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2012 - 20152
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Subject: Plant Pathology × Author: Ravichandran S. × End date: 2017 × Start date: 2010 ×
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    ThesisItemOpen Access
    Studies on Soil Borne Fungal Diseases of Chickpea
    (University of Agricultural Science, Dharwad, 2015-11) Ravichandran S.; Hegde, Yashoda R.
    Chickpea (Cicer arietinum L.) is the most important Rabi pulse crop in India. Important soil borne fungal diseases observed during survey were wilt caused by Fusarium oxysporum f.sp. ciceri,(FOC) (27.07%), dry root rot caused by Rhizoctonia bataticola (RB) (37.06%) and collar rot caused by Sclerotium rolfsii (0.65%), alone and in combination (34.32%) with the disease incidence ranging from 1.4 to 23.4 per cent. In interaction studies, JG 11 and JAKI 9218 were moderately resistant to FOC, however were susceptible to RB and S. rolfsii. In cultural studies, FOC and RB attained maximum growth at 16 and 14 days respectively. Temperature of 25 – 300C and pH of 6 to 7 were optimum for growth of these two pathogens. 32 isolates of FOC were collected and classified into three groups based on growth rate virulence index and dry mycelial weight. 20 isolates of RB collected varied in growth and dry mycelial weight. In race identification of FOC by using differentials indicated that all isolates belong to race 1a and further confirmed by amplification with specific primer. ITS rDNA sequence analysis and specific primers confirmed the identity of isolates of FOC and RB. Twenty six genotypes showed resistant reaction against FOC in wilt sick plot in two years and five genotypes remained resistant even in glasshouse screening. All tested triazoles and comi product fungicides and eucalyptus leaf extract was effective in mycelial inhibition of both pathogens. Highest inhibition of FOC was observed in Trichoderma harzianum and RB was by Pseudomonas fluorescens. Seed treatment with carboxin + thiram recorded the lowest per cent disease incidence with the highest yield and cost benefit ratio in field experiment studies in Farmer’s field, (Bailhongal) and sick plot at Kalaburgi.
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    ThesisItemOpen Access
    Epidemiology and Management of Purple Blotch of Onion Caused by Alternaria porri (Ellis) Cif.
    (UAS, Dharwad, 2012) Ravichandran S.; B.C. Kamanna
    Onion (Allium cepa L.) (2n=16) one of the most important commercial vegetable crops of India belonging to the family Alliaceae. Purple blotch caused by Alternaria porri (Ellis) Cif. is a destructive disease and causes extensive damage to bulbs as well as seed crop. Survey during kharif 2011, revealed that, highest per cent disease index (69.33) was noticed in Vonnali village in Uttara Kannada district. While the lowest (17.33) was recorded in Annigeri village in Dharwad district. On the basis of morphological and pathological studies, the pathogen was identified as Alternaria porri (Ellis) Cif. The pathogen was grouped into six isolates viz., Dharwad, Gokak, Savanur, Navalgund, Mundargi and Kumta isolates. The cultural and morphological characters were studied on different media where the growth was fast in Czapeks Dox medium and slow growth in the Corn meal agar. The weather studies revealed that PDI was progressing at linear rate throughout the plant growth and it was negatively correlated with minimum temperature, relative humidity (morning and evening). While, positively correlated with maximum temperature and negatively non significant with rainfall. Out of twelve different fungicides tested in vitro, Zineb 68% + Hexaconazole 4%WP, Mancozeb 75%WP at all the concentrations completely inhibited the mycelial growth of Alternaria porri. Among the six plant extracts, garlic clove extract and NSKE extracts were highly inhibitory to Alternaria porri, while periwinkle leaf extract proved to be least inhibitor. Among six bioagents, Trichoderma harzianum was most effective. In case of field evaluation field evaluation of different fungicides botanicals and bioagents indicated that, lower disease index (30.66), high bulb yield (20.60 t/ha) and maximum B:C ratio (5.30) was recorded in plots receiving three sprays of Avatar (0.15%). In botanicals and bio agents Garlic clove extract @ 5 per cent recorded highest yield of (16.13 t/ha) and incremental B:C ratio of 4.07.