Early and accurate diagnosis is a critical first step in mitigating losses caused by plant diseases. An incorrect diagnosis can lead to improper management decisions, such as selection of the wrong chemical application that could potentially result in further reduced crop health and yield. In tomato, initial disease symptoms may be similar even if caused by different pathogens, for example early lesions of target spot (TS) caused by the fungus Corynespora cassicola and bacterial spot (BS) caused by Xanthomonas perforans. In this study, hyperspectral imaging (380–1020 nm) was utilized in laboratory and field (collected by an unmanned aerial vehicle; UAV) settings to detect both diseases. Tomato leaves were classified into four categories: healthy, asymptomatic, early and late disease development stages. Thirty-five spectral vegetation indices (VIs) were calculated to select an optimum set of indices for disease detection and identification. Two classification methods were utilized: (i) multilayer perceptron neural network (MLP), and (ii) stepwise discriminant analysis (STDA). Best wavebands selection was considered in blue (408–420 nm), red (630–650 nm) and red edge (730–750 nm). The most significant VIs that could distinguish between healthy leaves and diseased leaves were the photochemical reflectance index (PRI) for both diseases, the normalized difference vegetation index (NDVI850) for BS in all stages, and the triangular vegetation index (TVI), NDVI850 and chlorophyll index green (Chl green) for TS asymptomatic, TS early and TS late disease stage respectively. The MLP classification method had an accuracy of 99%, for both BS and TS, under field (UAV-based) and laboratory conditions.
Plant Foods for Human Nutrition - The effects of cocoa-derived polyphenols on cognitive functions have been analyzed through numerous studies using different interventions (doses, vehicles, time... 相似文献
Plant Foods for Human Nutrition - ADP-glucose pyrophosphorylase (AGPase) is a key enzyme of starch synthesis in seeds, tubers and fruits. UDP-glucose pyrophosphorylase (UGPase) is an important... 相似文献
Paddy and Water Environment - Most of the lands of the southern coastal zone of Bangladesh are protected from tidal flooding and storm surges by embankments constructed during the 1960s and 1970s,... 相似文献
Designing fishing policies without knowledge of past levels of target species abundance is a dangerous omission for fisheries management. However, as fisheries monitoring started long after exploitation of many species began, this is a difficult issue to address. Here we show how the ‘shifting baseline’ syndrome can affect the stock assessment of a vulnerable species by masking real population trends and thereby put marine animals at serious risk. Current fishery data suggest that landings of the large Gulf grouper (Mycteroperca jordani, Serranidae) are increasing in the Gulf of California. However, reviews of historical evidence, naturalists’ observations and a systematic documentation of fishers’ perceptions of trends in the abundance of this species indicate that it has dramatically declined. The heyday for the Gulf grouper fishery occurred prior to the 1970s, after which abundance dropped rapidly, probably falling to a few percent of former numbers. This decline happened long before fishery statistics were formally developed. We use the case of the Gulf grouper to illustrate how other vulnerable tropical and semi‐tropical fish and shellfish species around the world may be facing the same fate as the Gulf grouper. In accordance with other recent studies, we recommend using historical tools as part of a broad data‐gathering approach to assess the conservation status of marine species that are vulnerable to over‐exploitation. 相似文献
A radiographic study was carried out on 2-year groups of pre-smolt parr to detect the comparative frequency of vertebral change in a range of defined pedigreed families of high growth rate of Atlantic salmon, Salmo salar L., reared under identical conditions. The observed frequency of deformity was related to the observed deformity level in the seawater parental generation, and to a potentially uncontrolled environmental determinant, i.e. stripping date. High and low parental deformity groups of families were found to produce offspring that had very similar levels of radiographically detectable spinal deformities in the pre-smolt parr, suggesting no genetic link. With regard to stripping date, the overall incidence was nearly half that seen in the preceding year (8.7% cf 16.6%). However, a non-significant trend to fewer radiographic spinal deformities was seen in the later stripping period. 相似文献
1. Many coastal lagoons in eastern Australia have changed as a result of recent human activities. However, it is often difficult to determine the extent of change and the ecological implications. A palaeoecological approach allows a quantitative assessment of how an aquatic ecosystem changes and responds to human impacts beyond what is possible with historical data or monitoring programmes.
2. Orielton Lagoon (south‐east Tasmania, Australia) is a Ramsar‐listed coastal wetland of international importance for conservation. This study was undertaken at the site to determine whether recent anthropogenic hydrological modifications to the lagoon had influenced its ecology, particularly salinity, and compromised its Ramsar status.
3. A diatom–salinity transfer function was constructed from a training data set of 96 diatom taxa from 34 sampling sites in 19 lagoons along the east coast of Tasmania.
4. The salinity of Orielton Lagoon has changed in response to a causeway constructed across its mouth, which has transformed the lagoon from an open marine environment to an enclosed, virtually stagnant, brackish water body.
5. These changes have compromised the protected coastal wetland status of Orielton Lagoon. Environmental remediation attempts have since partially restored the natural hydrology of the lagoon and it is now returning towards the state it was in prior to causeway construction.
6. A palaeoecological approach using diatoms was found to be successful in reconstructing recent salinity changes and investigating human impacts on Orielton Lagoon over the last 50–55 years.
1. The freshwater pearl mussel Margaritifera margaritifera L. is globally endangered and is threatened by commercial exploitation, pollution and habitat loss throughout its range. Captive breeding would be a valuable tool in enhancing the status of M. margaritifera in the UK.
2. We have developed a semi‐natural system for successfully infecting juvenile brown trout with glochidial M. margaritifera, and culturing juvenile mussels in experimental tanks where glochidial M. margaritifera can excyst from fish gills and settle into sediment.
3. Infected fish had less than 1% mortality. Levels of infection varied among fish. Two yearly cohorts of juvenile M. margaritifera were identified from samples of sediment taken from each experimental tank. Individuals range in size from 1.4 mm (2000 cohort) to >3 mm in length (1999 cohort).
4. The number of juvenile M. margaritifera present in the two experimental tanks are estimated to be between 3600 (tank A) and 0 (tank B) for the putative 1999 cohort and between 6000 (tank A) and 13 000 (tank B) for the putative 2000 cohort.
5. This pioneering method for large‐scale cultivation of juvenile M. margaritifera is intermediate between the release of infected fish into rivers and the intensive cultivation systems developed in continental Europe and the USA for other species of unionid. This is the first time that large numbers of M. margaritifera have been cultured and represents a significant breakthrough in the conservation of this globally endangered Red Data List species. The method is straightforward and is most cost‐effective when undertaken alongside established hatchery processes.