A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10- µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15(±5)°C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness. 相似文献
Reactions of 60 water yam ( Dioscorea alata ) cultivars to three isolates of the yam anthracnose fungal pathogen ( Colletotrichum gloeosporioides ) were evaluated using tissue culture-derived whole-plant assay. Three disease parameters: single score on a scale of 0–6 at the seventh day after inoculation (SD7); area under the disease progress curve (AUDPC); and disease progress rate ( R d) were compared, and cultivars were classified into disease-response groups using a rank-sum method based on AUDPC scores for the two most virulent isolates. A wide range of variation in resistance of the D. alata cultivars, and significant effects of pathogen isolate and isolate–cultivar interactions, were observed for all disease parameters. The three disease parameters were positively correlated; however, four cultivars showed great dispersions from the regression lines for comparisons of SD7 with the multiple assessments based AUDPC and R d. The 60 cultivars were separated into resistant ( n = 12), moderately resistant ( n = 19), moderately susceptible ( n = 18) and susceptible ( n = 11) groups. The potential of the tissue culture-derived whole-plant assay to resistance breeding programmes and further understanding of the yam anthracnose pathosystem is discussed. 相似文献
There is a growing body of literature showing that physical activity and nature have a positive effect on people's health and well-being. Additionally literature indicates that there may even be a synergic benefit from being physically active whilst simultaneously being directly exposed to nature. This insight is used in recovery programmes for work related stress and mental health care settings. However, as primary care is usually people's first point of contact with the health care system, the greatest benefits for people's health can probably be obtained in primary health care settings. The aim of the present study is therefore to investigate to what extent general practitioners advise patients on physical activity and whether they refer to the additional health benefits of physical activity in a natural environment.
A secondary analysis was performed on a random sample of 2784 video-taped patient consultations of 100 general practitioners in The Netherlands. Many characteristics of these consultations were known on the basis of earlier analyses: diagnosis, age and sex of patient and whether or not the issue of physical activity had been brought up by either patient or doctor. First, we investigated to what extent and with which health problems advice was given concerning physical activity. Second, from these consultations, a stratified sample of 100 consultations was observed in order to investigate whether an advice was given by the general practitioner concerning the additional benefits of nature. In 26% of all consultations advice on physical activity was given by the general practitioner. Physical activity was mentioned more often in cases of vague complaints than in cases with a clear cut diagnosis. As could have been expected, physical activity was mentioned relatively frequently in cases of musculoskeletal complaints and complaints of the nervous system. The additional benefits of physical activity in natural environments was not mentioned during any of the consultations.
In conclusion, general practitioners regularly give advice on physical activity. However, they fail to mention that physical activity in nature areas might have additional health benefits. Given the fact that medical treatment is increasingly evidence based, we think the evidence for the health benefits of physical activity in nature needs to be stronger. Results from such research could eventually find their way into the guidelines of the general practitioners. 相似文献
When the conidia of Blumeria graminis f. sp. hordei (Bgh) are inoculated on barley coleoptile cells they produce short germ tubes called primary germ tubes (PGTs) about 2 h after inoculation. We evaluated the positive role of a PGT in inducing accessibility of the host cell under the germ tube. When an appressorium (APP) penetrated the same cell on which a PGT was present, the ratio of haustorium formation (penetration efficiency) was significantly higher than when an APP penetrated the cell adjacent to the one on which a PGT was present. When an APP penetrated the cell laterally adjacent to the one on which a PGT was present we killed the cell under the PGT by puncturing it with a microneedle and then investigated the penetration efficiency of the cell adjacent to the dead cell. As a control we killed the cell longitudinally adjacent to the one on which a PGT was present and investigated the penetration efficiency of the laterally adjacent cell. The results showed that the penetration efficiency of the former was significantly lower than that of the latter. This suggests that some accessibility factor might transfer from a cell on which a PGT is present to a laterally adjacent cell. The existence of a conidium body but not a PGT was not effective for induced accessibility of the host cell. Moreover, when a Bgh germling was removed 6 h after inoculation and another germling was transferred to the same cell, the penetration efficiency was significantly higher than that of control. As a control, a Bgh germling was transferred to a cell on which no germling was present. These results suggest that the existence of PGT is effective for induced accessibility of a host cell when penetrated by Bgh. However, it is unclear whether or not a PGT secretes some substance(s) which suppresses the resistance induction of a host cell. 相似文献