for the presence of the virus by subjecting it to DAC- ELISA. The absorbance of the plantlet regenerated from healthy and infected meristem were found to be 0.22 and 0.31 respectively which was on par with the healthy field sample (0.28) but much lower than that of the infected field sample (1.23) which was used as the positive control. The virus free plantlets were transferred to pots containing sand, soil and compost in 1:1:1 ratio and were grown in a green house. Meristem culture and virus indexing by use of protein and nucleic acid based detection thus, can be used as a viable strategy for the early detection and elimination of the virus and hence for the production of virus free planting materials.