Polygalacturonase-inhibiting protein (PGIP) from Japanese pear: possible involvement in resistance against scab

Venturia nashicola is the causal agent of scab, a fungal disease affecting Asian pears. The Japanese pear cv. ‘Kousui’ is highly susceptible to the race 1 of this fungus whereas the cv. ‘Kinchaku’ and the non-host European pear cv. ‘Flemish Beauty’ are resistant. The aim of this work is to investigate the role of polygalacturonase-inhibiting proteins (PGIPs) of pear during the interactions with V. nashicola leading to susceptibility or resistance. PGIP protein was detected from immature fruit of Kousui and Kinchaku. It showed a molecular mass of 42 kDa that shifted to 35 kDa after chemical deglycosylation. The gene pgip was amplified by PCR using genomic DNA and/or cDNA from young leaves of Kousui, Kinchaku, and European pear cvs. Flemish Beauty, ‘Bartlett’, and an Asian wild pear strain ‘Mamenashi 12’, then sequenced after sub-cloning. Some conserved variations were identified in the sequence indicating that gene family also exists in pgip of Japanese pear and confirmed by Southern blot analysis. The expression of PGIP was studied in scab-inoculated leaves of the susceptible Kousui and the resistant Kinchaku and Flemish Beauty. pgip Gene and its encoding protein were highly and rapidly activated in these resistant plants. In addition, PGIP extracts derived from Kinchaku and Flemish Beauty partially inhibited the activity of polygalacturonase (PG) from V. nashicola suggesting a possible role of PGIP in limiting fungal growth frequently observed in these resistant cultivars.     

干旱胁迫下梨枣抗旱性研究

为探索陕北黄土丘陵区梨枣的抗旱性与耐旱能力,以大规格盆栽梨枣（Ziziphus jujuba Mill.cv.Lizao）2年生苗木为试验材料,在连续不供水情况下研究了梨枣的萎蔫到致死过程。依据干旱缺水后枣树生长衰退过程中的特征将枣树萎蔫致死分为：暂时萎蔫、初始萎蔫、表征永久萎蔫及耐旱致死四个阶段。结果表明：梨枣的初始萎蔫系数在2.017%～3.054%之间,平均为2.494%;表征永久萎蔫系数在1.199%～1.998%之间,平均为1.489%,永久萎蔫系数在1.250%～1.489%之间;耐旱致死点为1.250%,致死时间为135±11 d。试验结果证明枣树是一种十分抗旱的树种,在半干旱黄土丘陵区枣树不会出现干旱致死。     

Japanese pear black spot and apple alternaria blotch

The pathogenicity and taxonomy of 15 isolates of Alternaria spp. from pear and apple were compared. Only isolates from Asian pear ( Pyrus pyrifolia ) from Italy and Korea were virulent on leaves and young fruits of the susceptible Asian pear cv. Nijisseiki. Their conidial morphology was typical of A. gaisen (= A. kikuchiana ). Only isolates of A. mali from USA were virulent on susceptible American apple cvs Indo and Red Gold. No virulence was demonstrated in any isolate/host combination among isolates from stem infections of Asian and European pear ( Pyrus communis ), leaf spots of European apple, and ripe fruit rots of Chinese pear ( Pyrus ussuriensis ), European pear and apple. These non-virulent isolates could be readily distinguished from A. gaisen and A. mali by their pattern of branching of conidial chains, the branching associated with A. alternata sensu stricto being most common among non-virulent isolates. This limited survey implies that A. gaisen is only virulent to Asian pear and the toxigenic form of A. mali to certain American apple cultivars; also that A. gaisen is not established outside eastern Asia or the toxigenic form of A. mali outside eastern Asia and parts of USA.     

Ultrastructural study on scab resistance expressed in epidermal pectin layers of pear leaves

Proliferation and collapse of subcuticular hyphae of Venturia nashicola race 1 were studied ultrastructurally, after inoculation of susceptible Japanese pear cv. Kousui, resistant Japanese pear cv. Kinchaku, resistant Asian pear strain Mamenashi 12 and nonhost European pear cv. Flemish Beauty leaves, to understand the nature of the resistance mechanism. After cuticle penetration by the pathogen, the hyphae were observed at lower frequency in epidermal pectin layers and middle lamellae of leaves of the three resistant plants than in those of susceptible ones. This result suggested that fungal growth was suppressed in the incompatible interaction between pear and V. nashicola race 1. In the pectin layers of all inoculated plants, some hyphae had modifications such as breaks in the plasmalemma with plasmolysis, necrotic cytoplasm and degraded cell walls. More hyphae had collapsed in the leaves of the three resistant plants than in those of the susceptible cv. Kousui. In collapsed hyphae, the polymerized cell walls broke into numerous fibrous and amorphous pieces, showing that the scab resistance might be associated with cell wall-degrading enzymes from pear plants.     

Infection Behavior of Venturia nashicola, the Cause of Scab on Asian Pears

ABSTRACT The infection of Japanese pear by Venturia nashicola, the cause of scab on Asian pears (Japanese pear, Pyrus pylifolia var. culta; Chinese pear, P. ussuriensis), was examined using light and electron microscopy to determine the mechanism of resistance in pears. Early stages of infection were similar on the susceptible cv. Kosui, the resistant cv. Kinchaku, and the nonhost European pear (P. communis) cv. Flemish Beauty. V. nashicola penetrated only the cuticle layer on pear leaves and formed subcuticular hyphae on all three cultivars. Hyphae were localized in the pectin layer of pear leaves and never penetrated into the cytoplasm of epidermal cells. This restriction of fungal growth suggested that pectinases released by infection hyphae or subcuticular hyphae may be important in infection. Subcuticular hyphae were modified ultrastructurally in the pectin layer of resistant pear cultivars accompanied by fungal cell death. In contrast, fungal cells appeared intact in susceptible pear cultivars, suggesting the existence of resistance mechanisms.     

Viruses of pome fruit trees in Syria

A survey was conducted to evaluate the sanitary status of pome fruit trees in Syria during spring 2003 and 2004 in 6 governorates: Damascus, Al-Qunaitara and Al-Sweida (Southern region), Homs and Hama (Central region) and Latakia (Costal Western region), as the main production areas of pome fruits. Leaf samples from 1077 apples, 54 pears and 14 quince were collected and tested for the presence of Apple chlorotic leaf spot virus (ACLSV), Apple stem grooving virus (ASGV) and Apple mosaic virus (ApMV) in 70 commercial orchards and 3 varietal collections by ELISA. Results showed that the virus infection rates were 34 and 2% in apple and pear, respectively. Quince trees were found to be virus tested free. ACLSV was prevailing on apple with 34%, whereas ASGV and ApMV were found in 2 and 0.2% of tested trees, respectively. Pear trees were infected only with ACLSV (2%). 21 apples and 15 pears representative budwood samples were indexed by grafting on the following indicators: (i) Malus pumila cvs. Virginia Crab and Radiant for apple and (ii) M. pumila cv. V. Crab and Pyrus communis cv. Nouveau Poiteau for pear. The virus infection rates by woody indexing were much higher than ELISA, Apple stem pitting virus (ASPV) and ASGV were found in 86 and 82% of apple tested samples, whereas they were 80 and 60% of pear tested samples, respectively. Additional RT-PCR testing carried out for a limited number of samples confirmed the high incidence of ACLSV ASPV, ASGV and the presence of ApMV. This is the first report on pome fruit viruses in Syria, indicating an unsatisfactory sanitary status of the industry. As a consequence, a certification program is recommended for producing locally healthy propagating material.     

基于性诱剂监测的梨小食心虫防治指标

为明确梨小食心虫性诱剂水盆诱捕器诱蛾量与梨果着卵量的关系,建立一种简单实用,基于梨小食心虫成虫发生量的防治指标,于2010和2011年在陕西蒲城梨园调查了梨小食心虫在早酥梨上的着卵情况及其与性诱剂水盆诱捕器诱蛾量之间的关系.结果显示,梨小食心虫在梨果胴部的着卵量显著高于其它部位,占总卵量的92.00％;百果卵数、卵果率随果实的增大而增加,直径70mm以上果实的百果卵数和卵果率均显著高于直径65 mm以下的果实.据此建立了诱蛾量与卵果率、百果卵量的回归方程,分析得出当以卵果率1％和百果卵量1粒为防治指标时,基于性诱剂监测的梨小食心虫的防治指标分别为每天每诱捕器2.27和2.32头;以卵果率2％和百果卵量2粒为防治指标时,则分别为每天每诱捕器2.61和2.58头.     

Evaluation of Likelihood of Co-Occurrence of Erwinia amylovora with Mature Fruit of Winter Pear

ABSTRACT Phytosanitary concerns about fire blight prohibit export of U.S.-grown pears to some countries without this disease. To examine these concerns, we evaluated the potential for co-occurrence of Erwinia amylovora with mature, symptomless winter pear fruit by inoculation experiments and by survey of commercial orchards. Immature pear and apple fruit were inoculated in orchards with E. amylovora strain 153N as resuspended lyophilized cells or as ooze from diseased tissues. Regardless of inoculum source, population size of Ea153N on fruit declined by an order of magnitude every 3 to 4 days during the first 2 weeks after inoculation; at 56 days after inoculation, Ea153N was not detected, except on 1 of 450 fruit with 4 colony forming units (CFU). After inoculation of flowers, calyx-end survival of Ea153N on pear and apple fruit declined from high populations at petal fall to a few cells at harvest, with no detection of the pathogen after a 7-week cold storage. Migration of Ea153N into symptomless pear fruit from diseased branches was evaluated by enrichment assay and nested polymerase chain reaction of internal fruit core tissues; these assays failed to detect the pathogen in healthy fruit from diseased trees. At harvest, E. amylovora could not be detected on 5,599 of 5,600 fruit of d'Anjou pear sampled from commercial orchards in major production areas of the Pacific Northwest; one fruit yielded 32 CFU of the pathogen. Postharvest, mature pear fruit contaminated with Ea153N and subsequently wounded required a dose of >10,000 cells at the wound site to allow for persistence of the pathogen through a 7-week-cold storage. We conclude that epiphytic E. amylovora shows similar survival characteristics on both pear and apple fruit, this pathogen is not an endophyte within mature symptomless pear fruit, its presence is exceptionally rare on commercially produced fruit, and that epiphytic survival of E. amylovora through a postharvest chilling period is unlikely given the unrealistically high population size required for persistence.     

Enhancement of Postharvest Disease Resistance in Ya Li Pear (Pyrus bretschneideri) Fruit by Salicylic Acid Sprays on the Trees during Fruit Growth

The Ya Li pear (Pyrus bretschneideri) trees were sprayed three times with 2.5 mM salicylic acid (SA) around 30, 60 and 90 days after full flowering. The fruit were harvested at commercial maturity (about 120 days after full flowering), inoculated with Penicillium expansum, and incubated at 20 °C, 95–100% RH. The results showed that resistance to the pathogen of the mature pear fruit was remarkably enhanced by the SA sprays. Disease incidence in the SA-treated fruit was 58.0% or 26.5%, and lesion diameter on SA-treated fruit was 58.4% or 29.0% lower than that in/on fruit without SA treatment (control) on day 12 or 17 after incubation, respectively. The SA spray applied to the trees around 30 days after full flowering notably enhanced accumulation of hydrogen peroxide in the young fruit. Meanwhile, activities of defense enzymes, including peroxidase, phenylalanine ammonia-lyase (PAL), chitinase or β-1,3-glucanase in the young fruit from SA-treated trees was 29.5%, 60.0%, 24.4% or 35.7% higher than that in the control fruit 4 days after the SA spraying. Furthermore, after harvest, activities of PAL, chitinase and β-1,3-glucanase were still significantly higher in the mature pear fruit from the trees sprayed three times with SA than those of the control fruit. Activities of the antioxidant enzymes including catalase and ascorbate peroxidase in the young fruit were significantly reduced by SA spraying. However, the activity of another antioxidant enzyme, glutathione reductase in the young fruit was significantly enhanced by SA spraying. These results suggest that enzymes exerting their functions in different ways may be coordinately regulated by SA in the pear fruit. Our study indicates that treatment of SA sprays on the trees may provide further protection against postharvest disease of Ya Li pear fruit in practice and could be used as an alternative and economical approach to reduce application of chemical fungicides.     

Detection and characterization of phytoplasmas in diseased stone fruits and pear by PCR-RFLP analysis in Turkey

During the late summer-early autumn of 2002, surveys were carried out in Turkey to determine the presence of phytoplasma diseases in fruit trees. Phytoplasmas were detected and characterized by PCR-RFLP analysis and TEM technique in stone fruit and pear trees in the eastern Mediterranean region of the country. Six out of 24 samples, including almond, apricot, peach, pear and plum, gave positive results in PCR assays. RFLP analysis usingSspI andBsaAI enzymes of PCR products obtained with primer pair f01/r01 enabled identification of the phytoplasmas involved in the diseases. Stone fruit trees, including a local apricot variety (‘Sakıt’) and a pear sample, were found to be infected with European stone fruit yellows (ESFY, 16SrX-B) and pear decline (PD, 16SrX-C) phytoplasmas, respectively. This is the first report in Turkey of PD phytoplasma infecting pear and of ESFY phytoplasma infecting almond, apricot, myrobalan plum and peach; ESFY phytoplasma infecting Japanese plum was previously reported. http://www.phytoparasitica.org posting July 21, 2005.     

单植和混植香梨园梨小食心虫的种群动态

梨小食心虫Grapholitha molesta(Busck)是为害‘库尔勒香梨’的主要害虫。本研究利用性诱剂诱捕器系统调查了不同栽培管理条件、果树种类和用药次数下梨小食心虫各世代的发生动态。结果表明:单植梨园全年成虫有5个高峰期,混植梨园成虫有4个高峰期。单植梨园和混植梨园梨小食心虫种群世代发生量不同,混植梨园中梨小食心虫种群世代重叠严重,发生数量是单植香梨园的4.02倍;单植梨园中管理粗放的河边梨园梨小食心虫发生较重,打药频繁的母本园发生较轻,梨小食心虫成虫第1～第4代峰期延迟8～28 d,属于迁入为害。研究还表明:在混植梨园中梨小食心虫产卵有8个高峰,幼虫孵化期有6个高峰,在世代发展中相邻峰值叠加,形成成虫期4个大峰。因此,研究不同栽培管理条件下梨园梨小食心虫的发生规律有助于对其进行科学的防治。     

橘小实蝇在上海局部暴发成因分析

橘小实蝇是近年来传入上海并局部暴发危害的检疫性有害生物。本文根据上海地区实蝇监测及现场调查的结果,从入侵生物的一般特点着手分析橘小实蝇传入上海并暴发的成因。结果表明:橘小实蝇通过水果贸易传入到上海,废弃水果的无效管理是造成橘小实蝇疫情传入的重要原因;上海自然气候适合橘小实蝇的生存与繁殖,桃、梨、李等大量的寄主植物为其生存和种群扩张提供了充足的食物源。     

Factors affecting mummification and sporulation of pome fruit infected by Monilinia fructigena in Dutch orchards

A 2-year field experiment (1997–98, 1998–99) was conducted to study mummification and subsequent sporulation in spring of apple (cvs James Grieve, Golden Delicious) and pear (cv . Conference) fruits infected by Monilinia fructigena . Most mummified fruits were found in James Grieve and Conference, whereas in late-infected Golden Delicious, fruits were still soft when examined in April. In the first year, these late-infected fruits had a significantly higher sporulation intensity per sporulating fruit ( P  = 0·05) compared with Golden Delicious fruits infected 9 and 5 weeks before harvest maturity, which were partly mummified. It was concluded that early- and late-infected fruits contributed to primary inoculum in the next season. In a postinfection regime of 25°C and 65–75% relative humidity under controlled conditions, the number of Conference fruits sporulating decreased rapidly, and after 12 weeks' incubation sporulation had completely ceased. After 8 weeks' incubation, sporulation intensity in the postinfection regime at 10°C was significantly higher than that at 20 and 25°C in a first experiment with inoculated unripe fruit ( P  = 0·05). Results of a second experiment with ripe fruit were less clear. These results are discussed in relation to orchard disease management.     

梨和苹果种质对阿太菌果腐病菌的抗性评价及其防治药剂筛选

为明确不同梨和苹果种质对阿太菌果腐病菌Athelia bombacina的抗性以及筛选防治其有效杀菌剂,采用离体菌丝块有伤接种方法对40份梨种质和154份苹果种质进行病斑直径测定,通过聚类分析法和平均病斑直径法对不同种质进行了抗病性分级,并利用菌丝生长速率法测定了13种常用杀菌剂对阿太菌果腐病菌的毒力。结果表明,根据聚类分析法和平均病斑直径法均可将梨和苹果种质划分为高抗、抗、中抗、感和高感5类。与平均病斑直径法相比,梨和苹果种质分别以欧式距离为14和10作为最佳聚类分割点时进行聚类分析能够更加科学地划分类别,从40份梨种质中筛选出金锤子梨1个高抗种质,仅占总数的2.50%,从154份苹果种质中筛选出垂丝海棠、莫斯科透明、新疆苹果、路边石、伏帅等32个高抗种质,占总数的22.73%。药剂试验结果表明,戊唑醇、腈菌唑、咯菌腈和噻呋酰胺对阿太菌果腐病菌菌丝生长的抑制效果较好,抑制中浓度EC_(50)分别为0.027、0.048、0.054和0.095 mg/L。表明梨和苹果种质均可被阿太菌果腐病菌侵染,但不同种质间抗病性差异明显,戊唑醇是采前防治阿太菌果腐病菌菌丝生长的最佳药剂。     

性信息素迷向丝对不同果树梨小食心虫的防控效果

2017年在宁夏果园开展了性信息素迷向丝(北京中捷四方生物科技公司生产的长效迷向丝,有效成分占30%)对为害不同果树的梨小食心虫的防控效果研究。试验地共5.5 hm~2,栽植有成龄苹果树、梨树和李树。试验区按树种设置3个处理区,3个对照区。处理区在边缘区域每株树平均悬挂3条迷向丝,内部区域隔树悬挂,每树悬挂1条迷向丝,悬挂高度为距离地面2 m。调查各树种全年诱蛾量、诱蛾下降率、蛀果率等指标,研究迷向丝对不同果树上梨小食心虫的防控效果,分析苹果、梨和李树分区域集中栽培下梨小食心虫为害特点。研究结果显示:3个处理区的诱蛾下降率均达96%以上,果实膨大期蛀果下降率均达50%以上,成熟期蛀果下降率均达57%以上,说明性信息素迷向丝对3种果树区域的梨小食心虫防控效果明显且稳定;不同果树区域梨小食心虫发生高峰期一致;梨园中诱捕的梨小食心虫成虫最多,说明其具有寄主选择性;李园蛀果率明显高于苹果园和梨园,李果实成熟采摘后成虫诱捕量减少,同时期苹果园与梨园成虫诱捕量增加,说明梨小食心虫具有迁移为害特性。     

Fruit rot of Strawberry pear (pitaya) caused by <Emphasis Type="Italic">Bipolaris cactivora</Emphasis>

Strawberry pear (pitahaya, pitaya) [Hylocereus undatus (Haw.) Britt. and Rose] postharvest fruit rot was found at an agricultural products store in Itoman city, Okinawa Prefecture in 2006. The symptoms included depressed, water-soaked lesions with olive to black powdery spots coalescing into a soft rot. The causal fungus was identified as Bipolaris cactivora (Petrak) Alcorn. This is the first report of strawberry pear fruit rot caused by B. cactivora.     

Occurrence of indole-3-acetic Acid-producing bacteria on pear trees and their association with fruit russet

ABSTRACT A relatively high percentage of epiphytic bacteria on pear leaf and fruit surfaces had the ability to produce indole-3-acetic acid (IAA) in culture media supplemented with tryptophan. While over 50% of the strains produced at least small amounts of IAA in culture, about 25% of the strains exhibited high IAA production as evidenced by both colorimetric and high-performance liquid chromatography analysis of culture supernatants. A majority of the strains that produced high amounts of IAA were identified as Erwinia herbicola (Pantoea agglomerans), while some strains of Pseudomonas syringae, Pseudomonas viridiflava, Pseudomonas fluorescens, Pseudomonas putida, and Rahnella aquaticus that produced high amounts of IAA also were found on pear. Fruit russeting was significantly increased in 39 out of 46 trials over an 8-year period in which IAA-producing bacteria were applied to trees compared with control trees. A linear relationship was observed between fruit russet severity and the logarithm of the population size of different IAA-producing bacteria on trees in the 30 days after inoculation, when normalized for the amount of IAA produced by each strain in culture. On average, the severity of fruit russet was only about 77% that on control trees when trees were treated at the time of bloom with Pseudomonas fluorescens strain A506, which does not produce IAA. Both total bacterial populations on pear in the 30-day period following full bloom and fruit russet severity varied greatly from year to year and in different commercial orchards over a 10-year period. There was a strong linear correlation between the logarithm of total bacterial population sizes and fruit russet severity.     

亚洲梨黑星病菌致病性及其寄主抗病机制的研究进展

梨黑星病是亚洲梨的主要病害之一。该病是由纳雪黑星病菌(Venturia nashicola)感染所致。V.nashicola主要寄生在亚洲梨叶片表皮细胞壁的果胶质层中。该菌的感染可能主要与分泌的细胞外分泌物质、角质分解酶、过氧化氢和果胶质分解酶有关。而亚洲梨对V.nashicola的抗性可能主要与多聚半乳糖醛酸酶抑制蛋白、多种病程相关蛋白、富亮氨酸重复类受体蛋白激酶等有关。另外,不具直接杀菌能力的系统抗性诱导剂acibenzolar-S-methyl(ASM)在大田试验中对梨黑星病菌有较好控制效果。这与ASM诱导的植物防御反应,包括多聚半乳糖醛酸酶抑制蛋白和几丁质酶等有关。     

3类功能助剂对酥梨的安全性及其对 重要害虫防效的影响

为明确3类不同功能助剂在酥梨园的安全使用技术及其对梨园重要害虫防效的影响, 在田间梨树不同发育期, 调查3类?共6种功能助剂对果实和叶片的药害率; 调查3种安全助剂与4种农药混配后对梨小食心虫和梨木虱的防效?结果表明, 6种功能助剂对梨果药害率从高到低依次为15 d幼果?45 d小果和75 d膨大期果实; 6种助剂对叶片均安全?在较低温度下施药可显著降低功能助剂对梨果的药害率?6种助剂对果实药害率从高到低依次为NF100?Silwet 408?GY-Tmax?GY-T1602? GY-T12和迈道?迈道?GY-T12显著提高22.4%螺虫乙酯悬浮剂?20%呋虫胺可溶粒剂和5%阿维菌素微乳剂对梨木虱的防效, GY-T1602显著提高了22.4%螺虫乙酯悬浮剂和20%呋虫胺可溶粒剂的对梨木虱的防效; 迈道?GY-T12和GY-T1602显著提高了5%阿维菌素微乳剂?20%呋虫胺可溶粒剂和4.5%高效氯氰菊酯微乳剂对梨小食心虫的防效?该结果为功能助剂在酥梨园的安全使用提供了科学依据?