Browsing by Author "Karunakaran, P"

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Leaf blight of Dioscorea Esculenta (Lourd.) Berk.
(Kerala Agricultural University, 1980) Chandrasekharan Nair, M; Karunakaran, P; Gokulapalan, C
Leaf spot disease of Dioscorea alata Linn.
(Kerala Agricultural University, 1980) Abraham, M; Karunakaran, P; James Mathew
Little leaf disease of clove in Kerala
(Kerala Agricultural University, 1980) Karunakaran, P; Chandrasekharan Nair, M
Mode of entry of Cercospora personata (Berk. And Curt.) Ell- & Ev. In the leaf of groundnut plant (Arachis Hypogaea L.)
(Kerala Agricultural University, 1972) Karunakaran, P; Sam raj, J
Role of ascorbic acid on 'tikka' disease of groundnut
(Kerala Agricultural University, 1980) Karunakaran, P; Sam Raj, J
Severe leaf blight of palmyra palm (Borassus Flabelliformis) caused by Pestalotiopsis palmarum in Kerala
(Kerala Agricultural University, 1982) Balakrishnan, B; Karunakaran, P; Chandrasekharan Nair, M
Strain variation in colletotrichum Gloeosporioides (Penz.) Penz & Sacc.
(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Alice, K J; Karunakaran, P
Colletotrichum gloeosporioides (Penz.) Penz. & SAcc. Is observed as a major pathogen infecting a number of crop plants, ornamentals and weeds. Detailed studies on the variability of this pathogen on important vegetables and ornamental plants in different locations of Thiruvananthapuram and Thirissur districts of Kerala were undertaken to distinguish different strains of C. gloeosporioides. Studies on the symptoms and pathogenecity tests of the 69 isolates showed that there were variations in the exoression of symptoms and in initiating symptoms indicating that the isolates were highly variable. Great variability in growth rate, colony characters, degree of sporulation and size of conidia were observed in different isolates. Based on the protein production and enzyme activity three groups of isolates could be distinguished. The isolates varied in their growth under varying temperature and relative humidity. Light intensity had no significant effect on the growth of the pathogen. Among the solid media tested, all the selected isolates exhibited the maximum growth on PDA. Richard’s medium was found to be the best liquid medium for mycelial growth. The degree of sporulation of selected isolates was the highest at 92.9 per cent RH and the lowest at 100 per cent RH. The highest sporulation was observed when exposed for 24 h of continuous light (125 lux) and poor when exposed for 24 h darkness. Basal medium was found to be best for sporulation. The results of host range studies and cross inoculation studies showed that the selected isolates were not host specific even though there were variations among the isolates in the intensity of infection. Inhibition of germination of selected seeds was observed when bioassayed with exotoxin. The purified toxin produced more or less identical symptoms as did by the casual organism. Coon’s medium was found to be the best for production of endotoxin. The maximum production of toxin was observed in 25 day old cultures. Biological groupings of all the 69 isolates studied were done based on the correlation matrix of different characters. Eight different groups of isolates could be distinguished and designated as G1, G2, G3, G4, G5, G6, G7 and G8 strains of C. gloeosporioides.
Studies on the leaf spot diseases of oil palm (Elaeis guineensis jacq.) in Kerala
(Department of Plant Pathology, College of Agriculture, Vellayani, 1989) Thomas John; Karunakaran, P
A survey was conducted in the oil palm growing areas of Palode, Anchal, Kulathupuzha and Thodupuzha. Six leaf spot diseases were noticed. They include the leaf spots caused by Bipolaris hawaiiensis, Botryodiplodia theobromae, colletotrichum gloeosporioides, curvularia geniculata, fusarium pallidoroseum and phoma sorghina. All these are new records from India. Out of the six leaf spot diseases, the leaf spot caused by C.gloeosporioides was found to be the most severe causing damage in all the four plantations and it was considered to be of major economic importance. Other diseases recorded during the present investigation were of minor importance. Inoculation studies with six leaf spot causing pathogens showed that injury to leaves makes the plant more susceptible to leaf spot disease. The percentage of infection was more in injured leaves than in uninjured leaves. In invitro evaluation of fungicides showed that Bordeaux mixture, Dithane M-45 and Foltaf were effective, Bavistin controlled all the pathogens, except B. hawaiienis and C. geniculata. The leaf spot disease caused by C.gloeosporioides was observed in all oil palm plantations in Kerala in a serious proportion, especially during monsoon periods. Field evaluation of fungicides against the above disease indicated that Bavistin, Dithane M-45 Foltaf and Cuman L were effective.
Survival of Cercospora personata (berk, and curt.) Ell. & ev., Cercospora hibisci tracy and earle., and Cercospora henningsii allesch in the soil
(Kerala Agricultural University, 1973) Karunakaran, P; Sam Raj, J
Twig blight and flower shedding disease of clove trees
(Kerala Agricultural University, 1980) Karunakaran, P; Chandrasekharan Nair, M