北京地区西瓜枯萎病生理小种分化研究

对在北京大兴、顺义、通县等西瓜主产区采集，经单孢分离得到的８个西瓜枯萎病菌株进行了生理小种分化研究。应用国际通用的３个鉴别寄主ＳｕｇａｒＢａｂｙ、ｃｈａｒｌｅｓｔｏｎＧｒａｙ、ｃａｌｈｏｕｒＧｒａｙ和国内京欣１号、苏蜜１号２个品种，采用全国协作组统一的苗期抗病鉴定方法，进行人工接种鉴定。结果表明北京地区西瓜枯萎病菌株均系同一生理型，为西瓜枯萎病生理小种１号。     

再生稻再生芽萌发期降水量和作物需水量的年际变化特征分析

基于遂宁、内江、泸州、宜宾、纳溪和叙永等6个气象站1951—2007年的逐日气象资料,采用FAO推荐的Penman-Monteith公式计算再生稻作物需水量,并结合同期降水量,以自然降水量/作物需水量(R/ETc)为指标,探讨了川东南地区中稻再生芽萌发期(即7月下旬—8月中旬)的降水量和作物需水量的地区差异特征和年际变化特征。结果表明,遂宁、内江、泸州、纳溪、宜宾和叙永再生芽萌发期多年平均降水量分别为156.7、175.4、168.5、66.7、227.5 mm和153.4 mm。需水量多年平均分别为141.5、138.6、144.5、146.0、128.5 mm和142.7 mm。除了纳溪外,其余各地区再生芽萌发期的降水量均高于其作物需水量。从自然降水量和作物需水量之间的关系上看,宜宾、内江、泸州及叙永均较适合再生稻发展,而纳溪则存在较大的风险。进一步分析内江、泸州再生芽萌发期作物需水量和自然降水量的年际变化特征,发现从1951—2007年,内江降水量与需水量的比值1的年份占了63%,比值在0.85~1之间的概率为3%,比值在0.5~0.7之间的概率为11%,降水量与需水量的比值0.5为12%。从1951—2002年,泸州降水量与需水量的比值1的年份占了52%,比值在0.85~1之间的概率为13%,比值在0.5~0.7之间的概率为21%,降水量与需水量的比值0.5的概率为4%。相对而言,内江中稻再生芽萌发期仍然存在较大的受旱风险。根据以上结果,探讨了川东南再生稻发展适宜区及高产栽培策略,纳溪受旱风险较大不宜晒田,遂宁、宜宾、内江、泸州、叙永均能进行中期晒田。     

基于声振信号对称极坐标图像的苹果霉心病早期检测

为实现苹果早期霉心病较高精度的检测,该研究采用对称极坐标法（Symmetrized Dot Pattern,SDP）将苹果声振信号变换为雪花图,然后采用AlexNet、VGG16和ResNet50卷积神经网络以迁移学习方式深度挖掘SDP雪花图像的特征信息,将其输入到支持向量机（Support Vector Machine,SVM）分类器,对霉心程度≤7%的苹果进行检测。研究结果表明,当时间间隔系数为25和角度放大因子为50°时,健康果与早期霉心果声振信号的SDP图形状特征差异最大,在此条件下获取的SDP图经卷积神经网络AlexNet、VGG16和ResNet50提取特征并构建了不同核函数的SVM霉心果检测模型,在各类SVM模型中,ResNet50-SVM-gaus（高斯基）模型用相对较少的训练时间和参数量可取得训练集霉心果较高分类准确率,经超参数优化训练该模型对健康果和早期霉心果测试集不平衡样本（10∶1）的总体分类准确率达到96.97%,平均查准率、平均查全率、平均加权调和均值、Kappa系数和马修斯相关系数值分别为80.19%、90.36%、86.21%,82.54%和82.68%,该模型不仅对多数类的健康果保持较高分类准确率,而且对少数类的早期霉心果也具有较高判别能力。这些研究结果为声振法应用于果蔬内部病害的早期在线检测系统研发提供了技术支撑。     

Automated identification of sugar beet diseases using smartphones

Cercospora leaf spot (CLS) poses a high economic risk to sugar beet production due to its potential to greatly reduce yield and quality. For successful integrated management of CLS, rapid and accurate identification of the disease is essential. Diagnosis on the basis of typical visual symptoms is often compromised by the inability to differentiate CLS symptoms from similar symptoms caused by other foliar pathogens of varying significance, or from abiotic stress. An automated detection and classification of CLS and other leaf diseases, enabling a reliable basis for decisions in disease control, would be an alternative to visual as well as molecular and serological methods. This paper presents an algorithm based on a RGB‐image database captured with smartphone cameras for the identification of sugar beet leaf diseases. This tool combines image acquisition and segmentation on the smartphone and advanced image data processing on a server, based on texture features using colour, intensity and gradient values. The diseases are classified using a support vector machine with radial basis function kernel. The algorithm is suitable for binary‐class and multi‐class classification approaches, i.e. the separation between diseased and non‐diseased, and the differentiation among leaf diseases and non‐infected tissue. The classification accuracy for the differentiation of CLS, ramularia leaf spot, phoma leaf spot, beet rust and bacterial blight was 82%, better than that of sugar beet experts classifying diseases from images. However, the technology has not been tested by practitioners. This tool can be adapted to other crops and their diseases and may contribute to improved decision‐making in integrated disease control.     

Molecular cloning and functional analysis of duck Toll-like receptor 5

Toll-like receptor 5 (TLR5) is responsible for the recognition of bacterial flagellin in vertebrates. In this study, we cloned the single-exon TLR5 gene of the Maya breed of Common Shelduck (Tadorna tadorna). The TLR5 open reading frame is 2580 bp in length and encodes an 859-amino acid protein. The putative amino acid sequence of duck TLR5 consisted of a signal peptide sequence, 11 leucine-rich repeat domains, a leucine-rich repeat C-terminal domain, a transmembrane domain, and an intracellular Toll-interleukin-1 receptor domain. The duck TLR5 gene was highly expressed in the lung, bone marrow, spleen, and liver; moderately expressed in kidney, small intestine, large intestine, and brain. A plasmid expressing duck TLR5 was constructed and transfected into HEK293T cells, and expression was confirmed by indirect immunofluorescence assay. HEK293T cells transfected with duck TLR5- and NF-κB-luciferase-containing plasmids significantly responded to flagellin from Salmonella typhimurium, indicating that it is a functional TLR5 homolog.     

The role of ectomycorrhizal fungi in alleviating pine decline in semiarid sandy soil of northern China: an experimental approach

The decline of Mongolian pine (Pinus sylvestris var. mongolica) trees on sandy land in northern China has caused serious ecological concerns. Mongolian pine is an ectomycorrhizal fungus (ECM)-dependent species. Three ECM species (Boletus sp., Lactarius deliciosus and L.sp.) were collected from Mongolian pine plantation stands to test their beneficial effects on Mongolian pine seedlings and their responses to environmental factors such as pH, drought stress and temperature. The results indicated that ECM inoculation significantly increased the rate of ECM colonization and the length of seedling shoots. The three ECM could grow in a pH range from 4 to 7, but did not grow under heavy drought stress (?1.53 MPa). High temperatures (over 37 °C) caused death of ECM. When related to soil pH, soil water content and temperature in the Mongolian pine plantations, water conditions and temperature were unfavorable for ECM growth in surface soil, but suitable in deeper soil. Therefore, it was concluded that the failure of natural regeneration in Mongolian pine plantations might be influenced by the lack of ECM in the surface soil because of high temperatures causing ECM death. Moreover, the majority of the root area is distributed in deeper soil, which alleviates the stresses on ECM development and arrests pine decline; this is beneficial for tree growth.     

Physicochemical and Structural Characteristics of Flours and Starches from Waxy and Nonwaxy Wheats

A waxy spring wheat (Triticum aestivum L.) genotype was fractionated into flour and starch by roller and wet‐milling, respectively. The resultant flour and starch were evaluated for end‐use properties and compared with their counterparts from hard and soft wheats and with commercial waxy and nonwaxy corn (Zea mays L.) starches. The waxy wheat flour had exceptionally high levels of water absorption and peak viscosity compared with hard or soft wheat flour. The flour formed an intermediate‐strength dough that developed rapidly and was relatively susceptible to mixing. Analysis by differential scanning calorimetry and X‐ray diffractometry showed waxy wheat starch had higher gelatinization temperatures, a greater degree of crystallization, and an absence of an amylose‐lipid complex compared with nonwaxy wheat. Waxy wheat and corn starches showed greater refrigeration and freeze‐thaw stabilities than did nonwaxy starches as demonstrated by syneresis tests. They were also similar in pasting properties, but waxy wheat starch required lower temperature and enthalpy to gelatinize. The results show analogies between waxy wheat and waxy corn starches, but waxy wheat flour was distinct from hard or soft wheat flour in pasting and mixing properties.