Browsing by Author "Yamini Varma, C K"

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Bio intensive management of blast disease of rice (Oryza sativa L.)
(Bio intensive management of blast disease of rice (Oryza sativa L.), 2012) Yamini Varma, C K; Santhakumari
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; Yamini Varma, C K
Characterization of biointensive management of fungal fruit rots of cucurbits
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2019) Muhammad Suhaib, Ismayil M; Yamini Varma, C K
Cucurbits are the most popular and widely cultivated vegetables in Kerala. One of the main constraints in the production of these crops is the occurrence of fungal fruit rots, on which no detailed and systematic studies have been conducted in Kerala. The study was carried out during 2017-2019 at College of Agriculture, Padannakkad with the objective to identify and characterize the fungal pathogens causing fruit rots in cucurbits, occurring in the northern zone of Kerala and to study the management of selected fruit rot diseases under in vitro and most severe and predominant disease in vivo conditions. Purposive sampling surveys were conducted for the occurrence of fungal fruit rots in cucurbits in Kasargod, Kannur and Kozhikkode districts. Diseased plant samples were collected. Results of survey showed prevalence of seven different fungal diseases with a range of 6- 51 per cent disease incidence. Isolations done from the infected fruit samples collected during the survey yielded seven genera of fungal pathogens. Characterization 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 Choanephora cucurbitarum, Sclerotium rolfsii, Rhizoctonia solani, Phytophthora nicotianae, Pythium deliense, Corynespora cassiicola and Fusarium equiseti. Symptomatologies of these fungal diseases were studied in detail both under natural and artificial conditions. In vitro evaluation of fungicides, botanicals and biocontrol agents was done against the selected five pathogens. Four fungicides and three botanicals at three concentrations and five biocontrol agents were selected for the studies. In vitro studies showed that, against Choanephora cucurbitarum fruit rot, tebuconazole 5EC showed 100 per cent inhibition at all the three concentrations. Among botanicals, garlic extract at medium and higher concentrations and azadirachtin 0.1% at lower concentration were the best. Among biocontrol agents, Trichoderma viride was the best. Against Sclerotium rolfsii fruit rot, tebuconzole 5EC (Folicur), were significantly superior than all other fungicides at lower concentration, which showed 100 per cent inhibition. The fungicides tebuconzole 5EC and mancozeb 64% + cymoxanil 8% were superior at recommended and higher concentration and both of them showed cent per cent inhibition. Among botanicals, garlic extract and azadirachtin 0.1% were the most effective at the lower and recommended concentrations. At higher concentration garlic extract was the best. Among biocontrol agents, Bacillus subtilis and PGPM were the most effective treatments and they were at par with each other. Against Rhizoctonia solani fruit rot, all the chemical fugicides recorded cent per cent inhibition at all concentrations. Garlic extract was the best at all concentrations. The best biocontrol agets against Rhizoctonia solani was Trichoderma viride. Against Phytophthora nicotianae fruit rot, all the fungicides at all concentrations showed cent per cent inhibition. The data on the botanicals revealed that, garlic extract shows maximum inhibition (66.66%, 77.77%, 100%) at all concentrations. Among biocontrol agents, Trichoderma viridae and PGPM were the best treatments and they showed cent per cent inhibition. Against Corynespora cassiicola fruit rot, mancozeb 64% + cymoxanil 8% were superior (100% inhibition) at the lower concentration. At recommended concentrations, mancozeb 64% + cymoxanil 8% and mancozeb 64% + carbendazim 12% showed cent per cent inhibition. At higher concentrations, tebuconzole 5EC, mancozeb 64% + cymoxanil 8% and mancozeb 63% + carbendazim 12% were showed 100 per cent inhibition and they were significantly not different. Among the botanicals garlic extract was the most effective at all concentrations. The best biocontrol agent against Corynespora cassiicola was PGPM, which showed cent per cent inhibition. In vivo evaluation of management of Choanephora cucurbitarum fruit rot in pumpkin emphasized that tebuconazole 5 EC and mancozeb 64%+cymoxanil 8% are the best treatments. Botanicals viz., azadirachtin 0.1 % and garlic extract came as next best treatments and biocontrol agents, T. viride and B.subtilis were the least effective treatments. These can be recommended as effective antipathogenic agents for field application for the management of the fungal fruit rot disease in pumpkin. The present work resulted in a detailed and systematic study on the fungal fruit rots of cucurbits in northern zone of Kerala. Future line work should be concentrated on the field level studies of all the fruit rots of cucurbits in different districts of Kerala and on the recommendations of local specific management practices.
Characterization of medicinal mushroom, cordyceps sp. from Kasargod district
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2018) Laya, P K; Yamini Varma, C K
Effect of azospirillum inoculation on establishment and growth of bush pepper
(Department of Plant Pathology, College of Agriculture, Vellayani, 1995) Yamini Varma, C K; Sasi Kumar Nair
The study on the effect of Azospririllum inoculation on root induction, establishment and growth of bush pepper was conducted at Collage of Agriculture, Vellayani, Trivandrum during 1992 – 94. Out of the 25 different cultivars of pepper used for initial isolation, Azospirillum was isolated from 16 cultivars. These 16 isolates along with a culture from TNAU were screened for the production of IAA and gibberellins under in vitro conditions. The native isolate 34 produced maximum quantity of IAA equivalent to 69 µg/ml of culture broth. The production of this phytohormone was maximum during the second week of culture growth. However, none of these isolates produced gibberellins under in vitro conditions. Based on the requirement of biotin for growth isolate 34 and TN culture were tentatively identified as Azospirillum brasilense and A. lipoferum respectively. The isolate 34 and TN culture had their maximum growth at pH 6.0 and 8.0 respectively. Azospirillum isolate 34 and TN culture were selected for root induction studies in Panniyur – 1 and Karimunda varieties of bush pepper. The percentage of rooted cuttings varied from 23.3 – 26.8 percent in Panniyur -1 and 17.5 – 17.9 in Karimunda. However, the average number of roots per cuttings and root dry weight were maximum in bacterial treatment. Between the two varieties of bush pepper, root induction was better in Panniyur – 1 variety. The study on the establishment and growth of bush pepper was conducted by using 3 sets of rooted cuttings of Panniyur – 1 and Karimunda varieties where root induction was done by using carrier a based inoculum of Azospirillum and 1000 ppm IBA or without any of the above treatments. These were grown in potting mixture supplemented with 25 g or 100g of isolate 34 and with or without chemical fertilizer application. After 180 days of plant growth, 100 percent establishment was obtained in Panniyur – 1 in treatments such as 100 g Azo 34-F of group 1, 25 g Azo 34-F and 100 g Azo 34+F of group 2 plants. In these treatments the number of roots produced per cutting, fresh and dry weight of roots were significantly high or on par with each other. In Karimunda, also, in treatments such as 25 g Azo 34-F and 100 g Azo 34-F of group 1, 100 g Azo 34-F of group 2 and 25 g Azo 34-F of group 3 plants where 100 percent establishment was obtained, the number of roots produced per cuttings, fresh and dry weights of roots were statistically on par with best treatment for these parameters. The production of new leaves, branches and fresh and dry weight of shoot were significantly high only in Panniyur – 1 and these were in the treatments 100 g Azo 34-F of group 1 and 25 g Azo 34-F of group 2 plants. But in Karimunda, no such treatment effects were noticed except for fresh and dry weight of branches. In Panniyur – 1 the total fresh and dry weight of plants were significant also in 100 g Azo 34-F of group 1 and 25 g Azo 34-F of group 2 plants. In most of the treatments where significant results were obtained, chemical fertilizer application had no significant effect on different growth parameters studied. Further, between the two varieties, Panniyur – 1 responded better than Karimunda in rooting, establishment and growth of bush pepper.
Efficacy of pink pigmented facultative methylotrophs for the management of leaf blight disease in Amaranthus (Amaranthus tricolor L.)
(Department of Plant Pathology, College of Agriculture,Vellanikkara, 2023) Rengima Nambiar; Yamini Varma, C K
Amaranthus (Amaranthus tricolor L.), ("poor man's spinach") is one of the widely cultivated tropical leafy vegetables of Southern India. It is attacked by the most destructive disease, leaf blight by Rhizoctonia solani Kuhn, causing more than 90 per cent of yield loss. Chemical management of this pathogen causes health hazards due to pesticide residue. PPFM naturally occurring on the phyllosphere of amaranthus have great value in giving protection against leaf diseases, on which no detailed systematic studies have been conducted in Kerala. In this context, the present study was undertaken with the objectives of identification of Pink Pigmented Facultative Methylotrophs (PPFM) from amaranthus phyllosphere and to evaluate their efficiency for the management of leaf blight disease in amaranthus. The experiment was carried out in Pepper Research Station, Panniyur, during March 2022 – November 2022. Purposive sampling surveys were conducted in amaranthus growing fields of five different AEUs in Kannur district of Kerala viz.Thalassery, Kuttiyattoor, Panniyur, Punnad and Kanichar from April to May, 2022. The disease incidence and severity were maximum in the Kuttiyattoor area with 89.40 and 74.60 per cent, respectively. The fungus was isolated from leaf samples and the pathogenicity was proved. Symptomatology was studied both under natural and artificial conditions. The fungus was characterized and identified as Rhizoctonia sp. by studying their cultural and morphological characteristics. Highly virulent isolate, LB-3 was selected for further studies. PCR amplification of large subunit (LSU) region of the fungal genome followed by sequencing and in silico analysis confirmed that the suspected fungus, LB3 as Rhizoctonia solani. A total of 10 isolates of Pink Pigmented Facultative Methylotrophs (PPFM) from amaranthus phyllosphere were isolated and cultural, morphological and biochemical characterization was done. All the isolates were screened for their antagonistic potential against selected R. solani using dual culture technique. PPFM-2 and PPFM-5 showed 53.18 and 53.69 (in solid medium) and 77.77 and 74.04 (in liquid broth) per cent inhibition respectively. Hence, these two most promising isolates were selected for further field studies. The bacterial isolates PPFM-2 and PPFM-5 were confirmed as Microbacterium testaceum and Methylobacterium hispanicum through the amplification of 16S rRNA region of the genome followed by sequencing and in silico analysis. Under in vitro conditions, antagonistic activity of PPFM-2 and PPFM-5 were compared with biocontrol agents, botanical and fungicide against R. solani. Dual culture assay showed that PPFM-2 (52.77 %) and PPFM-5 (53.88 %) were more effective than Pseudomonas fluorescens (43.42 %) and less effective than Trichoderma asperellum (72.50 %) for inhibition of R. solani. Poisoned food technique showed that PPFM-2 and PPFM-5 were in line with mancozeb 75 WP, as both showed 100 per cent inhibition to R. solani. And they were more effective than Raksha at 0.6 (36.00 %), 1.0 (74.40 %) and 2.0 (82.20 %) per cent concentration. Efficacy of selected strains of PPFMs (M. testaceum and M. hispanicum), biocontrol agents (T. asperellum and P. fluorescens), botanical (Ready to Use Neem Oil Garlic Soap, Raksha) and fungicide (Mancozeb 75 WP) against R. solani under field conditions were tested. The natural disease incidence in the field was delayed to 28 days by M. hispanicum and to 23 days by M. testaceum. Maximum per cent reduction over control for disease incidence and disease severity was showed by M. testaceum and M. hispanicum. Biometric observations at 30, 45 and 65 days after transplanting, showed maximum increase over control for plant height, number of leaves per plant, fresh and dry weight of shoots and shoot root ratio in PPFM treated plots. In contrast, the root length as well as fresh and dry weight of roots were maximum in P. fluorescens treatment. Recording the PPFM population in the phyllosphere at harvest, it is revealed that plants with the highest population of PPFM displayed significantly enhanced biometric characters as compared to plants with a substantially lower population.