Several studies were carried out to determine (i) thermal requirements for development, egg production and emergence of juveniles, and completion of the life cycle of Meloidogyne incognita and Meloidogyne javanica on cucumber, (ii) the maximum multiplication rate and the equilibrium density of root-knot nematodes on cucumber and yield losses in pot and plastic greenhouse experiments, and (iii) the relationships between relative leaf chlorophyll content (RLCC) and relative cucumber dry top weight biomass (RDTWB) in relation to increasing nematode densities at planting (P-i) in pot experiments. Thermal requirements of M.incognita and M.javanica on cucumber did not differ, irrespective of the biological stage. In the pot experiments, M.javanica completed one generation. The maximum multiplication rate (a) was 833, and the equilibrium density (E) varied according to the effective inoculum densities. The relationship between RDTWB and P-i fitted the Seinhorst damage function model. The RLCC value at 40 or 50days post-inoculation also fitted the damage model and was related to RDTWB. In greenhouse experiments, conducted from 2009 to 2012, M.incognita completed three generations. The values for a and E were 1147 and 625second stage juveniles (J2) per 250cm(3) soil, respectively. The tolerance limit was below zero, and the minimum relative yield ranged from 012 to 034.Postprint (published version

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With a surface area of 37 000 ha and an annual yield of 3 × 106 t, the south-east of Spain, predominantly the coast of Almeria, is the largest horticultural growing area under protected cultivation in Europe. A survey on perception of the impact of root-knot nematodes on vegetable production was carried out in this area by face-to-face interviews with 120 farm advisors. The survey was designed to evaluate opinions about prevalence and severity of root-knot nematode-induced diseases, percentage of infested area and effectiveness of root-knot nematode control methods. According to the answers, 17.7% of the fields were infested with root-knot nematode and 18.8% of the cultivable area within each site showed root-knot nematode disease symptoms, which came to 2.0% of the total area used to grow vegetables in the region. Average yield loss was estimated at about 30.8% of total vegetable production, and 38.1% of the farm advisors considered that root-knot nematode infections had increased over the last 5 years. Most farm advisors (78.3%) stated that the most commonly used control method was chemical soil fumigation. Non-fumigant nematicides were cited by 59.8% of them, grafting and resistant cultivars by 42.3%, soil solarisation 38.1%, plant extracts 14.4% and biofumigation 6.2%. The majority of farm advisors considered the application of fumigant nematicides combined with soil solarisation, and grafting onto resistant rootstocks as the most effective methods of root-knot nematode control. In addition to the interviews, plant and soil samples were taken from plastic greenhouses throughout the region to determine species of root-knot nematode present. Meloidogyne javanica was the most prevalent species followed by M. incognita and M. arenaria, but species distribution was linked to the predominating crop sequence in each area, since M. javanica occurred less frequently when sweet pepper rather than tomato appeared in the crop sequence.

Pot studies on the effects of mycorrhizal root colonization on plant growth and nematode reproduction in tomato-Meloidogyne incognita and carrot-Pratylenchus penetrans pathosystems were carried out. The mycorrhizal fungus Glomus mosseae did not protect tomato plants inoculated with the pathogen M. incognita when it was inoculated simultaneously with the mycorrhiza, as plants inoculated with M. incognita died before harvest. On the other hand, when tomato seedlings were inoculated with the nematode three weeks after mycorrhization, colonization of tomato roots by G. mosseae compensated for the reduction of plant growth caused by M. incognita infection. Tomato shoot weight was 24% greater and gall index 33% lower than plants inoculated with the nematode alone, and final soil densities of M. incognita were reduced by 85% when tomato roots were colonized by the mycorrhiza. Root infection by P. penetrans reduced carrot growth, but soil inoculation with Glomus sp. spores compensated for the damage caused by P. penetrans. Addition of Glomus spores to soil reduced P. penetrans soil densities by 49%.

A common drawback in evolutionary science is the fact that the evolution of organisms occurs in geological timing, completely out of the time scale of laboratory experimental work. For this reason, some relevant hypotheses on evolution of Metazoans are based on correlations more than on experimental data obtained for testing the robustness of those hypotheses. In the current work, we implement an experimental methodology to analyze the role of infections as a driving force in the evolution of Metazoans (Haldane's hypothesis). To that goal, we have used simple models of virulence with short reproduction times, large populations, and that are easily testable in the laboratory. Using the bacteriovirus nematode Caenorhabditis elegans as a model organism under evolution and their infection by the environmental opportunistic bacterial pathogen Pseudomonas aeruginosa as the selective force, we have demonstrated that bacterial infection selects an evolved nematode lineage resistant to infection, with changes in its respiration and capability of consuming novel food resources. Using an experimental approach, we show that infection is a selective force in the evolution of Metazoans as proposed earlier by Haldane.Pseudomonas aeruginosa ͉ Caenorhabditis elegans ͉ opportunistic pathogens ͉ experimental evolution