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ThesisItem Open Access Fungal diseases of selected medicinal plants of Kerala(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1991) Sukumara, Varma A; KAU; ; Abi, CheeranThesisItem 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 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 Strain variation in Colletotrichum gloeosporioides (Penz.) Penz & SAcc.(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Alice, K J; KAU; Karunakaran, PColletotrichum 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.
