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Title: An investigation into the epidemiology and control of Rhizoctonia spp. on Calluna vulgaris and Erica spp.
Author: Litterick, Audrey Michele
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1991
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Rhizoctonia spp. were isolated from 22% of cuttings and 10% of rooted plants of C. vulgaris and Erica spp., collected from UK nurseries, which showed browning of the foliage. Rhizoctonia spp. were most often isolated from cutting bases at compost level and from stem-base and foliage at compost level on rooted plants. Thirty two per cent of Rhizoctonia spp. isolates obtained from nursery stock species possessed multinucleate hyphal cells and were designated R. solani Kuhn. The remaining 68% which had two nuclei in each cell were termed binucleate Rhizoctonia spp. Rhizoctonia spp. were isolated from between 3% and 13% of samples of used nursery materials including cutting trays, capillary matting, polythene and composts collected from UK nurseries. They were not isolated from any samples of new, unused materials or composts. Spread of Rhizoctonia spp. and subsequent disease development was initiated from contaminated plastic trays, polythene, capillary matting, gravel, sand, compost and infected cuttings. Root development and the level of foliar browning due to disease caused by Rhizoctonia spp. on cuttings of C. vulgaris and Erica spp. , varied significantly depending on isolate. There was evidence of a relationship between number of nuclei and the level of both foliar browning and root development. The susceptibility of cuttings of E. cinerea and C. vulgaris, to disease caused by binucleate Rhizoctonia spp. differed significantly depending on both cultivar and environment. The susceptibility of C. vulgaris cvs Cuprea and Silver Queen cuttings to disease caused by binucleate Rhizoctonia sp. isolate D1, also varied depending on the environment in which stock plants were kept, and on whether cuttings were taken from shoot-tips or shoot-bases. The level of disease caused by binucleate Rhizoctonia sp. isolate 48 on C. vulgaris and E. vagans cuttings was related to the quantity of inoculum present in the compost. Disease development was most severe when inoculum of binucleate Rhizoctonia sp. isolate D1 was spread on the surface, and least severe when it was spread on the base of cutting trays 5 cm below the compost surface. The optimum pH for growth of isolates of R. solani and binucleate Rhizoctonia spp. in vitro lay between 5.4 and 7.4, and differed significantly depending on isolate. Disease development on C. vulgaris cuttings grown in compost amended with binucleate Rhizoctonia sp. isolate D1, was significantly lower in unlimed propagation compost (pH 3. 8) than in composts limed to pH values ranging from 4.9 to 6.0.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available