Electromagnetic Flowmeter for Rapid Metering of Microfluidics Based on an Ag/AgCl/Porous Graphite Electrode Sensor.

The imposed interference by the signal electrodes limits the expansion of the measurement range in electromagnetic flow sensors (EFS). This is because the interference makes it difficult to increase the signal-to-noise ratio in the state of the microfluid. In this paper, an Ag/AgCl/porous graphite electrode sensor is successfully prepared by a chemical vapor deposition (CVD) method. This enables a high-reliability and wide measurement range surveillance system, which is also maintenance-free and cost-effective and has a long lifetime. AgCl is facilely synthesized by a mild method, and our analysis and experiments show that as-prepared AgCl nanoparticles demonstrate a high crystalline level and high quality. Further system testing and experiments are also conducted on EFS in cases where the Ag/AgCl/porous graphite electrode sensor is set as the core. It is seen that, within the flow range of 0.003-4 m3/h, the induced electromotive force is linearly related to the flow rate of the fluid. The measurement accuracy of the EFS using the transient measurement method is below 1%, and its sensitivity is not affected by the fluid temperature.

Clonal Expansion and Dispersal Pathways of Puccinia polysora in China.

Southern corn rust (SCR) caused by Puccinia polysora is one of the most devastating diseases in the world. In recent years, SCR has been upgraded from a minor to a major disease around the world, including in China. However, little is known about its population genetics and structure in China. In this study, we analyzed 288 isolates collected from various localities during 2017 in seven Chinese provinces: Guangxi, Guangdong, Anhui, Hunan, Shandong, Henan, and Shaanxi. The isolates were analyzed using nine microsatellite markers. The population structure, genetic diversity, and reproduction mode of P. polysora were investigated based on genotype data. Strong genotypic diversity was detected and clonal reproduction was dominant. The populations collected from the pathogen's winter-reproductive regions harbored more genotypes than those collected from the pathogen's epidemic regions. The spatial differences in genotypic richness, and evenness among the populations were significant, and showed a decreasing trend from south to north. Most isolates were clustered into two clonal groups. Two high-frequency multilocus genotypes (MLGs), MLG1 and MLG2, were widely distributed in all populations. Our analyses confirmed that P. polysora employed clone dispersal from the pathogen's winter-reproductive regions to the pathogen's epidemic regions, and in addition to the sources from the pathogen's winter-reproductive regions, the pathogen in Anhui and Hunan might also have other sources from areas such as Taiwan, China, or/and Southeast Asia, and the pathogen went through a genetic bottleneck during its dispersal. These findings provide initial insights into the reproduction mode and dispersal pathways of P. polysora in China.

Degradation mechanisms of perovskite nanocrystals in color-converted InGaN micro-light-emitting diodes.

The metal halide perovskite nanocrystals (NCs) have attracted much attention because of their excellent optical properties and potential for application in optoelectronic devices. However, their photo- and thermostability are still practical challenges and need further optimization. Here, we have studied the degradation behaviors of CsPbI3 NCs utilized as optical conversion layer in InGaN based blue micro-LEDs in situ. Furthermore, the effects of temperature and light irradiation on perovskite NCs were investigated respectively. The results indicate that both blue light irradiation and high temperature can cause the increased nonradiative recombination rate, resulting in the degradation of perovskite NCs and reduction of the photoluminescence quantum yield (PLQY). Especially in high-temperature condition, both the single-exciton nonradiative recombination rate and the biexciton nonradiative recombination rate are increased, causing the significant reduction of PLQY of perovskite NCs in high temperature environment than blue light irradiation. Our work provides a detailed insight about the correlation between the light irradiation and temperature consequences for CsPbI3 NCs and may help to pave the way toward optoelectronic device applications.

Assessing Macro Disease Index of Wheat Stripe Rust Based on Segformer with Complex Background in the Field.

Wheat stripe rust (WSR) is a foliar disease that causes destructive damage in the wheat production context. Accurately estimating the severity of WSR in the autumn growing stage can help to objectively monitor the disease incidence level of WSR and predict the nationwide disease incidence in the following year, which have great significance for controlling its nationwide spread and ensuring the safety of grain production. In this study, to address the low accuracy and the efficiency of disease index estimation by traditional methods, WSR-diseased areas are segmented based on Segformer, and the macro disease index (MDI) is automatically calculated for the measurement of canopy-scale disease incidence. The results obtained with different semantic segmentation algorithms, loss functions, and data sets are compared for the segmentation effect, in order to address the severe class imbalance in disease region segmentation. We find that: (1) The results of the various models differed significantly, with Segformer being the best algorithm for WSR segmentation (rust class F1 score = 72.60%), based on the original data set; (2) the imbalanced nature of the data has a significant impact on the identification of the minority class (i.e., the rust class), for which solutions based on loss functions and re-weighting of the minority class are ineffective; (3) data augmentation of the minority class or under-sampling of the original data set to increase the proportion of the rust class greatly improved the F1-score of the model (rust class F1 score = 86.6%), revealing that re-sampling is a simple and effective approach to alleviating the class imbalance problem. Finally, the MDI was used to evaluate the models based on the different data sets, where the model based on the augmented data set presented the best performance (R2 = 0.992, RMSE = 0.008). In conclusion, the deep-learning-based semantic segmentation method, and the corresponding optimization measures, applied in this study allow us to achieve pixel-level accurate segmentation of WSR regions on wheat leaves, thus enabling accurate assessment of the degree of WSR disease under complex backgrounds in the field, consequently providing technical support for field surveys and calculation of the disease level.

Clinical Features and Outcomes of Pulmonary Artery Sarcoma.

OBJECTIVES: A retrospective cohort study was designed to describe the clinical features and outcomes of pulmonary artery sarcoma (PAS). METHODS: Twenty-two (22) consecutive patients diagnosed with PAS by pathological examination were enrolled and followed up until they died or until January 2020. The medical records were retrospectively reviewed to evaluate the clinical characteristics, image findings, and outcomes. RESULTS: 1) Twenty-one (21, 95.5%) patients were firstly misdiagnosed. Dyspnoea was the most common presenting symptom (19 of 22, 86.4%). 2) Filling defects in the right pulmonary artery were seen in 17 patients (77.3%) with computed tomography pulmonary angiography or magnetic resonance pulmonary angiography. Among those patients, 14 underwent positron emission tomography-computed tomography detection and 13 (92.9%) were found to have increased uptake value in the pulmonary artery. 3) The median survival (from diagnosis to death or January 2020) of the total series was 11.6 months (range, 0.7-68.5 months). The estimated cumulative survival rates at 1, 2, and 3 years were 52.6%, 32.8%, and 19.7%, respectively. Patients who received surgery and/or chemo-radiotherapy treatment had a better survival rate compared with patients without treatment (the estimated cumulative survival rates at 1, 2, and 3 years were 60.3%, 39.1%, and 29.3%, respectively, vs 33.3%, 16.6%, and 0, accordingly) and better survival time (median survival 17.02 vs 3.16 months, respectively) (p=0.025). CONCLUSIONS: Pulmonary artery sarcoma is easily misdiagnosed, as the symptoms and routine image detection are nonspecific. Positron emission tomography-computed tomography may be helpful in diagnosis. Surgery and/or chemo-radiotherapy offer a chance for better outcomes.

Genetic Structure and Asymmetric Migration of Wheat Stripe Rust Pathogen in Western Epidemic Areas of China.

Puccinia striiformis f. sp. tritici causes severe global epidemics of wheat stripe rust primarily by airborne urediniospores. Understanding long-distance migration patterns of P. striiformis f. sp. tritici is critical for disease forecasting and management. Although the western epidemic areas in China have been considered as the source of inoculum spread eastward across the country, migration pathways among different populations within the western epidemic areas are poorly understood. In this study, we investigated the population genetics of 200 P. striiformis f. sp. tritici isolates from western epidemic areas using amplified fragment length polymorphism and simple sequence repeat markers. A coalescent approach was also used to calculate the migration rates among populations. Data analyses with both marker systems indicated high genetic diversity in each regional population. The Mantel test revealed significant positive correlation between genetic and geographic distances. Both discriminant analysis of principal components and STRUCTURE analysis supported moderate population structure shaped by seasonality and geography. The calculated migration rates indicated the presence of asymmetric migration between major populations in western epidemic areas, with greater migration rates from high elevation, oversummering areas to low elevation, overwintering areas. Sichuan Basin, one of the low elevation, overwintering areas, sampled in both fall and spring, was inferred as a recipient in fall but a donor in spring. Migration among P. striiformis f. sp. tritici populations may be partly attributable to terrace farming and prevailing wind direction in different seasons. Our study provides a better understanding of fine-scale population structure and the interregional migration pattern of P. striiformis f. sp. tritici in northwestern China and will inform future rust management.

Optical and frequency degradation behavior of GaN-based micro-LEDs for visible light communication.

In this study, optical power and frequency response degradation behavior of GaN-based micro-LEDs with bandwidth up to 800MHz were investigated under different modes, including direct current (DC) mode, alternating current (AC) mode and DC plus AC small signal mode at room temperature. The electroluminescence (EL), current-voltage (I-V) characteristics and small signal frequency response were measured during the stress. The results show that micro-LEDs under AC mode have better reliability because of the decreased junction temperature, but the high current density would still generate some defects within or around the active region, which can increase the trap-assisted tunneling (TAT) current and non-radiative recombination. The electrical stress-related defects not only reduce the effective carrier concentration injected into QWs but also increase the carrier lifetime for radiative recombination and Auger recombination and decrease the modulation bandwidth. These results will help to understand and improve the reliability of micro-LEDs operated under high current density and promote the application of micro-LEDs for visible light communication.

Efficacy and Safety of Bronchial Artery Embolization on Hemoptysis in Chronic Thromboembolic Pulmonary Hypertension: A Pilot Prospective Cohort Study.

OBJECTIVES: Managing hemoptysis in chronic thromboembolic pulmonary hypertension can be challenging due to the difficulties in maintaining coagulation homeostasis in affected patients. In this study, we evaluated the efficacy and safety of bronchial artery embolization in treating hemoptysis in chronic thromboembolic pulmonary hypertension patients. DESIGN: Pilot, prospective cohort study. SETTING: A large respiratory medical institute. PATIENTS: From January 1, 2012, to December 31, 2017, hospitalized chronic thromboembolic pulmonary hypertension patients were eligible for inclusion. Patients with pulmonary hypertension caused by other conditions, or who failed to participate in the follow-up were excluded. INTERVENTIONS: Hemoptysis in chronic thromboembolic pulmonary hypertension patients was treated with or without bronchial artery embolization based on whether the bleeding could be stopped with medication alone and patient willingness for bronchial artery embolization treatment. MEASUREMENTS AND MAIN RESULTS: A total of 328 patients diagnosed with chronic thromboembolic pulmonary hypertension were consecutively collected, 317 patients were completed the follow-up. There were 15 chronic thromboembolic pulmonary hypertension patients with hemoptysis in total, and the occurrence rate of hemoptysis in chronic thromboembolic pulmonary hypertension patients was 4.7%. Among the hemoptysis chronic thromboembolic pulmonary hypertension patients, 10 (67%) underwent bronchial artery embolization, and five (33%) were treated with medication only. The median follow-up period for hemoptysis patients was 7.6 months. In patients underwent bronchial artery embolization treatment, oxygenation index and right heart function showed no significant difference between pre bronchial artery embolization and post bronchial artery embolization. Hemoptysis relapse (20% vs 80%; p = 0.025) and hemoptysis-related mortality (0% vs 40%; p = 0.032) were significantly lower, whereas the overall survival (90% vs 40%; p = 0.040) was higher in patients treated with bronchial artery embolization than in patients treated without bronchial artery embolization. CONCLUSIONS: Bronchial artery embolization procedure demonstrated effectiveness and safety to treat hemoptysis in chronic thromboembolic pulmonary hypertension patients at our center, but further controlled studies are needed before it can be considered as an effective therapy for these patients.

Improved Evaluation of Wheat Cultivars (Lines) on Resistance to Puccinia striiformis f. sp. tritici Using Molecular Disease Index.

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is one of the most destructive diseases of wheat worldwide. Sichuan Province plays an important role in interregional epidemics in China. Application of host resistance is important in disease management, and efficient approaches to evaluate resistance level are necessary to obtain useful varieties. In this study, 100 wheat cultivars (lines) growing in Sichuan were selected to evaluate their resistance to stripe rust. Field experiments were conducted with a mixture of three P. striiformis f. sp. tritici races for inoculations at seeding and adult stages in the 2014 to 2015 season and the 2016 to 2017 season. Leaf samplings were conducted four times during the latent period at early growth stage of wheat. The sampled leaves were processed to extract DNA. The DNA of both wheat and P. striiformis f. sp. tritici was quantified using real-time quantitative polymerase chain reaction, and the molecular disease index (MDI) was used to evaluate the resistance level. The area under the disease progress curve in terms of disease index (AUDPC-DI) was obtained for each studied cultivar (line) in the fields. Among the 100 studied cultivars (lines), 61% of them showed seedling resistance, and 63 and 65% showed adult resistance in the 2014 to 2015 and 2016 to 2017 seasons, respectively, based on the infection type. High consistency in resistance grouping by cluster analysis as the percentage of the studied cultivar (line) belonging to the same group based on AUDPC-DI data and based on MDI data was obtained. The correlations between AUDPC-DI and MDI from samples collected on 9 and 14 or 15 days after inoculation during the latent period were all significant at P < 0.01. This study provided a new and efficient method for evaluation of varietal resistance to wheat stripe rust.

Differential Diagnosis of Pulmonary Artery Sarcoma and Central Chronic Pulmonary Thromboembolism Using CT and MR Images.

BACKGROUND: Clinical and imaging manifestations are similar in pulmonary artery sarcomas (PAS) and thromboembolic diseases, especially central chronic pulmonary thromboembolism (CPTE). The feasibility of utilising clinical imaging tools such as computed tomography (CT) and magnetic resonance imaging (MRI) for differential diagnosis of PAS and CPTE has not been fully explored, especially MRI. METHODS: Patients with PAS (n=18) and central CPTE (n=20) treated at our hospital between January 2013 and September 2016 were identified retrospectively. Computed tomography and MRI findings of pulmonary artery (PA) filling defects including the location, the involvement of pulmonary artery, morphology, signal intensities and enhancement in MRI, calcification, sizes of right atrium and ventricle, inner diameters of the pulmonary artery trunk and branches, and mediastinal collateral circulation in both groups were examined, and differences were analysed by Fisher exact test and independent sample t-test. RESULTS: Compared to those of central CPTE, PAS lesions were in full shape or expansive growth (p<0.001), and the proximal end of the tumours was often bulging or lobulated (p<0.001). These lesions were aneurysm- or grape-like distally (p<0.01) with inhomogeneous enhancement (p<0.001). The MRI contrast enhancement pattern of PAS lesions were cloudy with inhomogeneous delayed enhancement and the time-density curves for some of the lesions increased gradually. CONCLUSION: Computed tomographic and MR imaging manifestations may resemble PAS and central CPTE; however, some manifestations still have great value for the differential diagnosis of these two conditions, specifically the morphology and MRI enhancement patterns.

Echocardiographic characteristics of pulmonary artery involvement in Takayasu arteritis.

BACKGROUND: Up to 50% patients with Takayasu arteritis have pulmonary artery involvement. Hence, the early identification of pulmonary artery involvement to facilitate prompt treatment is required. METHODS: This retrospective study was performed in patients diagnosed with Takayasu arteritis between January 2009 and January 2016. Pulmonary artery involvement was confirmed with computed tomographic pulmonary angiography. Images from transthoracic echocardiography in three windows (suprasternal right pulmonary artery long-axis view, parasternal aortic short-axis view, and subxiphoid view) were documented and analyzed. RESULTS: A total of 27 patients had Takayasu arteritis and pulmonary artery involvement. Characteristic changes identified by echocardiography included luminal medium-to-high echogenic signals, stenosis, and occlusion, as well as intimal thickening. Left pulmonary artery involvement was revealed in the parasternal aortic short-axis view. Right pulmonary artery involvement was best observed in the suprasternal right pulmonary artery long-axis view, with complementary views from the parasternal aortic short-axis and subxiphoid angles. Pulmonary trunk involvement was not observed in all three windows. CONCLUSIONS: Transthoracic echocardiography could be a useful noninvasive test to detect pulmonary artery involvement in patients with Takayasu arteritis.

Emergence of Bacterial Soft Rot in Cucumber Caused by Pectobacterium carotovorum subsp. brasiliense in China.

During 2014 to 2015, a devastating bacterial soft rot on cucumber stems and leaves occurred in Shandong, Shanxi, Hebei, Henan, and Liaoning provinces of China, resulting in serious economic losses for cucumber production. The gummosis emerged on the surface of leaves, stems, petioles, and fruit of cucumber. The basal stem color was dark brown and the stem base turned to wet rot. Yellow spots and wet rot emerged at the edge of the infected cucumber leaves and gradually infected the leaf centers. In total, 45 bacterial strains were isolated from the infected tissues. On the basis of phenotypic properties of morphology, physiology, biochemistry, and 16S ribosomal RNA gene sequence analysis, the pathogen was identified as Pectobacterium carotovorum. Multilocus sequence analysis confirmed that the isolates were P. carotovorum subsp. brasiliense, and the pathogens fell in clade II. The pathogenicity of isolated bacteria strains was confirmed. The strains reisolated were the same as the original. The host range test confirmed that strains had a wide range of hosts. As far as we know, this is the first report of cucumber stem soft rot caused by P. carotovorum subsp. brasiliense in China as well as in the world, which has a significant economic impact on cucumber production.

Effects of Climate Change on Epidemics of Powdery Mildew in Winter Wheat in China.

Powdery mildew is a highly destructive winter wheat pathogen in China. Since the causative agent is sensitive to changing weather conditions, we analyzed climatic records from regions with previous wheat powdery mildew epidemics (1970 to 2012) and investigated the long-term effects of climate change on the percent acreage (PA) of the disease. Then, using PA and the pathogen's temperature requirements, we constructed a multiregression model to predict changes in epidemics during the 2020s, 2050s, and 2080s under representative concentration pathways RCP2.6, RCP4.5, and RCP8.5. Mean monthly air temperature increased from 1970 to 2012, whereas hours of sunshine and relative humidity decreased (P < 0.001). Year-to-year temperature changes were negatively associated with those of PA during oversummering and late spring periods of disease epidemics, whereas positive relationships were noted for other periods, and year-to-year changes in relative humidity were correlated with PA changes in the early spring period of disease epidemics (P < 0.001). Our models also predicted that PA would increase less under RCP2.6 (14.43%) than under RCP4.5 (14.51%) by the 2020s but would be higher by the 2050s and 2080s and would increase least under RCP8.5 (14.37% by the 2020s). Powdery mildew will, thus, pose an even greater threat to China's winter wheat production in the future.

A Case of Pulmonary Hypertension Due to Fistulas Between Multiple Systemic Arteries and the Right Pulmonary Artery in an Adult Discovered for Occulted Dyspnoea.

BACKGROUND: Pulmonary hypertension (PH) can be caused by a fistula between the systemic and pulmonary arteries. Here, we report a case of PH due to multiple fistulas between systemic arteries and the right pulmonary artery where the ventilation/perfusion scan showed no perfusion in the right lung. METHODS: A 32-year-old male patient was hospitalised for community-acquired pneumonia. After treatment with antibiotics, the pneumonia was alleviated but dyspnoea persisted. Pulmonary hypertension was diagnosed using right heart catheterisation, which detected the mean pulmonary artery pressure as 37mmHg. The anomalies were confirmed by contrast-enhanced CT scan (CT pulmonary angiography), systemic arterial angiography and pulmonary angiography. RESULTS: Following embolisation of the largest fistula, the haemodynamics and oxygen dynamics did not improve, and even worsened to some extent. After supportive therapy including diuretics and oxygen, the patient's dyspnoea, WHO function class and right heart function by transthoracic echocardiography all improved during follow-up. CONCLUSIONS: Pulmonary hypertension can be present even when the right lung perfusion is lost. Closure of fistulas by embolisation, when those fistulas act as the proliferating vessels, may be harmful.

Effects of statin therapy on progression of mild noncalcified coronary plaque assessed by serial coronary computed tomography angiography: A multicenter prospective study.

BACKGROUND: There are limited data assessing statin therapy in patients with nonobstructive coronary plaque on coronary computed tomography angiography (CCTA). METHODS: Two hundred six consecutive patients with mild noncalcified plaque on CCTA were enrolled in this multicenter prospective observational study. Subjects were divided into 3 groups according to subsequent statin therapy: intensive statin therapy (n = 55), moderate statins (n = 85), and no statin (n = 66). Serial scans were performed after a median interval of 18 months. Low-attenuation plaque (LAP) volume, total plaque volume, and percent plaque volume were measured. RESULTS: The LAP volume, total plaque volume, and percent plaque volume showed significant regression among intensive-statin compared with no-statin group (annualized changes: -7.1 ± 13.1 vs 0.9 ± 12.7 mm(3), P< .001; -16.4 ± 35.0 vs 12.3 ± 32.4 mm(3), P< .001; and -6.2% ± 11.8% vs 3.5% ± 12.1%, P< .001, respectively). Progression of LAP volume, total plaque volume, and percent plaque volume was retarded among moderate-statin compared with no-statin group (annualized changes: -2.8 ± 7.6 vs 0.9 ± 12.7 mm(3), P= .041; -0.1 ± 25.6 vs 12.3 ± 32.4 mm(3), P= .014; and -1.8% ± 11.2% vs 3.5% ± 12.1%, P= .006, respectively). On multivariable model predicting change in total plaque volume, higher baseline LAP volume, moderate statin therapy, and intensive statin therapy were each independent predictors of plaque regression (standardized coefficients: baseline LAP volume -0.36, P< .001; moderate statin -0.21, P= .004; intensive statin -0.36, P< .001, respectively). CONCLUSIONS: This study suggests that statin treatment can retard progression and even induce regression of mild noncalcified coronary plaque. Patients with greater baseline LAP volume are more likely to benefit from statin therapy.

Population Genetic Structure and the Migration of Puccinia striiformis f. sp. tritici Between the Gansu and Sichuan Basin Populations of China.

Puccinia striiformis f. sp. tritici is the causal pathogen of interregional epidemics of wheat stripe rust in China via long-distance migration. Gansu Province serves as putative inoculum center providing oversummering inoculum, while Sichuan Basin area serves as a region providing huge amounts of overwintering inoculum. Thus, the relationship between these two regions in population exchange and migration become important in prediction of interregional epidemics. In this study, we compared the population genetic structure and race composition between Gansu and Sichuan Basin populations to infer their migration relationships. A total of 526 isolates, spanning 3 years, were genotyped using eight pairs of amplified fragment length polymorphism markers, and a subset of 98 isolates were inoculated onto 19 Chinese differentials to perform the race analysis. Twenty-three common races and 26 shared genotypes supplied molecular evidence for migration between Gansu and Sichuan Basin populations. Bayesian assignment and principal component analysis revealed that the genetic group assignment of the Sichuan Basin populations (10SB and 11SB) changed in the spring to align with the fall Gansu populations in the prior seasons (09GS and 10GS), which indicated an asymmetric migration from Gansu Province to the Sichuan Basin area. The linkage disequilibrium and the parsimony tree length permutation test revealed a strong annual recombination signal in the Gansu populations and an inconsistent signal in the Sichuan Basin populations.

Population Subdivision of Fusarium graminearum from Barley and Wheat in the Upper Midwestern United States at the Turn of the Century.

Fusarium graminearum, the causal agent of Fusarium head blight (FHB) in wheat and barley, is one of the most economically destructive pathogens of these grains worldwide. Recent population genetic studies of the pathogen obtained from wheat in North America supported population subdivision in part correlated with the spectrum of trichothecene mycotoxins (chemotype) produced by individuals within each population. In contrast, a recent study of F. graminearum obtained from diseased barley in the upper Midwestern United States concluded that only a single population was present, consisting of individuals with various chemotypes. To test whether strains derived from different hosts potentially have different population dynamics, we obtained the barley strains used in the previous study and compared them with wheat strains isolated at a similar time and geographic origin. A total of 247 F. graminearum isolates from barley were assigned firmly into two clusters using a Bayesian clustering method. Subdivision within the barley population corresponded to the previously described NA1 (correlated with the 15ADON chemotype) and NA2 (correlated with the 3ADON chemotype) populations from wheat. However, in both sampling periods the barley population exhibited a higher level of genetic differentiation between NA1 and NA2 populations, fewer admixed individuals and evidence of unidirectional gene introgression (15ADON strains with NA2 genetic backgrounds). These results suggest less recombination between NA1 and NA2 populations on barley compared with wheat. The frequency of 3ADON chemotype strains in the most recently surveyed barley population suggests a latitudinal cline from the northern (49%), central (40%) to the southern (29%) sampling area. The potential to produce a novel trichothecene, 3α-acetoxy,7α,15-dihydroxy-12,13-epoxytrichothe-9-ene (NX-2), was not detected in the barley population but occurred at a low rate (2.4%) in the wheat population.

Population Genetic Structure of Puccinia striiformis in Northwestern China.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most important fungal diseases of wheat in China. Xinjiang, Qinghai, and Gansu Provinces, located in the northwest of China, are the key regions for interregional epidemics of wheat stripe rust due to their geographic as well as crop-planting features, in relation to pathogen's life cycle, reproduction, and population genetics. To study the population genetic structures of the pathogen in these areas, 217 isolates of P. striiformis f. sp. tritici were collected from different geographic locations at various elevations in the three provinces. The amplified fragment length polymorphism (AFLP) genotypes and virulence phenotypes were analyzed for Xinjiang, Qinghai, and Gansu populations. Frequent genotypic exchanges between Xinjiang and Qinghai and between Qinghai and Gansu populations were detected, demonstrating that the populations of Xinjiang and Gansu may not be completely isolated. Genotypic diversity in Gansu Province was much higher than that in Xinjiang or Qinghai Province. The Xinjiang population was genetically closer to the Qinghai population than to the Gansu population. The race dynamic patterns in Qinghai were consistent with those in Gansu but the similar component pattern of the race dynamics in Xinjiang appeared late, following those in Gansu and other interior epidemic regions of China. No significant correlation between the AFLP genetic distance and the virulence distance in the Xinjiang, Qinghai, and Gansu populations was determined. A possible recombination signature of the pathogen population was detected in Gansu population and some subpopulations in Qinghai but not in Xinjiang population.

[Identification and classification of disease severity of wheat stripe rust using near infrared spectroscopy technology].

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici, is an economically important disease in the world. It is of great significance to assess disease severity of wheat stripe rust quickly and accurately for monitoring and controlling the disease. In this study, wheat leaves infected with stripe rust pathogen under different severity levels were acquired through artificial inoculation in artificial climate chamber. Thirty wheat leaves with disease severity equal to 1%, 5%, 10%, 20%, 40%, 60%, 80% or 100% were picked out, respectively, and 30 healthy leaves were chosen as controls. A total of 270 wheat leaves were obtained and then their near infrared spectra were measured using MPA spectrometer. According to disease severity levels, 270 near infrared spectra were divided into 9 categories and each category included 30 spectra. From each category, 7 or 8 spectra were randomly chosen to make up the testing set that included 67 spectra. The remaining spectra were treated as the training set. A qualitative model for identification and classification of disease severity of wheat stripe rust was built using near infrared reflectance spectroscopy (NIRS) technology combined with discriminant partial least squares (DPLS). The effects of different preprocessing methods of obtained spectra, ratios between training sets and testing sets, and spectral ranges on qualitative recognition results of the model were investigated. The optimal model based on DPLS was built using cross verification method in the spectral region of 4000-9000 cm(-1) when "centralization" was used as the preprocessing method of spectra and the spectra were divided into the training set and the testing set with the ratio equal to 3:1. Accuracy rate of the training set was 95.57% and accuracy rate of the testing set was 97.01%. The results showed that good recognition performance could be acquired using the model based on DPLS. The results indicated that the method using near infrared reflectance spectroscopy technology proposed in this study is feasible for identification and classification of disease severity of wheat stripe rust. A new method was provided for monitoring and assessment of wheat stripe rust.

[Application of near infrared spectroscopy to qualitative identification and quantitative determination of Puccinia strii formis f. sp. tritici and P. recondita f. sp. tritici].

To realize qualitative identification and quantitative determination of Puccinia strii formis f. sp. tritici (Pst) and P. recondita f. sp. tritici (Prt), a qualitative identification model was built using near infrared reflectance spectroscopy (NIRS) combined with distinguished partial least squares (DPLS), and a quantitative determination model was built using NIRS combined with quantitative partial least squares (QPLS). In this study, 100 pure samples including 50 samples of Pst and 50 samples of Prt were obtained, and 120 mixed samples including three replicates of mixed urediospores of the two kinds of pathogen in different proportions (the content of Pst was within the range of 2. 5% 100% with 2. 5% as the gradient) were obtained. Then the spectra of the samples were collected using MPA spectrometer, respectively. Both pure samples and mixed samples were divided into training set and testing set with the ratio equal to 2:1. Qualitative identification model and quantitative determination model were built using internal cross-validation method in the spectral region 4,000--10,000 cm(-1) based on the training sets from pure samples and mixed samples, respectively. The results showed that the identification rates of the Pst-Prt qualitative identification model for training set and testing set were both up to 100. 00% when scatter correction was used as the preprocessing method of the spectra and the number of principal components was 3. When 'range normalization + scatter correction' was used as the preprocessing method of the spectra and the number of principal components was 6, determination coefficient (RZ), standard error of calibration (SEC) and average absolute relative deviation(AARD) of the Pst-Prt quantitative determination model for training set were 99.36%, 2.31% and 8.94%, respectively, and R2, standard error of prediction (SEP) and AARD for testing set were 99.37%, 2.29% and 5. 0%, respectively. The results indicated that qualitative identification and quantitative determination of Pst and Prt using near infrared spectroscopy technology are feasible and that the Pst-Prt qualitative identification model and the Pst-Prt quantitative determination model built in this study were reliable and stable. A new method based on NIRS was provided for qualitative identification and quantitative determination of plant pathogen in this study.