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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 Survival of Xanthomonas campestris pv. Oryzae and its Control in Kuttanad(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Mary, C A; KAU; Sasikumar NairThe present investigation was taken up to understand the factors responsible for the recurrence of bacterial blight disease in a severe from only during the additional crop season in Kuttanad. The mode of survival of the pathogen during and in between the two major cropping seasons of Kuttanad region were also studied in detail. An extensive survey was also conducted among 115 farmers in 12 Krishibhavans of Kuttanad taluk for this purpose to collect specific informations on existing cultural practices, crop variety, nature and distribution of weed flora and self sown rice plants in and around rice fields and on wether data from June 1992 to March 1994. The efficacy of two different methods of spraying, prophylactic and curative using streptocycline, mixture of streptomycin and oxytetracycline in the proportion 1:9, Bactrinol – 100 cowdung extract on the control of bacterial blight disease was tested under field condition at Nedumudi in Kuttanad. The survey showed that there was considerable variation in the incidence of bacterial blight in Kuttanad taluk. Among the 12 Krishibhavan areas the disease incidence was maximum in Ramankari and Nedumudi and minimum in Kavalam, Kainakary and Muttar. In Neelamperoor and Thalavadi areas there was no incidence of this disease during the period of survey. Between the two major cropping seasons the disease incidence was more during the additional crop season than during Punja season. Red Triveni and Jyothy were the most popular varieties cultivated in the area and more than 50% of the farmers cultivate Red Triveni. It was observed that the variety Red Triveni as highly susceptible to bacterial blight disease. The isolate of the pathogen Xanthomonas oryzae pv. Oryzae from the rice variety Red Triveni was capable of both gelatin liquefaction and starch hydrolysis. The pathogen X. oryzae pv. oryzae was found to survive for a maximum period of 42 days in infected seed, 105 days in infected straw, 56 days in infected stubbles at room temperature, 24 days in infected stubbles under dry land condition and 14 days under wet land condition. The pathogen did not survive in soil and water. Weeds like Oryza sativa var. fatua and Paspalum conjugatum served as alternate host for the pathogen. Bacterial blight infected self sown rice plants could be seen in Kuttanad during the cropping and non cropping seasons. Due to certain specific reasons, the cultivation practices were often found to extend beyond the normal cropping seasons in the region resulting in the chances of survival of bacterial blight pathogen in the host plant itself. The specific weather conditions during the additional crop season played an important role for the severity of bacterial blight desease in this season in Kuttanad. The pathogen X. oryzae pv. oryzae was tested for sensitivity to antibiotics, Bactrinol – 100 and cowding extract under in vitro conditions. The maximum growth inhibition was obtained with oxytetracycline followed by chloramphen icol which was statistically on par with oxytetracycline. The effect of increasing concentrations of oxytetracycline in combination with streptomycin on growth of X. oryzae pv. oryzae was studied with 100, 250 and 500 ppm concentrations. The growth inhibition increased not only with the concentrations of antibiotic from 100–500 ppm but also with increasing concentration of oxytetracycline. The maximum zone of growth inhibition was obtained with 1:9 proportion of streptomycin and oxytetracycline. The five treatments selected for field evaluation trial included streptocycline at 500 ppm, streptomycin + oxytetracycline (1:9) at 250 ppm and 500 ppm, Bactrinol -100 at 500 ppm and fresh cowdung extract at 20g/1. Two different spraying methods, prophylactic and curative were evaluated in two rice varieties, T(N) 1 and jyothy. The reduction in disease index by prophylactic and curative sprayings was maximum after spraying with cowdung extract 20g/1. As regards to two methods of spraying, significant reduction in per cent disease index was obtained with curative spraying. The maximum per cent increase in grain yield over control was obtained after curative spraying with 500 ppm streptomycin and oxytetracycline mixture in jyothy followed by cowdung extract 20 g/l. In T(N) 1 and jyothy both by prophylactic and curative spraying, the thousand grain weight was maximum with cowdung extract 20 g/1. As regards to two method of spraying, significant increase in grain yield and thousand grain weight was obtained after curative spraying. In T(N) 1, both by prophylactic and curative spraying the per cent increase in straw yield was maximum with a mixture of streptomycin and oxytetracycline at 500 ppm and jyothy with cowdung extract 20g/1. In T(N)1 significant reduction in chaff per cent was recorded by prophylactic spraying while in Jyothy no significant difference was obtained by the two methods of spraying. In both these varieties the reduction in chaff per cent was maximum by spraying with cowdung extract (20g/1). It was observed that two prophylactic spraying with selected bactericidal agents, neither resulted in any significant reduction in disease index nor increase in yield as compared to curative spraying. This could be due to the fact that in Kuttanad bacterial blight disease usually occurred only around the panicle initiation stage or even later. Therefore a need based curative spraying schedule would be most effective for the control of bacterial blight disease in Kuttanad. On working out the economic benefits of controlling bacterial blight it was observed that there will be economic return only from spraying infected plants of both (T(N) 1 and jyothy with cowdung extract 20g/1. The return from plants sprayed with all other treatments in the investigation was low when compared to unsprayed control plants. Thus it will be economically advantageous to use cowdung extract to control bacterial blight of rice.ThesisItem Open Access Management of foot rot of black pepper (piper nigrum L.) with va mycorrhiza and antagonists(Department of Plant Pathology, College of Agriculture, Vellayani, 1998) Christin Robert, P; KAU; Sivaprasad, PExtensive investigation was carried out to develop a native microbial inoculant based technology involving Arbuscular Mycorrhizal Fungi (AMF) and fungal antagonists for the foot rot disease management and growth improvement of black pepper in the nursery and field. Phytophthora capsici Leonian emend A. Alizadeh and P.H. Tsao, the foot rot pathogen isolated from Peringammala, Thiruvananthapuram district was found most virulent isolate. Seven native AMF cultures and fifty fungal antagonists were isolated from Kerala soils. AMF isolates were screened in the green house for plant growth improvement and disease tolerance in comparison with identified species-Glomus fasciculatum, G.clarum and Gigaspora margarita. Of the ten AMF tested isolates Is - 6, Pi - 11, Pi - 9, G. fasciculatum and Gigaspora margarita were very effective in stimulating growth and nutrient (P, K, Ca, Mg, Cu, Fe, Mn and Zn) uptake of black pepper. Regarding the ability of AMF in reducing the foot rot incidence, Glomus fasciculatum recorded the lowest plant mortality and root rot index (53.35% and 62.50%) followed by Is - 6 (60.00% and 64.77%) and Pi - 11 (60.64% and 68.18%) as against 100 per cent mortality and 98.60 per cent root rot index noticed in control. The above five cultures were subjected for further studies. Characterisation of AMF associated with different genotypes of black pepper grown in various soil types indicated the definite influence of soil type on AMF colonization. Sandy soil (oxyaquic quartpsamment) harboured maximum root colonization while forest soil (haplic argiustoll) had the lowest. Species of Glomus particularly G. fasciculatum was the predominant AMF associated with black pepper irrespective of soil type. As an exception Acaulospora and Gigaspora species were frequently noticed in sandy soils. Based on the ability of the fungal antagonists to suppress P. capsici in vitro either through mycoparasitism, antibiosis or soil fungistasis, 24 isolates were selected for green house studies. In the further testing isolates A1, A13, A21, A22and A35 significantly reduced the foot rot infection and increased the plant growth. They showed better population build up in the soil and suppressed the P. capsici population considerably. These native antagonists were further tested in combination with selected AMF in the green house and field. Under green house condition, combination of G. fasciculatum x A1 or A21 showed significant influence on growth stimulation, while Is - 6 x A22 recorded lowest mortality of 32.90 per cent due to foot rot incidence as against 97 per cent in control. The dual inoculation of Is - 6 x A21 and Pi - 11 x A1 was highly effective in plant growth stimulation and disease suppression. Both the combination recorded less than 60 per cent infection and mortality due to the disease, while control showed 95.66 per cent infection and plant mortality. Bordeaux mixture and copper oxychloride recorded 66.67 and 59.68 per cent mortality respectively. AMF colonization and multiplication of antagonists were also favoured by dual inoculation. The potential AMF isolates Is - 6 and Pi - 11 were identified as species of Glomus while, the antagonistic isolates A1, A13, A21, A22, and A35 were confirmed as aspergillus fumigatus Fres., Fusarium oxysporum Schlecht. Ex Fr. Aspergillus sydowii (Bain. & Sart.) Thom. & Church, Trichoderma viride Pers. Ex Gray. And Gliomastix murorum (Corda) Hughes respectively. A technique for AMF inoculation to established pepper vines was developed using ‘carrier plants’. Raising sorghum with AMF inoculation around the pepper vines was found effective to achieve intense colonization in pepper roots by the introduced AMF in the field. This technique developed for the pepper vines may be tried for extending to other perennial crops for AMF inoculation. Promising AMF cultures Pi - 11, Is - 6, G. fasciculatum and antagonists Aspergillus fumigatus, A. sydowii, Trichoderma viride were further tested on eight year old established pepper vines following ‘carrier plant’ based AMF inoculation and cowdung - neem cake based antagonist inoculation. The treatment Pi - 11 x A. Sydowii was most effective with no symptom development, followed by Is- 6 x T. Viride or A. sydowii with disease score of 2.0 as against 7.0 recorded for control. The disease score for bordeaux mixture and copper oxychloride application was 3.5 and 3 respectively. Neem cake-cowdung food base was highly favourable for multiplication and activity of fungal antagonists. The amino acids, total sugar and reducing sugar and total phenols and orthodihydroxy phenol content and activity of cellulose and chitinase were influenced by AMF colonization particularly by Is - 6 and Pi - 11. The positive change could be related with the relative disease tolerance recorded for various AMF isolates. The development of native AMF and antagonists through extensive testing in the green house and field and also the technology of AMF inoculation for established pepper vines are the first record of work.ThesisItem Open Access Effectiveness of soil solarization for the control of soft rot disease in ginger(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1996) Vilasini, T N; KAU; Peethambran, C KThe effectiveness of soil solarisation for the control of soft rot disease in ginger was studied at the College of Horticulture, Vellanikkara, Thrissur during March 1992 to December 1993. The beds were inoculated with Pythium aphanidermatum, five days before the solarisation. Transparent, 150 guage polyethylene sheets were used for solarizing the beds. Maximum soil temperatures recorded were 63.00, 59.00 and 46.50 at 5, 10 and 15 cm depths in solarized soil, while, that in non-solarized soils were 49.50, 43.00 and 40.00C, respectively, at 5,10 and 15 cm depths. Temperature in the solarized soil at 5 cm depth was above 50.00 C for the entire solarisation period and above 55.00 C for 38 days, while, at 10 cm depth the temperature was above 50.00 C for 35 days and above 55.00 for five days. The soil temperature at 15 cm depth never reached 50.00 C during the solarisation period. Based on the soil and air temperature recorded, two simple regression equations at 5 and 10 cm depths, one simple equation at 15 cm depth and one multiple regression equation at 10 cm depth were developed for predicting soil temperature under polyethylene mulch. Rate of germination in ginger was enhanced by solarisation. Significant effect of solarisation was observed in controlling the pre and post-emergence rotting in ginger. Increasing the period of solarisation from 30 to 45 days did not result in a corresponding reduction in the pre-emergence rotting. Trichoderma incorporated neem cake amended 30 day solarized treatment was highly effective and recorded cent percent control of the soft rot disease, while, maximum disease incidence (90.67%) was in Trichoderma incorporated neem leaves amended 45 days solarized plots. Reduction in Pythium population ranging from 79.49 to 99.1 per cent was observed in solarized plots immediately after the removal of polyethylene sheets. Solarization reduced the total fungal, bacterial, actinomycetal and Pseudomonas sp. population in the field. Plants grown in solarized plots showed better colonization of VAM and Azospirillum. Significant reduction in the nematode population was recorded by solarisation. Solarization had a profound suppressive effect on the weed population and it lasted till harvest. Solarization effect was more pronounced in dicots. Eventhough, solarisation substantially reduced weed population, its effect was less in the edges. Bulbostylis barbata, Cynodon dactylon and Cyperus rotundus survived the solarisation effect. Increased growth response of ginger plants was observed as a result of solarization. Growth parameters like height, number of leaves/plant, number of tillers, number of roots, leaf length, leaf breadth, fresh weight of shoots and rhizomes were influenced by solarisation. Significant increase in the yield was obtained through solarisation. Trichoderma incorporated and neem cake amended 30 days solarized treatment gave the maximum yield/plant (623.23 g) and also per plot yield (10159.57 g), which was 5361 per cent more than that of control. Availability of nitrogen, phosphorus and potassium was improved by solarisation. The initial cost of solarization is comparatively high, an amount of Rs. 52,500/- is required for solarizing one hectare of ginger field. An additional profit generated from this technique was Rs. 40,136/ha for 30 days solarisation.ThesisItem Open Access Distribution of species of phytophthora affecting coconut and pepper in Kerala(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Veena, S S; KAU; Peethambaran, C KThe present investigation was undertaken to correctly identify the species of Phytophthora causing bud rot of coconut and foot rot of pepper in Kerala and to find out their comparative role in causing diseases on coconut and pepper. The study also aimed at isolation of viable antagonistic agents against the pathogen, so as to utilize them in future for biological control. The study was conducted during 1992-96 at College of Agriculture, Vellayani and Indian Institute of Spices Research, Kozhikode. Detailed symptomatology of both the diseases at different locations were studied. Periodic collections were made from diseased coconut and pepper from seven districts of Kerala. The morphological characters of the isolates were studied in detail. The length, breadth, L/B ratio, pedicel length and caducity of sporangia of coconut isolates were smaller than pepper isolates. The sporangial shapes differed considerably between and among the isolates. All the isolates except those collected from Kannur and Kasaragod districts (C7 - C16), produced abundant number of sporangia on carrot agar. Phytophthora are either heterothallic or homothallic. Generally P. palmivora and P. capsici are heterothallic. But ten coconut isolates obtained from Kannur and Kasaragodu districts produced abundant number of sexual structures on carrot agar, indicating their homothallic nature and this is the first report of homothallic Phytophthora causing bud rot of coconut in Kerala. All other 52 isolates were mated with known A1 and A2 mating type and all the coconut isolates produced oospores with A1 and all the pepper isolates produced oospores when mated with A2. Zoospore production was induced from sporangia using cold treatment. The number of zoospores in sporangia ranged from 6-15 in number. Chlamydlospore production was a rare phenomenon in pepper isolates while all the coconut isolates and five pepper isolates produced chlamydospores. All the isolates were inoculated into pepper seedlings, coconut leaves, tender coconut and coconut seedlings and the time required for infection, variation in symptom expression by different isolates etc. were studied. All the sixteen coconut isolates produced foot rot in pepper. Fourty six isolates of pepper produced lesions on coconut leaves and nut rot in tender coconut, while, only six isolates of pepper produced bud rot in coconut plants. The cross infectivity of pepper isolates needed further confirmation to prove the point beyond doubt. Eight cultivated plants, 9 ornamental plants and 12 weed plants were tested for the host range of coconut and pepper isolates. Many plants belonged to the above three groups took infection successfully. The microorganisms found associated with healthy and diseased pepper and coconut plantations and microorganisms from soils of pepper and coconut gardens of different parts of Kerala were isolated. Out of more than 200 microorganisms, only 28 fungi inhibited the growth of Phytophthora in vitro. On pepper plant, 12 isolates had inhibitory action. Three organisms, viz., Verticillium chlamydosporium, Aspergillus terreus and Chaetomium sp checked the pathogen completely even after seven days of spraying with the organisms.ThesisItem Open 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, MIntensive 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.ThesisItem Open 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, PManagement 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.ThesisItem Open Access Development of acid tolerant strains of Bradyrhizobium sp. suitable for certain pulse crops of Kerala(Department of Plant Pathology, College of Agriculture, Vellayani, 1998) Meena Kumari, K S; KAU; Sasikumar NairThe present investigation on "Development of acid tolerant strains of Bradyrhizobium sp. suitable for certain pulse crops of Kerala" was conducted at College of Agriculture, Vellayani, Trivandrum during 1993-96. The initial isolation of acid tolerant strains of Bradyrhizobium suitable for cowpea, blackgram and green gram was done from seven different locations in Kerala. These locations were broadly grouped into category A and B. The root nodulation and plant dry weight were uniformly higher in category A locations compared to category B locations in all the three crops. In all, 43 native isolates of Bradyrhizobium were obtained including 17 from cowpea, 13 each from blackgram and greengram. The native isolates of Bradyrhizobium obtained were screened as per the Bureau of Indian Standard specification. The screening trial was done both under unamended and amended soil conditions. Thus in unamended soil, the isolates KA-G- C-4, VE-G-B-2 and PA-G-G-5 for cowpea, blackgram and green gram respectively were selected based on plant dry weight and in amended soil, the isolates KA-F-C-7, KA-F-B-6 and PI-G-G-8 for cowpea, blackgram and greengram respectively were selected for further studies. The colony characteristics of the selected isolates were typical of Bradyrhizobium forming white translucent glistening and elevated colonies with entire margin on YEMA with congored. All •the six isolates were gram negative and fast growers attaining satisfactory growth on YEMA within three days. The carbohydrate utilization pattern showed that arabinose, a pentose sugar was the most preferred carbon source for the native isolates. At the sametime, the growth of - the exotic isolates were maximum in glucose. The ability to tolerate low levels of acidic pH upto 4.5 was more for the native isolates. The growth of both these isolates gradually improved and attained a peak level at pH 7.5. The in vitro tolerance to Fe and Al were almost identical for both the native and exotic isolates. In general, the growth was progressively inhibited with an increase in the concentration of these elements from 50 to 250 ppm. The antibiotic resistant markers for ampicillin, streptomycin and kanamycin were same for both the native and exotic isolates. The growth of these isolates were not inhibited at concentrations upto 1000 ppm of ampicillin, 250 ppm of streptomycin and 50 ppm of kanamycin. In the serological characterisation it was observed that one of the heterologous antigens (PI-G-G-8) for green gram showed positive agglutination with that of the cowpea isolate, KA-F-C-7. The effect of application of FYM, liming or pelleting on root nodulation and plant growth characters in cowpea, blackgram and greengram was studied. Significant increases in nodule number, nodule dry weight and plant dry weight were obtained in the treatment combination of Bradyrhizobium inoculation along with FYM and lime application in all the three crops. An almost similar result was also obtained when liming was substituted with calcium carbonate pelleting. The efficacy of the selected isolates of cowpea, blackgram and green gram were tested under field conditions at two locations namely College of Agriculture, Vellayani and Rice Research Station, Kayamkulam during identical cropping season for two years. The seed treatment effects of the two selected Bradyrhizobium isolates for cowpea (KA-G-C-4 and KA-F-C-7), blackgram (VE-G-B-2 and KA-F-B-6), greengram (PA-G-G-5 and PI-G-G-8.) were evaluated with and without POP recommendations along with appropriate cont~ol treatments. In general, the root nodulation, plant growth and yield were significantly improved in all the three crops where Bradyrhizobium inoculation was practised along with the POP recommendation for each crop. Thus at Vellayani, the nodule number, nodule dry weight, leaf area, plant dry weight and yield in cowpea were maximum in the treatment combination of POP+KA-F-C-7. A similar response was also obtained with POP+KA- G-C-4 treatment. At Rice Research Station, Kayamkulam also, the yield increase was maximum in the treatment combinations of POP+KA- F-C-7 and POP+KA-G-C-4. In blackgram and greengram also the treatment effects were more or less similar to that of cowpea. In the last part of the present investigation, the influence of the POP recommendations on plant and soil nutrient status was studied. The nitrogen content of plants was significantly higher in . Bradyrhizobium inoculated plants in cowpea and blackgram at both the locations. In greengram, at Vellayani there were no significant differences between treatments in the NPK content of plants. At Rice Research Station, Kayamkulam, also significant increases in nitrogen content of plants were obtained due to Bradyrhizobium inoculation. Unlike the nitrogen content a uniform treatment effect was not observed in the P and K content of plants. In the studies on soil nutrient status, it was observed that in general the availability of P, K, Ca and Mg were increased in the treatment combinations where POP recommendation was practised along with Bradyrhizobium inoculation. However, there was no significant difference between treatments in soil pH, organic carbon, Fe and Al content of different soil samples.ThesisItem Open Access Purification and serology of banana bunchy top virus(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1998) Estelitta, S; KAU; Sukumara Varma, ABanana is one of the major fruit crop in Kerala and is often affected by the bunchytop disease caused by banana bunchytop virus. The disease is easily spread through infected suckers, which are used as the planting materials. Secondary spread is also seen through banana aphid, Pentalonia nigronervosa. Though field level quarantine measures may check the spread of the disease, rapid and convenient methods for the detection and identification of the virus in the suckers as well as in micropropagated plants have not been developed. In this background a study was designed and carried out to purify the BBTV, to produce antisera for developing a serological technique for the pre-symptomatic detection of virus in the planting materials of banana. Studies were also conducted to identify the type of nucleic acid of the virus and its morphology by direct electron microscopy. The study revealed that the disease incidence was maximum during August-November. The virus was not mechanically transmitted and tissue culture plants were the most susceptible planting materials for aphid transmission. Basic studies of virus-vector relationship were also conducted and the adult aphids were found to be effective vectors. In purification studies, among the different portions of banana plants used, the midribs of younger leaves yielded high concentration of the virus. Tissue culture plants yielded more virus concentration than other planting materials. Electron microscopy of the purified BBTV preparation revealed isometric particles of 18-22 nm size. Nucleic acids extracted from both healthy and infected samples were compared. The bands obtained were sensitive to DNase 1 and SI nuclease but not to RNase A, confirming the nucleic acid BBTV as ssDNA. SDS-PAGE analysis of BBTV coat protein revealed that it contained a major protein component of Mr 21000 with Rf value between that of β lactoglobulin (Mr 18400) and α chymotrypsinogen (Mr 25700). Antiserum of BBTV was produced in the rabbit and used for detection of virus specific antigens in different parts of the plant (midrib, petiole, leafsheath and rhizome) by chloroplast agglutination, agar gel diffusion, tube precipitation and ELISA. Among these methods ELISA was found to be highly sensitive for identification of the virus.ThesisItem Open Access Interaction between VA mycorrhiza and bradyrhizobium in cowpea(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1999) Beena, S; KAU; Rajendran Pillai, M VAn investigation . I. on Interaction between VA mycorrhiza and Bradyrhizobium in cowpea was carried out at the College of Horticulture, Vellanikkara during the period 1994-97. The main objectives of the study were to explore the beneficial effects of dual. inoculation of VA mycorrhiza and Bradyrhizobium in enhancing the uptake of nitrogen and phosphorus and to evolve specific recommendation on the use of these inoculants together in reducing the use of nitrogenous and phosphatic fertilizers. The results of this investigation revealed the following conclusions. The survey on the natural occurrence of VAM in cowpea showed a fairly good VAM colonisation in all the plant samples collected from the five locations. VAM colonisation was found more in lateral roots than in tap root. The VAM colonisation and spore count were more during rainy season compared to summer. The predominant spores present in all the survey locations were identical to that of Glomus sp. After the screening of V AM, the local isolate from farmer's field at Nadathara was selected for further studies based on its performance. Observation of cowpea plants at 10 days after sowing showed the presence of nodules and VAM colonisation in the roots of inoculated plants. Both the nodulation and VAM colonisation were found to reach a peak at 40th day after sowing. Dual inoculation was found to have a synergistic effect in nodulation and VAM colonisation. Light microscopy of VAM infected roots showed both 'H' and 'V' shaped branching of hyphae, arbuscules and vesicles of VAM fungus. : j Electron microscopy revealed two types of fungal penetrations into the roots. It also showed the terminal attachment of oval shaped vesicles and highly branched arbuscules with short twisted branches with bulged tips in the root cortex. Electron microscopic study of nodules revealed that the nodule surface was free of V AM hypha, but the inner tissues of nodules had the hyphal presence. The pot culture experiment recorded synergistic effect in dual inoculation with VAM and Bradyrhizobium in enhancing five biometric characters, viz. number of leaves, fresh and dry weights of plant, number of nodules and fresh weight of nodules. : i Among the inoculant-fertilizer interactions, eventhough all observations except fresh weight of plant recorded non significance between treatments, those in I which VAM was a partner, recorded the maximum values for all the observations except root length. Dual inoculation with VAM and Bradyrhizobium improved the level of six nutrients, viz. nitrogen, phosphorus, magnesium, calcium, zinc and manganese in cowpea. The result of interaction with microsymbionts and fertilizer levels recorded inconsistent values. Treatment with VAM + B + 1/4 N + P + K recorded maximum nitrogen, VAM + ½ N + P + K and N + ½ P + K alone recorded maximum phosphorus and dual inoculation along with ½ N+P+K recorded maximum magnesium and calcium content of plant. Inoculation of VAM + Bradyrhizobium along with ½ N + P + K ranked top III increasing the soil nitrogen to the maximum. There were no significant differences among treatments and its combinations in influencing the phosphorus J status of soil. The application of either VAM or Bradyrhizobium or its combinations reduced the potassium content of soil. The results of the field experiment revealed that the treatment T 10 (VAM+B+ ½ N+ ½ P+K) out perform other treatments in five characters, viz. plant height, fresh and dry weights of plant, nodule number and fresh weight of nodules at 50 per cent flowering. At harvest this treatment recorded the maximum values in fresh and dry weights of plant, nodule number and fresh and dry weights of nodules. Treatment T 10 increased nodulation to 180 per cent over Bradyrhizobium inoculation alone. Bradyrhizobium+ ½ N+P+K was found to be the best treatment in improving the nitrogen content of plant, whereas VAM+B+ ½ N+ ½ P+K was the best for improving the phosphorus, potassium, magnesium and zinc content of plant. Another finding was that the different treatments involving microsymbionts and different fertilizer doses were not able to influence the nitrogen, phosphorus and potassium content of soil to a significant level. The percentage of V AM colonisation was not significantly affected by dual inoculation and also by the application of different levels of fertilizers. Dual inoculation had no influence on the spore count of V AM. 'The high level of phosphorus in soil had some negative influence on the spore count. Treatment B+ ½ N+ P+K was the best in increasing the yield to the maximum, which was on par with T 10. The overall results showed that T10 (VAM+B+ ½ N+ ½ P+K) where dual inoculation was done and nitrogen and phosphorus fertilizers were reduced to half of the recommended dose, was the best treatment in improving the biometric characters and nutrient status and yield of cowpea. Thus a judicious treatment would be VAM+B+ ½ N+ ½ P+K to get the best performance of cowpea. The percentage of V AM colonisation recorded a significant positive correlation with nodule number and fresh and dry weights of nodule. There was a significant positive correlation between nodule number and plant dry weight and also with yield. The percentage of VAM colonisation had a significant positive correlation with calcium content and significant negative correlation with manganese content of plant.
