苹果潜隐病毒(Latent virus)研究——Ⅱ.苹果品种和矮生砧木潜隐病毒鉴定

 在1980-1985年,对我国主要苹果产区的潜隐病毒种类进行调查鉴定,基本明确渤海湾果区、黄河故道果区和西北高原果区主栽苹果品种普遍潜带褪绿叶斑病毒、茎痘病毒和茎沟病毒,未检出其他病毒。营养系矮生砧木也普遍潜带这三种病毒。解决潜隐病毒为害的主要途径是培育无病毒母本树,栽培无病毒苗木。这方面的研究工作正在进行中。     

Epiphytic Occurrence of Pseudomonas syringae pv. papulans (Rose) in France, Where Blister Spot has Never Been Seen

Pseudomonas syringae pv. papulans (PSP) the causal agent of blister spot, on the apple cultivar Mutsu in the USA, Canada and Italy, has not been described in France. A study on epiphytic populations of P. syringae isolated from French apple orchards revealed two isolates called KA54 and E121, whose biochemical characterisation showed high similarities with PSP strains. Identical symptoms were obtained with KA54, E121 and PSP strains, after vacuum inoculation of detached immature fruits of the cultivar Fuji, and young leaves of the cultivars Fuji, Mutsu, Gala and Golden Delicious. Koch's postulate was verified. These results indicate the presence of PSP in France. Differential characterisation criteria including serological, molecular and pathogenicity tests are proposed.     

苹果潜隐病毒的研究——苹果主栽品种脱毒研究

 西北地区的苹果主要栽培品种都普遍带有苹果潜隐病毒,其带毒株率高达80-100%。1985-1988年在37±1℃的恒温下、热处理28天,对苹果主要栽培品种进行了脱毒研究。目前,已培育出金冠、红星、红富士和秦冠的无毒母树。     

Infection of apple fruit by Sphaeropsis pyriputrescens in the orchard in relation to Sphaeropsis rot in storage

Sphaeropsis rot, caused by Sphaeropsis pyriputrescens, is an important postharvest disease of apple in the United States. The objectives of this study were to determine the timing of apple fruit infection in the orchard in relation to development of Sphaeropsis rot in storage and to identify infection courts and mode of penetration by S. pyriputrescens on apple fruit. Fruit of apple cvs Red Delicious, Golden Delicious, and Fuji were inoculated in the orchard from 3 weeks after petal fall to 2 weeks before harvest at 5 to 6-week intervals in three consecutive seasons. All fruit were harvested and stored at 0?ºC to monitor decay development. Light and scanning electron microscopy were used to examine the infection courts and mode of penetration of the fungus on/in the host tissues. At harvest, the fungus was re-isolated from the stem (pedicel), sepal, anther, or filament of the inoculated fruit, but decay did not develop on fruit. Sphaeropsis rot developed on inoculated fruit during cold storage beginning 1–3 months after harvest. Stem-end rot was prevalent on cv. Golden Delicious, whereas calyx-end rot was prevalent on cv. Fuji. Both stem- and calyx-end rots were common on cv. Red Delicious. Infection also occurred at lenticels on fruit skin, particularly on cv. Golden Delicious, but at low incidence. Relationships between the incidence of Sphaeropsis rot in stored apple fruit and the timing of inoculation in the orchard varied with cultivar and year. On cv. Red Delicious apples, the incidence of Sphaeropsis rot generally increased as the timing of infection approached harvest. Histological studies indicated that infection took place through natural openings of plant organs such as stomata on stems and sepals and lenticels on fruit skin. Fungal penetration also was observed at micro-cracks on the stem and sepal and at trichome sockets where mechanical damage occurred in sepals. Direct penetration was observed on the stem and sepal of fruit, but most invasions were restricted between the cuticle and the epidermis. Our results indicate that wounding is not required for infection of apple fruit by S. pyriputrescens, though it may facilitate infections.     

Real-time PCR as a promising tool to monitor growth of Venturia spp. in scab-susceptible and -resistant apple leaves

Apple scab, the most important disease of apple worldwide, is caused by Venturia inaequalis. Currently, evaluation of fungal pathogenicity and host resistance is based on a symptomatic disease rating. However, this method does not provide an accurate measurement of the degree of infection and cannot detect early fungal development in symptomless leaves. In this study, a Venturia-specific real-time PCR assay was developed using primers designed around the specific internal transcribed spacer 2 (ITS2) region of the 5.8S rRNA gene. Using SYBR? Green I technology, the assay can accurately quantify Venturia DNA over a concentration range of at least five orders of magnitude. Detection sensitivities were in the order of 100?fg. The method was used to quantify Venturia genomic DNA levels in leaves of three apple cultivars with different levels and types of scab resistance and artificially infected with V. inaequalis. The assay clearly discriminated between Venturia levels in monogenic resistant (‘Topaz’), polygenic resistant (‘Discovery’), and susceptible (‘Golden Delicious’) cultivars, and proved especially useful to quantify pathogen levels during the initial latent stage of infection. The real-time PCR data of ‘Golden Delicious’ were consistent with the observed evolution of the degree of sporulation during a time-course experiment. Although measurements were influenced by the presence of co-extracted PCR-inhibitors, the impact of these compounds was independent of the apple cultivar or the initial amount of fungal DNA present. In conclusion, real-time PCR amplification of the ITS2-5.8S rDNA of Venturia spp. is a faster, more objective and more sensitive method to monitor fungal growth and to evaluate host resistance than phenotypic disease rating scores.     

云南昭通苹果早期落叶病流行动态

苹果早期落叶病是影响苹果生产的重大病害,据报道苹果早期落叶病是褐斑病[Marssonina coronaria(Ell.et Davis)Davis]、斑点落叶病(Alternaria mali Roberts)、灰斑病(Phyllosticta pirinaSacc.)等多种病害的统称。通过在云南昭通系统调查影响苹果早期落叶病的主导因素品种及栽培模式,检测和统计病原菌种类及数量,调查早期落叶病发病率和病情指数,结果表明云南昭通苹果产区早期落叶病主要包括由M.coronaria引起的褐斑病和由A.mali引起的斑点落叶病,没有发现由P.pirina引起的灰斑病和其他病害。早期落叶病发病时间与品种关系密切,‘金帅’从5月下旬开始发病,8月初为发病高峰,9月底病害结束。‘红富士’则5月中旬开始发病,8月底达到发病高峰,10月底结束。不同品种和栽培方式对早期落叶病的发生程度有显著影响。     

抗苹绵蚜的苹果砧木免疫系——山荆子JIN67

苹绵蚜为害苹果属值物地上部及根部,根部被害程度重于枝梢,但目前对其防治方法较少。采用枝梢罩微型笼和根部罩木箱的接种法测试苹果属8个种30个品种或品系,选出了山荆子 Jin67免疫系,用它作砧木可使根部免受苹绵蚜为害,并兼有矮化性、抗干腐病、白粉病和抗寒力强等优良特性,适合作苹果抗苹绵蚜及矮化的砧木。如在 Jin 67砧木上高位芽接栽培品种,主干主枝换成抗性植物后,能更好地发挥砧木抗苹绵蚜作用。     

Components of resistance of apple to powdery mildew (Podosphaera leucotricha)

Components of resistance of apple to Podosphaera leucotricha were assessed in the glasshouse by spraying shoot tips of cultivars with conidia. Disease incidence (proportion of leaf surfaces with mildew) and colony numbers were higher and incubation periods correspondingly shorter on the older leaves. unrolled at the time of inoculation. Numbers of colonies were higher on the lower surface. Spore production per colony was higher on the younger leaves. In general, a short incubation period on a cultivar was associated with a high disease incidence, many colonies and high spore production. For some cultivars the association between these components permitted resistance to be classified as very high (cv. Discovery), very low (cv. Golden Delicious), or intermediate(cvs Bramley's Seedling. Suntan). The effects of inoculum concentration and post-inoculation environment (glasshouse or outdoors) on components of resistance were assessed in a further study. No interactions between cultivar and inoculum concentration were detected. There was generally an associated variation in components between cultivars within an environment, but inconsistencies in cultivar rankings were noted between the two environments and the two studies. Mean incubation period was shorter and colony area larger in the glasshouse than outdoors. There were significant differences in conidia/cm² colony between cultivars only in the glasshouse. Components conferring high resistance in cv. Discovery and low resistance in cv. Golden Delicious were confirmed in both environments and in both studies.     

Size does matter – susceptibility of apple for grey mould is affected by cell size

Apple is a seasonal product that is stored for long periods of time, during which fungal-caused decay can occur. Previous infection experiments of intact Jonagored apple with Botrytis cinerea displayed apparent differences in lesion expansion rate with respect to inoculation position on the fruit (on, above or below the equator). The goal of this study was to investigate whether these differences are consistent or not and if so, to relate them to fruit characteristics. The study involved measuring the hue angle of the intended inoculation spots prior to inoculation, and firmness and total soluble solids content of fruit from the same batch. Results showed that firmness correlated somewhat (−0.55 and −0.72 for shadow and sun side, respectively) with lesion diameter expansion rate. In a subsequent step, X-ray imaging was carried out for samples from each position. Analysis of 3D reconstructions by microcomputed tomography of these diffraction images showed that cell size was strongly correlated (0.996) to lesion diameter expansion rate. Finally, it was investigated if cell size could also be used to rank different apple cultivars for their susceptibility to B. cinerea. The result shows that there is a clear distinction between Jonagold and Golden Delicious (non-blushing variety), which have a smaller cell size, and Braeburn and Kanzi, which have a larger cell size (overall correlation of 0.87). This indicates that cell size may also be an important factor in determining susceptibility across cultivars.     

Traditional and commercial apple and pear cultivars as sources of resistance to fireblight1

In Hungary, fireblight research programmes were initiated on pear in 1999 and on apple in 2000, with the aim of evaluating the susceptibility or resistance of commercial cultivars. Sources of resistance for future breeding were also sought among traditional apple cultivars collected from Ukraine and pear cultivars in the Hungarian gene bank (Szigetcsép). Experiments were done under secure conditions. Inocula were mixtures of characteristic Erwinia amylovora isolates from pear and apple in Hungary. Host responses (symptom development, disease severity and multiplication rate of bacterial cells in host tissues) were assessed on shoots, flowers and fruits. About 30 pear and 30 apple cultivars, and 35 apple hybrids, were tested and grouped into four categories for pear and three for apple. Of the pear cultivars tested, 50% were susceptible, 30% moderately susceptible and only 10% of low susceptibility. Different plant organs occasionally displayed different responses. Members of the last two groups might serve as useful candidates for growing under IPM conditions. Among the traditional Hungarian varieties tested, we found high resistance in ‘Sikulai’ and ‘Szemes alma’, which could be used as sources of fireblight resistance in breeding programmes and also grown in organic orchards. Furthermore, among the offspring of the apple ‘Prima’ (scab‐resistant), we have found highly resistant lines.     

Distribution of the predatory mite Amblyseius andersoni Chant (Acari: Phytoseiidae) on different apple cultivars

The effect of apple cultivar on the distribution of Amblyseius andersoni was studied in an experimental orchard where tetranychids were virtually absent and eriophyids reached low to moderate populations. Seven apple scab-resistant cultivars, showing some differences in their leaf morphology, were compared. Each cultivar was grafted onto three different rootstocks inducing increasing vigor. The intraplant distribution of A. andersoni was also studied by monitoring predator densities on basal and apical leaves. In the first year, the colonization of different cultivars by A. andersoni showed definite patterns, sometimes associated with the abundance of the eriophyid Aculus schlechtendali. In the second experimental season, eriophyids reached negligible levels and the effect of cultivar on A. andersoni abundance was less clear. Florina and N.Y. 18491 cultivars were colonized in both years by relatively high phytoseiid numbers, while TSR 29T219 and Priscilla showed low populations in at least one season. The results observed on the remaining cultivars were intermediate or indefinite. The role of leaf pubescence on phytoseiid colonization is discussed.     

Distribution of the predatory mite Amblyseius andersoni Chant (Acari: Phytoseiidae) on different apple cultivars

The effect of apple cultivar on the distribution of Amblyseius andersoni was studied in an experimental orchard where tetranychids were virtually absent and eriophyids reached low to moderate populations. Seven apple scab-resistant cultivars, showing some differences in their leaf morphology, were compared. Each cultivar was grafted onto three different rootstocks inducing increasing vigor. The intraplant distribution of A. andersoni was also studied by monitoring predator densities on basal and apical leaves. In the first year, the colonization of different cultivars by A. andersoni showed definite patterns, sometimes associated with the abundance of the eriophyid Aculus schlechtendali. In the second experimental season, eriophyids reached negligible levels and the effect of cultivar on A. andersoni abundance was less clear. Florina and N.Y. 18491 cultivars were colonized in both years by relatively high phytoseiid numbers, while TSR 29T219 and Priscilla showed low populations in at least one season. The results observed on the remaining cultivars were intermediate or indefinite. The role of leaf pubescence on phytoseiid colonization is discussed.     

Novel metrics to classify fire blight resistance of 94 apple cultivars

Fire blight (Erwinia amylovora), a potentially devastating disease in apple, can cause floral, fruit and structural damage and even tree death. Most commercial apple cultivars are susceptible and the resistance/susceptibility of many modern cultivars has not been evaluated. Fire blight resistance/susceptibility is difficult to phenotype due to quantitative resistance, impacts of tree vigour and environment on susceptibility, and the erratic nature of the disease. Resistance/susceptibility levels were determined for 94 apple cultivars and important breeding parents. In 2016 and 2017, multiple actively growing shoots per tree (about three trees per cultivar) were challenged with E. amylovora Ea153n via a cut-leaf inoculation method. Proportion of current season's shoot length blighted (SLB) was calculated for each shoot. To classify cultivar responses, estimated marginal SLB means were compared to four controls, representing highly susceptible (HS) to highly resistant (HR), via Dunnett's tests. Cultivar responses ranged from HS to HR with estimated marginal SLB means of 0.001–0.995 in 2016 and 0.000–0.885 in 2017. Most cultivars demonstrated similar resistance/susceptibility levels in both years (ρ = 0.657, P < 0.0001). K-means clustering was used to classify cultivars into three resistance/susceptibility groups based on incidence, average severity (SLB), and maximum severity values (maximum SLB and age of wood infected). Sixteen cultivars were consistently moderately resistant (MR) to HR while the remainder ranged from HS to MR. An updated comparison of susceptibility of important cultivars is provided. Resistance/susceptibility information gained could be used to identify genetic loci associated with resistance/susceptibility and/or inform parental selection in apple scion breeding programmes.     

Susceptibility of European pear cultivars to Pseudomonas syringae pv. syringae using immature fruit and detached leaf assays

The susceptibility of thirty-three pear cultivars and two pear rootstocks to four virulent strains of Pseudomonas syringae pv. syringae was evaluated by inoculating detached immature fruits and young leaves. The four strains were similarly virulent and did not show cultivar specificity although they were isolated from different pear cultivars and exhibited different biochemical profiles. The most frequently planted pear cultivars, Conference, Abate Fetel, General Leclerc, Williams, D. Comice, El Dorado, Alexandrine, B. Anjou, Passe Crassane and the rootstock OHxF 333 were susceptible to P. syringae pv. syringae. Maximal severity values were obtained on 'Preguystar' leaves (about 90%). The rootstock Winter Nelis was less susceptible. Results with immature fruit and detached leaf assays agreed with field observations on cultivar susceptibility to bacterial blast. However, the detached leaf test gave a more accurate prediction and has the advantages that symptoms develop quickly (48 h), and leaves are available for a longer period of time than fruits. This method is proposed as a rapid and reproducible screening system of cultivar susceptibility to bacterial blast of pear.     

新疆野苹果和秦冠的抗黑星病特性

 透射电镜观察表明, 苹果叶片上表皮角质层厚度在品种间存在显著差异, 新疆野苹果和秦冠叶片的角质层厚度显著高于富士和嘎啦的;同一品种不同龄期叶片的角质层厚度随着叶龄增长而增厚, 且黑星病严重度与叶片上表皮角质层厚度间存在显著的负相关关系。苹果品种抗病性组分分析结果表明, 新疆野苹果的病害严重度最低, 约为嘎啦的1/22, 潜育期最长, 为嘎啦的2.0倍, 无(或少有)病斑出现, 不产孢。秦冠的严重度约为嘎啦的1/14, 潜育期约为嘎啦的1.5倍, 产孢量约为嘎啦的1/26。黑星病菌在新疆野苹果和秦冠叶片上的侵染概率及病斑扩展速率均显著低于富士和嘎啦。因此, 新疆野苹果和秦冠对黑星病的抗病性表现在抗侵入和抗扩展两个方面。     

Effect of apple cultivar and of temperature on the biology and life table parameters of the twospotted spider mite<Emphasis Type="Italic">Tetranychus urticae</Emphasis>

Development duration and reproduction rate of the twospotted spider miteTetranychus urticae Koch (Acarina: Tetranychidae) were studied on five different apple cultivars (‘Amasya’ (local cultivar), ‘Golden Delicious’, ‘Granny Smith’, ‘Starking Delicious’ and ‘Starkrimson Delicious’) at 25°C, 65±10% r.h. and 16:8 L:D. In addition, the same parameters were determined on Golden Delicious leaves at three constant temperatures (20°, 30° and 35°C, 65±10% r.h. and 16:8 L:D) in the laboratory.T. urticae performed better on Granny Smith than on the other cultivars, due mainly to high daily egg production (4.6 eggs/♀/day) and the intrinsic rate of natural increase (r _m , which was 0.243 ♀/♀/day). The lowestr _m was observed on Amasya variety (0.231 ♀/♀/day). Development periods of immature stages ofT. urticae varied from 6.5 to 15.5 days at 35° and 20°C, respectively, for females, and from 5.9 to 14.5 days at 35° and 20°C, respectively, for males. The development thresholds of the eggs and pre-adult stages, respectively, were 10.78° and 8.43°C, and total effective temperatures were 57.80 and 172.41 degree-days. Mean generation time (T _o ) of the population ranged from 9.94 days at 35°C to 25.99 days at 20°C. The net reproduction rate increased from 66.99 ♀/♀ at 20°C to 92.19 ♀/♀ at 25°C, and decreased to 84.34 ♀/♀ at 30°C and to 12.04 ♀/♀ at 35°C. The highest r _m occurred at 30°C (0.302 ♀/♀/day) and the lowest at 20°C (0.161 ♀/♀/day). http://www.phytoparasitica.org posting Dec. 19, 2003.     

A rapid virulence assay for the Dutch elm disease fungus Ophiostoma novo‐ulmi by inoculation of apple (Malus × domestica ‘Golden Delicious’) fruits

Large‐scale virulence tests using trees or saplings are expensive, time‐consuming and require a considerable amount of space. The suitability of using ‘Golden Delicious’ apples as a rapid screen for identifying Ophiostoma novo‐ulmi transformants with reduced virulence was thus evaluated. When a collection of O. novo‐ulmi field isolates belonging to subspecies novo‐ulmi or americana was inoculated to apples, members of subsp. novo‐ulmi induced, on average, larger necrotic lesions than subsp. americana isolates. The size of the lesions on apples was not correlated with mycelial growth rate of isolates on nutrient agar. Insertional mutants from O. novo‐ulmi subsp. novo‐ulmi isolate H327 were inoculated to ‘Golden Delicious’ apples and Ulmus parvifolia × U. americana saplings in parallel experiments. Results clearly indicated that the O. novo‐ulmi transformants included several exhibiting significantly altered levels of virulence. Variability among replicates within a treatment was reduced in apple inoculation data compared to elm sapling data. Overall, the ‘Golden Delicious’ apple assay was found to be an excellent means for rapidly assessing the virulence level of O. novo‐ulmi isolates.     

Epidemics of apple powdery mildew (Podosphaera leucotricha) in a mixed cultivar orchard

Epidemics of apple powdery mildew were monitored on leaves of vegetative extension shoots in a mixed-cultivar orchard in 1979. 1980 and 1981. Cultivars Cox's Orange Pippin. Golden Delicious. Ida Red and Suntan were very susceptible but little mildew developed on cv. Discovery in any year. Results with cvs Crispin and Spartan were less consistent due, in part, to differing patterns of vegetative growth. The rankings of cultivars for disease incidence (proportion of leaves with mildew), number of colonies and mildewed area were similar, and were also consistent on fungicide-sprayed and unsprayed trees in 1981. Less disease occurred on fungicide-treated Golden Delicious than on Cox's Orange Pippin. Most infections occurred on the rolled leaves at the shoot tip. Spore production was greatest on leaves at positions -1 to -4 where leaf 0 was the youngest and leaf - 1 the adjacent and older unrolled leaf.     

Evaluation of apricot (Prunus armeniaca L.) resistance to Apple chlorotic leaf spot virus in controlled greenhouse conditions

Apple chlorotic leaf spot virus (ACLSV) seems to be the causal agent of apricot viruela disease. This disease has become an important problem for apricot production in Spain, mainly affecting the ‘Búlida’ cultivar, although no information is available about the behaviour of other cultivars with regards to ACLSV. In this study, the behaviour of 29 apricot cultivars against ACLSV (Apr 62 isolate) was evaluated under controlled conditions in an insect-proof greenhouse. Three different rootstocks, ‘GF305’ peach, ‘Real Fino’ apricot and ‘Adesoto’ plum, were first inoculated by grafting ACLSV-infected bark and were later grafted with the apricot cultivar to be evaluated. Apricot cultivars were evaluated during three cycles of study. ACLSV was asymptomatic on the leaves of all cultivars and rootstocks, so level of susceptibility or resistance was determined by virus detection through RT-PCR. ‘GF305’ rootstock showed a greater susceptibility level than ‘Real Fino’ and ‘Adesoto’. Most of the cultivars were susceptible to ACLSV with different levels of susceptibility, and only ‘Bergeron’ and ‘Mauricio’ were resistant.