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.

The formation of a lignified sclerenchyma ring that efficiently reduces the digestibility of the stem was not related to apex development but rather to a requirement for mechanical support. The observed good freezing tolerance of reproductive timothy tillers could be one important adaptation mechanism ensuring high yields in northern conditions. Both VRN1 and VRN2 homologues required a vernalization signal for expression so the development of yield-forming tillers in regrowth was regulated independently of the studied genes.

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Timothy {Phleum pratense L.) has earlier been characterized as a long-day plant, which neither requires vernalization to induce flowering nor shows a vernalization response. Variation in flowering time of timothy has thus been ascribed to differences in critical photoperiods. We studied vernalization response in a geographically diverse collection of timothy and found that vernalization accelerates heading in all 38 genotypes included in this study. In addition, considerable variation in vernalization response, ranging from 711 to >1400 growing degree days, was observed between genotypes, and a vernalization requirement to induce flowering was indicated for five genotypes of Nordic origin. While heading time, irrespective of vernalization treatment, was found to be correlated to geographic origin of genotypes, a strong vernalization response was identified in genotypes of different geographic origin. Genotypes of non-Nordic origin with a strong vernalization response were either di-or tetraploid, whereas respective Nordic genotypes were hexaploid. The ploidy level in relation to vernalization response is discussed. This study clearly demonstrates the presence of considerable genetic variation for vernalization response within timothy, and future studies will elucidate the underlying causative genetic variation.