No description available.

No description available.

No description available.

No description available.

This aim of the study was to investigate the effect of using less susceptible hybrids, and sailor foliar applied elicitor treatments (Milsana, chitin/chitosan) on powdery mildew disease severity and crop performance parameters in greenhouse grown tomato and courgette. The second aim of the study was to investigate potential mode of actions of elicitors against powdery mildew. Two glasshouse experiments were performed with tomato plants under environmental conditions which resulted in the absence of powdery mildew infection; this allowed the effects of elicitor treatments on tomato plant growth and fruit yield and quality parameters to be determined in the absence of confounding effects of mildew infection. These data were then combined with data sets from identical trials carried out under contrasting environmental conditions and mildew disease pressure and used in multivariate analyses designed to identify associations between a environmental and agronomic drivers on tomato performance. Tomato yield and sugar content were only affectcd by hybrid choice, with the less susceptible tomato hybrid Elpida showing higher yield and higher sugar fruit content. Truss and leaf numbers were reduced by the use of Milsana and the sulphur fungicide treatment, which was included in the study as a positive control. Leaf chlorophyll was found to be higher in plants of the less susceptible hybrid Elpida and those treated with Milsana. Total antioxidant activity was not significantly affected by elicitors, but there was a trend towards higher antioxidant levels where standard Milsana treatment \vas applied. Multivariate analyses suggest that the environmental factors, relative humidity, mean and maximum daily temperature, were significant drivers. Powdery mildew severity was strongly positively associated with relative humidity and negatively with mean and maximum daily temperature. Leaf chlorophyll content was strongly negatively associated with relative humidity and positive ly with mean and maximum daily temperature. The drivers non-use of chitin soil amendment and foliar treatment (untreated control) were also identified as highly significant. Total fruit yield, number of fruits and fruit diameter were strongly positively associated with these drivers.

Lettuce and tomato field trials were performed in an unheated polytunnel in Aberdeenshire to investigate the efficacy and mode of activity of <i>Brevibacillus brevis</i> against grey mould disease (<i>Botrytis cinerea</i>).  This was achieved by means of treating plants with whole cultures of <i>B. brevis</i> WT (containing gramicidin S and biosurfactant) and <i>B. brevis</i> E1 (containing biosurfactant only) and also with supernatant and spore fractions of such cultures so that the effects of treatments containing one, both or neither of the potentially active components, gramicidin S (bound to the bacterial spore) and biosurfactant (released into the culture medium) could be assessed.  In winter lettuce, WT and E1 reduced grey mould by up to 79% (p=0.05) with no significant disease (p=0.05) between efficacy of these treatments.  WT reduced disease by 59% in spring lettuce but at low significance (p=0.2) although marketable yields were significantly improved (p=0.05).  The biocontrol treatments WT, E1, SWT and SE1 reduced (p=0.05) grey mould by up to 48% in tomato leaves and 73% of WT treated plants had no stem lesions, significantly more (p=0.05) than lesion-free control plants (17%).  These results suggest that both the biosurfactant and gramicidin S play a role in disease reduction.  The biosurfactant appears to be responsible for disease reduction on aerial plant surfaces with large surface areas whilst Gramicidin S reduces disease in regions of higher humidity, such as the base of lettuce plants and on tomato stems.