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Thesis

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2012 - 20152
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Subject: Plant Pathology × Author: Veena × End date: 2017 × Start date: 2010 ×
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    ThesisItemOpen Access
    Studies on Groundnut Rust Caused By Puccinia Arachidis Speg.
    (University of Agricultural Science, Dharwad, 2015-10) Veena; Adiver, S.S.
    Groundnut rust caused by Puccinia arachidis Speg. is one of the most important foliar disease. Maximum disease severity of 86.42 PDI was recorded in Jambaldinni village of Raichur taluka. PaKUS isolate was found to be different from other isolates, which has recorded round shaped pustules, uredospores were oblong to ellipsoid in shape, bigger in size (585.84 µm2), showed maximum per cent germination of uredospores (90.00%) at 250C and 86.33% at pH 9. DNA amplication was observed at the region 600 bp. Variation was observed in nucleotide sequences from 77 to 99 per cent among the isolates. At -80 and -20 0C, viability of uredospores was noticed upto 90 days. Teliospores were found in Ranebennur isolate (PaRAN) but there was no production of teliospores under modified environmental conditions and detached leaf technique. Disease intensity increased in older plants compared to young plants. Maximum germination of uredospore was observed at 2.0 per cent sucrose solution (45.33%) at 24 h after incubation. Out of 108 genotypes screened, five genotypes viz., GPBD-4, GPBD-5, ICGV-86699, TG-72 and TG- 37A found highly resistant. Resistant genotypes had more quantity of reducing, non-reducing and total sugars as compared to susceptible genotypes. Under in vitro condition, Azadirachta indica leaf extract was highly significant in suppressing the uredospore germination. Culture filtrate of bioagents revealed that bacterial bioagents were better than fungal bioagents in inhibiting the uredospore germination Hexaconazole under systemic and mancozeb under non systemic fungicide were found highly effective in inhibition of germination of uredospore. In vivo studies revealed that, the treated check (Hexaconazole @ 0.1%) recorded significantly low disease (12.21 PDI) with 88.85 per cent reduction in disease severity over control and high yield (2696 kg/ha). The organic based treatment, Azadirachta indica leaf extract + Pseudomonas fluorescens recored 2511 kg/ha. Which was on par with the treated check.
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    ThesisItemOpen Access
    Investigations on Leaf Spot of Greengram Caused by Cercospora canescens Ellis and Martin
    (UAS, Dharwad, 2012) Veena; Yashoda R. Hegde
    Greengram [Vigna radiata (L.) Wilczek], an ancient and well known leguminous crop of Asia, commonly called as mungbean is an important pulse crop of India. Cercospora leafspot is of common occurrence in India. Leaf spot was noticed in all the locations surveyed with the range of 62.25 to 86.18 per cent. The maximum disease severity was noticed in Dharwad district (78.52%) followed by Belgaum district (71.35%) and disease was absent in Bagalkot and Gulbarga districts. Potato dextrose broth was used to study the growth phase of C. canescens. Maximum dry mycelial weight was recorded on 14th day of inoculation. Maximum mycelial growth was observed on Richard’s agar. The temperature of 250C was found to be the best for fungal growth. Maximum vigour index of sorghum was noticed in 16 days old culture filtrate at 200C indicating the maximum toxin production. Among different isolates, Amargola isolate produced more toxin with minimum vigour index. In host extract medium, maximum colony diameter was observed in Amargola isolate and sporulation was observed in Nippani isolate. Sporulation was observed in PDA with 6 and 8 % dextrose and maximum radial growth was observed in 6% dextrose. Among different isolates, the large sized conidia and more number of septa were found in Dharwad isolate. Screening of fifty four genotypes under natural condition revealed that none of the genotype was immune, three cultivars viz., IC 283869, R-86 and RM-8-6 were resistant to leaf spot disease. Under in vitro condition, hexaconazole, mancozeb and mancozeb+ carbendazim were effective fungicides. Ocimum sanctum at 15 and 20% botanical and Trichoderma spp. were able to reduce the growth of pathogen to a remarkable extent. In vivo studies revealed that spraying with 0.1% hexaconazole and difenconazole helped to manage the leaf spot successfully and recorded highest yield and yield parameters. Achook was least effective in managing the leaf spot.