基于斜率比法评定断奶仔猪对不同铜源的相对生物学利用率

本试验旨在研究不同铜源（硫酸铜、碱式氯化铜和柠檬酸铜）和铜添加水平（20和30 mg/kg）对断奶仔猪生长性能、血清铜含量与含铜酶活性以及组织铜含量的影响,探讨断奶仔猪对不同铜源的相对生物学利用率。试验采用3×2双因子随机区组设计,选取平均体重为（8.98±0.48） kg的杜×长×大三元杂交断奶仔猪112头,随机分为7组,每组4个重复,每个重复4头猪。对照组饲喂玉米-豆粕型基础饲粮（铜含量为7.80 mg/kg）,各试验组分别在基础饲粮中添加20或30 mg/kg硫酸铜、碱式氯化铜或柠檬酸铜（均以铜含量计）。试验预试期3 d,正试期28 d。结果表明：1）试验组与对照组断奶仔猪平均日增重、平均日采食量和料重比均无显著差异（P>0.05）。2）饲粮铜源和铜添加水平对断奶仔猪血清铜含量具有显著影响（P<0.05）,但对血清铜蓝蛋白和铜锌超氧化物歧化酶活性均无显著影响（P>0.05）。3）饲粮铜源和铜添加水平对断奶仔猪肝脏铜含量具有显著影响（P<0.05）,但对心脏、肾脏、胰脏和跖骨铜含量均无显著影响（P>0.05）。4）根据多元线性回归斜率比法计算,以血清铜...     

凝结芽孢杆菌对热应激肉鸡生长性能及肠道消化与吸收功能的影响

本试验旨在研究凝结芽孢杆菌对热应激肉鸡生长性能及肠道消化与吸收功能的影响。选择320只28日龄健康爱拔益加（AA）肉公鸡,随机分为5个组,每组8个重复,每个重复8只。常温对照组（TC组）肉鸡饲养于（22±1）℃的常温环境,饲喂基础饲粮;热应激组（HS组）肉鸡饲养于（34±1）℃的高温环境,饲喂基础饲粮;热应激试验组肉鸡饲养于（34±1）℃的高温环境,分别饲喂在基础饲粮中添加0.2×107(HS-BC0.2组)、1.0×107(HS-BC1.0组)、5.0×107CFU/g(HS-BC5.0组)凝结芽孢杆菌的试验饲粮。试验期14 d。结果表明：与TC组相比,HS组的末重、平均日增重（ADG）、平均日采食量（ADFI）,干物质和粗蛋白质表观代谢率,空肠食糜总淀粉酶和总蛋白酶酶活,空肠绒毛高度、绒毛高度/隐窝深度以及空肠钠/葡萄糖协同转运蛋白1(SGLT1)、基础氨基酸转运载体（r-BAT）、y+L氨基酸转运载体-1(y+LAT1) mRNA表达量均显著降低（P<0.05）,料重比（F/G）显著增加（P<0.05）。与HS组相比,HS-BC1.0和HS-BC5.0组的ADG、粗蛋...     

“WaterMan”: an on-farm water management game with heuristic capabilities

A modern computer-based simulation tool (WaterMan) in the form of a game for on-farm water management was developed for application in training events for farmers, students, and irrigators. The WaterMan game utilizes an interactive framework, thereby allowing the user to develop scenarios and test alternatives in a convenient, risk-free environment. It includes a comprehensive soil water and salt balance calculation algorithm. It also employs heuristic capabilities for modeling all of the important aspects of on-farm water management, and to provide quantitative performance evaluations and practical water management advice to the trainees. Random events (both favorable and unfavorable) and different strategic decisions are included in the game for more realism and to provide an appropriate level of challenge according to player performance. Thus, the ability to anticipate the player skill level, and to reply with random events appropriate to the anticipated level, is provided by the heuristic capabilities used in the software. These heuristic features were developed based on a combination of two artificial intelligence approaches: (1) a pattern recognition approach and (2) reinforcement learning based on a Markov decision processes approach, specifically the Q-learning method. These two approaches were combined in a new way to account for the difference in the effect of actions taken by the player and action taken by the system in the game world. The reward function for the Q-learning method was modified to reflect the suggested classification of the WaterMan game as what is referred to as a partially competitive and partially cooperative game.     

Occurrence of prophage and historical perspectives associated with the dissemination of huanglongbing in mainland China

Huanglongbing (HLB), associated with a non-culturable bacterium ‘Candidatus Liberibacter asiaticus’ (CLas), is a highly destructive citrus disease with a long but poorly documented history in China. No effective treatment for HLB is available. The identification of new prophages in abundant CLas genomic sequence data provides new insights into both the diversity of CLas strains and HLB management. In this study, CLas populations from nine provinces were surveyed for the presence of prophage. Two major prophage typing groups (PTGs) were discovered to be associated with two different altitude regions: strains of CLas in PTG1 from high altitude regions (HAR) mainly contained prophage Type 1 only or Types 1 and 3, whereas strains of CLas in PTG2 from low altitude regions (LAR) mainly contained prophage Type 2. The discovery of these CLas population patterns provides evidence for independent origins of HLB in HAR and LAR. Guangdong province is the generally recognized domestic region of origin for HLB and is primarily responsible for the dissemination of HLB in LAR through transport of seedlings. Both Yunnan and Sichuan provinces are the probable regions of origin for HLB in HAR. PTG2 was further divided into two subgroups: PTG2-1, found in Guangdong, Fujian and Guangxi and PTG2-2, found in Jiangxi, Zhejiang and Hunan. These regions and prophage types are correlated with early and late introductions of HLB in LAR. These molecular analyses were supported by studying the history of the dissemination of HLB in historical documents.     

Paraphoma root rot of alfalfa (Medicago sativa) in Inner Mongolia,China

Root rot symptoms were observed in fields of alfalfa in Chifeng city, Inner Mongolia, China in 2016. Disease incidences of seven alfalfa varieties planted in 2014 ranged from 56% to 95%, while incidence of Gongnong No. 1 planted in 2016 was 8%, 31% and 76% in 2016, 2017 and 2018, respectively. Paraphoma isolates were consistently recovered from black necrotic root tissues of diseased plants with a frequency of 77.1%. Based on morphological characters and phylogenetic analysis of rDNA internal transcribed spacer (ITS), elongation factor 1-α (EF1-α) and β-tubulin (TUB), this fungus was identified as Paraphoma radicina. Glasshouse pathogenicity experiments showed that P. radicina significantly reduced above- and below-ground biomass of alfalfa plants 2 months after inoculation. Paraphoma radicina infected 70% of the plants inoculated with a root dip in conidia, and these symptoms were consistent with the symptoms in the field. Paraphoma radicina was successfully reisolated from disease roots of the inoculated alfalfa plants. This is the first report of P. radicina as the causal agent of alfalfa root rot in China.     

BUILDING CLIMATE-RESILIENT FOOD SYSTEMS IN EAST AND SOUTHEAST ASIA: VULNERABILITIES,RESPONSES AND FINANCING

Food system resilience to climate change is uniquely imperative for bringing Sustainable Development Goals within reach and leaving no one behind. Food systems in East and Southeast Asia are interacting with planetary boundaries and are adversely affected by extreme weather-related events. A practical question for East and Southeast Asian stakeholders is how to foster climateresilient food systems in the face of lingering food system vulnerabilities and policy gaps. This paper reviews food syste...     

Temporal and spatial progress of the diseases caused by the crinivirus tomato chlorosis virus and the begomovirus tomato severe rugose virus in tomatoes in Brazil

Efficient management of whitefly-borne diseases remains a challenge due to the lack of a comprehensive understanding of their epidemiology, particularly of the diseases tomato golden mosaic and tomato yellowing. Here, by monitoring 16 plots in four commercial fields, the temporal and spatial distribution of these two diseases were studied in tomato fields in Brazil. In the experimental plots these diseases were caused by tomato severe rugose virus (ToSRV) and tomato chlorosis virus (ToCV), respectively. The incidence of each virus was similar in the plots within a field but varied greatly among fields. Plants with symptoms for both diseases were randomly distributed in three of four spatial analyses. The curves representing the progress of both diseases were similar and contained small fluctuations, indicating that the spread of both viruses was similar under field conditions. In transmission experiments of ToSRV and ToCV by Bemisia tabaci MEAM1 (former biotype B), these viruses had a similar transmission rate in single or mixed infections. It was then shown that primary and secondary spread of ToCV were not efficiently controlled by insecticide applications. Finally, in a typical monomolecular model of disease progress, simulation of the primary dissemination of ToSRV and ToCV showed that infected plants were predominantly randomly distributed. It is concluded that, although the manner of vector transmission differs between ToSRV (persistent) and ToCV (semipersistent), the main dispersal mechanisms are most probably similar for these two diseases: primary spread is the predominant mechanism, and epidemics of these diseases have been caused by several influxes of viruliferous whiteflies.     

Exogenous application of melatonin improves plant resistance to virus infection

In this study, melatonin (MEL)-mediated plant resistance to tobacco mosaic virus (TMV) was examined to study local infection in Nicotiana glutinosa and systemic infection in Solanum lycopersicum. Exogenous application of 100 µm MEL increased anti-virus infection activity to 37.4% in virus-infected N. glutinosa plants. The same treatment significantly reduced relative levels of virus RNA analysed by qRT-PCR and virus titres measured by dot-ELISA, and increased the relative expression levels of the PR1 and PR5 genes analysed by qRT-PCR, in virus-infected S. lycopersicum. MEL treatment induced considerable accumulations of salicylic acid (SA) and nitric oxide (NO) but did not significantly affect production of hydrogen peroxide (H₂O₂) in the virus-infected S. lycopersicum plants. Transgenic nahG N. tabacum was used to determine whether MEL-induced TMV resistance was dependent on the SA pathway. The results showed that the relative RNA level of the TMV analysed by qRT-PCR and virus titres analysed by dot-ELISA were not reduced by the MEL treatment in the nahG transgenic N. tabacum seedlings treated twice with 100 µm MEL. The increased relative expression levels of PR1 and PR5 were greatly reduced when cPTIO, an NO scavenger, was included in the MEL treatment. A working model of MEL-mediated plant resistance to TMV is proposed. MEL-mediated plant resistance to viruses provides a new avenue to control plant viral diseases.     

Distribution and genetic diversity among Aspergillus flavus isolates across three agro-ecologies essential for maize cultivation in Ghana

Fungal mycotoxins are important contaminants of agricultural commodities that pose serious concerns to producers, consumers and exporters. Aflatoxin is a carcinogenic metabolite produced by the fungi Aspergillus flavus and A. parasiticus. These fungi and other mould species living in the soil contaminate several crops including maize. This study was undertaken with the following objectives: (i) to assess the presence of A. flavus and other moulds in Ghanaian soil; (ii) to determine the distribution and density of A. flavus under three agro-ecologies noted for major maize production; and (iii) to assess the effect of percentage of carbon (C) and nitrogen (N) and soil pH on A. flavus population densities and diversity in the isolates found across the agro-ecologies. The data showed seven moulds that were common across the agro-ecologies. Significant differences (P < 0.05) were observed in the A. flavus density and distribution within and across these agro-ecologies. Fumesua soils recorded the highest levels of A. flavus (1.185 × 10³ cfu g⁻¹) while Akomadan recorded the least (9.76 × 10² cfu g⁻¹). Percentage available C, N and soil pH did not significantly influence A. flavus density. The A. flavus isolates identified in this study varied in genetic sequence within the aflatoxin gene cluster, but these differences were not distinguishable by origin.