Browsing by Author "Koshy Abraham"

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Bacterial wilt of pumpkin (Cucurbita Moschata Poir) and snakegourd (Trichosanthes Anguina L.) incited by pseudomonas solanacearvm (Smith) smith from India
(Kerala Agricultural University, 1994) Sally K Mathew; Beena Baby, S; Lissy Markose; Koshy Abraham
Characterization and management of bacterial wilt of chillies caused by Pseudomonas solanaceasum E F Smith
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Jyothi, A R; Koshy Abraham
Bacterial wilt is one of the most serious disease of chillies in Kerala. The pathogen was isolated from infected chilli plants and its pathogenicity established. Ten isolates of the pathogen viz., five from chillies , two each from tomato and brinjal and one from ginger were used in the study and they werre characterized and identified as blovar III of Pseudomonas solanacearum (Smith) Smith based on the morphological, cultural, biochemical and physiological characters, coupled with its pathogenicity. Twentynine accessions/varieties of chillies were screened for host resistance against bacterial wilt and the study revealed that the variety 'Manjari' (KAU Cluster/CA 33) was resistant to the disease. The accessions CA 205 and CA 207 exhibited moderately resistant reaction. There was no significant correlation between environmental factors and wilt incidence of all the accessions/varieties except CA 408, for which a positive correlation was noticed between soil moisture and wilt incidence.
Collar rot of Murraya koenigh L. by corticium rolfsii curzi
(Kerala Agricultural University, 1994) Anita Cherian, K; Beena, S; Koshy Abraham
Control of bacterial leaf spot of betel vine
(Kerala Agricultural University, 1982) Koshy Abraham; James Mathew
In the in vitro screening of antibiotics, chloramphenicol, Terramycin, Streptomycin, Streptocycline and Agrimycin-100 have showed inhibitory effect to X. campestris pv. betf/cota. Among these, chloramphenicol at 500 ppm exerted maximum inhibitory effect. None of the antibiotics tested in in vivo gave absolute control of the disease. But minimum percentage index of disease status and maximum percentage survival of diseased leaves were observed in plants receiving Terramycin 500 ppm spray.
Cylindrocladium leaf blight of Acacia auriculjformis A. cunn
(Kerala Agricultural University, 1996) Koshy Abraham; Beena, S; Anitha Cherian, K; Sally K Mathew
Management of Phytophthora disease in black pepper nursery
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2003) Reshmy Vijayaraghavan; Koshy Abraham
Phytophthora rot is the serious disease of black pepper nursery. An investigation was carried out to isolate and select the efficient antagonists from black pepper nurseries and use them alone or in combination with fungicides in the integrated management of the disease. The experiment was laid out at CCRP farm at College of Horticulture, Vellanikkara, The pathogen causing the disease was isolated and identified as Phytophthora capslcl Leonian emend A. Alizadeh and P.H.Tsao based on the cultural and morphological characters. Quantitative estimation of rhizosphere microflora from different pepper nurseries yielded more soil bacteria followed by fungi and actinornycetes. All the 22 fungi, five out of 20 bacteria and none of the actinomycetes tested were antagonistic to P. capsici. Among the fungal isolates, 13 isolates including standard culture of T. harzianum recorded cent per cent inhibition of P. capsici. Further, selection of the efficient isolates was carried out based on the antagonistic index (AI). The isolates 22 F and 34 F recorded an AI of3000 and 1500 respectively and these were identified as Trichoderma longibrachiatum and Trichoderma viride. The standard culture of T harzianum also recorded an AI of 1500. The three antagonists were found parasitic on Picapsici as evidenced by excessive coiling, penetration and disintegration of the hyphae. The fungicides viz., Bordeaux mixture, Kocide, Captaf and Kavach were incompatible with the three antagonists, while, lndofil M-45, Ridomil I\.1Z, Akomin and Anthracol were compatible. Fytolan showed partial compatibility with Tviride and 1~ harzianum but incompatible with T. longibrachiatum. Among the eight insecticides tested, Phorate and Carbofuran showed compatibility with the antagonists, whereas Monocrotophos, Quinalphos, Endosulfan, Dimethoate, Cypennethrin and higher concentration of Chlorpyrlphos were incompatible. In general, fertilizers like Urea, Rajphos, Ammonium sulphate and Muriate of potash (MoP) were compatible with antagonists, while, Factomphos and higher concentration of Urea did not support good growth. 149 Bordeaux mixture, Fytolan, Kocide, Indofil M-45, Ridomil MZ and Captafat all concentrations and higher concentration of Akomin-40 and Anthracol were inhibitory to P. capsici. The insecticides Phorate, Carbofuran and Chlorpyriphos showed comparatively good inhibitory effect against the pathogen but complete inhibition of pathogen was noticed with Monocrotophos, Endosulfan, Quinalphos, Dimethoate and Cypermethrin. The fertilizers viz., urea, MoP, Rajphos supported growth of the pathogen while, Factomphos and ammonium sulphate exerted an inhibitory effect. Solarization of potting mixture resulted in the build up of soil temperature and the build up was more in the upper layer of soil. Solarization of potting mixture and application of biocontrol agents had a positive effect in increasing the sprouting and reducing the pre-sprouting mortality of cuttings and is comparable to plants raised as per PoP. Observations on the incidence and severity of Phytophthora rot in black pepper showed that in general soil solarization, application of antagonists and spraying of Ridomil MZ had a favourable effect in checking the disease and the effect is almost similar to that of disease management as per PoP. A variation in the population of soil microfIora in different treatments was o~~rved. Thy cuttings raised in solarized potting mixture incorporated with native antagonists had a significant effect in increasing the height and number of leaves.
New bacterial wilt of Coleus Vettiveroides Jacob
(Kerala Agricultural University, 1992) Estelitta, S; Beena, S; Koshy Abraham; Ravi, S; Varadarajan Nair, P
New leaf spot disease of kodampuli (Garcinia cambogia) desr.
(Kerala Agricultural University, 1996) Anita Cherian, K; Beena, S; Koshy Abraham
Nursery diseases of black pepper (Piper nigrum L.) in Kerala with special reference to the management of Phytophthora capsici Leonian, emend. Alizadeh and Tsao
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2003) Mammootty, K P; Koshy Abraham
Nursery diseases are the major limiting factor in the production of quality planting materials of black pepper. Investigations were carried out to study the various diseases occurring in black pepper nurseries of northern districts of Kerala, the effect of nursery practices on the incidence of diseases and to evolve an integrated management strategy against Phytophthora rot in black pepper nursery. Four nursery diseases viz., Phytophthora rot, Colletotrichum rot, Rhizoctonia rot and Sclerotium rot were recorded from different nurseries surveyed. The pathogens causing the diseases were isolated and identified as Phytophthora capsici Leonian emend A. Alizadeh and P.H.Tsao, Colletotrichum gloeosporioides (Penz.) Penz. Sacc., Rhizoctonia solani Kuhn and Sclerotium rolfsii Sacc. Symptomatology of these diseases were studied. The pathogen P. capsid produced symptoms on all parts of the plant, while C. gloeosporioides infected mainly on leaves. R. solani and S. rolfsii infected both leaves and collar regions. The infected plants produced typical symptoms depending upon the pathogen and plant parts affected. Incidence of nursery diseases varied with locations and nursery seasons. Among the nursery diseases noticed during the survey, Phytophthora rot was the most predominant one. Incidence of other three diseases was comparatively less than that of Phytophthora rot. Various nursery practices followed for raising pepper nursenes viz., nursery structures, potting mixture, place of collection of planting materials, variety / cultivar planted, processing of runner vines, treatment of potting mixture, time of planting, frequency of irrigation and application of fungicides had an effect on the incidence of nursery diseases especially Phytophthora rot. However, cuttings raised under high density polyethylene sheet did not show any incidence of diseases. Screening for host resistance indicated tolerant and moderately susceptible reactions of Kalluvally-II and Panniyur-5 respectively against nursery diseases. The biochemical parameters of these genotypes, which impart this type of reactions, were studied in comparison with susceptible Panniyur-l. Total phenols, OD phenol and total free amino acid contents and peroxidase, catalase and esterase activities were more in tolerant Kalluvally-II, while total carbohydrates, starch and acid phosphatase activity were maximum in susceptible Panniyur-l. Reducing sugar content was high in moderately susceptible Panniyur-5. Quantitative estimation of rhizosphere microflora from different pepper nurseries yielded bacteria, actinomycetes and fungi. Fungal antagonists exerted more antagonistic activity against P. capsid both under in vitro and in vivo conditions. Among these two isolates F 14 and F 48 were selected based on their better antagonistic efficiency against P. capsid and they were identified as Trichoderma harzianum Rifai and Trichoderma viride Pers. ex S.F. Gray aggr. The established antagonists T. harzianum and T. viride also exerted good antagonistic efficiency against P. capsid. The native and established antagonists were compatible with Akomin-40 and Ridomil MZ, while Bordeaux mixture and Fytolan were not compatible with any ofthe four fungal antagonists. Better growth and minimum disease incidence in pepper cuttings were recorded when nurseries were raised during February-March. Pepper cuttings raised in solarized potting mixture for 30 days showed more sprouting, better plant growth and less incidence of disease. Integrated management of Phytophthora rot in black pepper nursery was carried out using tolerant Kalluvally-II, moderately susceptible Panniyur-5 and susceptible Panniyur-l. In all the three black pepper genotypes, all the treatments had a significant effect in reducing the incidence of Phytophthora rot when compared with control. The minimum disease incidence in Panniyur-l and Panniyur-5 was recorded in cuttings in treatment T14 (Solarization of potting mixture for 30 days + T. viride + Akomin-40), while in Kalluvally-II it was T20 (Solarization of potting mixture for 30 days + T. harzianum - F14 + Akomin-40). In general, solarization of potting mixture, application of Trichoderma spp. and fungicides like Akomin 40 and / or Ridomil MZ can be used for managing the incidence of Phytophthora rot in black pepper nursery
On the physiological variation of xanthomonas campestris Pv.betlfcola (Patel, Kulkarni and Dhande) dye
(Kerala Agricultural University, 1983) Koshy Abraham; James Mathew
Plant growth promoting rhizobacteria mediated induced systemic resistance against bacterial wilt in ginger
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2007) Reshmy Vijayaraghavan; Koshy Abraham
The pathogen causing bacterial wilt of ginger was isolated and identified as Ralstonia solanacearum biovar III based on its cultural, morphological and biochemical characters coupled with pathogenicity. Rhizosphere microflora of ginger from different locations of Thrissur, Waynad and Palakkad districts were isolated. Altogether, 163 rhizobacterial isolates were selected from these areas and their antagonistic activity against the pathogen assessed. Out of 163 isolates, only 45 showed antagonistic reaction. Further, study of these antagonists based on zone of inhibition resulted in selection of 20 isolates. The effect of these 20 isolates in promoting the growth of ginger was studied in pot culture in comparison with three reference cultures of P. fluorescens and B. subtilis. Result of this experiment revealed that only 11 isolates including the two reference cultures of P. fluorescens had growth promoting effect as evidenced in terms of yield and yield attributing characters of ginger. Factors which impart growth promotion in ginger by these isolates were assessed by estimating the inhibition zone, vigour index, hydrogen cyanide, indole acetic acid, ammonia production and ‘P’ solubilzation and based on that, PGPR index of the isolates was worked out. In addition to that, production of salicylic acid, antibiotics and siderphore by the isolates, the secondary metabolites which are known to play a role in disease suppression were assessed. The isolates varied in their ability to produce salicylic acid. Isolates RB-22 followed by RB-11, RB-144 and RB-66 produced more number of antibiotics which include pyoluteorin, pyrrolnitrin, 2,4DAPG etc. Similarly, isolate RB-22 and RB-11 produced maximum siderophores. The potential of these 11 rhizobacterial isolates in imparting resistance against the disease was assessed in another pot culture experiment by estimating phenol, proteins and amino acid content of ginger upon challenge inoculation. Here also, the isolates showed a profound effect on growth and yield of ginger especially by those plants bacterized with RB-11. There was no natural incidence of bacterial wilt in plants treated with RB-11 and RB-22. Upon challenge inoculation also, plants bacterized with RB-11 showed the least incidence. In general, rhizobacterial treated plants contained more amount of phenol, protein and amino acids than untreated ones. Upon challenge inoculation with the pathogen, the rate of increase of these compounds in rhizobacteria treated plants was more than that of control during different intervals of observations. A third pot culture experiment was conducted to assess the effect of rhizobacterial treatments on defense related enzymes of ginger upon challenge inoculation. Here, eight most promising ones including the reference cultures were used. In general, the study revealed more activity of peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) in rhizobacterial treated plants that too after challenge inoculation. Native PAGE analysis revealed six isoforms of PO and four isoforms of PPO in a majority of the rhizobacterial treated plants whereas only three were noticed in control. Similarly, difference in the protein profile of rhizobacterial treated plants and control was noticed. Chlorophyll, NPK and oil and oleoresin content varied among treatments where the highest was observed in rhizobacterial treated plants. An attempt was made to elucidate the molecular mechanism of induced systemic resistance (ISR) in ginger by synthesizing cDNA and was subjected to RAPD assay. However, no conclusive evidence on ISR was observed. The compatibility of eight rhizobacterial isolates including the two reference cultures with antibiotics, fungicides, insecticides and fertilizers were assessed which revealed variation in their sensitivity. Moreover, mutual compatibility of the rhizobacterial isolates and compatibility with Trichoderma spp. were also studied and it was observed that all bacterial isolates were mutually compatible. However, Pseudomonas aeruginosa, P. fluorescens (RB-66) and the reference culture of P .fluorescens (P.f2) were found incompatible with the Trichoderma spp. The promising six rhizobacteria isolates were identified based on cultural, morphological and biochemical characters and also in comparison with that of reference culture of P. fluorescens. They were tentatively identified as Pseudomonas aeruginosa (RB-22), Pseudomonas fluorescens (RB-82, RB-66, RB-11) and the remaining two, RB-144 and RB-77, as non-fluorescent Pseudomonads.
Potential of antagonistic endophytes against bacterial blight of anthurium
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2009) Sanju Balan; Koshy Abraham
One of the major constraints in anthurium cultivation is the severe incidence of bacterial blight disease. The pathogen causing bacterial blight of anthurium was isolated and identified as Xanthomonas axonopodis pv. dieffenbachiae based on its cultural, morphological and biochemical characters coupled with its pathogenicity. Endophytic microbes were isolated from different parts of healthy anthurium collected from various locations of Thrissur, Kannur, Kasargod and Thiruvananthapuram districts. Isolation yielded more number of bacteria than fungi. Out of 51 endophytes tested, only eight bacterial and two fungal isolates showed antagonism against the pathogen. The eight selected bacterial endophytes were subjected to various tests for understanding the parameters that may act to produce antagonism as well as enhanced growth of the plants. The antagonists varied in their ability to promote plant vigour, hydrogen cyanide, IAA, ammonia and siderophore production and Phosphorus solubilization capacity. The endophytes were compatible with Bavistin, Akomin and Contaf and incompatible with Indofil M 45, Saaf and Captaf. Six insecticides viz., Classic, Rogor, Ekalux, Malathion, Target and Hostathion, and four fertilizers viz. Muriate of potash, Rajphos, Urea and Factomphos were compatible with the isolates. However, the isolates exhibited variation in their sensitivity with the antibiotics tested. Further, all isolates were compatible to each other. A pot culture experiment was conducted to assess the field efficacy of selected endophytes in comparison with recommended management practices. The treatments were given as two pre inoculation and two post inoculation sprays. The incidence and severity of the disease were recorded at five days interval for a period of 30 days. The result indicated that plants treated with endophyte EB15 showed minimum disease incidence and severity. This was followed by treatment with EB 31 and Streptocycline. The promising endophytes, EB15 and EB 31 were tentatively identified as Bacillus sp. and Pseudomonas sp. respectively.
Screening of betelvine cultivars for host resistance against leaf spot pathogn Xanthomonas Betlicola Patel, Kulkarni and Dhande
(Kerala Agricultural University, 1981) Koshy Abraham; James Mathew
Seven cultivars of betelvine were screened for host resistance against the the leaf spot pathogen Xanthomonas betlicola. The study revealed that none of the cultivars were absolutely resistant to the disease, but the minimum disease severity was observed in the cultivar Tulasivettila. The minimum defoliation within 20 and 30 days after inoculation were observed in the cultivars Karilanchikarpuran and Tulasivettila.
Studies on the bacterial leaf spot of betel vine incited by Xanthomonas betlicola Patel et al..
(Department of Plant Pathology, College of Agriculture, Vellayani, 1980) Koshy Abraham; James Mathew
The bacterial leaf spot of betel vine incited by Xanthomonas betlicola Patel et al. is one of the most serious diseases recorded on the plant and was first reported in the year 1951. The occurrence and severity of the disease in Kerala was reported from 1978 onwards. The symptoms of the disease is characterised by water soaked lesions, bacterial exudations, dark brown patches with yellow halo, marginal infection, shot hole type symptoms, defoliation, stem and petiole infection. Minor variations in the above symptoms were observed with different isolates of the pathogen.