Nonpathogenic Fusarium oxysporum strain Fo47 controls the incidence of Fusarium wilt. Four bioassays in which a strain of the pathogen F. oxysporum f. sp. lycopersici and Fo47 were not in direct contact were developed to evaluate whether Fo47 could induce resistance to Fusarium wilt in tomato plants. Fo47 and the pathogen were separated either physically or in time. Bio-assays were carried out under hydroponic conditions (two bioassays), in potting mix, or in autoclaved soil. Strain Fo47 protected tomato against Fusarium wilt in all four bioassays. Inoculation with Fo47 increased chitinase, β-1,3-glucanase, and β-1,4-glucosidase activity in plants, confirming the ability of Fo47 to induce resistance in tomato. This report is the first to demonstrate that a nonpathogenic strain of F. oxysporum can induce resistance to Fusarium wilt in tomato plants. This result has important practical implications for biocontrol of tomato diseases under commercial conditions.

SynopsisThe reproductive cycle and sex inversion of the protandrous, tropical seabass, Lates calcarifer, reared in seacages in French Polynesia, were studied. In Tahiti, this species exhibits a single annual reproductive period from October to February beginning with the warm and wet season. Sex inversion begins at the end of this reproductive period in post-spawning males. The main histological features of this process were: degeneration of testicular tissue, appearance of peripheral female germinal cells, and centripetal proliferation of ovarian tissue. Completion of sex inversion required profound morphological changes in the gonads because of the strong dimorphism that exists between testis and ovary. All transitional gonads appeared morphologically smaller than testes and typically had a red-pink colour. About 45% of the three-year-old male stock underwent sex inversion, and males averaged smaller in size than did females and transitional fish.

A microarray spotted with 369 different 16S rRNA gene probes specific to microorganisms involved in the degradation process of organic waste during composting was developed. The microarray was tested with pure cultures, and of the 30,258 individual probe-target hybridization reactions performed, there were only 188 false positive (0.62%) and 22 false negative signals (0.07%). Labeled target DNA was prepared by polymerase chain reaction amplification of 16S rRNA genes using a Cy5-labeled universal bacterial forward primer and a universal reverse primer. The COMPOCHIP microarray was applied to three different compost types (green compost, manure mix compost, and anaerobic digestate compost) of different maturity (2, 8, and 16 weeks), and differences in the microorganisms in the three compost types and maturity stages were observed. Multivariate analysis showed that the bacterial composition of the three composts was different at the beginning of the composting process and became more similar upon maturation. Certain probes (targeting Sphingobacterium, Actinomyces, Xylella/Xanthomonas/ Stenotrophomonas, Microbacterium, Verrucomicrobia, Planctomycetes, Low G + C and Alphaproteobacteria) were more influential in discriminating between different composts. Results from denaturing gradient gel electrophoresis supported those of microarray analysis. This study showed that the COMPOCHIP array is a suitable tool to study bacterial communities in composts.

The impact of soil type, long-term soil management, and short-term fertility input strategies on the suppressiveness of soils against soil-borne (Ocimum basilicum -Rhizoctonia solani, Lepidium sativum -Pythium ultimum) as well as air-borne (Lycopersicon esculentum -Phytophthora infestans, Arabidopsis thaliana -Hyaloperonospora parasitica) diseases was studied. Soils from field trials established in five European sites with contrasting pedoclimatic conditions were examined. Sites included (i) a long-term management field trial comparing organic and conventional farming systems (DOKtrial, Therwil, Switzerland) (ii) a short-term fertility input field trial comparing mineral and organic matter fertilisation regimes (Bonn (BON), Germany) (iii) two short-term fertility input field trials (Stockbridge (STC) and Tadcaster (TAD), UK) comparing the impact of farmyard manure, composted farmyard manure, and chicken manure pellet amendements and (iv) soil from a site used as a reference (Reckenholz (REC), Switzerland). Soil type affected disease suppressiveness of the four pathosystems signficantly, indicating that soils can not only affect the development of soil-borne, but also the resistance of plants to air-borne diseases at relevant levels. Suppressiveness to soil-and air-borne diseases was shown to be affected by soil type, but also by long-term management as well as short-term fertility inputs.

Harnessing Microbiomes of Suppressive Composts of action of biocontrol strains. Integrating the benefits of these approaches will bring the long-term goals of employing microorganisms for a sustainable control of plant pathogens and developing reliable diagnostic assays to assess the suppressiveness of composts within reach.

Genetic variation and pathogenicity of Phytophthora infestans isolates collected from organic potato crops of the susceptible cv. Bintje and the moderately resistant cv. Santé were assessed in France, Norway, and the United Kingdom in 2001 and in Switzerland in 2001 and 2002. Population structures differed considerably between the four P. infestans populations. Those from France, Switzerland and the UK were mainly clonal populations showing restricted levels of genetic diversity, whilst those from Norway were mixed A1 and A2 mating type populations with high levels of genetic diversity, suggesting periodical sexual reproduction. Isolates collected from cv. Bintje were on average more aggressive than or comparable to isolates from cv. Santé. Race complexity varied considerably between the regional P. infestans populations, with isolates from France and Switzerland showing the highest number of virulence factors. In all pathogen samples but the French, isolates collected from cv. Santé were more complex than isolates collected from cv. Bintje. No directional selection towards increased aggressiveness towards the more resistant cultivar Santé was observed. This suggests that there is no shift towards increased levels of pathogenicity in P. infestans populations following the large-scale introduction of more resistant potato varieties in organic production systems in Europe.

The survival of Plasmodiophora brassicae was studied at digestion temperatures of 35 °C and 55 °C in laboratory batch digesters within one and two weeks, respectively. The study showed that digestion at 55 °C almost completely reduced the ability of infecting bait plants. The seeds of Rumex obtusifolius and Lycopersicon lycopersicum (tomatoes) were completely destroyed at 55 °C and a digestion time of 14 days, in laboratory batch digesters. The experiments carried out in a two stage pilot plant (Leach-Bed Solid Phase batch Digester for hydrolysis and a pulsating dynamic anaerobic filter for methanogenesis) showed that hydrolytic conditions are mainly responsible for the killing of weed seeds. Some additional data on the qualities of different digested substrates are presented.

The organic market has grown exponentially in Europe during the last ten years. However, the organic fruit industry has shown the lowest growth rates (1-5% market share) compared to other commodities. One major reason is the high production risk due to high disease and pest pressure in humid climates. Key pests and diseases in apple and pear include scab, sooty blotch, and fire blight as well as rosy apple aphid, pear sucker, and codling moth. In cherry, damages due to brown rot (Monilinia) and the cherry fruit fly make organic production almost unfeasible. In an ideal organic system, all possible measures that lead to improved stability of the system must be implemented. In fruit production, such measures include (i) use of resistant varieties (scab), (ii) active promotion of predators (rosy apple aphid), (iii) sanitation (cherry monilinia), (iv) microclimate management (planting density, covering trees), and (v) strengthening the plant self-defence system (e.g. building up of soil fertility, bio-dynamic preparations). At present, most organic orchards have been designed for conventional production and, therefore, lack most stabilising components. In consequence, organic fruit production still depends largely on direct pest and disease control methods. These include traditional pesticides such as copper, sulphur, and lime sulphur, pyrethrin, oil and soap preparations. More recently, new pest control compounds and techniques have been developed including neem products, granulosis virus, and mating disruption. New tools for disease control are less spectacular and focus on the replacement of copper (e.g. with clay powders and resistance inducers). The introduction of new equipment, materials, and Decision Support Systems (DSS) will further improve yield stability. However, other limiting factors such as weed competition, crop load regulation, and conventional market demands need innovative solutions.