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Kerala Agricultural University, Thrissur
The history of agricultural education in Kerala can be traced back to the year 1896 when a scheme was evolved in the erstwhile Travancore State to train a few young men in scientific agriculture at the Demonstration Farm, Karamana, Thiruvananthapuram, presently, the Cropping Systems Research Centre under Kerala Agricultural University. Agriculture was introduced as an optional subject in the middle school classes in the State in 1922 when an Agricultural Middle School was started at Aluva, Ernakulam District. The popularity and usefulness of this school led to the starting of similar institutions at Kottarakkara and Konni in 1928 and 1931 respectively.
Agriculture was later introduced as an optional subject for Intermediate Course in 1953. In 1955, the erstwhile Government of Travancore-Cochin started the Agricultural College and Research Institute at Vellayani, Thiruvananthapuram and the College of Veterinary and Animal Sciences at Mannuthy, Thrissur for imparting higher education in agricultural and veterinary sciences, respectively. These institutions were brought under the direct administrative control of the Department of Agriculture and the Department of Animal Husbandry, respectively. With the formation of Kerala State in 1956, these two colleges were affiliated to the University of Kerala. The post-graduate programmes leading to M.Sc. (Ag), M.V.Sc. and Ph.D. degrees were started in 1961, 1962 and 1965 respectively.
On the recommendation of the Second National Education Commission (1964-66) headed by Dr. D.S. Kothari, the then Chairman of the University Grants Commission, one Agricultural University in each State was established. The State Agricultural Universities (SAUs) were established in India as an integral part of the National Agricultural Research System to give the much needed impetus to Agriculture Education and Research in the Country. As a result the Kerala Agricultural University (KAU) was established on 24th February 1971 by virtue of the Act 33 of 1971 and started functioning on 1st February 1972. The Kerala Agricultural University is the 15th in the series of the SAUs.
In accordance with the provisions of KAU Act of 1971, the Agricultural College and Research Institute at Vellayani, and the College of Veterinary and Animal Sciences, Mannuthy, were brought under the Kerala Agricultural University. In addition, twenty one agricultural and animal husbandry research stations were also transferred to the KAU for taking up research and extension programmes on various crops, animals, birds, etc.
During 2011, Kerala Agricultural University was trifurcated into Kerala Veterinary and Animal Sciences University (KVASU), Kerala University of Fisheries and Ocean Studies (KUFOS) and Kerala Agricultural University (KAU).
Now the University has seven colleges (four Agriculture, one Agricultural Engineering, one Forestry, one Co-operation Banking & Management), six RARSs, seven KVKs, 15 Research Stations and 16 Research and Extension Units under the faculties of Agriculture, Agricultural Engineering and Forestry. In addition, one Academy on Climate Change Adaptation and one Institute of Agricultural Technology offering M.Sc. (Integrated) Climate Change Adaptation and Diploma in Agricultural Sciences respectively are also functioning in Kerala Agricultural University.
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ThesisItem Open Access Management of bitter gourd mosaic by enhancing host resistance(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2015) Ashwini, K N; KAU; Vimi, LouisBitter gourd (Momordica charantia L.) is one of the important vegetable crops that occupy a pivotal position among fruit vegetables, particularly in south India. The fruits of this crop which have high commercial value and are being used for culinary preparations and various medicinal preparations. In spite of the economic importance of this vegetable, the research work carried out on protection of crop from viral disease is quite scanty. In many case, cent per cent mosaic incidence was recorded in the crop resulting in substantial economic loss. So the present study was focused on screening of bitter gourd accessions and management of bitter gourd mosaic by enhancing host resistance using defense inducers. The three different viruses causing mosaic in bitter gourd are cucumber mosaic virus (CMV), potyvirus and bitter gourd distortion mosaic virus (BDMV). As these viruses causes mixed infection in field, the separation of individual viruses was carried out using systemic indicator host plants. For separation of CMV and potyvirus, systemic indicator host plants used were cosmos and papaya respectively. BDMV was separated by white fly transmission. The pure cultures of viruses were maintained on the susceptible bitter gourd variety Preethi. The symptoms developed by different viruses were recorded under natural and artificial conditions were recorded CMV produced mosaic specks, yellow-green mosaic patches, leathery leaves and downward rolling of leaf margin. Symptoms of potyvirus infection were vein clearing, puckering, malformed leaf with reduced leaf size and rugosity. BDMV infection produced mosaic, puckering, leaf distortion, hairy growth on leaves and vines with reduction in leaf size and internodal length. For the screening of bitter gourd accessions against CMV and potyvirus, potassium phosphate buffer pH 7.0 was found to be the most suitable buffer. Among 22 accessions screened, three accessions viz., TCR 285, TCR 39 and TCR 53 were highly resistant to CMV; one accession Biliagala was highly resistant to potyvirus and 11 accessions viz.,TCR 285, TCR 39, TCR 493 ,TCR 416, TCR 492, TCR 494,TCR 380, TCR 202 and TCR 149, Green long and Biliagala were highly resistant to BDMV. The field experiment was undertaken with the objective of management of bitter gourd mosaic by using defense inducers. The three different defense inducers viz., salicylic acid 25 ppm, barium chloride 0.1% and Pseudomonas fluorescens 2 % were evaluated on the moderately resistant cultivar white long and susceptible variety Preethi. The mosaic symptom was recorded after 51 days of sowing in salicylic acid treated plants and after 40 days of sowing in control. A time gap of 5-10 days after spray of defense inducer was required for development of resistance in plants. The lowest disease severity was observed in cultivar White long treated with salicylic acid. The highest yield was recorded in Preethi treated with Pseudomonas fluorescens.ThesisItem Open Access Etiology and ecofriendly management of fungal diseases of thippali ( piper longum L)(Department of Plant Pathology, College of Agriculture, Vellayani, 2007) Poornima, R; KAU; Santha Kumari, PA survey was carried out at the medicinal garden of College of Agriculture, Vellayani and medicinal garden of Ayurveda Research Institute, Poojappura, Thiruvananthapuram to study the diseases associated with Piper longum L. (Indian long pepper or thippali). The major disease observed was anthracnose caused by Colletotrichum gloeosporioides (Penz.) Penz and Sacc. Pathogenicity test proved that C. gloeosporioides was the pathogen associated with the disease. Cross inoculation studies conducted using C. gloeosporioides isolate of thippali, black pepper and betel vine - the sister plants – showed that the thippali isolate was highly host specific. The colony and conidial morphology of the three isolates also showed considerable difference. C. gloeosporioides of thippali had very small conidia and the culture was also found to be shy sporulating. Studies on the survival of C. gloeosporioides showed that the pathogen survived for 105 days in the infected leaves, under laboratory conditions. In the soil, it survived for 150 days. Of the eleven fungal and four bacterial isolates tested against C. gloeosporioides, T. viride and A.terreus were found to be most effective under in vitro condition. Among the different resistance inducers tested in vitro, SA (1 g/l) was selected for field evaluation, as it had no direct action on the pathogen. Of the two plant based chemicals tested, Ovis reported the highest suppression of the pathogen. These four eco friendly materials selected from the in vitro studies and neem cake were tested in the field to determine their effectiveness in controlling the disease. Their combinations were also studied. Among the different eco friendly materials tested in the field, treatment T12 (T2T5 - A. terreus + neem cake) was found to be best in disease suppression at 45 DAT. Estimation of DRE showed that PO and PPO activity was highest in T3 (Ovis) where as PAL activity was maximum in T1 (T. viride). Combination of treatments revealed that maximum PO activity was in treatment T14 (T3T5 - Ovis + neem cake).The PPO and PAL activity was maximum in T7 (T1T3 - T. viride + Ovis).ThesisItem Open Access Management of phytophthora disease of black pepper (piper nigrum L. walp) using plant growth promoting microbial inoculants(Department of Plant Pathology, College of Agriculture, Mannuthy, 2003) Beena Nair, S; KAU; Anith, K NThe study, "Management of Phytophthora disease of black pepper (Piper nigrum L. Walp) using plant growth promoting microbial inoculants" was conducted at the Department of Plant Pathology, College of Agriculture, Vellayani to investigate the effect of plant growth promoting rhizobacterial strains belonging to fluorescent pseudomonads and Bacillus spp. and the root endophytic fungus, Piriformospora indica on the suppression of nursery wilt of black pepper incited by Phytophthora capsici. Two strains of fluorescent pseudomonads viz., Pseudomonas putida strain 89B61 and P. jluorescens strain RCL3R4, two strains of Bacillus viz., BY -1 and BY -2 and P. indica were included in the study to explore their potential in plant growth promotion and disease suppression. P. capsici inoculated control, uninoculated healthy control, chemical control (0.20 per cent COC drenched at 15 days intervals) and combined application of Trichoderma harzianum and an AMF, Glomus fasciculatum were maintained for comparison. In the dual culture assay, conducted in vitro for preliminary screening, though P. indica exhibited a slight mycelial growth inhibition initially, the pathogen later overgrew the antagonist. Among the bacteria, fluorescent pseudomonad strains exhibited better mycelial growth inhibition 'on both PDA and Carrot Agar. The influence of different biocontrol agents on growth promotion of the black pepper cuttings was not statistically significant. However, the fluorescent pseudomonad, P. putida strain 89B61 exhibited maximum growth promotion. In the experiment conducted to test the potential of vanous plant growth promoting microbial inoculants in suppressing nursery wilt, the plants treated with spore suspension of P. indica exhibited the highest wilt percentage of 93.22 per cent which was more than that in the inoculated control (37.48). The plants treated with the fluorescent pseudomonad, P. jluorescens strain RCL3R4 recorded a wilt percentage of 6.70. All other treatments were highly effective and checked the infection completely. The Bacillus strain, BY -2 exhibited better disease suppression in vivo. The fluorescent pseudomonad, P. putida strain 89B61 also showed disease suppression in vivo, which indicated that it has the dual function of plant growth promotion and disease suppression.ThesisItem Open Access Physiological and cultural studies on blue oyster mushroom (Hypsizygus ulmarius (Bull.:Fr.) Readhead)(Department of Plant Pathology, College of Agriculture, Vellayani, 2016) Sumi, I; KAU; Geetha, DThe present study entitled “Physiological and cultural studies on blue oyster mushroom (Hypsizygus ulmarius (Bull.:Fr.) Redhead)” was carried out in the mushroom unit, Instructional Farm, College of Agriculture, Vellayani during 2014-2016, with the objective to standardize the technology for cultivation of Hypsizygus ulmarius and to study its morphological and physiological aspects. The initial culture of H. ulmarius was isolated from the mushroom beds maintained in the mushroom unit of instructional farm through tissue culture method and purified by hyphal tip method. Morphological studies of H. ulmarius showed that the sporocarps were medium to large in size having a dark blue colour in the pinhead stage which became creamy white on maturity with an irregularly shaped, convex pileus with gills attached to the stem, but not decurrent and cylindrical, smooth and eccentric stipe. Microscopic studies revealed septate hypahe with clamp connection, oval shaped, hyaline basidiospores and the spore print was white. Studies on developmental morphology showed that H. ulmarius took an average of five days from the day of pinhead formation to complete maturity. The maximum mycelial growth was recorded on potato dextrose agar. A temperature of 25 0C, pH of 8 and dark conditions are found favourable for maximum mycelial growth. Evaluation of different substrates for spawn production revealed that paddy grains was the best medium in which spawn run was completed in fifteen days with thick fluffy growth and recorded less contaminants followed by wheat and sorghum. Evaluation of different substrates for mushroom production revealed that paddy straw was the best material for the cultivation of blue oyster with a total yield of 985 g kg-1 from three harvests followed by rubber sawdust (905 g kg-1). The minimum time for mushroom production was recorded for sugarcane bagasse and the maximum time for rubber sawdust. The average weight of sporocarp was maximum in mushrooms harvested from rubber sawdust and the maximum number of sporocarps was recorded in paddystraw. Beds prepared from sugarcane bagasse were heavily contaminated with Trichoderma sp. When compared with Pleurotus florida, H. ulmarius took more time (18 days) for complete spawn run in paddy grains and the yield was higher on paddy straw (1.096 kg kg-1) than P. florida (976 g kg-1). Infestation of pests viz., phorid flies (Megaselia sp.) and staphylinid beetles were prevalent during spawn run as well as sporocarp formation. The competitor moulds recorded were Trichoderma sp., Aspergillus sp. and Coprinus sp. Analysis for the proximate constituents in H. ulmarius revealed that it contains appreciable amount of carbohydrate (29 %), protein (32 %) and fibre (17.69 %). Sensory evaluation was done on steam cooked mushrooms for attributes like appearance, colour, texture, flavor and taste using five point score card and an overall acceptability score of 3.6 was obtained for H. ulmarius compared to P. florida (3.0). In the preference study conducted for both the mushrooms using Hedonic rating scale, 30 per cent of evaluators extremely liked H. ulmarius than P. florida (10 %). The study on the keeping quality of mushrooms in normal atmospheric condition indicated a shelf life of eight hours for H. ulmarius compared to six hours for P. florida. The study also showed that blue oyster mushrooms stored under refrigeration (4 0C) in perforated polythene covers had better shelf life (5 days) compared to P. florida (3 days). The present study indicated that blue oyster mushroom can be cultivated successfully in tropical areas on locally available materials like paddy straw and rubber saw dust under favourable climatic conditions viz., 26-28 0C temperature, more than 90 per cent relative humidity and good aeration. The variety is superior to the presently growing oyster mushroom (P. florida) in terms of yield, presence of appreciable amount of proximate constituents and keeping quality.ThesisItem Open Access Integrated management of rhizoctonia leaf blight of amaranthus (Amaranthus tricolor L.)(Department of Plant Pathology, College of Agriculture, Vellayani, 2016) Gireesh; KAU; Radhakrishnan, N VThe study entitled “Integrated management of Rhizoctonia leaf blight of Amaranthus (Amaranthus tricolor L.)” was conducted at the College of Agriculture, Vellayani and Coconut Research Station, Balaramapuram during 2014-2016 with the objective to investigate the effect of soil solarization, biocontrol agents, chemical activator, indigenous formulations and new generation fungicides on growth, yield and severity of foliar blight of amaranthus. Samples of the infected leaves showing Rhizoctonia leaf blight in amaranthus were collected from Vellayani, Kalliyoor, Venganoor and Kakkamoola locations. Among the four isolates of the pathogen, the Vellayani isolate gave significantly superior growth rate with minimum of six days for sclerotial formation. Koch‟s postulates were proved for the pathogenicity of different isolates of Rhizoctonia solani. All the four isolates have taken three days for the first symptom development but the progression of lesion size of Vellayani isolate was maximum compared to all other isolates, hence the Vellayani isolate was selected as the most virulent isolate for use in further in vitro studies. Evaluation of biocontrol agents for in vitro suppression of R. solani showed that Trichoderma harzianum completely overgrown the pathogen with maximum inhibition of 49.56 % compared to Pseudomonas fluorescens (28.30 %). Under in vitro evaluation of chemical activator, different concentrations of Acibenzolar-S- Methyl (ASM) against pathogen, 100 ppm concentration recorded the maximum mycelial inhibition of 75.67 % and 5 ppm concentration recorded the minimum mycelial inhibition of 27.70 %. Among indigenous organic formulations, turmeric powder and baking soda combination inhibited the maximum growth of the pathogen by 64.40 %. In the in vitro studies with new generation fungicides,mancozeb in cow dung supernatant (0.4 %) and tebuconazole (0.1 %) recorded the 100 % mycelial inhibition of the pathogen. Field studies on disease suppression and plant growth promotion was carried out as two experiments, one in soil solarized plots and the other in non solarized plots. Soil solarization along with soil application of ASM (75 ppm) and foliar application of ASM (100 ppm) recorded the lowest disease incidence of 30.41 % and 30.42 % respectively, which was superior when compared with foliar application of ASM (100 ppm) and soil application of ASM (75 ppm) with the disease incidence of 37.06 % and 38.84 %. Soil solarization + foliar spray of tebuconazole (0.1 %) recorded the minimum disease index of 37.85 % which was superior compared to foliar spray of tebuconazole (0.1 %) with the disease index of 39.28 %. Among the biocontrol agents soil solarization + foliar spray of Pseudomonas fluorescens (2 %) gave minimum disease index of 45.22 % which was greater compared to foliar spray of P. fluorescens (2 %) with the disease index of 51.66 %. In case of indigenous organic formulations, soil solarization + foliar spray of fish amino acid (5 %) given the maximum control of the disease with the disease index of 49.51 % which was superior to foliar spray of fish amino acid (5 %) with disease index of 63.59 %. The number of days taken for flowering in soil solarized plots ranged from 28.67 to 35 days where as the number of days taken for the flowering of amaranthus in non solarized plots was ranged from 27.27 to 31.67 days. At the time of harvest, soil solarization + mancozeb in cow dung supernatant (0.4 %) recorded maximum plant height of 127.07 cm which was higher compared to foliar spray of azoxystrobin (0.15 %) with plant height of 117.60 cm. Maximum of 78.00 number of leaves were recorded by soil solarization + foliar spray of azoxystrobin (0.15 %) which was greater compared to foliar spray of azoxystrobin (0.15 %) with 67.67 number of leaves.Soil solarization + foliar spray of azoxystrobin (0.15 %) gave the highest yield in terms of fresh weight by 26975.00 kg/ha and dry weight of 4233.33 kg/ha which was superior when compared with foliar spray of tebuconazole (0.1 %) with the fresh weight of 23375.00 kg/ha and dry weight of 3362.50 kg/ha. It is concluded that soil solarization for 31 days with the foliar application of tebuconazole (0.1%) can effectively control the Rhizoctonia leaf blight disease severity with plant growth and yield promotion under field conditions.ThesisItem Open Access Molecular detection and characterization of phytoplasma infecting brinjal (solanum melongena L.)(Department of Plant Pathology, College of Agriculture, Vellayani, 2015) Saranya, S S; KAU; Umamaheswaran, KThe study entitled “Molecular detection and characterization of phytoplasma infecting Brinjal (Solanum melongena L.) was conducted at the Department of Plant Pathology, College of Agriculture, Vellayani, with the objectives to study the symptom development, transmission, molecular detection and characterization of phytoplasma infecting brinjal and its relationship with phytoplasma diseases of other crop plants. Brinjal little leaf (BLL), collected from the Crop museum, College of Agriculture, Vellayani and catharanthus little leaf (CLL) obtained from Coimbatore were maintained for further studies. Symptomatology revealed the characteristic little, narrow, soft, glabrous and smooth leaves produced as clusters along with yellowing, proliferation of axillary shoots, shortened internodes, stunted bushy or rosette appearance and phyllody, the conversion of floral parts into leaf like structures. The graft transmission was found to be 100% successful while the percentage transmission by dodder was only 10% in brinjal and 20% in catharanthus. Phytoplasma was maintained in vivo in plants by grafting and in vitro by culturing the infected explants on MS media supplemented with 0.2 mg l-1 BAP, 0.6 mg l-1 NAA and 0.4 mg l-1 IAA. Biochemical analysis of healthy and diseased plants revealed that the contents of protein, phenol and chlorophyll were reduced in the inoculated plants as a result of phytoplasma infection. Carbohydrate content in brinjal increased immediately after inoculation and then decreased. The activity of peroxidase (PO) was enhanced in the inoculated plants while that of polyphenol oxidase (PPO) was reduced. The activity of phenyl alanineammonialyase (PAL) was reduced immediately after the inoculation, but enhanced at 30 and 60 days after inoculation (DAI). 91 92 The electrophoretic analysis of proteins using SDS-PAGE revealed the presence of two extra protein bands in the infected samples with molecular weights of 29 kDa (Kilo Dalton) and 43 kDa. The isozyme pattern analysis of peroxidase using native PAGE revealed two isoperoxidase bands in the inoculated plants with Relative mobility (Rm) values, 0.17 and 0.47, but a single band in healthy plants with Rm value of 0.17. Molecular detection was done using nested PCR. PCR products of ~1.8 kb (Kilo base) were obtained in direct PCR with phytoplasma universal primer pair P1/P7 and the nested PCR with P1/P7 followed by R16F2n/R16R2 amplified the fragment of size 1.2 kb. The presence of phytoplasma in tissue culture plants was also confirmed using nested PCR. Comparative nucleotide sequence analysis of brinjal and catharanthus isolates with the existing data base from NCBI revealed a 100% homology with brinjal little leaf phytoplasma isolates from Haryana and IARI and 99% homology with potato witches’ broom, potato purple top, tomato big bud phytoplasma etc. The 16S rDNA sequences of BLL and CLL phytoplasma shared 99.7% similarity with that of ‘Candidatus Phytoplasma trifolii (Ca. Phytoplasma trifolii)’. Thus the two phytoplasma isolates were identified as the related strains of ‘Ca. Phytoplasma trifolii’.ThesisItem Open Access Management of bacterial blight of anthurium (anthurium andreanum linden) using botanicals(Department of Plant Pathology, College of Agriculture, Vellayani, 2002) Sabitha, S R; KAU; Mary, C AAnthurium (Anthurium andreanum Linden) suffers from a serIOUS disease viz., bacterial blight incited by Xanthomonas axonopodis pv. diefJenbachiae (McCulloch and Pirone) Vauterin et al. A survey was conducted in Thiruvananthapuram district and information on disease intensity and varietal reaction of the disease was studied from randomly selected thirty anthurium gardens. Plants with disease infection upto 50 per cent was noticed in most of the gardens. Generally pink varieties exhibited tolerance while red varieties were susceptible. Both foliar and systemic symptoms were observed. The bacterium was a gram negative, motile, short rod. Potato Sucrose Agar was the best solid medium for growth of the bacterium. Morphological, physiological and biochemical characters of the ten isolates were compared and some characters like nature and rate of growth, virulence and hydrolysis of starch were found varying. Aglaonema sp., Alocasia sanderiana, Anthurium ornatum, Colocasia esculenta, Dieffenbachia spp., Philodendron spp., Syngonium sp. and Xanthosoma sagittaefolium of Araceae family and ornamental plants like Orchid spp., Dracaena spp. Heliconia sp., Sterilitzia reginae and Maranta arundinaceae were hosts of the pathogen. Among the fifteen botanicals tested under in vitro conditions crude extract and 2 : 1 dilution of Allium sativum and Tagetes erecta, crude and two per cent concentration of neem cake extract and one and two per cent neem oil and coconut oil were 'effective in inhibiting the growth of the pathogen. The relative efficacy of five ecofriendly management practices viz., application of A. sativum, T. erecta, neem oil, coconut oil and neem cake extract, at two levels and 100 ppm streptocycline were tested on seven month old tissue culture plants. Pre and post inoculation sprayings with crude extract of neem cake and T. erecta reduced the disease by 85 per cent. When the same spraying schedule with these two botanicals and 100 ppm streptocycline was given on flowering plants, crude extract of neem cake was the most effective followed by crude extract of T. erecta. The effect of streptocycline 100 ppm was on par with T. erecta. The study thus indicates that botanicals could be used as a substitute for antibiotics in the management of bacterial blight of anthurium.ThesisItem Open Access Bioherbicidal potential of fungal pathogenes of water hyacinth [Eichhornia crassipes (Mart.) Solms](Department of Plant Pathology, College of Agriculture,Vellayani, 2003) Ancy Salim, M; KAU; Naseema, AThe study entitled "Bioherbicidal potential of fungal pathogens of water hyacinth [Eichhornia crassipes (Mart.) Solrns]", was conducted at College of Agriculture, Vellayani, Thiruvananthapuram during 2001-2003. Fourteen pathogenic fungi of water hyacinth obtained from the survey conducted as a part of the DST project on "Biocontro l of water hyacinth using mycoherbicides" were used for the study. Fungi which were not identified earlier were characterized and identified based on the cultural and morphological characters and was confirmed by sending to Agharkar Research Institute, Pune. These three fungi viz., Bipolaris tetramera, Drechslera sp. and Pestalotiopsis guepinii, were new records on water hyacinth. The fungi varied in the symptom development on water hyacinth with respect to nature of symptoms, parts affected and the time taken for the symptom development. The intensity of infection by the fungi varied from 9.94 to 58.80 per cent. Only five fungi viz., A.eichhorniae, F. moniliforme, F. oxysporum (isolate 2), F. pallidoroseum (isolate 3) and I M. advena gave more than 45 per cent intensity of infection. Cell free metabolites of the various fungi also varied in the symptom development. Intensity of damage varied from 8.03 to 89.00 per cent. Maximum was recorded by M. advena followed by F. pallidoroseum (49.80 per cent), A. eichhorniae (48.80 per cent) and F. oxysporum (47.20 per cent). Host range of A. eichhorniae, F. moniliforme and F. oxysporum was studied in detail. A. eichhorniae infected only three weed plants out of the 37 cultivated and 39 weed plants tested. F. moniliforme infected five 11 cultivated and 11 weed plants. F. oxysporum was found to be pathogenic to seven cultivated and nine weed plants. Combined application of A. eichhorniae and F. p allidorose um recorded higher intensity of infection than when sprayed alone. A. eichhorniae was found to give effective destruction of the weed at 107 spores per ml concentration. A. eichhorniae at 107 spores per ml and F. p all idoroseum at lOll spores per ml together recorded more intensity of infection of 89.84 per cent than when sprayed alone. Talc based combination product of A. eichhorniae and F. pallidoroseum when sprayed at 10.00 per cent concentration recorded an intensity of infection of 93.20 per cent, 10 days after spraying. The formulated product could retain the viability of spores of the pathogens at room temperature for 15 days.ThesisItem Open Access Biocontrol of bacterial wilt in tomato using arbuscular myaorrhizal fungi(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2003) Nandakumar, A; KAU; Surendra Gopal, KThe studies on "Biocontrol of bacterial wilt in tomato using arbuscular mycorrhizal fungi" were carried out at the Oept. of Plant Pathology, College of Horticulture, Vellanikkara during the period 2000 - 2002. The main objectives of the study were to identify suitable native AMF from high and low wilt incidence areas of Thrissur and Palakkad districts, screen them against Ralstonia solanacearum in pot culture under sterile and wilt sick conditions, to determine the optimum inoculation time and inoculum density of :\\1f and to test ~h,- ,,;;;cicncy 0: Aj,\1f in thc wilt sick field. The soil samples collected from Thrissur and Palakkad district were analyzed for their nutrient status, pH, Ralstonia population and total AMF spore count. The Vellanikkara soils were acidic with low ,K, Ca and Mg and high P content when compared to Ozhalapathy and Eruthiampathy soils. The Ralstonia population were generally higher in Vellanikkara soils. On the other hand, Ozhalapathy soils had higher AMF spore count. The Glomus sp. was found to be the most predominant AMF in the soils of high wilt (Vellanikkara, Thrissur district) and low wilt incidence (Ozhalapathy and Eruthiampathy, Palakkad district). The screening of the predominant native AMF cultures against R. solanacearum were carried out individually and in combinations under sterile conditions along with the TNAU commercial culture [or comparison. The treatments with the native AMF combinations 1'i2., GIOIllIlS sp. (OT) + Glomus sp. (ER), Glomus sp. (OT) + Glomus sp. (VM) and Glomus sp (OM) - Glomus sp. (VBT) recorded the least percent wilt incidence with the native A0.1F combination Glomus sp. (OM) + Glomus sp. (VBT) recording the maximum number of days of plant survival (11 days). The dry weight and root length were also higher for these three native AM F combinations. The determination of the optimum inoculation time (at the time of sowing, at 15 days before transplanting and at the time of transplanting) in combination with the inoculum density (@ 25 g kg 1 soil, 50 g kg 1 soil and 75 g kg -I soil) were carried out using different species of AMF in pot culture using wilt sick soil. The inoculation time at 15 days before transplanting 75 g kg -I soil was found to be optimum. This was evaluated further, under pot culture and field experiment studies using the native AMF combinations selected from the screening experiment. The selected native AMF combinations from the screening experiment were tried at 15 days before transplanting @ 75 g kg -I soil in pot culture using wilt sick soil in comparison with the TNAU commercial culture to select the best two combinations for the field experiment. The native AMF combinations recorded the least percent wilt incidence and maximum number of days of plant survival when compared to the TNAU commercial culture. The AMF combinations Glomus sp. (OM) + Glomus sp. (VBT) and Glomus sp. (OT) + Glomus sp. (VM) were found to be the best. A field experiment to test the efficacy of the selected native AMF culture combinations were carried out using the tomato varieties Pusa Ruby (susceptible) and Mukthi (moderately resistant). The native AMF combination Glomus sp. (OT) + Glomus sp. (VM) recorded maximum number of days of plant survival (32 and 50 days respectively) in both the tomato varieties. However, it could not prevent wilt incidence in the case of Pusa Ruby variety, which recorded 100 percent wilt, and Mukthi variety 97 .. 9 % wilt incidence. The same native AMF combinations Glomus sp. (OT) + Glomus sp. (VM) also recorded maximum fruit number in Mukthi whereas Pusa Ruby did not produce fruits as they did not survive even upto flowering. The present study clearly indicated that the native AMF combination Glomus sp. (OT) + Glomus sp. (VM) was the best in pot culture studies using wilt sick soil and could delay the disease incidence in the susceptible Pusa Ruby variety of tomato upto 82 days after transplanting. However, under field conditions it could delay the disease incidence in the susceptible variety Pusa Ruby only upto 32 days and in the moderately resistant variety Mukthi upto 50 days. So more extensive studies are needed to develop a suitable native AMF to control the bacterial wilt in tomato which is effective under field conditions.
