王正非林火蔓延模型改进研究

王正非林火蔓延模型是目前国内比较先进的森林火灾蔓延模型,但是由于林火行为的复杂性,此模型在准确率和普适性方面仍存在许多不足。本文结合已有的成果进一步改进王正非模型,增加了可燃物湿度对林火蔓延速度的影响,改进了林火初始速度的计算方式。针对各种坡度对林火蔓延行为的影响给出了一个计算公式。与改进前相比,改进后的模型使其对林火蔓延情况的预估更为精准。     

河南省食用菌科技推广存在的问题及对策

综合分析了河南省食有菌科技推广中存在的生产经营缺乏宏观引导，科技推广存在自发性和盲目性，体制不协调和食用菌生产本身的不可控因素较多等问题，提出了加强宏观引导，微观调控，建立健全食用菌行业管理，食用菌龙头企业建设，开发建设规模生产基地等具体措施，为食用菌的产业化大发展提供了参考依据。     

Effect of planting density of maize on the progress and spread of northern leaf blight fromExserohilum turcicum infested residue source

Effect of plant density (37,037, 44,444 and 55,555 plants/ha) on the increase of northern leaf blight in time and space on two maize cultivars planted at spacings of 90, 75 and 60 between rows and 30 cm within rows was investigated.Exserohilum turcicum infested maize residue was used as an inoculum source. Maize density did not significantly affect the disease indices, but significantly influenced the grain yield of the two cultivars. In contrast, the two cultivars differed significantly (P0.01) in disease severity, but not grain yield. Higher disease severities and grain yields were associated with higher plant densities, whereas the apparent infection rate was lower in higher plant density. Distance from the maize residue (inoculum source) significantly influenced disease severity. The percentage leaf area blighted, area under disease progress curve and disease progress curve intercept decreased with distance from the maize residue area, but the apparent infection rate on EV8429-SR appeared to increase with distance. Disease gradients (b) were higher in closely planted maize and flattened with time in one location only.     

Spread of potato virus Y in potato cultivars (Solanum tuberosum L.) with different levels of sensitivity

The aim of this work was to correlate the appearance of the symptoms, multiplication and spread of virus after mechanical inoculation of potato (Solanum tuberosum L.) cultivars showing different levels of susceptibility and sensitivity to Potato virus Y^NTN (PVY^NTN). The potato cultivars used were the resistant cultivar Sante and susceptible cultivars Igor, Pentland squire and Désirée. The spread of the virus PVY^NTN in infected plants was monitored using different methods: DAS-ELISA, tissue printing, immuno-serological electron microscopy and real-time PCR. In all three susceptible cultivars, the virus was detected in the inoculated leaves 4–5 days after inoculation. From there virus spread rapidly, first into the stem, then more or less simultaneously to the upper leaves and roots. Real-time PCR was shown to be very sensitive and enabled viral RNA to be detected in non-inoculated leaves of susceptible cultivar Igor earlier than other methods. Therefore, for exact studies of plant–virus interaction, a combination of methods which detect viruses on the basis of their different properties (coat protein, morphology or RNA) should be used to monitor the spread of viruses.     

Wind-mediated spread of Rice yellow mottle virus (RYMV) in irrigated rice crops

A study was carried out to demonstrate that Rice yellow mottle virus (RYMV), a virus known to be transmitted by beetles, can spread between rice plants by direct leaf contact caused by wind. Almost all healthy plants surrounding an infected plant became infected when exposed to a fan blowing for 15 min at a distance of 50 cm. Spread of RYMV by plant contact, mediated by wind, was also demonstrated in field experiments, the extent of spread depending on plant density. Infection was almost 10 times higher in plots with a density of 33 plants m⁻² than in plots with 16 plants m⁻². Less spread was observed in plots protected by 1·5 m high windscreens. It is suggested that wind-mediated spread of RYMV may result from abrasive contact between leaves of plants.     

树木体内水分长距离运输的负压传递机制

蒸腾能使木质部产生不超过-0.1MPa的有限负压,这个负压在木质部内自上而下依次向下传递。水分在导管或管胞内所受的吸附力、毛管力、真空力等综合作用力要大于或等于所受的重力,这个综合作用力可以将水分托住而不受重力作用而下移,使水分在负压作用下以分段移动的方式从根部上升到植物顶端。空穴和栓塞是两个不同的概念,其形成过程、恢复机制都有其本质的不同。空穴的发生与负压和水分的分段移动有密切的关系。     

Soil organic carbon stock variability in the Northern Gangetic Plains of India: interaction between agro‐ecological characteristics and cropping systems

Soil organic carbon (SOC) content and its spatial distribution in the Northern Gangetic Plain (NGP) Zone of India were determined to establish the cause–effect relationship between agro‐ecological characteristics, prevailing crop management practices and SOC stock. Area Spread Index (ASI) approach was used to collect soil samples from the NGP areas supporting predominant cropping systems. Exponential ordinary kriging was found most suitable geo‐statistical model for developing SOC surface maps of the NGP. Predicted surface maps indicated that 43.7% area of NGP had 0.5–0.6% SOC, while the rest of the area was equally distributed with high (0.61–0.75%) and low (< 0.5%) SOC content levels. Averaged across cropping systems, maximum SOC content was recorded in Bhabar and Tarai Zone (BTZ), followed by Central Plain Zone (CPZ), Mid‐Western Plain Zone (MWPZ), Western Plain Zone (WPZ) and South‐Western Plain Zone (SWPZ) of the NGP. The SOC stock was above the optimum threshold (> 12.5 Mg/ha) in 97.8, 57.6 and 46.4% areas of BTZ, CPZ and MWPZ, respectively. Only 9.8 and 0.4% area of WPZ and SWPZ, respectively, had SOC stock above the threshold value. The variation in SOC stock was attributed largely to carbon addition through recycling of organic sources, cropping systems, tillage intensity, crop or residue cover and land‐use efficiency, nutrient‐use pattern, soil texture and prevailing ecosystem. Adoption of conservation agriculture, balanced use of nutrients, inclusion of legumes in cropping systems and agro‐forestry were suggested for enhancing SOC stock in the region.     

辣椒传入中国的途径与传播路径

通过考证认为，一年生辣椒(Capsicum annuum L.)于16世纪80年代从日本传入中国，最早的传入点是浙江。以浙江为起点，向北、西、南3个方向传播。向北方向，经江苏传到山东，虽然江苏没有接受辣椒，但山东很快接受并把辣椒当作花椒的替代品，名称由番椒变成了秦椒；再以山东为中心，继续向河北、辽宁传播，东北的辣椒是闯关东的山东人传播的；向西传到了天津、山西、河南、北京、甘肃、内蒙古，形成华北传播路线。向西方向，从浙江沿长江西上，安徽、江西、湖北没有接受，但湖南很快接受了辣椒，并以湖南为中心，向贵州、四川、云南、广东、广西、陕西等地传播，形成影响最大的长江传播路线，新疆的辣椒是在左宗棠收复新疆时由湖南军人传过去的。向南传播的速度非常缓慢，传到江西、福建的时间都较晚。从荷兰传入台湾的灌木辣椒(Capsicum frutescens L.)和从印度尼西亚雅加达传入台湾的中国辣椒(Capsicum chinense Jacq.)，经福建传到海南和云南。     

农民大学生移动学习探索

通过调查分析农民大学生的特征以及移动学习的特点和优势，发现移动学习能够对农民大学生的课程学习起到促进作用，提高学习效率，是一种重要的远程教育方式。     

Genetic basis and origin of resistance to acetolactate synthase inhibitors in Amaranthus palmeri from Spain and Italy

BACKGROUND

Amaranthus palmeri is an aggressive annual weed native to the United States, which has become invasive in some European countries. Populations resistant to acetolactate synthase (ALS) inhibitors have been recorded in Spain and Italy, but the evolutionary origin of the resistance traits remains unknown. Bioassays were conducted to identify cross-resistance to ALS inhibitors and a haplotype-based genetic approach was used to elucidate the origin and distribution of resistance in both countries.

RESULTS

Amaranthus palmeri populations were resistant to thifensulfuron-methyl and imazamox, and the 574-Leu mutant ALS allele was found to be the main cause of resistance among them. In two Spanish populations, 376-Glu and 197-Thr mutant ALS alleles were also found. The haplotype analyses revealed the presence of two and four distinct 574-Leu mutant haplotypes in the Italian and Spanish populations, respectively. None was common to both countries, but some mutant haplotypes were shared between geographically close populations or between populations more than 100 km apart. Wide genetic diversity was found in two very close Spanish populations.

CONCLUSION

ALS-resistant A. palmeri populations were introduced to Italy and Spain from outside Europe. Populations from both countries have different evolutionary histories and originate from independent introduction events. ALS resistance then spread over short and long distances by seed dispersal. The higher number and genetic diversity among mutant haplotypes from the Spanish populations indicated recurrent invasions. The implementation of control tactics to limit seed dispersal and the establishment of A. palmeri is recommended in both countries. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.