1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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Subject: search.filters.subject.Sheath blight

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    Phenotyping and marker assisted screening of rice (Oryza sativa L.) germplasm for sheath blight(Rhizoctonia solani kuhn) resistance
    (Department of Genetics and Plant Breeding, College of Agriculture,Vellayani, 2024-12-16) Bandela Chandana.; Adheena Ram
    The study entitled “Phenotyping and marker assisted screening of rice (Oryza sativa L.) germplasm for sheath blight (Rhizoctonia solani Kühn) resistance” was carried out at the Department of Genetics and Plant Breeding, College of Agriculture, Vellayani during 2022 to 2024 with an objective of artificial screening and identification of rice genotypes for sheath blight resistance and validation with molecular markers linked to reported QTLs of sheath blight resistance. The phenotypic screening for sheath blight resistance was conducted, using thirty rice genotypes and different biometric, biochemical and computed parameters were analysed. Analysis of variance revealed significant difference for all the biometric characters except number of tillers per plant. All the biochemical parameters such as peroxidise, catalase, polyphenol oxidase and phenylalanine ammonialyase showed an increase in biochemical activity in genotypes under stress but only phenylalanine ammonialyase showed significant difference among them. Studies on phenotypic coefficient of variation and genotypic coefficient of variation revealed high variation for lesion height, number of grains per panicle, number of unfilled grains per panicle and grain yield per plant. In general, PCV values were higher than GCV for all characters indicating the influence of environment towards total variance. High heritability with high genetic advance was noticed for days to heading, days to 50 per cent flowering, number of productive tillers per plant, stem thickness, panicle length, number of grains per panicle, thousand grain weight and grain yield per plant indicating the influence of additive gene action and suitability of these traits for selection. Panicle length, days to 50 per cent flowering, number of tillers per plant and thousand grain weight had significant positive correlation with grain yield per plant where as plant height and lesion height were negatively correlated with grain yield per plant. The days to 50 per cent flowering has a strong positive direct effect on grain yield per plant and days to heading through the days to 50 per cent flowering showed a strong indirect effect on grain yield per plant. Based on genetic divergence analysis 30 genotypes were grouped into four clusters. Cluster III with nine genotypes was the largest followed by cluster I (eight genotypes) and cluster IV (seven genotypes). The clusters II had the least number of genotypes (six). Based on the inter-cluster distances, clusters III and IV had the lowest divergence (6.50) while clusters I and IV recorded the highest divergence (11.41). The highest intra cluster distance was noticed among genotypes of cluster IV (6.32) and the lowest was noticed among genotypes of cluster II (5.36). The genotypes Remanika, Chenthadi, Krishnanjana, Panchami, Karishma, Revathy, White Ponni and Bhadra in the cluster I had the highest mean value for days to heading, days to 50 per cent flowering, number of tillers per plant, number of productive tillers per plant, stem thickness, panicle length, number of grains per panicle, thousand grain weight and grain yield per plant. Based on scoring of sheath blight severity and percentage disease index the genotypes Gouri, Chenthadi, Krishnanjana, Panchami, White ponni, VYT-1, Chenkayama and Onam were found to be resistant for sheath blight. Moderate resistance to sheath blight was shown by the cultivars Karishma, Revathy, Bhagya, VYT-7, Karuna, Sreyas, Prathyasa, Karthika, Chettivirippu, Makom, Uma and Bhadra. The 15 SSR markers linked to the reported sheath blight QTLs used for validation were polymorphic with the PIC value ranging between 0.17 (RM16200) and 0.63 (RM71). RM105 linked to qShB9-1 had the maximum number of alleles (4). The cluster analysis for marker data grouped the rice genotypes into two major clusters with cluster II having the highest number of genotypes. The high yielding rice genotypes Chenthadi and Krishnanjana were identified as resistant to sheath blight based on phenotypic and genotypic data. These genotypes can be used as donors for sheath blight resistance in future breeding programmes.
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    Effect of application of plant protection chemicals on the survival of Rhizoctonia solani Kuhn
    (Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Lulu Das; Chandrasekharan Nair, M
    In Kerala, the incidence of sheath blight of rice is endemic causing great economic loss. The present investigation was undertaken to make a critical assessment of the efficacy of various palnt protection chemicals, viz., fungicides, insecticides and herbicides on the incidence and intensity of sheath blight of rice and on the survival of the pathogen. The organism was isolated from naturally infected rice fields and its pathogenicity proved. Studies on the viability of sclerotia revealed that they sclerotia remained viable upto 210 days in all the different types of soils namely sandy, clayey and loamy. The organism could survive on straw bits upto 180th ady only.
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    Evaluation of newer fungicides against diseases of rice especially rice blast
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 1981) Sheela Paul, T; Abi Cheeran
    The experiments for the evalution of newer fungicides against rice diseases were conducted at the Rice Research Station and Instructional Farm at Mannuthy during the first and second crop season of 1979-80. The objectives of this study were to find out the efficiency of the new foliar fungicide Panolil, against four rice diseases viz., blast, brownspot, sheath blight and stackburn and to evaluate the efficacy of the newer fungicides Panolil, Panoctine and Panoram as seed treatment fungicides. In the bioassay studies in vitro cent per cent inhibition of Pyricularia oryzae was obtained in 1000 ppm of Panolil, 2000 ppm of Panoctine, 500 ppm of Panoram, 250 ppm of Hinosan and Kitazin and 100 ppm of Agallol in potato dextrose agar medium. In all the fungicide incorporated liquid medium no growth was observed. Panolil (500 ppm), Panoctine (500 ppm), Panoram (1000 ppm), Hinosan (1000 ppm), Kitazin (1000 ppm) and Agallol (100 ppm) completely inhibited the growth of Drechslera oryzae in solid medium. In liquid medium also no growth was observed even in lowest concentration of Panoli, Panoctine and Agallol, 250 ppm and above concentration of Panoram and Kitazin. But growth was observed in all the lower concentrations of Hinosan. Cent per cent inhibition of corticium sasakii was not noticed even in 2000 ppm concentration of Panolil and Panoctine. Panoram and Kitazin at 250 ppm concentration and Hinosan at 500 ppm gave 100 per cent inhibition of C. sasakii. In liquid medium no growth of the fungus was obtained in any of the fungicidal treatments except in the lowest concentration of Kitazin. Panolil, Hinosan and Kitazin gave 100 per cent inhibition of Alternaria padwixkii only at 2000 ppm. Panoram at 1000 ppm and Agallol at 100 ppm gave 100 percent inhibition. In liquid medium growth was observed only in the lowest concentration of Panoram and Kitazin and in all the concentrations of Hinosan. The incidence of blast was low in both the seasons and in both the varieties. Two higher concentrations of panolil (1.5 kg/ha and 1 kg /ha) were equally effective as organophosphorus fungicides in reducing leaf infection, while against neck blast, Hinosan and Kitazin were better than Panolil. Brown spot disease was low in both the varieties during first crop and while in second crop season disease was notices only in Jaya. Panolil 1.5 kg/ha was found to be superior to Hinosan and Kitazin in reducing the disease. Sheath blight infection was low and was noticed only during the first crop in the variety Triveni. Panolil was as effective as organophosphorus fungicides in controlling the disease. Stackburn disease appeared on both the varieties in both the seasons. This disease was best controlled by higher concentrations of Panolil. Seed treatment and storage studies were conducted using the seeds collected from the first crop season. Newer fungicides panolil, Panoctine and Panoram and Agallol were used as seed treatment fungicides. The effect of delayed drying and storage, on seed microflora and deterioration of viability were also studied by using the seeds treated with different fungicides. An increased number of fungal flora was observed in untreated seeds compared to the treated ones. Generally the number of seeds associated with fungal flora increased on storage. For both rice varieties Agallol was found to be the best in reducing association of fungal flora on seeds while when the storage period was extended upto 32 weeks the highest concentration of newer chemicals were found to be on par with Agallol. When the seeds were stored for 16 weeks, the influence of delayed drying on germination was pronounced only when the drying was delayed beyond 6 days then the germination fell below 80 per cent. After 24 weeks of storage, the germination fell below 80 per cent even when the drying was delayed for three days. Agallol was found to be the best seed dresser, followed by the higher concentrations of newer fungicides. When the storage was prolonged for 32 weeks, satisfactory germination was obtained only for the seeds dried immediately and pretreated with Agallol and Panoram 1 g/kg and 1.5 g/kg.