<Emphasis Type="Italic">Platanus</Emphasis> × <Emphasis Type="Italic">acerifolia</Emphasis> genotypes surviving to inoculation with <Emphasis Type="Italic">Ceratocystis platani</Emphasis> (the agent of canker stain): first screening and molecular characterization

Canker stain, caused by the fungus Ceratocystis platani, is a destructive disease in Platanus spp. It has been recently proved that resistant accessions can be produced and grown in Europe. However, additional resistant genotypes are still needed in order to avoid the onset of virulent pathogen strains favoured by the selection pressures exerted by genetically homogeneous resistant plane tree plantings. In this study we present the results of two parallel experiments performed on 975 accessions of P. × acerifolia seedlings and P. × acerifolia clones derived by cutting propagation from mature trees grown in the urban environments. The selection process was based on inoculation with C. platani and yielded 13 accessions that showed different types of resistant reactions and survived in a stable manner thoughout the period of observation. Selected accessions were characterised by sequencing the rDNA-ITS region and by developing PCR procedures capable of detecting P. orientalis and P. occidentalis LEAFY homoeologues. These molecular analyses enabled us to confirm the identification of the species, its hybrid origin and to assess an evident genetic variability among the accessions, which therefore have to be considered as different genotypes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic structure of a population of Ganoderma boninense on oil palm

Ganoderma boninense (the causal agent of basal stem rot of oil palm in Papua New Guinea) has a tetrapolar mating system with multiple alleles. Investigations into the population structure of G. boninense , using interfertility between isolates as a marker, revealed that the population on oil palm was comprised predominantly of genetically distinct individuals, although a number of isolates were found to share single mating alleles. No direct hereditary relationship was found between isolates on neighbouring or spatially separated diseased palms, indicating that outcrossing had probably occurred over several generations in the founder population prior to colonization of oil palm. In this study, a total of 81 A and 83 B mating type alleles (factors) were detected with 18 allelic repeats at the A locus and 17 at the B locus. Alleles appeared to be randomly dispersed throughout the population in each study block, although there was a significantly ( P  < 0·01) higher proportion of allelic repeats between estates separated by several kilometres compared to within estates. This is the first study on the population structure of this species and confirms that sexual reproduction is a significant component of the epidemiology of this disease.     

STABILITY,NITROGEN MINERALIZATION CAPACITY AND AGRONOMIC VALUE OF COMPOST-BASED GROWING MEDIA FOR LETTUCE CULTIVATION

Seven composts were used as growing media for lettuce mixed with peat at 25 and 50% (v/v). On the unblended composts and the resulting 14 mixes were determined the main physical-chemical characteristics and the stability by means of a respirometric test in a liquid environment. The potential nitrogen (N)-mineralization capacity of the mixes was measured during the respirometric test solely by the ammonium (NH⁺ ₄-N) determination. The lettuce pot-growing test was performed with and without fertilization; plant biomass and total Kjeldahl nitrogen (TKN) tissue content were measured after cultivation for two months. Compost origin, rate in substrates and fertilization affected plant growth and nitrogen uptake. Multiple regression analysis showed that the stability, proved to be a good predictor for plant growth inhibition. Moreover N-mineralization capacity showed a good fitting with plant uptake. The coupled stability and nitrogen mineralization test gives reliable information about the potential constraints in compost-based growing media.     

Root and stem rot,and wilting of olive tree caused by Dematophora necatrix and associated with Emmia lacerata in Central Italy

European Journal of Plant Pathology - Lethal wilting was observed on young olive trees cv Favolosa in a grove in central Italy. White mycelial strands wrapped the basal portion of the stems that...     

Development of Real-Time PCR for in wood-detection of Ceratocystis platani, the agent of canker stain of Platanus spp.

Ceratocystis platani is a quarantine fungal pathogen agent of canker stain, a destructive disease affecting Platanus. Despite its diagnosis being critical for disease control, there is still no effective diagnostic tool as all known mycological and biological detection assays are problematical. In this study we developed highly effective Real-Time PCR methods based on the use of an intercalating dye, EvaGreen, and on a Taqman probe. We designed primers and probe on the internal transcribed spacer (ITS) region of rDNA, and used them for the amplification and detection of a 95?bp C. platani amplicon. Inference of standard curves revealed that both Real-Time procedures have similar and high values of amplification efficiency when applied to a range of templates, e.g. genomic fungal DNA and DNA extracted from diseased wood. The methods were sensitive with a detection limit of 10?fg???l^?1? C. platani genomic DNA. They were specific as they did not yield any detection signal when applied to non-target fungal taxa colonizers of Platanus wood. Reliability was demonstrated through the positive detection of a collection of C. platani isolates and of wood samples collected from naturally infected trees. Robustness was positively verified through detection on artificially infected trees, which were tested at different times after death, up to 27?months. Generating a standard curve with a target-amplicon-containing plasmid enabled an absolute quantification and a comparison between the discoloured wood of resistant and susceptible genotypes. The importance of the methods for studies on pathogen epidemiology and host resistance is also discussed.