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Title: Studies on Alternaria brassicae and Alternaria brassicicola infection of cruciferous crop plants
Author: Prasanna, Kothanur Papanna Rama
ISNI:       0000 0001 3498 5213
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1984
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In studies on Alternaría infection of cruciferous plants, A. brassicae and A. brassicicola were recognized to be the two main pathogenic species involved. The results of surveys of oilseed rape crops in east Scotland showed Alternaría disease to be a major problem, and A . brassicae was found to be the predominant pathogen: factors which were associated with a higher incidence included higher rainfall, previous cropping with oilseed rape and luxuriant growth. A. brassicicola occurred only occasionally, mainly where vegetable Brassicas provided a source of inoculum. From a survey of seed samples of cruciferous plants, A. brassicae appeared widespread in oilseed rape and A. brassicicola in other crop plant groups. In artificial inoculation studies both fungal species were found to adversely affect seed yield and quality of oilseed rape: A. brassicae acted as a more aggressive leaf pathogen, whereas A. brassicicola exhibited a capacity for prolific spore production and an ability to rapidly colonise senescing or immature, unprotected tissue. In assessing variation in levels of infection among different oilseed rape cultivars, differences were quantitative rather than qualitative in nature, with no evidence of major gene effects. A leaf disc method of assessment was developed to study host-pathogen interactions covering a wide range of cruciferous plants and different isolates of each pathogen. The patterns of response of the host range to both pathogens tended to be similar and there was no evidence of marked host specificity among isolates. Low infection levels in some host groups was associated with a high degree of waxiness of the cuticle. In further leaf disc studies, increased lesion development was found with increasing atmospheric humidity, while surface tension characteristics of spore suspension droplets appeared to influence the initiation of infection. The optimum temperature for leaf lesion development was 25°C, but maximum colonisation of inert substrate from infected seed occurred over a wider temperature range. Both pathogens were observed to be seed-borne either superficially or within the embryo. More deep-seated infection was associated with germination failure, while the incidence of seedling mortality was increased in moist germinating conditions. With deep-seated infection, only those treatments which had a penetrative effect substantially controlled transmission.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Crop infection