早期落叶果树土壤养分演变及对果实品质的影响

为了探求导致早期落叶病发生的土壤条件,分析果树栽培前与果园管理过程中存在技术问题,本研究以相同园龄、相同果树品种、落叶和不落叶的几个果园为研究对象,进行了果园土壤管理调查与土壤剖面化学性质的监测,测定了苹果果实的主要品质指标,结果表明:果园土壤有机质含量明显低于农田土壤,土壤表层,落叶果园土壤有机质含量要高于不落叶果园的,而在60 cm以下,落叶果园土壤有机质反而低于不落叶果园;而不落叶果园土壤中的碳酸钙含量略高于落叶果园;土壤剖面碱解氮含量随土层厚度的增加,呈递减趋势,不落叶与落叶果园土壤碱解氮含量在35 cm以上土层中基本相同,差异不明显(P>0.05);果实的密度测定结果为不落叶果园果实>落叶果园果实;在糖度上,不落叶果园果实>落叶果园果实。     

加强果树规范化采样和病毒检测,降低潜隐和危险性病毒对我国苹果产业的危害风险

苹果病毒病在世界各苹果产区广泛发生,危害严重,目前没有有效的防治药剂。苹果病毒具有潜隐危害、主要以嫁接方式传播的特点。危险性高的类病毒侵染导致苹果果实几乎失去经济价值。苹果病毒的检测是防止其传播和危害,繁育无病毒苗木和苹果树无毒化管理的一项关键技术。由于对病毒在苹果树体中的组织分布和浓度认知不到位,苹果病毒检测中存在样品采集和检测方法的误区。本文根据课题组十年来开展苹果病毒检测和研究工作的数据,简要概述了我国苹果病毒的发生危害特点,苹果病毒检测方法,详细给出了规范的样品采集、处理、总RNA提取、RT-PCR参数、检测引物、对照设置及检测结果判别的技术方法。     

Simultaneous detection and identification of eight stone fruit viruses by one-step RT-PCR

A sensitive and reliable one step RT-PCR reaction with an internal control has been developed to detect and differentiate eight important viruses that affect stone fruit tress: Apple mosaic virus (ApMV), Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), American plum line pattern virus (APLPV), Plum pox virus (PPV), Apple chlorotic leaf spot virus (ACLSV), Apricot latent virus (ApLV) and Plum bark necrosis stem pitting associated virus (PBNSPaV). In addition, we investigated the detection limit and the efficiency of three different nucleic acid extraction methods that avoid the use of organic solvents, for both multiplex RT-PCR and dot-blot hybridisation assays. The primer cocktail was used to analyse 38 stone fruits originating from nine different countries and six species. A large number of virus combinations was detected and up to three different viruses were observed in five samples. A decrease in sensitivity was observed when the primer cocktail contained more than five different pair primers. However, comparative analyses showed that the multiplex RT-PCR containing the eight virus pair primers was even more sensitive than the ELISA or molecular hybridisation assays. The use of the multiplex RT-PCR technology in routine diagnosis of stone fruit tree viruses is discussed.     

Identification of fruit tree phytoplasmas and their vectors in Bosnia and Herzegovina

Surveys were carried out in autumn 2004 and spring 2005 in the traditional areas dedicated to pome and stone fruit cultivation in Bosnia and Herzegovina to assess the presence, distribution and incidence of phytoplasma diseases in fruit trees. The occurrence of psyllid vectors was also considered. The detection of phytoplasmas in plant and insect samples and their identification were carried out by symptom observations in the field, double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA), nested polymerase chain reaction (nested-PCR) and restriction fragment length polymorphism (RFLP) analyses. Laboratory analyses showed the presence of phytoplasmas belonging to: (i) 16SrX group, subgroup A (' Candidatus Phytoplasma mali') in 23 out of 25 apple samples, in 4 groups out of 18 of Cacopsylla picta (synonym Cacopsylla costalis ) and in 2 groups out of 9 of Cacopsylla melanoneura ; (ii) 16SrX group, subgroup C (' Candidatus Phytoplasma pyri') in 11 out of 30 pears samples and in 2 groups out of 9 of Cacopsylla pyri ; (iii) 16SrX group, subgroup B (' Candidatus Phytoplasma prunorum') in 4 apricots, 2 peaches out of 42 stone fruit samples and in 1 group out of 14 of Cacopsylla pruni . The presence of different subtypes of Candidatus Phytoplasma mali, both in apple trees and in insects, was proven.     

Studies on residues and the metabolic pathway of methidathion in tomato fruit

The residues and metabolism of methidathion [S-(2, 3-dihydro-5-methoxy-2-oxo-1, 3, 4-thiadiazol-3-ylmethyl) O, O-dimethyl phosphorodithioate] and its secondary metabolites: demethyl-methidathion [S-(2, 3-dihydro-5-methoxy-2-oxo-1, 3, 4-thiadiazol-3-ylmethyl) O-methyl O-hydrogen phosphorodithioate] ( IV ), the sulphide (2,3-dihydro-5-methoxy-3-methylthiomethyl-1,3,4-thiadiazol-2-one) ( I ), tsulphoxide(2,3-dihydro-5-methoxy-3- methylsulphinylmethyl-1,3,4-thiadiazol-2-one) ( II ) and the sulphone (2,3-dihydro-5-methoxy-3-methylsulphonylmethyl-1,3,4-thiadiazol-2-one ( III ) were studied in laboratory-treated tomato fruit. The metabolites and residues of methidathion were determined for the applied doses of 1, 7 and 14 mg of methidathion kg^?1 of fruit. Methidathion was metabolised extensively over a 14-day period. The amount of metabolites formed was a function of both the applied dose as well as the time after application. Major water-soluble metabolites were found to be IV and the cysteine conjugate S-(2,3-dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-ylmethyl)-L-cysteine ( VI ). The chloroform-soluble metabolites were identified as the oxygen analogue of methidathion [S-(2,3-dihydro-5-methoxy-2-oxo-1,3,4-thiadiazol-3-ylmethyl) O, O-dimethyl phosphorothioate] ( V ), the sulphoxide II , and the hydroxy compound 2,3-dihydro-3-hydroxymethyl-5-methoxy-1,3,4-thiadiazol-2-one. The oxygen analogue of methidathion ( V ) was found in small amounts, corresponding to <5% of the added methidathion. Demethyl-methidathion ( IV ) appeared to be a precursor in the formation of the cysteine conjugate VI . The sulphide I seemed to be more reactive in forming the cysteine conjugate than the sulphoxide II or the sulphone III .     

椴树科树种抑虫机制的研究

通过调查研究发现 ,在不同立地条件下 ,光肩星天牛 ( Anolophora glabripennis)在椴树上卵的孵化率不尽相同 ,它与椴树韧皮部厚度、刻槽大小、卵的位置及生长速度没有直接的关系。椴树枝干的内含物直接影响着天牛幼虫的发育和存活     

葡萄座腔菌属（Botryosphaeria）引起的果树病害及研究进展

葡萄座腔菌属（Botryosphaeria）真菌在国内外分布广泛,是许多果树常见的病原菌、内生菌和腐生菌,能引起果实腐烂、叶斑、坏死、溃疡和流胶等症状。本文概述了该属真菌引起的果树病害的发生、危害症状、主要病原菌种类、流行学和病害控制、栽培管理策略;展望今后的研究方向。     

Development of RT‐PCR assays using fluorogenic‐3′ minor groove binder DNA probes for detection of fruit tree viruses*

In phytosanitary certification, there is currently a need for the development of reliable, sensitive and rapid tests for the routine detection of Ilarviruses and latent viruses from fruit trees during the dormant season. We have developed real‐time RT‐PCR assays that allow the reliable detection of Prunus necrotic ringspot ilarvirus, Apple chlorotic leafspot trichovirus and Apple stem pitting virus in bark tissues of dormant wood. These assays are well adapted for the routine detection of these three viruses because they eliminate one risk of contamination by performing the whole test in a single closed tube.     

Polygalacturonase-inhibiting protein activity in cantaloupe fruit as a function of fruit maturation and tissue origin

Netted cantaloupe (Cucumis melo var. cantalupensis cv. Magnum 45) were harvested from 5 to 35 days postanthesis. The fruit of each age group were divided into exocarp, outer mesocarp, mid mesocarp, inner mesocarp, placenta, and seed. Each tissue was extracted and assayed for polygalacturonase-inhibiting protein (PGIP) activity against polygalacturonases (PGs) from three fungal pathogens of cantaloupe fruit. The PGIP activity of all tissues except placenta was high from the flower stage through the first week of fruit development but decreased markedly between 5 and 10 days postanthesis. PGIP activity against Phomopsis cucurbitae PG remained high and nearly constant in placental tissue throughout fruit development. However in this same tissue, PGIP activity against Fusarium solani PG decreased during fruit development to about 25% of its level in the 5-day-old fruit. This differential change in PGIP activity toward the two PGs suggests that different forms of the inhibitor are expressed between early and late stages of cantaloupe fruit development. The results also illustrate the importance of using multiple pathogen enzyme systems that can provide an opportunity for more accurate elucidation of mechanisms involved in the host–pathogen interaction. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. All programs and services of the US Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap. The article cited was prepared by a USDA employee as part of his/her official duties. Copyright protection under US copyright law is not available for such works. Accordingly, there is no copyright to transfer. The fact that the private publication in which the article appears is itself copyrighted does not affect the material of the US Government, which can be freely reproduced by the public.     

麦草覆盖条件下施氮水平对旱地梨树生长发育和果实品质的影响

为探明覆草条件下施氮水平对旱地梨树（Pyrus bretschnei deri Rehd.）生长发育和果实品质的影响,设置在全园覆草条件下株施纯氮1 kg（T1）、0.5 kg（T2）、0.25 kg（T3）和不施氮（T4,CK）四种处理,2011年至2012年测定了土壤和叶片养分、树体营养生长和果实产量品质等指标。结果表明,麦草覆盖条件下施氮能显著降低土壤pH值,提高土壤钙、锌含量,明显促进了梨叶片组织结构生长。随着施氮量的增加,梨树新梢生长量、叶面积和百叶重量、叶绿素含量显著提高。不同施氮处理均能提高梨果品产量,T1、T2、T3处理分别比对照提高25.4%、17.0%、11.6%。施氮后梨果实可溶性糖、有机酸含量明显降低,而果实硬度、可溶性固形物、水分含量等品质指标 处理间差异不显著。     

芒果炭疽病菌对多菌灵的抗药性

对来自广东和海南等不同果园的芒果炭疽病菌进行了对多菌灵的抗性测定.结果表明,敏感菌株的最小抑制浓度(MIC)为0.110μg/mL,而抗性菌株在多菌灵500μg/mL下仍生长良好.抗性菌株经继代培养10代后抗性几乎不变,说明其抗性稳定.对抗、感菌株的生物学特性进行测定,然后以产孢量和致病力分别用MIC做简单相关性分析,证明病菌的生物学特性、产孢量、致病力与抗药性无关,因此可以认为病菌对多菌灵的抗药性突变并不影响其正常的生理功能.抗性菌株对甲基硫菌灵、苯菌灵、噻菌灵表现正交互抗性,而对乙霉威和咪鲜胺敏感.病菌在含药培养基上测定的敏感性与在经多菌灵处理过的离体果实上的敏感性有较好的对应关系,可用于大田抗药性的初步检测.