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ThesisItem Open Access Etiology and management of die back disease of mango grafts in nursery(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2009) Sangeetha, C; KAU; Beena, SA study on "Etiology and management of die back disease of mango grafts in nursery" was carried out in the Department of Plant Pathology, College of Horticulture, Vellanikkara during 2007 - 20008 to study various aspects, particularly the etiology, symptomatology, varietal reaction and management of die back disease. Surveys were conducted at ten different nurseries on the occurrence of die back disease of mango grafts and during the survey different leaf blight diseases were also noticed along with die back incidence. Pathogens associated with these diseases were isolated and proved pathogenicity by artificial inoculation under in vitro and in planta conditions. Isolation of pathogen on PDA medium yielded Colletotrichum sp. and Botryodiplodia sp. from die back symptom and Colletotrichum sp., Pestalotiopsis sp., Cylindrocladium sp., Drechslera sp. and Alternaria sp. from leaf blight symptom. Studies on symptomatology showed that die back and leaf blight symptoms produced by the respective pathogens at different locations were same, but different pathogens produced different type of symptom on mango grafts. The die back caused by Colletotrichum sp. was observed as small necrotic spots on the tip of shoot and at the base of leaf petiole which later coalesced and developed, large brownish black necrotic area. The leaves on the infected shoot dried up and fell down. Black discolouration and darkening of the bark of young green twigs were observed in mango grafts infected by Botryodiplodia sp. This infection spread downwards and resulted in typical die back symptom. In severe infection leaf shedding was also observed. The leaf blight caused by Colletotrichum sp. was also noticed on young leaves and appeared as dark brown circular spot with yellow halo which coalesced to form large blighted area. The pathogen produced the fruiting body, acervulus, on infected area and also showed shot hole symptom. Pestalotiopsis sp. infected matured leaves and produced light brown necrotic area from the leaf tip or margin which later spread towards the midrib with silvery grey coloured area on upper surface of leaf. The other three pathogens viz., Cylindrocladium sp., Drechslera sp. and Alternaria sp. initially produced dark brown spots on leaves. In all these infections, the spots were coalesced and produced large brown coloured blighted area on leaves. Cultural and morphological characters of the six pathogens were studied on PDA medium. Based on the etiological studies and cultural and morphological characters of organisms the pathogens causing die back disease were identified as Colletotrichum gloeosporioides (Penz.) Sacc and Botryodiplodia theobromae Pat and the leaf blight inciting pathogens were identified as Colletotrichum gloeosporioides (Penz.) Sacc, Pestalotiopsis mangiferae (Henn.) Steyaert, Cylindrocladium mangiferae sp. nov, Drechslera australiensis (Bugnicourt) Sub ram & Jain ex M.B.Ellis and Alternaria alternata (Fries) Keissler. There was no earlier report of C. mangiferae on mango and hence it is the first report of this fungus as a leaf blight pathogen on mango. The result of the genetic dissimilarity index computed by the seven different isolates of C. gloeosporioides showed a slight variability among the isolates. An in vitro experiment was conducted to evaluate the effectiveness of fungicides and antagonists against die back and leaf blight pathogens. Among the fungicides, Bordeaux mixture at all the three concentrations recorded cent per cent, inhibition on the growth of all the six pathogens. Carbendazim showed cent percent inhibition on the growth of C. gloeosporioides, P. mangiferae and C. mangiferae at all the three concentrations but it was not very effective against D. australiensis. Hexaconazole was found effective to control the growth of D. australiensis and recorded more than 85 per cent inhibition over control. The two fungal antagonists viz., T. viride (KAU) and T. harzianum (nSR) showed complete inhibition on the growth of all the six pathogens whereas the bacterial antagonist, P. jluorescens showed more than 50 per cent inhibition on the growth of C. gloeosporioides, B.theobromae, P. mangiferae and D. australiensis. After the in vitro evaluation of fungicides and antagonists, an in planta experiment was conducted two times to know the effect of various treatments on the management of die back and leaf blight diseases. Observations on per cent disease severity of die back and leaf blight disease revealed that all the treatments were superior to control. The data recorded on ten days after the last application of treatments during the first experiment revealed that the highest reduction in disease severity (90.47 per cent) was observed in plants treated with one per cent Bordeaux mixture, 0.3 per cent copper oxychloride, 0.1 per cent carbendazim, 0.15 per cent copper hydroxide. The treatments T9 (P. fluorescens), T10 (T. viride) and T11 (quinalphos) were also on par with the above treatments. The highest reduction in disease severity of leaf blight (79.63 per cent) over control was recorded in plants sprayed with one per cent Bordeaux mixture and was on par with all other treatments except mancozeb and zineb. The results of the second experiment revealed that the highest per cent reduction in disease severity of die back (80.02 per cent) over control was exhibited by one per cent Bordeaux mixture and was on par with all other treatments. Similarly Bordeaux mixture recorded the highest reduction in disease severity of leaf blight (85.64 per cent) over control, and was on par with all other treatments. Hence it is concluded that all the five fungicides viz., one per cent Bordeaux mixture, 0.15 per cent copper hydroxide, 0.3 per cent captan, 0.1 percent hexaconazole and 0.1 per cent carbendazim and the bioagents viz., T. viride (20 g/ lit) and P. fluorescens (2.0 per cent) were equally effective in the management of die back and leaf blight disease of mango grafts. The data on the screening of mango grafts of different varieties revealed that the two varieties, viz., Alphonso and Mulgoa were highly resistant to die back and leaf blight diseases. The highest total phenol content of 393.69J.lg/g was recorded in Alphonso and was followed by Mulgoa which recorded 283.59 J.lg/ of total phenol per gram of plant sampleThesisItem Open Access Performance of oyster mushroom (Pleurotus spp.) on organically amended agrowastes(College of Horticulture, Vellanikkara, 2009) Julie, I Elizabeth; KAU; Sheela, Paul TA study on “Performance of Oyster mushroom (Pleurotus spp.) on organically amended agrowastes” was carried out in the Department of Plant Pathology, College of Horticulture, Vellanikkara, during the year 2006 to 2008. The study was conducted to find out the best agrowaste substrate and organic amendment for the cultivation of five species of oyster mushrooms viz., P. florida, P. sajor-caju, P. eous, P. tuber-regium and Hypsizygus ulmarius. The substrates used were paddy straw, saw dust, banana sheath, areca sheath, coir pith and rice husk. Rice bran, neem cake, dry azolla, vermiwash and dry biogas slurry were the organic amendments used for the study. Nutrient composition of mushrooms grown on different substrates and organically amended agrowaste was studied. Shelf life studies were also undertaken to find out the best packaging to enhance the shelf life of mushrooms stored under room temperature and refrigerated condition. The result revealed that, paddy straw was the best substrate for oyster mushroom cultivation giving early spawn run, mushroom production and maximum yield for all species. Coir pith and rice husk were found to be the least effective, resulting in poor growth and yield. Nutritional analysis of mushrooms grown on different substrates revealed that, the components varied with substrates and species. The minimum pest incidence was observed in paddy straw followed by saw dust while the incidence of weed fungi was absent in saw dust. Among the different species studied, minimum pest incidence was noticed in P. tuber-regium followed by P. florida and P. sajor-caju. The weed fungi incidence was minimum in P. sajor-caju followed by P. eous. Studies on the effect of different substrates on the microbial population associated with growth and yield of oyster mushrooms revealed that the population of bacteria increased with time whereas in case of fungi, the maximum number was observed during spawn run than harvest stage. The bacterial population was maximum in saw dust during harvesting stage in all the species, whereas the weed fungi was (Penicillium, Aspergillus and Trichoderma) was maximum in saw dust for P. florida and in paddy straw for P. sajor-caju, P. eous and P. tuber-regium. Among the substrates, paddy straw gave higher amount of crude protein. Among the different species studied, sporophores of P. florida recorded maximum crude protein content. The total carbohydrate content was maximum in mushrooms grown on saw dust. Oyster mushrooms grown on banana sheath recorded maximum total free aminoacid. Among the different species studied, P. sajor-caju gave higher amount of total carbohydrate and total free aminoacid. None of the substrates evaluated had show marked effect on the crude fibre and moisture content whereas significant variation was observed among the species. Among the different species, P. tuber-regium gave higher amount of moisture and crude fibre. Nutrient components such as N, P, Fe and Zn content was found to be maximum in mushrooms grown on paddy straw. Mushrooms grown on areca sheath gave maximum K and Mg content whereas those grown on rice husk produced the highest Mn content. Sporophores of P. florida recorded significantly higher amount of N, P, Mg, Zn and Mn whereas K content was maximum in P. sajor-caju. The sporophores of P. eous gave maximum Fe content. Based on the results of first experiment, paddy straw was selected as the best substrate and used for the second experiment to evaluate organic amendments namely rice bran (4,5 & 6 per cent), neem cake (1,3 & 5 per cent), dry azolla (4,5 & 6 per cent), vermiwash (5, 10 & 15 per cent) and dry biogas slurry (1:0.25, 1:0.5 & 1:1). Except dry biogas slurry, all organic amendments had superior effect in reducing the time for spawn run and increasing the yield. The performance of different species varied with organic amendments. The maximum yield was obtained in treatment with 15 per cent vermiwash followed by 4 per cent dry azolla. Among the different species, P. sajor-caju recorded maximum yield followed by P. eous. Crude protein, nitrogen and total carbohydrate content were maximum in mushrooms grown on paddy straw amended with dry biogas slurry at 1:1 proportion whereas the maximum total free aminoacid content was obtained from treatments with lower concentrations of dry azolla. Among the different species, P. florida gave significantly higher amount of crude protein and nitrogen whereas P. sajor-caju recorded maximum total carbohydrate. The total free aminoacid content was maximum in H. ulmarius. Moisture and crude fibre content varied significantly with species. Among the species, P. tuber-regium recorded maximum moisture and crude fibre content. Paddy straw amended with 5 per cent neem cake gave maximum P content. Potassium content was found maximum in mushrooms grown on paddy straw amended with 6 per cent dry azolla. Sporophores of P. florida recorded significantly higher amount of P and K. Investigations on the shelf life of oyster mushrooms showed that, mushrooms stored under refrigerated conditions gave maximum shelf life up to seven days. Mushrooms packaged in PP bags with out ventilation, mushrooms kept under vacuum packaging and mushrooms packaged in pin pricked PP bags were found as the best treatments with minimum PLW and decay per cent under room temperature. Under refrigerated conditions, mushrooms packaged in pin pricked PP bags and in PP bags without ventilation were found to have the maximum shelf life.ThesisItem Open Access Potential of antagonistic endophytes against bacterial blight of anthurium(College of Horticulture, Vellanikkara, 2009) Sanju, Balan; KAU; Koshy, AbrahamOne of the major constraints in anthurium cultivation is the severe incidence of bacterial blight disease. The pathogen causing bacterial blight of anthurium was isolated and identified as Xanthomonas axonopodis pv. dieffenbachiae based on its cultural, morphological and biochemical characters coupled with its pathogenicity. Endophytic microbes were isolated from different parts of healthy anthurium collected from various locations of Thrissur, Kannur, Kasargod and Thiruvananthapuram districts. Isolation yielded more number of bacteria than fungi. Out of 51 endophytes tested, only eight bacterial and two fungal isolates showed antagonism against the pathogen. The eight selected bacterial endophytes were subjected to various tests for understanding the parameters that may act to produce antagonism as well as enhanced growth of the plants. The antagonists varied in their ability to promote plant vigour, hydrogen cyanide, IAA, ammonia and siderophore production and Phosphorus solubilization capacity. The endophytes were compatible with Bavistin, Akomin and Contaf and incompatible with Indofil M 45, Saaf and Captaf. Six insecticides viz., Classic, Rogor, Ekalux, Malathion, Target and Hostathion, and four fertilizers viz. Muriate of potash, Rajphos, Urea and Factomphos were compatible with the isolates. However, the isolates exhibited variation in their sensitivity with the antibiotics tested. Further, all isolates were compatible to each other. A pot culture experiment was conducted to assess the field efficacy of selected endophytes in comparison with recommended management practices. The treatments were given as two pre inoculation and two post inoculation sprays. The incidence and severity of the disease were recorded at five days interval for a period of 30 days. The result indicated that plants treated with endophyte EB15 showed minimum disease incidence and severity. This was followed by treatment with EB 31 and Streptocycline. The promising endophytes, EB15 and EB 31 were tentatively identified as Bacillus sp. and Pseudomonas sp. respectively.