Sarpo Mira, a potato variety with high resistance against the late blight pathogen Phytophthora infestans, is being used in breeding programs to increase late blight resistance in commercial varieties. Discovering genes that are important for P. infestans resistance will assist in the development of molecular markers for the selection of new resistant cultivars and the use of resistant varieties will reduce the environmental, health and financial costs associated with the use of pesticides. Using complementary DNA amplified fragment length polymorphism analyses, differentially expressed genes involved in the potato-P. infestans interaction were identified in the susceptible Bintje and in the resistant Sarpo Mira potato cultivars. Forty-eight differentially expressed transcript derived fragments (TDFs) were cloned and sequenced. The expression profiles of some of these genes were analyzed in detail using quantitative RT-PCR at seven time points: 1, 4, 17, 24, 30, 41 and 65 hours after inoculation (hai). We found that five transcripts with homologies to pathogenesis/defense-related genes and two TDFs with homology to transcription factors were significantly induced to higher levels in the resistant cultivar at very early stages of the infection (1 hai). Interestingly, most of these genes showed different expression profiles throughout the whole infection process between both cultivars. Particularly during its biotrophic growth phase, P. infestans triggered the down-regulation of infection responsive genes in the susceptible but not in the resistance cultivar. Our results suggest that these newly identified early-induced transcripts may be good candidates for conferring Sarpo Mira's resistance to late blight and they could be useful molecular markers for the selection of new resistant cultivars.

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Aims:  To establish a reliable and rapid protocol to simultaneously obtain high quality DNA from an infected host plant and the infecting pathogen. To develop an accurate and sensitive low‐cost assay for the quantification and in planta monitoring of Phytophthora infestans growth. Methods and Results:  In this study, we describe a SYBR Green‐based quantitative real‐time PCR (qPCR) method for the quantification of P. infestans. The method is based on a simultaneous plant‐pathogen DNA purification followed by a qPCR in which the relative quantification of pathogen and plant DNA is performed. Besides assuring an accurate quantification, the use of a plant gene provides a reliable indicator of sample quality, allowing the exclusion of inappropriate samples. By applying this methodology, we were able to detect P. infestans in potato leaf and tuber tissue before the first symptoms of the disease were observed and to monitor the in planta growth of the pathogen for 6 days. Conclusions:  This is a reliable low‐cost assay that provides rapid, accurate and sensitive quantification of the late blight pathogen, allowing the in planta monitoring of P. infestans growth. Significance and Impact of the Study:  The quantitative nature of the assay described in this study may be useful in plant breeding programmes and basic research. The method is appropriate for the comparison of cultivars with different, and even subtle, degrees of pathogen resistance and in the screening of new anti‐oomycete compounds. The method can be easily adapted to tomato and the model plant Nicotiana benthamiana.

Two selected examples of PIXE microanalysis in ecophysiology are presented. Studies of heavy metal distributions in mycorrhizal and non-mycorrhizal roots of Plantago lanceolata showed different filtration mechanisms of Zn/Pb and Fe/Mn, both enabling plants to cope with metals present in the environment. Studies of the mechanism used by the beetle Chrysolina pardalina to eliminate excessive amounts of Ni revealed that Malpighian tubules are responsible for the elimination of this metal from the hemolymph.In both examples GeoPIXE software was used for true elemental mapping using the Dynamic Analysis method and analysis of spectra from selected micro-areas. Specimen thickness and matrix composition were obtained from proton backscattering spectra.

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