Rapid and reliable DNA extraction and PCR fingerprinting methods to discriminate multiple biotypes of the nematophagous fungus Pochonia chlamydosporia isolated from plant rhizospheres.

AIMS: To develop a simple, rapid, reliable protocol producing consistent polymerase chain reaction (PCR) fingerprints of Pochonia chlamydosporia var. chlamydosporia biotypes for analysing different fungal isolates during co-infection of plants and nematodes. METHODS AND RESULTS: DNA extracted from different P. chlamydosporia biotypes was fingerprinted using enterobacterial repetitive intragenic consensus (ERIC)-PCR. Four extraction methods (rapid alkaline lysis; microLYSIS-PLUS; DNeasy; FTA cards) gave consistent results within each protocol but these varied between protocols. Reproducible fingerprints were obtained only if DNA was extracted from fresh fungal cultures that were free of agar. Some DNA degradation occurred during storage, except with the FTA cards, used with this fungus for the first time, which provide a method for long-term archiving. Rapid alkaline lysis and ERIC-PCR identified fungal isolates from root and nematode egg surfaces when plants were treated with different combinations of fungal biotypes; the dominant biotype isolated from the rhizosphere was not always the most abundant in eggs. CONCLUSIONS: ERIC-PCR fingerprinting can reliably detect and identify different P. chlamydosporia biotypes. It is important to use fresh mycelium and the same DNA isolation method throughout each study. SIGNIFICANCE AND IMPACT OF THE STUDY: This evaluation of methods to assess genetic diversity and identify specific P. chlamydosporia biotypes is relevant to other mycelial fungi.

Enantioselectivity in random deposition processes on template surfaces.

A molecular model is proposed to study the enantioselective adsorption of chiral species on metallic surfaces modified through the preadsorption of another chiral species, known as template surfaces. It is found that anisotropic and exclusive interactions among adsorbed species are essential factors in the enantioselective process. It is shown how the formation of compact structures explains the fact that an enantiomer of species B having the same symmetry as the template species A can be preferentially adsorbed with respect to the other enantiomer of species B, thus producing enantioselectivity. The model predicts enantioselectivity peaks on a limited range of the template coverage, as typically observed experimentally in some systems.

Ecotypes of the model legume Lotus japonicus vary in their interaction phenotypes with the root-knot nematode Meloidogyne incognita.

BACKGROUND AND AIMS: Knowledge of host factors affecting plant-nematode interactions is scarce. Here, relevant interaction phenotypes between a nodulating model host, Lotus japonicus, and the endoparasitic root-knot nematode Meloidogyne incognita are assessed via a genetic screen. METHODS: Within an alpha experimental design, 4-week-old replicate plants from 60 L. japonicus ecotypes were inoculated with 1000 nematodes from a single egg mass population, and evaluated for galling and nematode egg masses 6 weeks after inoculation. KEY RESULTS: Statistical analysis of data for 57 ecotypes showed that ecotype susceptibilities ranged from 3.5 to 406 galls per root, and correlated strongly (r = 0.8, P < 0.001, log scale) with nematode reproduction (ranging from 0.6 to 34.5 egg masses per root). Some ecotypes, however, showed a significant discrepancy between disease severity and nematode reproduction. Necrosis and developmental malformations were observed in other infected ecotypes. CONCLUSIONS: The first evidence is provided of significant variability in the interactions between L. japonicus and root-knot nematodes that may have further implications for the genetic dissection and characterization of host pathways involved in nematode parasitism and, possibly, in microbial symbiosis.

Functionality of resistance gene Hero, which controls plant root-infecting potato cyst nematodes, in leaves of tomato.

The expression of host genomes is modified locally by root endoparasitic nematode secretions to induce the development of complex cellular structures referred as feeding sites. In compatible interactions, the feeding sites provide the environment and nutrients for the completion of the nematode's life cycle, whereas in an incompatible (resistant) interaction, the host immune system triggers a plant cell death programme, often in the form of a hypersensitive reaction, which restricts nematode reproduction. These processes have been studied in great detail in organ tissues normally infected by these nematodes: the roots. Here we show that host leaves can support a similar set of programmed developmental events in the potato cyst nematode Globodera rostochiensis life cycle that are typical of the root-invading nematodes. We also show that a gene-for-gene type specific disease resistance that is effective against potato cyst nematodes (PCN) in roots also operates in leaves: the expression of the resistance (R) gene Hero and members of its gene family in leaves correlates with the elicitation of a hypersensitive response only during the incompatible interaction. These findings, and the ability to isolate RNA from relevant parasitic stages of the nematode, may have significant implications for the identification of nematode factors involved in incompatible interactions.

Random deposition of two annihilating species in the (1+1) dimension.

We present simulation results for the one-dimensional random deposition of two annihilating species A and B, falling with probabilities p and q (p+q=1), which then react to produce an inert product, i.e., A+B-->0. Two different annihilation rules are defined: top annihilation and nearest-neighbor annihilation (NNA), leading to distinct scaling behaviors. In particular, the values of the scaling exponents for NNA are found to be dependent on probability p, suggesting different universality classes.