鄂西山区柑橘大实蝇防治中的突出问题及预防对策

在柑橘大实蝇防治工作倍受重视的鄂西山区，其防治中的突出问题亦日显月彰。为引起对该类问题的广泛关注，达到解决问题的目的，在客观分析这些问题存在的原因基础之上，提出行之有效的预防措施，以推进大实蝇防治工作的完善和进步。     

贡柑黑腐病病原菌的分子鉴定

贡柑黑腐病是近年来在贡柑上发生的一种新型病害，该病害可导致嫩梢快速枯死，大量嫩叶脱落，严重影响树势和产量。本研究从病区采集发病枝叶，对贡柑黑腐病病原菌进行分离、纯化，并采用rDNA-ITS序列分析技术对其进行分子鉴定。结果表明，贡柑黑腐病病原菌为链格孢属（Alternaria Nees）真菌，rDNA-ITS序列与GenBank中芸薹链格孢菌(Alternaria brassicae (Berk.) Sacc.)和柑桔链格孢菌(Alternaria citri Ellis & Everhart)的ITS序列的同源性为99%。结合形态学特征，推断该病原菌为柑桔链格孢菌。     

Frequency of symptomatic trees removal in small citrus blocks on citrus huanglongbing epidemics

Among the recommended measures for citrus Huanglongbing (HLB) management, the systematic elimination of symptomatic trees is the most argued and difficult to be accepted and accomplished by citrus growers. Elimination of recently affected HLB trees represents a short term yield loss and cost increase due to the need of frequent inspections and removal operations. This work aimed to evaluate the effect of different frequencies of inoculum reduction applied at individual citrus blocks scale (or local inoculum reduction) on HLB temporal progress. Eight experiments were carried out in new planted and older citrus blocks with 504–1290 trees/plot. In all experiments, inspections to detect symptomatic trees were done in a fortnightly or monthly frequency. The treatments of frequencies of local inoculum reduction varied from fortnightly to 6 months. Annual disease progress rate was estimated by logistic model for each plot. No difference on HLB progress rates among treatments was observed, except in experiments 1 and 3 where less frequent tree removal resulted in higher disease progress rate. This ineffectiveness of local inoculum reduction on the disease progress rate was explained by the higher weight of primary spread on HLB epidemics than the secondary spread within plots associated with small size and narrow shape of treated plots (except for experiments 1 and 3), high dispersal capacity of HLB-insect vector among plots and groves, and strong control of psyllid within the plots (except for experiment 1, with poor insecticide spray program). Also, the high amount of inspections to detect symptomatic trees before the eradication treatment, which reduced the escapes (asymptomatic and non visual detectable diseased trees) contributed for these results. It is important to note that these results were obtained with only small citrus plots (0.8–2.9 ha) and they cannot be extended to larger groves and farms amenable to HLB management by the symptomatic tree removal and vector control.     

柑橘溃疡病拮抗芽孢菌株的筛选及其控病作用

从柑橘根际土壤中获得192个细菌分离物，通过平板拮抗测试，筛选出对柑橘溃疡病菌（Xanthomonas axonopdis pv. citri）有较强拮抗作用的6个芽孢菌株，抑菌圈直径达12.0～25.0mm，其中菌株G32对柑橘溃疡病菌抑制效果最好，稳定性高；温室控病试验表明，菌株G32的控病效果最佳，提前喷施拮抗菌其预防效果达60.7%，接种溃疡病菌后喷施的治疗效果为53.2%；根据其形态特征、培养性状、生理生化特性及16S rDNA序列比对分析，将G32鉴定为枯草芽孢杆菌Bacillus subtilis。     

Genetic Diversity and Global Distribution of Citrus tristeza virus （CTV） Strains

Citrus tristeza virus （CTV）, the most devastating viral pathogen in citrus, causes tremendous economic losses to citrus industry worldwide. The CTV isolates exhibit variable pathogenicities on their ho...     

Ontology-based simulation in agricultural systems modeling

A methodology and applications of ontology-based simulation are presented. An environment for building simulations based on the Lyra ontology management system is described which includes web-based visual design tools for constructing models and automatically generating simulation code. The ontology is used for representing all equations and all symbols appearing in these equations that are needed to describe a model. The example applications presented are models of soil, water, and nutrient management in citrus and sugarcane. Results thus far show that the ontology-based approach has advantages for representing the model structure, equations, and symbols, that complex models can be described in this format, and that efficient simulation code can be generated automatically from the ontology definition of the model. Potential applications, not yet fully explored, include ability to automatically connect models and data sources, using the ontology to organize model bases containing many models and model components, and using ontology reasoners to search for models, automatically discover model similarities and differences, and generate model instances from general principles.     

基于色调分形维数的柑橘糖度和有效酸度检

研究了宫川温州蜜柑糖度及有效酸度的机器视觉检测技术及影响检测精度的因素.对机器视觉系统采集的柑橘图像进行图像裁切、亮度法去图像背景和RGB空间至HSI空间的转换,将柑橘色调范围分割为0°～20°、20°～40°、40°～60°、60°～80°、80°～100°和100°～120°共6个区域,提取各区域色调分形维数,以此作为BP神经网络输入,无损检测宫川温州蜜柑糖度及有效酸度.167个测试样本的检测结果表明:在±1.5°Brix精度范围内糖度正确识别率为66.6175%,在±0.5精度范围内有效酸度正确识别率为73.9275%.宫川温州蜜柑糖度及有效酸度与果皮色调分形维数之间具有相关性,可用机器视觉检测其糖度及有效酸度.     

沙田柚感官品质的定量描述分析研究

【目的】建立沙田柚感官评定标准,用于评价和指导沙田柚的栽培管理。【方法】选取果皮香 气、果肉香气、果粒饱满度、多汁度、化渣度、甜度、酸度和苦味8个感官属性,由5个评定小组对7个不同产 地的沙田柚进行定量描述分析。同时,沙田柚果肉经真空冷冻干燥后测定含水量、可溶性糖含量、粗纤维含 量、总酸度、维生素C含量和灰分含量,分析感官评定结果与理化指标的相关性。【结果】酸度误差较大, 多汁度容易受到甜度的影响而误判,不适合用作感官评定指标,其他6个属性都能较好地反映沙田柚的感官品 质。可溶性糖含量与甜度（R=0.182）、多汁度（R=0.182）、总分（R=0.202）呈极显著正相关。 总酸度与化 渣度（R=0.183）呈极显著正相关,与甜度（R=-0.174）及果粒饱满度（R=-0.168）极显著负相关。维生素C 含量与果肉香气（R=0.198）、化渣度（R=0.195）有极显著正相关。灰分含量与甜度（R=0.237）、果肉香气 （R=0.196）、总分（R=0.193）呈极显著正相关,与果皮香气（R=0.156）、多汁度（R=0.143）有显著正相 关。不同评定小组对相同沙田柚的评定结果没有显著差异,说明评定方法具有可重复性。大多数感官属性（如 甜度、果肉香气等）评定值与理化指标（如可溶性糖、维生素C、灰分含量等）有极显著正相关,说明所采用 评定方法具有客观性。【结论】以中等感官品质的沙田柚作为参照物,选取果皮香气、果肉香气、果粒饱满 度、化渣度、甜度和苦味6个感官属性对沙田柚进行定量描述分析,结果与理化指标有很好相关性。     

四川柑橘适宜分布及其对气候变化的响应研究

柑橘是四川省和我国主要水果产品之一。以气候为主的环境变化,对作物空间布局产生了显著影响。为合理优化柑橘生产空间,本研究基于最大熵模型（MaxEnt）构建柑橘适宜分布与环境变量的关系模型,运用受试者工作特征曲线（ROC曲线）检测模型精度,刀切法（Jackknife）筛选主导环境变量;采用ArcGIS技术对比1980年、2010年四川柑橘适宜区分布,揭示近30 a气候变化背景下四川省柑橘适宜区的分布与变化情况。结果显示：四川柑橘适宜性的主导环境变量主要体现为以光、热、水为特征的气候环境变量。近30 a四川省气候暖干化的变化趋势改变了区域生态系统的结构和功能,引起了柑橘种植适宜区的时空变化。1980—2010年柑橘种植适宜性空间格局呈现出2个变化特征,一是高适宜区呈整体向北迁移的趋势,主要分布在成都平原区与川东北地区过渡地区;中适宜区界线向东南方迁移。二是适宜性级别呈现出逐级调整,低、中适宜区的等级调整变化明显。2010年高适宜区面积约为4.22万km²,中适宜区4.19万km²,低适宜区4.4万km²,大部分地区为不适宜区。以高适宜区为参照,通过政策措施,政府部门可增加在川南地区、成都平原地区南部的柑橘生产布局。本研究客观地反映了气候变化下,四川省柑橘种植适宜性变化特征,合理确定了柑橘适宜性面积及分布,为柑橘空间优化提供了科学依据。最大熵模型在对物种分布进行准确模拟和预测时具有较强应用价值,对作物气候适宜性区划具有重要指导意义。但对于不同区域和作物应选取合适的环境变量、空间尺度和物种采样位置,减少系统累计误差,提高作物气候适宜区划定精度。     

高通量测序鉴定柑橘黄化脉明病毒诱导柠檬差异表达microRNA

 柑橘黄化脉明病毒(Citrus yellow vein clearing virus,CYVCV)是我国新发生的危害柠檬的重要病毒。本研究对接种和未接种CYVCV的柠檬叶片样品进行了高通量小RNA测序,以甜橙基因组作为参考,采用生物信息学软件进行miRNA鉴定和靶基因预测。结果显示CYVCV侵染对13个保守miRNA和12个新鉴定的非保守miRNA的表达具有调控作用,对这些差异表达miRNA的靶基因进行预测和功能分析的结果显示,保守miRNA的靶基因功能在植物逆境反应及光合作用和能量代谢相关通路中具有明显的富集现象,推测与CYVCV侵染柠檬植株及诱导病害症状表现有关,而多数新鉴定的非保守miRNA的靶基因功能未能注释到KEGG通路。采用实时荧光定量PCR对部分miRNA的表达水平进行了分析,结果表明miRNA的表达水平在接种CYVCV后30~90 d呈时间动态变化。研究结果为进一步揭示CYVCV与柠檬互作机制提供了重要信息。