natural-products-in-plant-pest-management

254 M. Santos et al.Thermophilicactinomycete13 %Fungi 5%Yeast 2%Thermophilicactinomycete25%Fungi 3%Yeast 1%Mesophilicactinomycete24%Mesophilicbacteria 31%Mesophilicactinomycete9%Mesophilicbacteria 30%Thermophilicbacteria 25%Thermophilicbacteria 32%Fig. 12.2. Distribution of the different morphologies found in the fi rst (left) and second (right)analysis of grape marc compost microfl ora.the same compost were done, 6 months apart. Microbiological analysis ofGMC showed a high number of microbial morphologies in the compost. Inthe first analysis, 192 different morphologies were found, and 240 in the second,6 months later. Most of the morphologies present in the first and secondanalyses were bacteria, with the average percentages being 31% mesophylicbacteria, 28% thermophylic, 16% mesophylic actinomycetes and 20% thermophylicactinomycetes, and only a few moulds 4% and yeasts 1%; thedistribution of morphologies found in both assays is shown in Fig. 12.2.Most microorganisms, both aerobic and anaerobic, respond to conditionsthat restrict iron ions due to the production of siderophores, whereby ionsare kidnapped or assayed thus preventing their availability. Siderophorescan act as growth factors and some as powerful antibiotics (Neilands, 1981).Many studies have described suppressiveness in agricultural soil due to siderophores.Thus, the addition of different species of Pseudomonas to a conductivesoil infected with Fusarium oxysporum f. sp. lini makes this soilsuppressive, preventing the development of the disease. The addition ofFe-EDTA reverses this situation (Kloepper et al., 1980). This principle alsoapplies to Gaeumannomyces graminis var. tritici, and several species of Pythium(Becker and Cook, 1984; Weller et al., 1986).The presence of siderophores produced by the microorganisms presentin the grape marc aerated compost tea and their involvement in the developmentof eight phytopathogenic fungi in the soil and one mycopathogenicfungus was studied.The results obtained from the in vitro analysis of the inhibiting effect ofACT on fungal development are shown in Fig. 12.3. The effect of the incubationtime of ACT on the efficiency of the in vitro fungal suppression of thenine fungi tested highlighted an increase in inhibition percentages as thetime of incubation of the compost increased (1, 7 or 14 days) being 80–100%for extract F (Filtered), in extractions after 1 and 7 days, and 100% after