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Open Access
Physiological and cultural studies on blue oyster mushroom (Hypsizygus ulmarius (Bull.:Fr.) Readhead)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2016) Sumi, I; KAU; Geetha, D
The present study entitled “Physiological and cultural studies on blue oyster mushroom (Hypsizygus ulmarius (Bull.:Fr.) Redhead)” was carried out in the mushroom unit, Instructional Farm, College of Agriculture, Vellayani during 2014-2016, with the objective to standardize the technology for cultivation of Hypsizygus ulmarius and to study its morphological and physiological aspects. The initial culture of H. ulmarius was isolated from the mushroom beds maintained in the mushroom unit of instructional farm through tissue culture method and purified by hyphal tip method. Morphological studies of H. ulmarius showed that the sporocarps were medium to large in size having a dark blue colour in the pinhead stage which became creamy white on maturity with an irregularly shaped, convex pileus with gills attached to the stem, but not decurrent and cylindrical, smooth and eccentric stipe. Microscopic studies revealed septate hypahe with clamp connection, oval shaped, hyaline basidiospores and the spore print was white. Studies on developmental morphology showed that H. ulmarius took an average of five days from the day of pinhead formation to complete maturity. The maximum mycelial growth was recorded on potato dextrose agar. A temperature of 25 0C, pH of 8 and dark conditions are found favourable for maximum mycelial growth. Evaluation of different substrates for spawn production revealed that paddy grains was the best medium in which spawn run was completed in fifteen days with thick fluffy growth and recorded less contaminants followed by wheat and sorghum. Evaluation of different substrates for mushroom production revealed that paddy straw was the best material for the cultivation of blue oyster with a total yield of 985 g kg-1 from three harvests followed by rubber sawdust (905 g kg-1). The minimum time for mushroom production was recorded for sugarcane bagasse and the maximum time for rubber sawdust. The average weight of sporocarp was maximum in mushrooms harvested from rubber sawdust and the maximum number of sporocarps was recorded in paddystraw. Beds prepared from sugarcane bagasse were heavily contaminated with Trichoderma sp. When compared with Pleurotus florida, H. ulmarius took more time (18 days) for complete spawn run in paddy grains and the yield was higher on paddy straw (1.096 kg kg-1) than P. florida (976 g kg-1). Infestation of pests viz., phorid flies (Megaselia sp.) and staphylinid beetles were prevalent during spawn run as well as sporocarp formation. The competitor moulds recorded were Trichoderma sp., Aspergillus sp. and Coprinus sp. Analysis for the proximate constituents in H. ulmarius revealed that it contains appreciable amount of carbohydrate (29 %), protein (32 %) and fibre (17.69 %). Sensory evaluation was done on steam cooked mushrooms for attributes like appearance, colour, texture, flavor and taste using five point score card and an overall acceptability score of 3.6 was obtained for H. ulmarius compared to P. florida (3.0). In the preference study conducted for both the mushrooms using Hedonic rating scale, 30 per cent of evaluators extremely liked H. ulmarius than P. florida (10 %). The study on the keeping quality of mushrooms in normal atmospheric condition indicated a shelf life of eight hours for H. ulmarius compared to six hours for P. florida. The study also showed that blue oyster mushrooms stored under refrigeration (4 0C) in perforated polythene covers had better shelf life (5 days) compared to P. florida (3 days). The present study indicated that blue oyster mushroom can be cultivated successfully in tropical areas on locally available materials like paddy straw and rubber saw dust under favourable climatic conditions viz., 26-28 0C temperature, more than 90 per cent relative humidity and good aeration. The variety is superior to the presently growing oyster mushroom (P. florida) in terms of yield, presence of appreciable amount of proximate constituents and keeping quality.
Open Access
Integrated management of rhizoctonia leaf blight of amaranthus (Amaranthus tricolor L.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2016) Gireesh; KAU; Radhakrishnan, N V
The study entitled “Integrated management of Rhizoctonia leaf blight of Amaranthus (Amaranthus tricolor L.)” was conducted at the College of Agriculture, Vellayani and Coconut Research Station, Balaramapuram during 2014-2016 with the objective to investigate the effect of soil solarization, biocontrol agents, chemical activator, indigenous formulations and new generation fungicides on growth, yield and severity of foliar blight of amaranthus. Samples of the infected leaves showing Rhizoctonia leaf blight in amaranthus were collected from Vellayani, Kalliyoor, Venganoor and Kakkamoola locations. Among the four isolates of the pathogen, the Vellayani isolate gave significantly superior growth rate with minimum of six days for sclerotial formation. Koch‟s postulates were proved for the pathogenicity of different isolates of Rhizoctonia solani. All the four isolates have taken three days for the first symptom development but the progression of lesion size of Vellayani isolate was maximum compared to all other isolates, hence the Vellayani isolate was selected as the most virulent isolate for use in further in vitro studies. Evaluation of biocontrol agents for in vitro suppression of R. solani showed that Trichoderma harzianum completely overgrown the pathogen with maximum inhibition of 49.56 % compared to Pseudomonas fluorescens (28.30 %). Under in vitro evaluation of chemical activator, different concentrations of Acibenzolar-S- Methyl (ASM) against pathogen, 100 ppm concentration recorded the maximum mycelial inhibition of 75.67 % and 5 ppm concentration recorded the minimum mycelial inhibition of 27.70 %. Among indigenous organic formulations, turmeric powder and baking soda combination inhibited the maximum growth of the pathogen by 64.40 %. In the in vitro studies with new generation fungicides,mancozeb in cow dung supernatant (0.4 %) and tebuconazole (0.1 %) recorded the 100 % mycelial inhibition of the pathogen. Field studies on disease suppression and plant growth promotion was carried out as two experiments, one in soil solarized plots and the other in non solarized plots. Soil solarization along with soil application of ASM (75 ppm) and foliar application of ASM (100 ppm) recorded the lowest disease incidence of 30.41 % and 30.42 % respectively, which was superior when compared with foliar application of ASM (100 ppm) and soil application of ASM (75 ppm) with the disease incidence of 37.06 % and 38.84 %. Soil solarization + foliar spray of tebuconazole (0.1 %) recorded the minimum disease index of 37.85 % which was superior compared to foliar spray of tebuconazole (0.1 %) with the disease index of 39.28 %. Among the biocontrol agents soil solarization + foliar spray of Pseudomonas fluorescens (2 %) gave minimum disease index of 45.22 % which was greater compared to foliar spray of P. fluorescens (2 %) with the disease index of 51.66 %. In case of indigenous organic formulations, soil solarization + foliar spray of fish amino acid (5 %) given the maximum control of the disease with the disease index of 49.51 % which was superior to foliar spray of fish amino acid (5 %) with disease index of 63.59 %. The number of days taken for flowering in soil solarized plots ranged from 28.67 to 35 days where as the number of days taken for the flowering of amaranthus in non solarized plots was ranged from 27.27 to 31.67 days. At the time of harvest, soil solarization + mancozeb in cow dung supernatant (0.4 %) recorded maximum plant height of 127.07 cm which was higher compared to foliar spray of azoxystrobin (0.15 %) with plant height of 117.60 cm. Maximum of 78.00 number of leaves were recorded by soil solarization + foliar spray of azoxystrobin (0.15 %) which was greater compared to foliar spray of azoxystrobin (0.15 %) with 67.67 number of leaves.Soil solarization + foliar spray of azoxystrobin (0.15 %) gave the highest yield in terms of fresh weight by 26975.00 kg/ha and dry weight of 4233.33 kg/ha which was superior when compared with foliar spray of tebuconazole (0.1 %) with the fresh weight of 23375.00 kg/ha and dry weight of 3362.50 kg/ha. It is concluded that soil solarization for 31 days with the foliar application of tebuconazole (0.1%) can effectively control the Rhizoctonia leaf blight disease severity with plant growth and yield promotion under field conditions.
Open Access
Integrated management of anthracnose of snake gourd (Trichosanthes cucumerina L.)
(Department of Plant Pathology,College of Agriculture, Vellayani, 2016) Aswani Devi; KAU; Kamala Nayar
The objective of present study entitled “Integrated management of anthracnose of snake gourd (Trichosanthes cucumerina L.)” was to make a comparative evaluation of foliar application of newer fungicides and biocontrol agents for the management of anthracnose disease of snake gourd. Surveys were conducted during October 2015 in snakegourd fields of five different locationsof Thiruvananthapuram district , viz., Instructional Farm, College of Agriculture,Vellayani, Department of Olericulture, College of Agriculture, Vellayani, Kalliyoor, Kakkamoola and Palapoor. Maximum disease incidence (90.00 per cent) and disease severity/ percentage disease index (44.22) were recorded in the snake gourd fields of Instructional Farm, Vellayani whereas disease parameters were minimum (21.89 per cent and 70.00 per cent) in the fields of Palapoor Pathogenicity tests revealed that the isolate C1 obtained from Instructional Farm, Vellayani produced maximum lesion size both on detatched leaf (2.53 cm2) as well as and on intact leaves of 30-days old potted plant (10.06 cm2). The smallest lesion size of 1.33 cm2 on detatched leaf and 1.53 cm2 on 30 days old potted plant was produced by the isolate C4 from Kakkamoola. Based on lesion size and virulence rating, C1 was screened as the most virulent isolate. Results of the cultural studies among the five isolates, showed that potato dextrose medium, oat meal medium and Richard’s medium were screened as the best media both in solid and liquid states for the growth of the tested isolates. Effect of different light sources (Fluorescent light: 253.7 - 185 nm, L.E.D light: 365 nm and UV light: 10 - 380 nm) on growth and sporulation of anthracnose pathogen indicated that the cultures exposed to fluorescent light and darkness for alternate cycles of 12 h of each day resulted in maximum mycelial growth and minimum days for sporulation for all the isolates. Growth was less when the cultures of the isolates were exposed to UV light for a period of 45 min. The morphological characters studied indicated that average conidial size of isolate C1, C2, C3 and C5 ranged from 11.40μm- 13.14μm x 4.48μm-4.82 µm and that they were cylindrical in shape with obtuse ends. The isolate C4 was ellipsoidal in shape and had a conidial size of 10.52μm x 4.40 µm. The isolates C1, C2, C3 and C5 were further identified at National Fungal Collection Culture India (NFCCI) - Pune, as C. coffeanum F.Noack and the isolate C4 was identified as C. musae (Berk. & M.A. Curtis) Arx. Isolate C1 of C. coffeanum which was earlier screened as the most virulent isolate was used for the subsequent studies conducted for the management of anthracnose disease in snake gourd. In the invitro assayconducted for screening of newer fungicides and bio control agents, effective for the inhibition of the isolate C1 of C. coffeanum, the nutrient potassium silicate (0.5 per cent) and fungicide mancozeb (0.4 per cent) resulted in hundred per cent mycelial inhibition while, KAU talc based formulations of the bio control agents viz., P. fluorescens (2 per cent) and T. viride (2 per cent) resulted in inhibition of 88.33 per cent and 87.33 per cent respectively and were selected for further evaluation in green house study. Minimum spore germination was recorded due to amendment of medium with T. viride (1.33 per cent). Conidia were also reduced in size when growth medium (PDA) were amended with tested chemicals and bio-control agents. In the green house studies using the snake gourd variety Kaumudi, maximum disease suppression was observed when plants were sprayed with 0.5 per cent potassium silicate (89.12 per cent) and 0.4 per cent of fungicide mancozeb (84.99 per cent) at fifteen days interval. Biometric parameters observed were also maximum for plants sprayed with 0.5 per cent potassium silicate followed by mancozeb and KAU talc based formulation of bio-control agents P. fluorescens and T. viride. Anthracnose affecting the foliage of snake gourd is a serious disease in snakegourd fields of Thiruvanathapuram district. The nutrient potassium silicate which was tested for the first time in Kerala against a plant pathogen, Colletotrichum sp. is found to be a promising chemical for management of the disease. The present study has also revealed the prospects of utilizing the mineral nutrient, potassium silicate for control of anthracnose disease as well as attainment growth promotion, flowering behavior, yield components and increases in yield of snake gourd which is an important vegetable crop of Kerala. Besides, this study also has highlighted the scope for integrating the fungicide mancozeb with bio-control agents like P. fluorescens and T. viride which were was also highly beneficial for the disease management as well as in improving the growth parameters of the crop under green house conditions. Such integration of fungicide mancozeb with bio-control agents will also be useful in minimizing the detrimental effects of continous and intensive use of this fungicide which is otherwise very effective in disease management. In the background of the promising results obtained from this thesis project especially from the use of potassium silicate, trials for confirming the beneficial effects of the treatments in field grown snake gourd plants would be useful for the vegetable growers in Kerala.
Open Access
Management of cercospora leaf spot of vegetable cowpea (Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Chinnu Ravi; KAU; Radhakrishnan, N V
The study entitled “Management of Cercospora leaf spot of vegetable cowpea Vigna unguiculata subsp. ungiculata (L.) Verdcourt) was undertaken at the Department of Plant Pathology, College of Agriculture Vellayani and Coconut Research Station, Balaramapuram during 2015-2017 with the objective to study the symptomatology and etiology of Cercospora leaf spot of cowpea and to develop a management strategy. Symptomatology and etiology of Cercospora leaf spot disease was studied during the flowering or pod bearing stage of the crop from different locations near to College of Agriculture, Vellayani. Symptoms were observed on the leaves, pods and stem .Conidial dimension of the pathogen ranges from 24.64 to 57.6 µm x 1.06 to 2.7 µm and the conidial septation was around 10 to 18. Based on the conidial and mycelial characters, the pathogen was tentatively identified as Cercospora sp. The identity of the pathogen was further confirmed based on the morphological characteristics and the herbarium specimen send to National Fungal Culture Collection of India, (N.F.C.C.I), Pune as Pseudocercospora sp. aff. Pseudocercospora vignigena (F: Mycosphaerellaceae) In vitro pathogen suppression by spore germination assay revealed that the fungicide difenoconazole (0.1%) recorded 42.96 per cent reduction over control and was followed by propiconazole (0.1%) and hexaconazole (0.1%) which recorded 36.85 and 31.10 per cent reduction over control, respectively. The organic formulations, mineral oil (0.1%) and neem oil (0.5%) recorded only 21.88 per cent reduction over control and were statistically on par .KAU talc based formulation of Pseudomonas fluorescens at 2.0 % recorded 11.88 per cent reduction of spore germination over control. The pot culture studies conducted using eight best treatments (difenoconazole (0.1%), propiconazole (0.1%), hexaconazole (0.1%), carbendazim (0.05%), azoxystrobin (0.05%), mineral oil (0.1%) neem oil (0.5%) and P. fluorescens 2.0 %) selected from in vitro studies revealed that the foliar spray of 0.1 per cent difenoconazole recorded the minimum disease incidence (23.80%) and disease severity (8.23 %) that accounts to 54.80 and 76.06 per cent disease reduction over control respectively. In the case of organic formulations, mineral oil (0.1%) recorded the minimum disease incidence (30.04%) and disease severity (16.54%). The plant sprayed with KAU talc based formulation of P. fluorescens (2.0%) recorded 33.69 % disease severity reduction over control. With regard to pod yield, the plants treated with difenoconazole (0.1%) registered the maximum (0.523 kg/pot) yield with 88.80% yield increase over control while ,the untreated control plants registered the lowest yield (0.277kg/pot). Based on the results of pot experiment, a field study was conducted at Coconut Research Station, Balaramapuram to evaluate the efficacy of five best treatments (difenoconazole (0.1%), propiconazole (0.1%), mineral oil (0.1%) neem oil (0.5%) and P. fluorescens 2.0 %) selected from the pot culture studies. Among the fungicides, difenoconazole (0.1%) recorded the minimum (31.88%) disease incidence and disease severity (13.97%) compared to all other treatments. In the case of organic formulations, mineral oil (0.1%) gave the maximum (14.32%) disease suppression and the lowest disease incidence of 40. 57 %. With regard to yield, maximum pod yield was from the plot sprayed with difenoconazole (1620 kg /ha) followed by propiconazole (1386.5 kg /ha) treated plants. Even though, the application of P. fluorescens gave only 29.23 per cent of the disease suppression, it enhanced the yield by 52.27 per cent yield over the control. It was concluded that foliar application of difenoconazole ( 0.1% ) at an interval of 35, 50 and 65 DAS was found to be the most effective treatment in managing Cercospora leaf spot in vegetable cowpea besides supporting proportionately attractive pod yield (1620 kg/ha) at an acceptable B:C ratio (2.44:1).Among the organic formulations, mineral oil (0.1%) was found to be the effective treatment in controlling leaf spot with a pod yield of 1293 kg/ha . While, P. fluorescens recorded a pod yield of 1318 kg/ha with B: C ratio of 2.02:1
Open Access
Exploration of natural products from botanicals and fungal root endophytes for the management of cowpea mosaic virus
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Theresa Alex; KAU; Umamaheswaran, K
The present study entitled “Exploration of natural products from botanicals and fungal root endophytes for the management of Cowpea mosaic virus” was carried out at Department of Plant Pathology, College of Agriculture, Vellayani during 2014-2016, with the objective to develop serological and molecular tools for the early detection of Cowpea mosaic virus; and its management using natural products from botanicals and fungal root endophytes. Cowpea mosaic virus was maintained in local lesion host Chenopodium amaranticolor and cowpea (Vigna unguiculata var. sesquipedalis (L.) Verdcourt) variety Sharika by mechanical inoculation. On the newly emerged trifoliate leaves of cowpea, typical symptoms like mosaic and vein banding followed by leaf distortion were expressed seven days after inoculation (DAI). In C. amaranticolor, symptoms were expressed five DAI and on the inoculated leaves, localized yellow chlorotic lesions were observed. Fungal root endophytes Piriformospora indica and Fusarium pallidoroseum were maintained by continuous subculturing in Potato dextrose agar medium. The P. indica produced nine centimetre radial growth on nine DAI whereas F. pallidoroseum produced nine centimetre radial growth on five DAI in petri dishes. Serological studies carried out using Direct antigen coating – Enzyme linked immunosorbent assay (DAC-ELISA) and Dot immunobinding assay (DIBA) and molecular detection viz., Reverse transcription-polymerase chain reaction (RT- PCR), identified the mosaic causing virus in cowpea as Blackeye cowpea mosaic virus (BlCMV). Botanicals for the management of BlCMV were first screened on C. amaranticolor to find out their efficiency. Among the seven botanicals, Phyllanthus niruri recorded more than 80 per cent inhibition of local lesions in C. amaranticolor even at one per cent concentration. Highest inhibition (94.84 per cent) was observed for pre inoculation application of P. niruri at five per cent concentration. Standardization of co-cultivation method for the fungal root endophytes with C. amaranticolor and cowpea were conducted in jam bottles but no colonization of any fungal endophytes were observed in both C. amaranticolor and cowpea. Colonization studies in vermiculite-perlite (3:1) medium at the rate of 1% (w/v) conducted in protrays showed no colonization during the co-cultivation studies of F. pallidoroseum with both cowpea and C. amaranticolor. In case of P. indica, no colonization was observed for C. amaranticolor whereas 40.70 per cent root colonization was recorded in cowpea. In a study conducted to determine the effect of age of seedlings on colonization pattern observed using compound microscope, the highest efficiency (42.30 per cent) was recorded for five day old seedlings at twenty days after co-cultivation. Root biomass, number of secondary roots, tertiary roots, number of leaves and leaf area also showed high values for five day old seedlings at twenty days after co-cultivation whereas shoot biomass and root hairs per unit area showed highest values for seven day old seedlings at twenty days after co-cultivation. The best antiviral principle (AVP) and fungal endophyte viz., Phyllanthus niruri and Piriformospora indica respectively were evaluated in cowpea against BlCMV. Vulnerability of cowpea plants to BlCMV was found to reduce with P. niruri and P. indica treatments compared to that of control plants. The biochemical analysis to study the mechanisms involved revealed that cowpea plants pre inoculated with P. niruri was found to be superior followed by pre inoculation treatment with P. indica except for total sugar where maximum values for healthy was followed by pre inoculation treatment with P. niruri. Many defense and pathogenesis related (PR) proteins were induced in response to various treatments. The induction of novel proteins were more in cowpea leaves which were treated with P. niruri and P. indica than in control plants. Thus it is proved by serological and molecular detection methods that the virus causing mosaic disease in cowpea is BlCMV. For the management of this virus pre inoculation treatment of P. niruri (extract of one gram sample in 100 ml water) and pre inoculation treatment of P. indica (one gram mycelia in 100 ml vermiculite-perlite media) has been proved to be effective. It can be further validated under field condition.
Open Access
Cataloguing, Documentation and Management of fungal diseases of strawberry (Fragaria x ananassa Duch.)
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Amrutha, P; KAU; Reshmy Vijayaraghavan
Strawberry (Fragaria x ananassa Duch.), hybrid species of genus Fragaria, cherished for its characteristic flavour, colour and tentalizing aroma, is becoming an important table fruit of millions of people around the world. However, the crop is inflicted by several fungal diseases that reduce its commercial value. Hence, the present investigation was carried out to identify and catalogue the major fungal diseases of strawberry growing in Kerala. Purposive sampling surveys were carried out in strawberry growing tracts of Kerala viz., Wayanad, Idukki and Malappuram to collect infected samples and also to assess the incidence of fungal diseases during different periods viz., December-January, March-April and July-August. During the survey, four leaf spots (LSW-1, LSI-1, LSM-1 and LSI-2), four leaf blights (LBW-1, LBI-1, LBI-2 and LBM-1), one fruit rot (FRW-1) and two crown and root rots (CRI-1 and CRM-1) were noticed. Among the crown and root rot diseases, CRM-1 recorded the highest per cent disease incidence (PDI) of 82 per cent. Leaf blight (LBW-1) recorded maximum severity of 25.2 per cent among foliage diseases. Correlation studies were carried out to elucidate the influence of weather parameters on disease development. Symptomatology of different diseases was studied both under natural and field conditions. Pathogenicity was proved by mycelial bit inoculation and spore suspension method. Cultural and morphological characterisation of the isolates were carried out and for further confirmation of the identity upto species level, the isolates were sent to National Centre for Fungal Taxonomy (NCFT), New Delhi. The pathogens causing LSW-1, LSI-1 and LSM-1 were identified as Colletotrichum gloeosporioides, LSI-2 as Alternaria alternata, LBW-1 as Rhizoctonia solani, LBI-1 as Phoma exigua, LBI-2 as Curvularia lunata, LBM-1 as Pestalotiopsis longisetula and FRW-1 as Rhizoctonia solani. The two crown and root rot pathogens, CRI-1 and CRM-1 were confirmed as Fusarium oxysporum and Lasiodiplodia theobromae respectively. In order to recommend an appropriate management strategy for the aforesaid diseases, in vitro and in vivo evaluation were carried out using fungicides, biocontrol agents and organic formulations. Fungicides viz., carbendazim 12% + mancozeb 63%, propineb 70 WP, Bordeaux mixture, cymoxanil 8% + mancozeb 64%, difenoconazole 25EC and carbendazim 50WP were found effective against various foliage diseases. Carbendazim 12% + mancozeb 63%, cymoxanil 8% + mancozeb 64%, copper hydroxide 77WP and carbendazim 50 WP recorded cent per cent reduction in mycelial growth of Fusarium oxysporum (CRI-1). Similarly, carbendazim 12% + mancozeb 63%, copper hydroxide 77WP, cymoxanil 8% + mancozeb 64% recorded 93-100 per cent reduction of Lasiodiplodia theobromae (CRM-1). Results of dual culture studies with Trichoderma asperellum and Pseudomonas fluorescens against pathogens revealed 66.67 to 100 and 0 to 70.55 per cent control respectively. Likewise, organic formulations like Calphomil recorded an inhibition ranging from 13.3 to 75.33 per cent, whereas neem oil, panchagavya and baking powder + vegetable oil mixture could restrict the growth of pathogen only upto 34 per cent. In vivo experiment was conducted to study the efficacy of fungicides and biocontrol agents under natural conditions also. Accordingly, four major selected pathogens viz., C. gloeosporioides, P. longisetula, F. oxysporum and L. theobromae were subjected to molecular characterisation prior to in vivo studies. The sequence homology on molecular studies revealed that the isolates showed similarity to C. gloeosporioides, Neopestalotiopsis clavispora, F. oxysporum and L. theobromae. Results of the pot culture experiment revealed that Trichoderma asperellum showed better control against C. gloeosporioides compared to other treatments followed by carbendazim 12% + mancozeb 63%. Propineb 70 WP, T. asperellum and carbendazim 12% + mancozeb 63% reduced the severity caused by Neopestalotiopsis leaf blight disease. The combination fungicide carbendazim 12% + mancozeb 63% (0.2%) was found equally efficient against F. oxysporum and L. theobromae. Thus, the study has enlightened our knowledge on the various fungal diseases inflicting strawberry as well as the role of weather in disease development and the management practices using plant protection chemicals and bioagents both under in vitro and in vivo conditions. Hence, further studies should be focused to carry out multilocational trials in strawberry growing tracts of Kerala.
Open Access
Characterization and management of fungal pathogens of cabbage (Brassica oleracea var. capitata L.) and cauliflower (Brassica oleracea var. botrytis L)
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2017) Nusrath Beegum, C H; KAU; Yamini Varma, C K
Cabbage (Brassica oleracea var. capitata L.) and cauliflower (Brassicaa oleracea var. botrytis L.) are the most popular and widely cultivated cruciferous vegetables in Kerala. One of the main constraints in the production of these crops is the occurrence of fungal diseases, on which no detailed systematic studies have been conducted in Kerala. The study was carried out during 2015-2017 at College of Agriculture, Padannakkad with the objective to identify and characterize the fungal diseases of cabbage and cauliflower occurring in the selected districts of Kerala and to study the management of most severe and predominant diseases under in vitro and in vivo conditions. Purposive sampling surveys were conducted for the occurrence of fungal diseases in cabbage and cauliflower in Thrissur, Wayanad, Idukki and Kasargod districts and diseased plant samples were collected. Results of survey showed prevalence of eight different fungal diseases with a range of 5.4-69.3 per cent disease incidence and 8.1-68.3 percent disease severity in case of cabbage. In cauliflower, PDI and PDS were with a range of 3.1-52.2 percent and 4.9-44.2 percent respectively. Isolations done from the infected specimens collected during the survey yielded eight genera of fungal pathogens. For selecting the most potent isolate, virulence test was conducted, and used for further studies. Characterisation of the selected pathogens were carried out based on the cultural and morphological characters and identified up to generic level. Further identification of species of each genus was done by molecular characterization by sequencing the ITS region of each fungus by in silico analysis and confirmed as Alternaria brassicicola, Rhizoctonia solani, Collectotrichum gloeosporioides, Curvularia lunata, Choanephora cucubitarum, Pythium aphanidermatum and Fusarium equiseti. Symptomatology of these fungal diseases were studied in detail both under natural and artificial conditions. In vitro evaluation of fungicides and biocontrol agents was done against the selected sever pathogens. Ten fungicides at three concentrations and three bio control agents were selected for the studies. In vitro studies showed that against A. brassicicola the most effective fungicides at the recommended concentration were, trifloxystrobin 25% + tebuconazole 50%, tebuconazole 5EC and Bordeaux mixture with 100 percent inhibition. Against R. solani and C.lunata six fungicides viz., tebuconzole 5EC, copper oxy chloride 50 WP, trifloxystrobin 25%+tebuconazole 50%, propineb 70 WP and Bordeaux mixture produced 100 percent inhibion. Trifloxystobin 25%+tebuconazole 50%, tebuconazole 5EC and Bordeaux mixture were the three effective fungicides against C.gloeoporioides, F.equiseti and C. cucurbitarum which recorded 100 percent inhibition over control. But against P.aphanidermatum from cauliflower, copper fungicides showed a lead in the inhibition viz., copper oxycholride 50WP, copper hydroxide 77WP, Bordeaux mixture followed by mancozeb 75 WP. In vitro evaluation of biocontrol agents showed that T.viride was the most effective for controlling P.aphanidermatum with 75 percent inhibition followed by A.brassicicola with 67 percent inhibition. Antagonistic reaction of T.asperellum was mostly overgrowth on test pathogen. Similarly, P.fluorescens also showed maximum inhibition against P.aphanidermatum (50%). Effectiveness of the bacterial bioagent, B.subtilis showed maximum inhibition against R.solani. Three major pathogens viz., A. brassicicola, R.solani in cabbage and P.aphanidermatum in cauliflower were selected for the in vivo studies. Three biocontrol agents and funficides which showed inhibition above 60 percent were selected for in vivo evaluation. In vivo evaluation of fungicides for the management of Alternaria leaf blight of cabbage showed that trifloxystrobin 25%+tebuconazole 50% (0.03%) and tebuconazole 5EC (0.1%) were the best two fungicides showed 50 percent disease reduction over control followed by Bordeaux Mixture(1%). Yield of cabbage was also highest for these three treatments. Among biocontrol agents, T. viride was most effective in controlling the disease with a higher yield. For the management of Rhizoctonia leaf blight of cabbage, same two fungicides viz., trifloxystrobin 25%+tebuconazole 50% (0.03%) and tebuconazole 5EC(0.1%) were found to be most effective. B.subtilis was more effective than other two biocontrol agents which was significantly higher than control treatment. In vivo studies for the management of Pythium curd rot of cauliflower showed that trifloxystrobin 25%+tebuconazole 50% could produce 79 percent of disease reduction over control with higher yield. Among the bioagents, T.viride produced higher yield with 62 percent disease reduction. The present work resulted a detailed systematic study on the fungal pathogens of cabbage and cauliflower in selected districts of Kerala and emphasizes that trifloxystrobin 25%+tebuconazole 50% (0.03%) is the best chemical and T.viride is the effective biocontrol agent for field application for the management of these fungal diseases. Future line work should be concentrated on the residue analysis of these fungicides and formulation of a bio-intensive management strategy.
Open Access
Management of collar rot of cowpea caused by rhizoctonia solani kuhn using biofumigants
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Aparna, K P; KAU; Girija, V K
The study entitles “Management of collar rot of cowpea caused by Rhizoctonia solani kuhn using biofumigants” was undertaken in the Department of Plant Pathology, College of Agriculture, Vellayani during 2015-2017 with the objective to evaluate biofumigant nature of plants, plant oils and oil cakes against Rhizoctonia solani and to develop an ecofriendly management strategy for collar rot of cowpea using biofumigation. The pathogen causing collar rot disease of cowpea was isolated from the infected cowpea plants collected from the Instructional Farm, College of Agriculture, Vellayani. Pathogenicity was confirmed, virulence rating was done and the collar rot isolate R1 was found to be the most virulent one. Based on morphological and cultural characteristics, the pathogen was identified as the Rhizoctonia solani kuhn (Accession no. EF429212). This was further confirmed using molecular identification by ITS sequencing and showed 100 per cent similarity with Thanatephorus cucumeris, the perfect stage of R. solani. The antifungal and biofumigant action of ten different plants, four plant oils and four oil cakes/seed meals on mycelial growth of R.solani was evaluated under in vitro conditions in petridishes. Among these, incorporation of the leaf extracts of cabbage/ garlic creeper, lemongrass oil/ tea tree oil and mustard oil cake extract in PDA medium caused 100 per cent suppression of the pathogen. The invitro biofumigant activity of cabbage/cassava/garlic creeper/mustard, lemon grass oil/tea tree oil and the mustard oil cake was found to be statistically superior to all other treatements, and resulted in 100 per cent suppression of mycelial growth. The biofumigant action of ten different plants, four plant oils and four oil cakes with biocidal principles was tested by subjecting the sclerotia of R.solani to biofumigant action under confined conditions in sealed containers. Biofumigation with plants, plant oils and oil cakes, in general, exerted suppression of mycelial regeneration from sclerotia. The extent of suppression was found to increase with increase with increase in period of incubation with the biofumigants. Cabbage, cassava, garlic creeper and mustard were found to completely suppress the regeneration of mycelial growth from the treated sclerotia. Biofumigation with lemongrass oil/ tea tree/ mustard oil cake resulted in 100 percent suppression of regeneration of mycelium. Accordingly, plants such as cabbage, cassava, garlic creeper and mustard, plant oils such as lemongrass oil and tea tree oil, oil cakes such as mustard and groundnut oil cake were selected for further in vivo studies. An experiment was conducted under pot culture conditions to evaluate the efficacy of selected biofumigants involving 11 treatments and 5 replications in C.R.D. The treatments included the selected plants (50 g kg-1 soil), plant oils (5% soil drench) and oil cakes (10 g kg-1 soil) for suppression of collar rot of cowpea. The inoculated untreated control showed severe collar rot incidence (94.44%) compared to the treated pots. The maximum disease suppression (100%) was observed in cowpea plants grown on soil biofumigated with mustard plant/mustard oil cake which was on par with both chemical control check (0.1% carbendazim) and un-inoculated control. But the highest pod yield was recorded form plants grown on soil biofumigated with mustard oil cake (209.0 g) followed by treatment with mustard plant (185.4 g), which were significantly superior to the chemical control check (155.0 g) and un-inoculated control (143.0 g). These results revealed the enhanced effects of biofumigation for both disease suppression and growth enhancement. The population of soil microflora exhibited a decrease in the biofumigated treatements and an increasing trend after raising the crop. Among the predominant saprophytic fungi obtained from biofumigated soil, the isolated F1 exhibited 47.44% and among the two bacterial isolates, the isolate B2 caused 44.44% inhibition of the pathogen. The experiments revealed the scope of biofumigation for the management of R. solani under in vitro as well as in vivo. The collar rot caused by soil-brone pathogen, R. solani could be successfully managed by incorportation of either mustard plant (50g kg-1 soil) or tea tree oil (5% soil drench) or mustard/groundnut oilcake (10 g kg-1 soil)two weeks before raising cowpea.
Open Access
Evaluation and improvement of production technology of paddy straw mushroom (volvariella sp.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Brinda, G B; KAU; Susha S Thara
The study entitled “Evaluation and improvement of production technology of paddy straw mushroom (Volvariella sp.)” was performed in College of Agriculture, Vellayani during 2015-2017, with the objectives to explore the native isolates of Volvariella sp. and to study their morphological characters, improvement of techniques for production of paddy straw mushroom and to make an evaluation of the nutritional and organoleptic qualities. As a part of the study collections were made from various locations of Thiruvananthapuram and Kollam districts and thirteen different isolates of paddy straw mushroom were obtained. Morphological studies of different isolates of paddy straw mushroom showed that the sporocarps have black colour during the egg stage which become ashy to purplish white on maturity. Pileus is sub-umbonate with regular margin having free, smooth, pale salmon to moderate brown gills and central, cylindrical stipe with bulbous base encased in a thick volva. Microscopic studies revealed septate hyphae without any clamp connection, bottle shaped cheilocystidia, club-shaped basidia with four ovoid pink/moderate brown basidiospores. Cultures were isolated from the freshly collected mushrooms at egg stage through tissue culture technique and purified the cultures by hyphal tip method. Evaluation of cultural characters showed that the local isolate collected from Poonkulam had faster mycelial growth and it was taken as best isolate for further study. The morphological characters like size, weight of sporocarp of the selected isolate were also found promising. Study on different substrates for spawn production recorded that wheat grain, sorghum grain and paddy grain supported thick and fluffy mycelial growth. Considering the keeping quality, easy availability and nature of mycelial growth paddy grains was selected as the suitable substrate for spawn production in Kerala conditions. Comparison on the effect of different substrates for paddy straw mushroom production showed that paddy straw along with oil palm bunch waste on equal proportion amended with 5% gram flour was the best substrate for cultivation with a biological efficiency of 16.33%. Studies on the developmental morphology revealed that the fruiting body of paddy straw mushroom took 4-5 days for maturation from the pinhead emergence. Evaluation of different supplements for paddy straw mushroom production showed that 200ppm IAA supplementation during spawn run period yielded maximum (10.78% increase in biological efficiency over control). Assessment of different bed systems on production of Volvariella sp. recorded polybag method as more user friendly with maximum yield. Phorid flies were observed as the major pest during cultivation period. The competitor moulds identified were Trichoderma sp., Aspergillus sp., Penicillium sp. and Coprinus sp. Analysis for the proximate constituents in paddy straw mushroom exposed that it contains appreciable amount of protein (41.36 %) and fibre (16.98 %). Sensory evaluation was done using sauted mushroom recipe with Hedonic rating scale and observed that Volvariella sp. exceeded in colour, flavour, texture and taste attributes than Agaricus sp., Pleurotus sp. and Calocybe sp. Molecular characterization of the best isolate was carried out using ITS sequencing and the blast sequence was analysed in ClustalX2 software. Dendrogram was also constructed using TreeView software showing the phylogenetic relationship. Best isolate was identified as V. hypopithys and deposited in Directorate of Mushroom Research, Solan with the accession number DMRO – 943. The present study recommends that paddy straw mushroom can be successfully cultivated in Kerala using paddy straw and oil palm bunch waste in equal proportion as substrate having 5% gram flour amendment, supplemented with 200 ppm IAA on mycelial development stage by polybag method or wooden box method. Paddy straw mushroom was found to be high in terms of protein content and organoleptic attributes.

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