Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), and huanglongbing disease do not exist in the Stapleton Station area of the Northern Territory of Australia

Abstract  A series of specimens of the Asian citrus psyllid, Diaphorina citri , collected from the Northern Territory (NT) in 1915 was recently rediscovered in the Natural History Museum, London. Surveys were conducted in 2002 on suitable hosts in the locality of the 1915 collections to see if the infestation had persisted. These failed to detect either D. citri or the bacterium that it transmits and that causes huanglongbing disease in citrus. It is presumed that D. citri was eradicated fortuitously by the removal of all citrus plants above latitude 19°S during an eradication program for citrus canker in the NT from 1916 until 1922.     

巴氏新小绥螨对柑桔全爪螨处理的枳橙叶片挥发物的行为反应

【目的】研究巴氏新小绥螨Neoseiulus barkeri对柑桔全爪螨Panonychus citri及刺吸式昆虫为害柑桔叶片释放的挥发物的行为反应,揭示巴氏新小绥螨的嗅觉反应特点。【方法】采用GC-MS顶空进样法对枳橙叶片常见挥发性化合物、针刺枳橙叶片及其柑桔全爪螨雌成螨取食枳橙叶片挥发物进行定性分析,确定每类化合物的相对保留指数,构建枳橙叶片常见及受害挥发性化合物特征谱库。利用嗅觉测定技术分析巴氏新小绥螨对枳橙叶片挥发物的行为反应。【结果】针刺处理和柑桔全爪螨取食影响枳橙叶片挥发物的组成和含量。两种方法处理时枳橙叶片释放的主要物质为α-蒎烯、水芹烯、4-异丙基甲苯。随着处理加重,增量释放的物质为:cis-π-罗勒烯、月桂烯、柠檬烯、异松油烯,减量表达的物质为2-乙基-1-乙醇和十一烷。在10~(-2)、10~(-4)、10~(-6)和10~(-8)g/m L浓度下,正己醛、正壬醛、乙酸辛酯和正庚醛对巴氏新小绥螨有强烈的引诱作用(P>0.05);月桂烯在10~(-2)、10~(-4)和10~(-6)g/m L浓度下对巴氏新小绥螨有强烈的引诱作用(P>0.05);正壬醇和正辛醇随着浓度增加,对巴氏新小绥螨的引诱作用降低;苯甲醛对巴氏新小绥螨的引诱作用较弱。【结论】巴氏新小绥螨对柑桔全爪螨及刺吸式口器昆虫为害柑桔叶片释放出的挥发物各组分具有不同的行为反应,柑桔及其刺吸式害虫生境中的嗅觉线索在巴氏新小绥螨的寄主定位和生境选择中起着重要作用。     

Drought tolerance of apple rootstocks: Production and partitioning of dry matter

The drought tolerance of the commercial apple ( Malus domestica Borkh.) rootstocks M9, M26, M27 and MM111, and some new selections from the rootstock breeding programme at HRI-East Malling (AR69-7, AR295-6, AR360-19, AR486-1 and AR628-2), was assessed using potted, glasshouse-grown, unworked rootstocks. After an initial period of growth under well-watered conditions the amount of irrigation was gradually reduced, for some treatments, to simulate natural drying in the soil. At the end of a six-month growth period, the rootstocks were harvested and the production of dry matter and its partitioning to various plant parts determined. The rootstocks exhibited large differences in shoot and root dry matter, and root length but not all the rootstocks showed declines in root mass or length in response to the droughting treatment. The dwarfing rootstocks tended to have smaller amounts of both coarse (>2 mm diameter) and fine roots (<2 mm diameter), than the more vigorous rootstocks. Irrespective of rootstock or irrigation treatment there was a close linear relationship between coarse and fine root. There was also no change in the length/weight relationship for fine roots irrespective of rootstock or irrigation treatment, i.e. 42 m of fine root weighed 1 g dry weight. In some cases the amount of root produced could be directly correlated with the rootstock known potential to control scion vigour, but this was not true for all the rootstocks examined. The absence of this relationship was particularly evident in some of the new selections of rootstock. The possible causes for these differences, compared with commercially used rootstocks, is discussed in relation to the origin and parentage of the rootstock selections. Despite this lack of a root length/vigour relationship, the amount of dry matter partitioned to shoot growth reflected the rootstocks' known vigour. The different responses of these rootstocks to drought are discussed along with their implications for understanding the mechanisms by which rootstocks are thought to dwarf scion shoots.     

广东省橘园黄龙病发生与危害的影响因素研究

【目的】柑橘黄龙病是世界柑橘生产上的毁灭性病害。探明广东省橘园黄龙病发生与危害的影响因素,可为该病的科学防控提供依据。【方法】在广东省惠州、肇庆、云浮、江门、阳江、清远、韶关等柑橘产区,调查了不同柑橘品种、不同气候和地理条件、不同种植模式和不同管理水平果园的黄龙病发病率,并以常规PCR和实时荧光定量PCR对样品进行了分子检测。【结果】不同柑橘栽培品种发病率:红江橙为78.05%,马水橘为76.04%,砂糖橘为73.20%,贡柑为69.30%,年橘为63.00%,沙田柚为58.68%,柠檬为56.96%;砧木品种发病率:酸橘为15.30%,枳壳为6.57%,柠檬为4.43%;低纬、高温、多台风地区果园的黄龙病发病率较高;山地果园的黄龙病发病率低于平地果园;连片种植果园的黄龙病发病率高于零散种植果园;管理不善的果园中黄龙病发病率高于管理较好的果园。【结论】除了自然因素(低纬、高温、多台风、平原地形)外,聚集种植和管理不善等因素也有利于黄龙病的发生与流行。因此,有针对性地安排果园布局和加强果园管理可以减轻黄龙病的危害。     

两结实类型柑橘果实铁锰锌铜含量的年周期变化(英文)

对单性结实的龟井温州蜜柑和自花授粉结实的鄂柑1号柑橘果实的铁、锰、锌和铜含量的年周期变化进行了测定。结果表明:(1)龟井子房的锌和铜含量在花前至花期居较高,花后趋下降,而鄂柑1号对应值在花期出现明显下降并居较低,花后却有一明显上升;两品种子房(幼果)的铁和锰含量变化却无明显差异,花后呈类似的下降趋势。(2)幼果阶段的果实铁、锰、锌和铜含量均居较高,在果实膨大初期(干旱期)均出现一明显下降,而在果实膨大中期却出现显著上升,之后又趋下降。本文还对果实发育中的微量元素含量动态及其与果实发育之间的关系进行了讨论。     

不同砧穗组合葡萄植株对部分根区干旱的生理生化响应

利用自制木箱对嫁接在3309C、420A和110R砧木上的玛瓦斯亚葡萄（M）进行双侧根区交替灌溉（AI）和单侧灌溉（UI）两种水分胁迫处理,以探讨不同葡萄砧穗组合对干旱的适应能力.结果表明：水分胁迫导致葡萄叶片ABA浓度大幅度增加,AI和UI的3种组合平均分别提高了267.5％和394.7％,而气孔导度和蒸腾速率显著下降.UI处理的3种组合叶片SOD和CAT活性显著增加,脯氨酸（Pro）含量极显著增加,且均以M/110R增幅较大,M/3309C增幅较小;而AI处理的SOD和CAT活性增加较小,但Pro含量显著增加.干旱胁迫导致葡萄叶片质膜透性、MDA和H₂O₂含量极显著增加,以M/3309C增加最多,M/110R增加较少.不同砧穗组合适应干旱逆境的能力主要取决于砧木品种,110R适应干旱逆境的能力强于420A和3309C,其对应的嫁接植株的生长量亦呈同样趋势.与根区单侧灌溉相比,双侧根区交替灌溉对植株造成的伤害较小,是可推广的节水灌溉方式.     

DNA barcoding of genus Toxoptera Koch (Hemiptera: Aphididae): Identification and molecular phylogeny inferred from mitochondrial COI sequences

Abstract Identification of aphid species is always difficult due to the shortage of easily distinguishable morphological characters. Aphid genus Toxoptera consists of species with similar morphology and similar to Aphis in most morphological characters except the stridulatory apparatus. DNA barcodes with 1 145 bp sequences of partial mitochondrial cytochrome‐coxidase I (COI) genes were used for accurate identification of Toxoptera. Results indicated mean intraspecific sequence divergences were 1.33%, whereas mean interspecific divergences were greater at 8.29% (0.13% and 7.79% if T. aurantii 3 and T. aurantii 4 are cryptic species). Sixteen samples were distinguished to four species correctly by COI barcodes, which implied that DNA barcoding was successful in discrimination of aphid species with similar morphology. Phylogenetic relationships among species of this genus were tested based on this portion of COI sequences. Four species of Toxoptera assembled a clade with low support in maximum‐parsimony (MP) analysis, maximum‐likelihood (ML) analysis and Bayesian phylogenetic trees, the genus Toxoptera was not monophyletic, and there were two sister groups, such as T. citricidus and T. victoriae, and two clades of T. aurantii which probably presented cryptic species in the genus.     

Differential expression of pathogenicity- and virulence-related genes of Xanthomonas axonopodis pv. citri under copper stress

In this study, we used real-time quantitative PCR (RT-qPCR) to evaluate the expression of 32 genes of Xanthomonas axonopodis pv. citri related to pathogenicity and virulence that are also involved in copper detoxification. Nearly all of the genes were up-regulated, including copA and copB. Two genes homologous to members of the type II secretion system (xcsH and xcsC) and two involved in the degradation of plant cell wall components (pglA and pel) were the most expressed in response to an elevated copper concentration. The type II secretion system (xcs operon) and a few homologues of proteins putatively secreted by this system showed enhanced expression when the bacteria were exposed to a high concentration of copper sulfate. The enhanced expression of the genes of secretion II system during copper stress suggests that this pathway may have an important role in the adaptative response of X. axonopodis pv. citri to toxic compounds. These findings highlight the potential role of these genes in attenuating the toxicity of certain metals and could represent an important means of bacterial resistance against chemicals used to control diseases.