Classical and augmentative biological control against ... - IOBC-WPRS

Nicot et al. (Appendix for Chapter 1)
to regulate the cell growth rate by controlling interactively the nutrient feed rate, temperature, pH and agitation speed based on dissolved oxygen. In batch cultivation, the process suffered from low yield
of cell mass (3.2 g litre-1) and antifungal activity because of high initial glucose concentration followed by acetate formation which the causal agent for inhibition of cell growth. Constant and exponential
fed-batch strategies were adopted to circumvent this potential problem. Fed-batch cultivation of B. subtilis was conducted at the specific growth rate of 0.13 and 0.1 h-1 for constant and exponential
strategies, respectively. High cell density of 12.8 and 14.6 g litre-1 for both operations, with an overall biomass yield of 0.45 g g-1 was achieved. The inhibitory activity of antifungal in supernatant
reached its maximum value of 2 and 2.2 cm for constant and exponential fed-batch cultivations.
Mazurier, S., T. Corberand, et al. (2009). "Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt." ISME Journal 3(8): 977-991.
Natural disease-suppressive soils provide an untapped resource for the discovery of novel beneficial microorganisms and traits. For most suppressive soils, however, the consortia of microorganisms and
mechanisms involved in pathogen control are unknown. To date, soil suppressiveness to Fusarium wilt disease has been ascribed to carbon and iron competition between pathogenic Fusarium oxysporum
and resident non-pathogenic F. oxysporum and fluorescent pseudomonads. In this study, the role of bacterial antibiosis in Fusarium wilt suppressiveness was assessed by comparing the densities,
diversity and activity of fluorescent Pseudomonas species producing 2,4-diacetylphloroglucinol (DAPG) (phlD+) or phenazine (phzC+) antibiotics. The frequencies of phlD+ populations were similar in
the suppressive and conducive soils but their genotypic diversity differed significantly. However, phlD genotypes from the two soils were equally effective in suppressing Fusarium wilt, either alone or in
combination with non-pathogenic F. oxysporum strain Fo47. A mutant deficient in DAPG production provided a similar level of control as its parental strain, suggesting that this antibiotic does not play a
major role. In contrast, phzC+ pseudomonads were only detected in the suppressive soil. Representative phzC+ isolates of five distinct genotypes did not suppress Fusarium wilt on their own, but acted
synergistically in combination with strain Fo47. This increased level of disease suppression was ascribed to phenazine production as the phenazine-deficient mutant was not effective. These results
suggest, for the first time, that redox-active phenazines produced by fluorescent pseudomonads contribute to the natural soil suppressiveness to Fusarium wilt disease and may act in synergy with carbon
competition by resident non-pathogenic F. oxysporum.
Minerdi, D., S. Bossi, et al. (2009). "Volatile organic compounds: a potential direct long-distance mechanism for antagonistic action of Fusarium oxysporum strain MSA 35." Environmental Microbiology
11(4): 844-854.
Fusarium oxysporum MSA 35 [wild-type (WT) strain] is an antagonistic Fusarium that lives in association with a consortium of bacteria belonging to the genera Serratia, Achromobacter, Bacillus and
Stenotrophomonas in an Italian soil suppressive to Fusarium wilt. Typing experiments and virulence tests provided evidence that the F. oxysporum isolate when cured of the bacterial symbionts [the
cured (CU) form], is pathogenic, causing wilt symptoms identical to those caused by F. oxysporum f. sp. lactucae. Here, we demonstrate that small volatile organic compounds (VOCs) emitted from the
WT strain negatively influence the mycelial growth of different formae speciales of F. oxysporum. Furthermore, these VOCs repress gene expression of two putative virulence genes in F. oxysporum
lactucae strain Fuslat10, a fungus against which the WT strain MSA 35 has antagonistic activity. The VOC profile of the WT and CU fungus shows different compositions. Sesquiterpenes, mainly
caryophyllene, were present in the headspace only of WT MSA 35. No sesquiterpenes were found in the volatiles of ectosymbiotic Serratia sp. strain DM1 and Achromobacter sp. strain MM1. Bacterial
volatiles had no effects on the growth of the different ff. spp. of F. oxysporum examined. Hyphae grown with VOC from WT F. oxysporum f. sp. lactucae strain MSA 35 were hydrophobic whereas
those grown without VOCs were not, suggesting a correlation between the presence of volatiles in the atmosphere and the phenotype of the mycelium. This is the first report of VOC production by
antagonistic F. oxysporum MSA 35 and their effects on pathogenic F. oxysporum. The results obtained in this work led us to propose a new potential direct long-distance mechanism for antagonism by F.
oxysporum MSA 35 mediated by VOCs. Antagonism could be the consequence of both reduction of pathogen mycelial growth and inhibition of pathogen virulence gene expression.
Nam, M. H., M. S. Park, et al. (2009). "Biological Control of Strawberry Fusarium Wilt Caused by Fusarium oxysporum f. sp fragariae Using Bacillus velezensis BS87 and RK1 Formulation." Journal of
Microbiology and Biotechnology 19(5): 520-524.
Two isolates, Bacillus sp. BS87 and RK1, selected from soil in strawberry fields in Korea, showed high levels of antagonism towards Fusarium oxysporum f. sp. fragariae in vitro. The isolates were
identified as B. velezensis based on the homology of their gyrA sequences to reference strains. BS87 and RK1 were evaluated for control of Fusarium wilt in strawberries in pot trials and field trials
conducted in Nonsan, Korea. In the pot trials, the optimum applied concentration of BS87 and RK1 for pre-plant root-dip application to control Fusarium wilt was 10(5) and 10(6) colony-forming units
(CFU)/ml, respectively. Meanwhile, in the 2003 and 2005 field trials, the biological control efficacies of formulations of RK1 were similar to that of a conventional fungicide (copper hydroxide) when
compared with a non-treated control. The RK1 formulation was also more effective than BS87 in suppressing Fusarium wilt under field conditions. Therefore, the results indicated that formulations of B.
velezensis BS87 and RK1 may have potential to control Fusarium wilt in strawberries.
Narayan, M., P. Tini, et al. (2009). "Biological and chemical management of tomato wilt caused by Fusarium oxysporum f.sp. lycopersici." Journal of Soils and Crops 19(1): 118-121.
Wilt of tomato is one of the most important known disease caused by Fusarium oxysporum f. sp. lycopersici. In the present study four bioagents (Trichoderma harzianum, T. viride, Bacillus subtilis and
Pseudomonas fluorescens) and two fungicides (Carbendazim and Thiram) were evaluated both in vitro and in vivo conditions. In vitro evaluation, of Carbendazim (0.1%) completely inhibited the growth
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