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The etiology of the sporadic form of Alzheimer's disease (AD) remains largely unknown. Recent evidence has suggested that geneenvironment interactions (GxE) may play a crucial role in its development and progression. Whereas various susceptibility loci have been identified, like the apolipoprotein E4 allele, these cannot fully explain the increasing prevalence of AD observed with aging. In addition to such genetic risk factors, various environmental factors have been proposed to alter the risk of developing AD as well as to affect the rate of cognitive decline in AD patients. Nevertheless, aside from the independent effects of genetic and environmental risk factors, their synergistic participation in increasing the risk of developing AD has been sparsely investigated, even though evidence points towards such a direction. Advances in the genetic manipulation of mice, modeling various aspects of the AD pathology, have provided an excellent tool to dissect the effects of genes, environment, and their interactions. In this paper we present several environmental factors implicated in the etiology of AD that have been tested in transgenic animal models of the disease. The focus lies on the concept of GxE and its importance in a multifactorial disease like AD. Additionally, possible mediating mechanisms and future challenges are discussed. [ABSTRACT FROM AUTHOR]

During 2 years and at five locations in Europe, 56 winter wheat genotypes were evaluated for resistance to Fusarium head blight (FHB). The genotypes were both parents and selected recombinants taken from the following populations previously tested for FHB resistance: ‘Arina’/‘Forno’, ‘Arina’/‘Riband’, ‘Dream’/‘Lynx’, G16-92/‘Hussar’, ‘Renan’/‘Récital’, SVP-72017 × ‘Capo’ and ‘Capo’/‘Sumai-3’. In addition, a few control lines were included. FHB resistance was evaluated in replicated experiments under artificial inoculation, disease severity was assessed by repeated visual scorings. The highest level of FHB resistance was found in lines selected from crosses of FHB-resistant winter wheat × ‘Sumai-3’. The best lines selected from crosses of moderately resistant winter wheat with susceptible winter wheat were similar in their resistance response to the resistant parent. The level of FHB resistance was correlated with stability of resistance. Susceptible wheat lines tended to exhibit severe symptoms under high disease pressure. The symptoms on resistant lines remained comparatively low even under high disease pressure. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB or head scab) has become a major limiting factor for sustainable wheat ( Triticum aestivum L.) production around the world. For quantitative trait loci (QTL) analysis of resistance to FHB, F3 plants and F3 : 5 lines, derived from a ‘Frontana’ (moderately resistant)/‘Seri82’ (susceptible) cross, were spray-inoculated in 2001 and 2002, respectively. Artificial inoculations were carried out under field conditions. Of 273 SSR and AFLP markers, 250 could be mapped and they yielded 42 linkage groups, covering a genetic distance of 1931 cM. QTL analysis was based on the constructed linkage map and area under the disease progress curve (AUDPC). The analyses revealed three consistent QTLs associated with FHB resistance on chromosomes 1BL, 3AL and 7AS explaining 7.9%, 7.7% and 7.6% of the phenotypic variation, respectively, above 2 years. The results confirmed the previously described resistance QTL of ‘Frontana’ on chromosome 3AL. A combination of ‘Frontana’ resistance with ‘Sumai-3’ resistance may lead to lines with augmented resistance expression. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a devastating disease that reduces the yield, quality and economic value of wheat. For quantitative trait loci (QTL) analysis of resistance to FHB, F3 plants and F3:5 lines, derived from a ‘Wangshuibai’ (resistant)/‘Seri82’ (susceptible) cross, were spray inoculated during 2001 and 2002, respectively. Artificial inoculation was carried out under field conditions. Of 420 markers, 258 amplified fragment length polymorphism and 39 simple sequence repeat (SSR) markers were mapped and yielded 44 linkage groups covering a total genetic distance of 2554 cM. QTL analysis was based on the constructed linkage map and area under the disease progress curve. The analyses revealed a QTL in the map interval Xgwm533–Xs18/m12 on chromosome 3BS accounting for up to 17% of the phenotypic variation. In addition, a QTL was detected in the map interval Xgwm539–Xs15/m24 on chromosome 2DL explaining up to 11% of the phenotypic variation. The QTL alleles originated from ‘Wangshuibai’ and were tagged with SSR markers. Using these SSR markers would facilitate marker-assisted selection to improve FHB resistance in wheat. [ABSTRACT FROM AUTHOR]

The impact of nitrogen (N) fertilization on the development of Fusarium head blight (FHB) in wheat and the resulting deoxynivalenol (DON) contamination in the kernels was studied. In a first experiment, the disease was assessed on two locations under natural infection pressure. Five different types of nitrogen fertilizer (both organic and mineral) were investigated, each applied at five input rates from 0 to 160 kg N/ha. With all fertilizers, a significant increase of disease intensity was observed with increasing N input, while the type of N fertilizer had poor or no effects on FHB. Depending on the fertilizer used, the percentage of diseased spikelets increased from 2.2% at zero N rate up to 6.6% at 160 kg N input per hectare. In a second series of trials, three spring wheat varieties including one Durum wheat line were artificially inoculated with a Fusarium graminearum and a F. culmorum strain, known producers of DON. A mineral N fertilizer was applied at five input levels from 0 to 160 kg N/ha. A significant increase in FHB intensity and DON contamination in the grain was observed with increasing N from 0 to 80 kg/ha. At higher input rates, relevant in contemporary crop husbandry, disease intensity and toxin contamination remained at constant levels. It is concluded that adaptation of N fertilization represents no relevant tool in managing FHB in practical wheat cultivation. [ABSTRACT FROM AUTHOR]