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ThesisItem Open Access Anthracnose disease of vegetable cowpea [Vigna unguiculata subsp. sesquipedalis (L.) verdcourt](Department of Plant Pathology, College of Horticulture, Vellanikkara, 1999) Praveen Kumar, M; KAU; Sally Mathew, KA study on vanous aspects of anthracnose disease of cowpea was conducted at College of Horticulture, Vellanikkara during 1997-98. Etiological studies revealed Colletotrichum lindemuthianum (Sacc. and Magn.) Br. and Cav. as the main pathogen causing anthracnose disease in Kerala and the pathogen was found to be seed borne. Among the 50 genotypes tested, Kanakamony was found immune to the disease and seven genotypes were highly resistant to the disease. In ( disease management studies, all fungicides, botanicals and antagonist Trichoderma viride were equally effective under in vitro and field conditions. As far as disease control, yield and C:B ratio were concerned, mancozeb was found to be the best treatment. Summer season was found to be the best season for cowpea cultivation in areas where anthracnose is a problem. In crop loss assessment, significant difference was noticed between carbendazim treated and untreated plots in case of disease infection and yield, and yield loss of 53.85 per cent was recorded under natural condition due to this-disease.ThesisItem Open Access Biocontrol of rhizome rot of ginger using selected antagonists(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1999) Julie George, K; KAU; Sukumaravarma, MRhizome rot of ginger cas used by Pythium aphantdermatum (Edson) Fitzpatrick is one of the most destructive diseases of ginger in Kerala. The pathogen was isolated and its pathogenecity was established by Koch's postulates in ginger variety Rio-de-Jenerio. Among the various food bases evaluated, for the mass multiplication of selected antagonists, rice hull was found to be significantly superior to all others to obtain maximum growth for Trichoderma viride and Aspergillus flavus. For Aspergillus niger, rice bran was found to be significantly superior. The results on the effect of various treatments on germination showed that there was no significant difference among the treatments. The effect of antagonists on the pre- emergence rotting and post-emergence rotting (rhizome rot) were studied. In plots where antagonists (T viride, Aflavus or A. niger) or fungicides (mancozeb or copper oxychloride) were applied either as seed treatment or as soil incorporation at the time of planting, the pre-emergence rotting was not observed. The plot in which the antagonists T. vtride, A. mger and At flavus were applied in combination at 60 and 120 OAP, recorded the minimum rhizome rot incidence compared to other treatments. The plots in which the antagonists were applied twice, i.e., 60 and 120 OAP, the rhizome rot incidence was minimum compared to the plots with only one time application of antagonists. The maximum population of the pathogen P. aphanidermatum. was observed in plot where A. flavus was applied in combination with mancozeb. The multiplication of selected antagonists, 7: viride, A. flavus and A. niger in soil was found out by estimating their population at different stages. The population of T. virtde was maximum in plots where it was applied in combination with mancozeb in most of the period. The soil application of the combination of antagonists T. viride, A. flavus and A. niger did not affect the multiplication of anyone of them in soil. In general, soil incorporation of antagonists was found to helping in their mulitplication profusely compared to the seed treatment. The incorporation of the antagonists A. flavus and A. niger to the plots, twice was found to be superior than applying them only once, for getting maximum multiplication of propagules in soil. The result on the compatibility of antagonist with fungicide in field condition revealed that the antagonist T viride was quite compatible with mancozeb whereas A. flavus and A. niger were compatible with both fungicides tested (mancozeb and copper oxychloride). The treatments which was found to be superior in minimising the incidence of rhizome rot of ginger viz., T 16 (soil incorporation of T vir/de, A. niger at 60 and 120 DAP) and TI9 (soil incorporation of I: viride, A. niger and A. flavus) also recorded the maximum yield of ginger.ThesisItem Open Access Associative effect of azospirillum and bradyrhizobium on nodulation and growth of cowpea (viqna unquiculata (l.) walp,(Department of Plant Pathology College of Horticulture Vellanikkara, 1992) Sunitha, Menon S.; KAU; Rajendran, Pillai M .VThesisItem Open Access Leaf blight of banana and its control(Department of Plant Pathology, College of Agriculture, Vellayani, 1993) Saj, KV; KAU; Sulochana, K KSurvey conducted to study the fungal pathogens causing leaf blight disease in banana in the three agricultural subdivisions of Thiruvananthapuram district, yielded seven fungal pathogens viz., colletotrichum musae, Curvularia sp, Guignardia musae, khuskia oryzae, Nodulisporium gregarium, Pestalotiopsis versicolor and Phaeoseptoria sp. Among these, Curvularia sp, Khuskia oryzae and Nodulisporium gregarium are new reports. Morphological characters and pathogenicity tests of all the seven isolated cultures were studied and described. Detailed studies were conducted on five fungal pathogens viz., C. musae, G. musae, K. oryzae, N. gregarium and Phaeoseptoria sp., since severe infections could be noticed by these fungi. Studies conducted on the growth and sporulation of pathogens on different, media indicated that Richard’s medium was the best for C. musae and G. musae, potato dextrose medium for K. oryzae and Phaeoseptoria sp. In the case of N. gregarium, potato dextrose agar and Czapek (Dox) broth were found to be the best solid and liquid media respectively for its growth. Best growth of C. musae, N. gregarium and Phaeoseptoria sp was obtained with maltose as the carbon source, whereas G. musae and K. oryzae utilized maximum starch and sucrose for their growth. Maximum mycelial weight of C. musae was obtained with sodium nitrate as nitrogen source, G. musae and K. oryzae with potassium nitrate, N. gregarium with glutamine and Phaeoseptoria sp. with asparagine. Potato dextrose broth and Richard’s solution were found to be best media for the toxin production by C. musae K. oryzae , G. musae and Phaeoseptoria sp. produced maximum toxin in Richard’s solution and N. gregarium in potato dextrose broth. Host range studies of the pathogen (s) conducted indicated that they can infect a number of economically important plants like, clove, cocoa, colocasia, nutmeg and tapioca, but none of the pathogens could infect clerodendron. Dithane M-45, calixin and Bavistin were able to inhibit the growth of the leaf blighting pathogens under laboratory conditions and under field conditions Dithane M-45 (0.2%) was found to be the best. Varietal screening trials showed that variety Rasakadali was moderately resistant/tolerant among the four popular varieties screened, whereas Nendran was the most susceptible variety.ThesisItem Open Access Vascular streak dieback of cocoa and its management(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1996) Ajay Kumar, K M; KAU; Koshy, AbrahamVascular streak dieback (VSD) is a destructive disease of cocoa. Corticium culture medium, Water agar, Potato dextrose agar gave promising results in isolation of the pathogen. Petiole and midrib gave maximum success in isolation. Potato dextrose agar and Corticium culture media supported the growth of the fungus. Fusarium sp. And Colletotrichum gloeosporioides were the major contaminants interfering in the isolation of VSD. The morphological characters of the pathogen were studied from the sporophores occurring on naturally infected cocoa plants. Based on these characters, the pathogen causing VSD was identified as Oncobasidium theobromae Talbot and Keane. The disease produced various typical symptoms on leaves and stems of infected plants like pale green colour of leaves and subsequent yellowing with green islets, defoliation, brown marks on the scars of fallen leaves, axillary bud growth of the infected stem, rusty discolouration of cambium, vascular streak, whitish sporophores on the leaf scar of fallen infected leaves and finally the death of the infected twig. Histopathological studies showed the presence of fungal mycelium in the xylem vessels. Transmission studies by grafting and budding revealed no establishment of buds or grafts. But there was vascular streaking. No seed transmission was observed. In general Kitazin and Bavistin as a seed treatment had an effect on the height of plant and leaf production. Evaluation of cocoa types planted at three seed gradens indicated that some of them possess resistance/tolerance against VSD. Variation in disease incidence and intensity of VSD was noted in germplasm VI. Calixin spraying had an effect in preventing the incidence of the disease in seedlings.ThesisItem Open Access Biocontrol of water hyacinth using fungal pathogens(Department of Plant Pathology, College of Agriculture, Vellayani, 1997) Susha Thara, S; KAU; Naseema, ADetailed study was conducted on the host range of the already identified fungal pathogens of water hyacinth viz. Colletotrichum gloeosporioides, Fusarium eguiseti and F.pallidoroseum on thirty cultivated plants including vegetables, pulses and oil seeds, field crops, fruits and forest crops and ornamental plants and forty one common weed plants which are seen in and around water ways infested with water hyacinth. It was observed that C. gloeosporioides could infect amaranthus, bhindi, chilli, Euphorbia hirta, Hydrocotyl asiatica and Phyllanthus niruri. Of the thirty cultivated plants and forty one weed plants tested F. eguiseti was seen to be pathogenic to amaranthus, Amaranthus viridis, Commelina . bengalensis, C. jacobi and Monochoria vaginalis. F. pallidoroseum could produce symptoms on napier grass, Axonopus sp., boerhaavia diffusa, C.benghalensis, C.jacobi, Echinochloa colonum, Euphorbia hirta, Justicia diffusa, J.prostrata, M.vaginalis and Oldenlandia umbrellata and Scorpia dulcis. For the effective destruction of the weed, lxl011 spores per ml concentration of Q. gloeosporioides, E. eguiseti and F. pallidoroseum were found to be more effective than lxl09 and lxl010 spores per ml concentration. Cell free metabolites of the pathogenic fungi were found to produce symptoms on water hyacinth plant. Metabolite produced by E. pallidoroseum caused considerable damage than by E.equiseti and C. gloeosporioides. When pathogens were applied singly and in combination on water hyacinth it was observed that the combined application of F. pallidoroseum and F. equiseti followed by F. pallidoroseum alone gave maximum intensity of infection. Eventhough C. gloeospoirioides gave least intensity of infection it can be used as a co-pathogen with E. eguiseti. Metabolite of the pathogens individually and in combination when applied on healthy water hyacinth plants, maximum damage was caused by F.pallidoroseum alone and the combination of metabolite of three fungi viz. C. gloeosporioides,F equiseti and F. pallidoroseum. Least damage was caused by metabolite of C. gloeosporioides. An experiment was conducted to find out suitable carrier materials for the mass multiplication and storage of pathogen. It was observed that for C. gloeosporioides maximum sporulation was in water hyacinth leaf followed by guinea grass straw and rice bran. But the spore viability was maximum for rice straw, and on coir pith. Maximum infection was caused by fungus grown on guinea grass straw and rice straw. In the case of E. equiseti spore counts was higher in guinea grass straw followed by coir pith. The spore germination was maximum in rice bran and coir pith. Maximum infection was produced by the fungi on guinea grass straw, coir pith and waterhyacinth leaf. E. pallidoroseum produce maximum number of spores on rice bran followed by guinea grass straw. It was observed that the germination percentage of spores were maximum on coir pith. Out of the six carrier materials used the fungus produced maximum infection when grown on rice bran and guinea grass straw. In the study for testing the storage life of metabolities, it was observed that the efficiency to produce symptom was reduced on storage in the case of C. gloeosporioides and E. pallidoroseum whereas for E. eguiseti on storage the effeciency of the metabolite to cause damage increased. Metabolite stored on refrigerated condition performed poorly for all the three fungi. Different methods of application of the three fungi were tried. Of the five treatments, placement of bits and dusting the inoculum along with the carrier materials produced maximum infection. In the experiment conducted to characterize the toxin presented in the cell free metabolite of pathogenic fungi, observed the presence of Fusaric acid in the metabolite of Fusarium spp.ThesisItem Open Access Combatibility of certain fungicides and insecticides used for the control of major diseases and insect pests infesting the rice crop(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1992) Kalpana, T A; KAU; Sally Mathew, KThe efficacy of four fungicides and four insecticides alone and in combination was studied at different concentrations recommended, three-fourth and half the recommended concentrations against two major diseases of rice namely, rice blast caused by Pyricularia oryzae Cavara and sheth blight caused by Rhizoctonia solani kahn. And two major insect-pests namely, leaffoldar Cnaphalocrocis medinalis medinalis Guen. And brown planthopper Nilaparvatha lugens stal. At tillering, panicle initiation and flowering stage of the crop. The experiment was conducted in vivo and in vitro conditions during 1989-91, at the college of Horticulture, Vellanikkara, Thrissur. In general combind application of fungicides and insecticides controlled the diseases and insect-pests more effectively than the treatments given separately. At tillering stage, a synergistic effect of fungicide was observed, when it was sprayed along with insecticides. Among different combinations tried, tridemorph (o.1 per cent) + monocrotophos (0.0375%) and carbendazim (0.075 ) + guinalphos (0.025 per cent) were the best combinations against blast and sheath blight respectively. In the case of leaffolder and brown planthopper, quinalphos was found to be the best insecticide, when used alone and also in combination with fungicides. At panicle initiation stage, combined sprays of higher concentrations of carbendazim and monocrotophos was the best combination in controlling both R. solani and N. lugeas. But ediphenphos-phosphamidon combination was found to be the superior against N. lugens. When combind spraying was given at flowering stage, captafol (0.225 per cent) + quinalphos (0.0375 per cent, and carbendazim (0.075 per cent) + monocrotophos (0.0375 per cent) were found to be the best combinations against P. oryzae and R. solani respectively. But, combination of recommended doses of quinalphos with tridemorph and ediphenphos and, phosalone with ediphenphos were the effective treatments in controlling C. medinalis and N. lugens respectively. In in vitro studies, a total inhibition of the test organisms, viz.P. oryzae and R. solani were observed in all the treatments. Whereas, in the case of C. medinalis recommended doses of quinalphos in combination with ediphenphos and carbendazim and phosalone with tridemorph recorded highest mortality; while, highest dose of quinalphos with captafol and phosalone with ediphenphos were the superior combinations against N. lugens. From the above findings it could be concluded that, the fungicides viz. ediphenphos, carbendazim, captafol and tridemorph are compatible with all the four insecticides tried viz. Phosphamidon, quinalphos, phosalone and monocrotophos in controlling the diseases, blast and sheath blight and insect pests leaffolder and brown planthopper.ThesisItem Open Access Disease resistance in the management of cowpea aphid-borne mosaic virus(Department of Plant Pathology, College of Agriculture, Vellayani, 1999) Radhika, N S; KAU; Umamaheswaran, KInvestigations were undertaken on the virus causing severe mosaic on cowpea (Vigna unguiculata (L.) Walp) in Kerala. The characteristic symptoms appeared as vein clearing, light and dark green mottling, severe mosaic, dark green vein banding, blistering, distortion and reduction in leaf size. The virus was mechanically transmitted through sap extracted in 0.01 M phosphate buffer (pH 7.0). The virus was efficiently transmitted by the aphid vector, Aphis craccivora. Seed transmission of eleven per cent was recorded in the variety Sharika. Thermal inactivation point was recorded at a range of 60 - 65° C, dilution end point at a range of 10-3 - 10-4 and longevity in vitro for four hours at room temperature (28 ± 4° C) and six hours under refrigerated condition (8° C). A. craccivora could efficiently transmit the virus with an acquisition access of ten minutes and inoculation access of one minute. Pre-acquisition starvation increased the rate of transmission while post-acquisition starvation decreased the rate. A single aphid was capable of transmitting the virus. The virus causing severe mosaic was identified as blackeye cowpea mosaic virus by ELISA. The virus could also be detected by Ouchterlony immunodiffusion test. Electron microscopic studies revealed the presence of flexuous, filamentous particles of 750 nm in length. Two varieties Co-6 and Cc-Selection were grouped as no symptom producing among 65 genotypes screened for resistance. Fifty three F2 progenies of the cross Sharika and Co-6 and twenty five F2 progenies of the cross Co-Selection and Sharika were long poded and resistant. Biochemical changes indicated a lower carbohydrate content in resistant compared to susceptible. Chlorophyll content decreased in the susceptible variety due to virus infection. Increase in protein was observed in both resistant and susceptible. The phenol content did not show variation between the varieties. Peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase activities increased in the resistant variety. Bioassay of chemicals and neem oil on local lesion host (c. amaranticolor) indicated a per cent inhibition of 68.92 by neem oil in pre-inoculation application and 65.45 per cent inhibition by manganese chloride in post-inoculation application. On cowpea plants, pre-inoculation application of neem oil (ten per cent) concentration was found to be effective in reducing the symptoms due to viral infection.ThesisItem Open Access Etiology and control of seedling blight of cocoa(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1995) Edwin Prem, E; KAU; Koshy, AbrahamThe seedling blight is a serious nursery disease of cocoa. The fungus causing seedling blight of cocoa was isolated and Koch’s postulates were established. On carrot agar medium, the fungus produced sparse, striate growth. The mature sporangia were near spherical to ovoid with round base, papillate, caduceus with an average L/B ratio of 1.74. Sporangia were borne terminally in a sympodial fashion. It had a short and thick stalk with an average length of 4.1µm. Based on these characters, the pathogen causing seedling blight of cocoa was identified as Phytophthora palmivora (Butler) Butler. For maximum growth of the fungus, oat meal and corn agar were the best. But, for maximum sporangial production, carrot agar and oat meal agar were good. Among the liquid media, oat meal and corn meal broth supported good growth of the fungus. The disease produced various type of symptoms on leaves and stem of seedlings and budded plants like water soaking, leaf blight, defoliation, black discolouration, cotyledonary infection, wilting and die back. Stem of budded plants were more prone to infection than that of seedlings. The seedlings blight pathogen infected plants such as Piper nigrum L., Cocos nucifera L., Hevea brasiliensis L., Bougainvillea sp. And Colocasia esculenta L. but did not infect Areca catechu L., Piper betle L. and Piper longum L. on artificial inoculation. The youngest seedlings of age group less than 18 days after germination were more vulnerable to infection. Similarly, the youngest budded plants of age group 45 days after budding showed maximum infection. Among the 62 cocoa types screened for host resistance the cocoa types GIV-36.6 (local), GVI-23 (P9 x P4), GIV-4.6 (local) and S-45.5 (local) showed minimum percentage of mortality. Among the different fungicides/antibiotics screened in in vitro, Fytolan, Captaf, Bordeaux mixture, Akomin and Ridomil at all concentrations and 0.3 per cent Foltaf and, Chloramphenicol and Terramycin each at 400 and 500 ppm completely inhibited the growth of the fungus. Indofil-M.45, Aureofungin and Amoxycillin exhibited less inhibitory effect. Foltaf, Fytolan and Akomin each at 0.3 per cent concentration showed better effect in cheching the lesion development on detached cocoa leaves. Result of the different in vivo control experiment indicated that, the fungicides like Akomin, Foltaf, Fytolan and Bordeaux mixture had promising effect in checking the incidence and severity of the disease.
