Botany
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/3747
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Item Carbon Source dependent - anaerobic Soil Disinfestation (ASD) Mitigates the Sclerotial Germination of Sclerotinia Sclerotiorum(Tropical Plant Pathology (2020), 2020) Mahalingam, T.; Rajapakse, C.S.K.; Somachandra, K.P.; Attanayake, R.N.Though Sclerotinia sclerotiorum IS a well-studied plant pathogen that causes significant economic damage worldwide, sustain able and environmental friendly control methods are difficult to establish due to it wide host range, cosmopolitan distribution and production of recalcitrant structures that can survive in soil for a long time. The pathogen was found causing a severe disease incidence on cabbage in 2016 in Sri Lanka. It was hypothesized that a) isolates of the recent disease outbreak display cross resistance to commonly applied fungicides and b) carbon (C) source supplemented Anaerobic Soil Disinfestation (ASD) is effective in mitigating the germination of sclerotia. In vitro fungicide sensitivity assays showed large variation in mycelial growth inhibition indicating high adaptability of the population towards environmental fluctuations and management practices. Signatures of cross resistance were evident. ASD was carried out using cabbage (Brassica oleracea) and leek (Allium ampeloprasum) cull piles, durian (Durio zibethinus) peels and grass cuttings (Axonopus compressus) as C sources and determined the sclerotial viability. Cabbage and leek cull piles at rates of 60—100 mg/g soil completely inhibited sclerotial germination. Maintaining anaerobic condition along with C source amendments was found to be a critical step in mitigating the sclerotial germination. GC-MS analysis of the volatiles of cabbage leaves, leeks and durian further confirmed the presence of various bioactive compounds with potential antifungal activity. Therefore, in addition to elevated microbial activity in treatments, the volatiles of C sources may have helped mitigating sclerotial germination.Item Phenotypic variation of cabbage white mold pathogen, Sclerotinia sclerotiorum in the upcountry commercial cabbage fields in Sri Lanka(Journal of the National Science Foundation of Sri Lanka 2018 46 (2): 159 – 164, DOI: http://dx.doi.org/10.4038/jnsfsr.v46i2.8416, 2018) Mahalingam, T.; Guruge, B.M.A.; Somachandra., K.P.; Jayasekara, E.A.E.S.S.; Rajapakse, C.S.K.; Attanayake, R.N.Sclerotinia sclerotiorum is a cosmopolitan, necrotrophic and soil borne plant pathogen, capable of infecting many economically important crops. Although it is a well-studied pathogen elsewhere, there is no research conducted in Sri Lanka. The objectives of the current research were to study the phenotypic variations among isolates within the pathogen population in the upcountry commercial cabbage fields in Sri Lanka and to determine their sensitivity to a commonly applied fungicide, Mancozeb. Forty-six isolates obtained from infected cabbage heads were identified as S. sclerotionun based on its unique morphological characteristics. Colony diameter was measured on potato dextrose agar (PDA) plates at 23 °C and mycelia' colour was observed after two-week incubation. All the isolates were grown in pH indicator media to determine their add producing abilities. Sensitivity of the isolates to Mancozeb was assayed in vitro. There was a significant difference in colony growth among the isolates and sensitivity to Mancozeb. Two isolates showed abnormal mycelia' growth characteristics; a slower growth rate on PDA and reduced pathogenicity on cabbage leaves. Two levels of mycelia' pigmentation were observed on PDA. All the isolates were acid producers, inferring that all of them were pathogenic. In summary, the upcountry S. sclerotiorton pathogen population was found to be diverse for selected phenotypic traits, especially for mycelia( growth, and fungicide sensitivities inferring that the pathogen population is capable of adapting to changing environmental conditions. Therefore, disease management will be challenging if an epidemic occurs, and it is recommended that a proper management system should be identified before further expansion of upcountry cabbage cultivation.