Loading...
Theses
Browse
14 results
Search Results
ThesisItem Open Access Study of bacterial leaf spot of betel vine- biochemical changes and control(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Koshi, Abraham; KAU; James, MathewThe bacterial leaf spot is one of the most serious diseases of betel vine in Kerala. The bacterium is one of the most serious disease of betal vine. Confidering the seriouness of the disease , studies were undertaken on the different aspects of the disease and to find out a suitable control /management practice.ThesisItem Open Access Varietal screening of banana against anthracnose disease(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1984) Srinagesh, K L; KAU; Jose, P CLaboratory and field studies of the varietal screening of banana against anthracnose disease were conducted at the college of Horticulture. Vellanikkara and at Banana Research Station, Kannara respectively during 1981-1983. In the field the infection started at the distal end of the banana fruit and in course of time the infected fruit became blackened, shriveled and mummified. After Harvest, the symptoms appeared as small brown spots which enlarged quickly and coalesced forming larger patches. The affected areas were covered with orange to salmon pink coloured conidial masses. The detailed morphological studies of the fungus proved that the anthraemose disease of banana is caused by colletrichum cloeosporioides cooko and massee, the imperfect stage of glomerella cinoulata spauld and shrenk. Twenty five varieties of banana fruit were screened in vitro at different stages of development against anthracnose disease. The varieties showed different degrees of susceptibility at various developmental stages of the fruit. The pooled analysis of the data showed that the variety nendra padaththi followed by palayankodan, jurmani kunthali, boodida bontha bathes, peyan, kanchikela, pisang mas and kapok were found to be highly resistant. The varieties Zanzibar, adakka kunnan, klue teparod, chinia, nendran, venneettu mannan, koduppilla kunnan, hybrid sawai, poocha kunnan, red banana and boodles altafort were found to be resistant to the disease. The variety robusta was found to be susceptible. The varieties njalipoovan, pisang lilin, dwarf Cavendish, matti and gros Michel were found to be highly susceptible. The major chemical constituents of banana fruit viz. reducing sugars, total sugars starch, crude fibre, crude protein and tannin at different developmental stages of twenty five varieties were analysed. The reducing sugars and total sugar were found to increase steadily from immediately after female phase to ripened stage in all the varieties. The starch and crude fibre contents, though increased steadily upto full maturity. Declined sharply at the ripening stage. The crude protein and tannin contents were maximum at immediately after female phase but steadily decreased and were minimum at ripening phase. There was a significant positive correlation between reducing sugars, total sugars and per cent disease intensity at three fourth maturity. High sugars were responsible for susceptibility to the disease. A significant negative correlation was obtained between crude protein and per cent disease intensity at half maturity. A significant negative correlation was also obtained between tannin and per cent disease intensity at one fourth and half maturity stages. High crude protein and high tannin contents were responsible for resistance to the disease.ThesisItem Open Access Ochratoxicosis in the goat(Department of Pathology, College of Veterinary and Animal Sciences, Mannuthy, 1983) Maryamma, K I; KAU; Krishnan Nair, MAn experimental study was carried out to delineate the pathological effects of ochratoxin in goats. A comparative assessment of ochratoxin production by A. ochraceus and A. sulphureus on what and rice under static and shake cultures was also made. A. ochraceus was found to be a better toxin producing strain in both substrates under static and shake cultures systems and wheat was a better substrate than rice. Toxicity studies were conducted in Sannen – Malabari cross-bred goats of 1 to 3 months age. Purified ochratoxin produced in the laboratory was administered by oral, intra-peritoneal and intravenous routes. The different dose levels adopted were 2.5 mg/kg body weight, 1 mg/kg body weight and 0.5 mg/kg body weight. The synergistic effect of ochratoxin and aflatoxin in goats was studied by adminstering the crystalline toxins simultaneously (Makor Chemicals, Israel) by itraperitoneal route. The parameters of study were: clinical signs, haematological and biochemical alterations, pathological changes in urine, and macroscopic, microscopic and ultra-structural alterations in organs. Varying degree of clinocopathological changes were noticed in the test animals. The animals became weak and listless and in general there was reduction of total erythrocyte count, PCV, haemoglobin and lymphocyte count. Serum protein level was lowered while BUN and creatinine and blood coagulation time were high. There was rise in ALP, SGOT and SGPT in some of the test animals. The changes and degree of variation depended on the dose, total quantity and rate of administration of the toxin and duration of the experiment. More severe alterations were noticed when ochratoxin and aflatoxin were administered simultaneously. Important changes in the urine were lowering of pH, albuminurea and presence of epithelial cells and casts. Pathological changes varied in severity in different organs and were observed in the following descending order: kidney, liver, intestines, stomach, lymph nodes, spleen, thymus, genital organs, endocrines. In the kidneys, the order of intensity of pathological alterations was: proximal convoluted tubules, Henle’s loop, distal convoluted tubule, glomeruli, collecting tubules. Retrogressive changes of different degree and necrosis of the lining epithelial cells of tubules and endothelium and epithelium of glomeruli were the important lesions. Changes in glomeruli and Bowman’s capsule noticed in the higher dose group included shrinkage of glomeruli and presence of proteinaceous material in the capsular space. Eosinophilic granular casts and PAS positive bodies were present in the lumen of tubules. The necrobiotic renal changes were more intense when orchatoxin and aflatoxin were administered simultaneously. Hepatic lesions were mainly fatty infiltration, necrosis of hepatocytes and haemorrhage. The changes were most severe in combined toxicity. Mallory bodies and mild biliary hyperplasia were noticed in a few sections. Necrosis and subsequent depletion of lymphocytes wee the lesions in lymph nodes, spleen and thymus in some test animals. Degenerative changes were also noticed in testis, ovary, pituitary, adrenals and pancreas in experimental groups. In the combined toxicity group the pathological effect was more intense. At the ultra-structural level, the hepatcytes as well as the epithelial cells in the kidney showed severe changes. The cell organelles were either completely damaged or showed partial configurational alterations. Mitochondria showed changed in the density of matrix as well as disorientation and destruction of the limiting membranes and cristae. Cytolysosomes incorporating damaged cell organelles were abundant. Disaggregation of ribosomes and fragmentation of ER were noticed. In the glomerulus, there was destruction of the basement membrane and disruption of the regular arrangement of the foot processes of podocytes. In the cytoplasm of hepatocytes, Mallory bodies and lipid droplets were present. Varying degree of nuclear changes like clumping, condensation and disappearance of chromatin and fragmentation of nucleolus and nuclear membrane were observed. Changes occurred in the tight junctions of epithelial cells of bile ducts. Pathological alterations were more pronounced when ochratoxin was administered by the pwerenteral route. Oral administration of toxin also effected structural alterations which indicated that some fraction of ochratoxin escaped degradation in the rumen. From this study it became evident that aflatoxin potentiated the effect of ochratoxin. The structural damage to the cells might be due to the inhibition of oxidative enzymes which is reflected by the extensive ultra- structural alteration observed in the mitochondria and RER. Biochemical changes like high BUN and creatinine were evidently due to necrobiotic changes in the kidney. Interference in the synthesis of proteins due to damage of hepatic cells and escape of protein molecules due to alteration in the podocyte foot processes and basement membranes may account for the reduced serum protein levels. The nature of organellar destruction and configurational changes in the cells indicate the toxic potency of the mycotoxin on the biological system.ThesisItem Open Access Studies on purple top roll (PTR) of potato in Karnataka(Department of Plant Pathology, University of Agricultural Sciences, Bangalore, 1983) Sreedharan, A; KAU; Reddy, H R1. Survey for the incidence of potato purple top roll revealed that the disease was present in Bangalore, Belgaum, Dharwad, Hassan and Kolar districts of Karnataka. The average percentage of incidence varied from 8.94 to 50.07. The survey also indicated that there was low incidence of the disease in summer and high incidence in kharif and rabi. 2. The pathogen was transmissible by wedge, side and core grafting. 3. The disease was transmitted through dodder, Cuscuta chinensis Lam. 4. The disease was not transmissible through sap and aphids Myzus persicae Sulz. And Aphis gossypil Glov. 5. The etiological agent was transmitted by the leafhopper, Orosius albicinctus Distant and not by Hishimonus phycitis Distant. 6. The vector, O. albicinctus could acquire the pathogen in two hr and inoculate to healthy plants in 30 min. The percentage of active transmission was 35 – 40 and the minimum incubation period in the plant was between 20 and 25 days. Maximum percentage of transmission was obtained on 40th day after inoculation. 7. Characteristic symptoms of the disease was inward rolling of basal parts of top leaflets, purple/pink pigmentation, smalling of leaves, excessive proliferation of axillary buds, erect appearance, production of purple coloured, aerial tubers and stunting and dwarfing of plants. 8. The etiological agent infected tomato, tree tomato, Datura stramonium and D. metel by grafting. 9. The pattern of spread of the disease in the field was from external source in the beginning and later the spread was within. 10. The vector population was correlated with the disease incidence in the field. The increase in the incidence of the disease followed the increase in the vector population. 11. The leafhopper vector, O. albicinctus Distant was high in the months from late June to December and low from January to early June. 12. The high population of leafhoppers was correlated with low temperature and high humidity and low population was correlated with high temperature and low humidity. 13. The disease appeared 40 days after planting in the field and then it gradually increased reaching the peak by 90th day. 14. The pathogen was transmitted through tubers for two successive generations but to a lower percentage in the second generation. 15. Of the 36 cultivars/varieties of potato tested under field conditions, none were found to be resistant, However, the vars. JF 542, JF 4612, JG 676, JG 900, JC 750 and JE 812 had less than five per cent infection. Kufri Chandramukhi and Kufri Jyoti were highly susceptible having 48.3 and 47.6 per cent incidence, respectively. The highest average incidence of PTR in these cultivars in farmer’s fields was 35.85 and 26.03 per cent, respectively. 16. There was considerable loss in yield in many cvs. Viz., JC 750, BS/F 100, JC 182 and EM/F 2120. 17. The weight of tubers produced by the infected plants was always less than the tubers obtained from the adjacent healthy plants. The infected plants produced more number of smaller tubers which aggregated close to the main stem attached on short stolons. 18. Complete remission was obtained at 500, 1000 and 2000 ppm, incomplete remission at 100 and 250 ppm and no remission at 50 ppm of tetracycline given alternatively for 20 days.ThesisItem Open Access Studies on the seed borne diseases of rice in Kuttanadu(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Jose Joseph; KAU; Susamma PhilipSeveral fungi were isolated from the seeds of twelve varieties/cultivars of rice collected from different localities of Kuttanadu, the major rice growing tract of Kerala. Fungi were encountered extrenally as well as internally. Among the externally seed borne fungi, Aspergillus flavus was the most common with its occurrence on nine varieties followed by Bipolaris oryzae and Curvuleria lunata. Other fungi included Rhizopus stolonifer, Chaetomium gracile, Syncephalestrum racemosum, Fusarium moniliforms, Trichoderma virde, Sarocladium oryzae. Aspergillus niger, Alternaria padwickii, Fusarium gramineazum, Piricularia oryzae, A. fumigatus, A. quadrilineatus, Nigrospora oryzae and Penicillium spp. Among the varieties Jaya was found to harbour the maximum fungal population. The germination percentage was not found to be affected due to seed inoculationwith the predominant fungi viz. A. flavus, A. padwickii, B. oryzae, C. lunata and S. oryzae.ThesisItem Open Access Epidemiology and control of sheath rot disease of rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Krishnakumaran Nair, B; KAU; Chandrasekharan Nair, MStudies on symptomatology, epidemiology and control aspects of sheath rot disease of rice caused by Serocladium oryzae Cams & Hawksworth (= Acrocylindrium oryzae Saw.) were done in detail. The disease initiated as purplish-brown oblong lesions on the sheath of the flag leaf. At maturity lesions enlarged in size with grey -white centres and often covered the entire flag leaf sheath. Panicle often did not emerge but choked inside the affected sheaf itself. Artificial inoculation studies showed that under sufficient humid conditions the pathogen took an average five to eight days for initiation and 15 to 20 days for the complete development of the disease in rice plants. The pathogen was isolated from four naturally infected rice varieties, collected from three different culture (isolates viz., S1, S2, S3, S4, S5, S6 & S7) were selected based mainly on symptomatological variations and their comperative morphological characters were studied in detail. No appreciable differences were noticed in the morphological characters between isolates.ThesisItem Open Access Strain variation in Rhizoctonia solani Kuhn [Thanatephorus cucumeris (Frank) Donk] causing sheath blight of rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Vijayan, M; KAU; Chandrasekharan Nair, NSymptoms of sheath blight disease usually develop towards the tillering stage of the rice crop. Discolouration initially appearing on the sheath at or above the water level develop into ellipsoidal lesions. The lesions are light greenish gray in colour with dark brown margin. As the disease progress the lesions coalesce and become oblong to irregular in shape. In severe condition the lesions encircle the culm and cause rotting of the sheath. The disease then spreads to the leaves and such plants are killed. Sclerotia and silvery threads of the fungal mycelium appear on the affected regions under high humid conition. The casual organism was Isolated and identified as Rhizoctonia solani Kuhn. The hyphae branched near the distal septus with a costriction at the branch base. Hyphae were multinucleate and in culture showed brown pigmentation. Nature sclerotia were subglobose with rough regular surface.ThesisItem Open Access Effect of application of plant protection chemicals on the survival of Rhizoctonia solani Kuhn(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Lulu Das; KAU; Chandrasekharan Nair, MIn Kerala, the incidence of sheath blight of rice is endemic causing great economic loss. The present investigation was undertaken to make a critical assessment of the efficacy of various palnt protection chemicals, viz., fungicides, insecticides and herbicides on the incidence and intensity of sheath blight of rice and on the survival of the pathogen. The organism was isolated from naturally infected rice fields and its pathogenicity proved. Studies on the viability of sclerotia revealed that they sclerotia remained viable upto 210 days in all the different types of soils namely sandy, clayey and loamy. The organism could survive on straw bits upto 180th ady only.ThesisItem Open Access Studies on the effect of age of plant and host nutrition on bacterial leaf blight of rice and its control(Department of Plant Pathology, College of Agriculture, Vellayani, 1985) Sreelatha, K; KAU; Sasikumar NairA study on tho effect of age of plants and host nutrition on the incidence of bacterial leaf blight of rice caused by Xanthomonas camoestris pv oryzae was conducted at the College of Agriculture, Vellayanl, Trivandrum during 1933-84. The field experiment to evaluate the comparative efficacy of different control measures of bacterial leaf blight was laid out in a farmers field at Kainakary in Kuttanad. The effect of age of plants on the incidence of bacterial leaf blight was studied using three popular varieties of rice namely T (N)l Jay a and IR-20 at four critical stages of plant growth ouch as seedling maximum tillering panicle initiation and early flowering stages. At flowering stage the onset of disease symptoms was noticed only on the seventh day while it was observed on the fifth day in all the three varieties for the remaining three stages of plant growth* T(N)1 was found to be the most susceptible variety to bacterial leaf blight followed by Jaya and IR-2Q. Among the four stages maximum tillering stage was the most susceptible stage to bacterial leaf blight. The study on the effect of host nutrition on the incidence of bacterial leaf blight indicated that when higher doses of nitrogen were added, the onset of symptoms were earlier on the fifth day after inoculation with the pathogen while at lower levels# the symptom appeared only on the seventh day. The main effect of nitrogen and potassium on the disease intensity was significant while the effect of phosphorus and minor element was insignificant. The application of nitrogen in general increased the disease intensity while the application of potassium decreased toe same. But at higher levels of nitrogen a similar positive effect of potassium was not observed
