Interaction of red raspberry cultivars with isolates of Phragmidium rubi-idaei

Seven cultivars of red raspberry ( Rubus idaeus ) showed different susceptibility to infection by yellow rust ( Phragmidium rubi-idaei ) at two commercial plantations in Scotland and North Wales, The cultivars Latham, Chief and Boyne were completely resistant. Mailing Delight and Glen Clova supported more telial more than Mailing Jewel. In contrast the last named was the most susceptible cultivar at the aecial stage in Scotland but developed similar numbers of aecia to Glen Clova and Mailing Delight in Wales.
Meeker had an extended latent period, fewer and smaller pustules and a very small yield of urediniospores compared to the other susceptible cultivars, thus showing the characteristics of slow-rusting genotypes. At the Scottish site in 1982, where rust was less than in Wales, Meeker and Mailing Jewel performed differently to the other cultivars at the telial stage. Inoculation studies under controlled environmental conditions with urediniospores from each site revealed an interaction between cultivars and isolates suggesting that variation in pathogenicity is present in populations of P. rubi-idaei in the UK.     

Identities and pathogenicities of phytophthora spp. causing root rot of red raspberry

Phytophthora syringae, P. drechsleri, P. cactarutn, P. cambiuora and P. megasperma were isolated from the roots of red raspberry plants affected by severe root and crown rot with associated cane death. Phytophthora megasperma occurred most frequently and consisted of two types of isolates which differed in colony morphology, growth rates, and oogonial, oospore, sporangial and zoospore size, and pathogenicity to a range of plants. One type with large oospores was typical of P. megasperma var. megasperma , and was non-pathogenic to red raspberries, while the other with smaller oospores and which grew more slowly in culture than the first, was highly pathogenic, producing symptoms similar to those observed in the field. Highly pathogenic isolates from Germany and the USA were of this type.
All red and black raspberry cultivars tested were susceptible to the pathogenic type, although North American cultivars were generally less affected than British ones. Inoculated plants had reduced shoot and root weights, stem lesions and wilted and yellowed leaves. The blackberry × raspberry hybrid Tayberry and its blackberry parent were immune.
Phytophthora drechsleri, P. cactorum and P. cambivora produced small to moderate amounts of root rot on red raspberry, and P. cambivora also caused slight symptoms on shoots.     

The effect of waterlogging on Phytophthora root rot of red raspberry

Red raspberry plants were subjected to waterlogging after inoculation with different species of Phytophthora isolated from field outbreaks of root rot. The commonest species, a form of P. megasperma , was highly pathogenic to raspberry whether the plants had been waterlogged or not, but waterlogging increased the severity of disease caused by other species. P. cambivora and P. drechsleri were moderately pathogenic and non-pathogenic respectively in non-waterlogged conditions but killed plants that had been waterlogged for 4 days. P. megasperma var. megasperma required longer periods of waterlogging to cause severe symptoms and did not kill plants. Root rotting of waterlogged and non-waterlogged plants was controlled with a metalaxyl and copper mixture. The results indicated that several species of Phytophthora may contribute to poor growth and death of raspberries grown in poorly drained sites.     

Phytophthora species attacking strawberry and raspberry1

Phytophthora frugariae causes red core root rot of strawberries. Although the disease is probably most acute in northern Europe, serious outbreaks have been reported from a number of Mediterranean countries, especially France and Italy. Leather rot of fruit and crown rot, which are caused by P. cuctorum, can also be severe problems in warmer climates. Both fungi survive in soil for long periods, but the most common form of spread is in diseased planting material. Sensitive tests have been developed to detect red core in planting material, and been used to effect in certification schemes. Root rot of raspberry has gained prominence in the last 10 years in Europe as raspberry growing has expanded, but the disease has been known for many years in France. Nine species of Phyfophthora have been recovered from affected plants, but two of these, one with affinities with P. megasperma, and P. cumbiuora, are responsible for most major outbreaks. The other species are only troublesome where drainage is poor. Again, spread is mainly in infected material. Few raspberries are resistant to root rot, but some wild RubuP spp., blackberries and raspberry x blackberry hybrids are resistant and may be useful in breeding programmes.     

非洲菊疫霉根腐病的快速分子诊断

 隐地疫霉引起的根腐病是非洲菊生产上的主要病害,为发展该病的快速诊断技术,本文比较了卵菌核糖体基因ITS的序列,在此基础上设计了2条针对隐地疫霉的特异性PCR引物PC1和PC2。供试的23种不同真菌和疫霉菌的46个菌株中,利用这对引物能从隐地疫霉基因组DNA中扩增出一条分子量为620bp的特异性条带,该引物的检测灵敏度可达10pg。采用快速组织碱裂解法提取发病植物组织的DNA,结合PCR检测技术,4h内可从发病的非洲菊根部组织中特异性地检测到隐地疫霉菌。结果表明,建立的非洲菊疫霉根腐病菌分子检测方法可用于该病害的快速分子诊断。     

Methods for assessing the resistance of raspberry genotypes to Phytophthora root rot

Zoospores and agar discs of the fungus causing raspberry root rot (Phytophthora fragariae) were used as inoculum to assess the resistance of raspberry genotypes in pot experiments. High zoospore concentrations resulted in more severe symptoms than low concentrations. There was a strong correlation between the results obtained with zoospores and with colonized agar discs as inocula. although disease was generally more severe with the former. The severity of root rot was correlated with a number of other symptoms, in particular growth reductions, stem lesions and leaf wilting, and some of these symptoms could possibly be used as measures of resistance. There was no evidence of physiological specialization with the range of isolates and raspberry genotypes used. Pot tests in general gave results which matched reported resistances in the field, and could be used to assess the resistance of breeding lines and selections.     

Prevalence and pathogenicity of spinach root pathogens of the genera Aphanomyces, Phytophthora, Fusarium, Cylindrocarpon, and Rhizoctonia in Sweden

In a 4-year disease survey in commercial spinach fields, pathogens were isolated from spinach root pieces placed on selective agar media. Aphanomyces cladogamus was the most abundant pathogen, followed by Phytophthora. cryptogea and Fusarium oxysporum. Rhizoctonia solani was found only occasionally. Other pathogens isolated were F. redolens, F. sambucinum and Cylindrocarpon destructans. P. cryptogea was the most severe pathogen, causing death of most plants, but A. cladogamus also caused severe root damage. Isolates of F. oxysporum ranged from highly pathogenic, i.e. P. oxysporum f.sp. spinaciae race 1. to moderately pathogenic and non-pathogenic, Rhizoctonia solani isolates also varied widely in their pathogenicity. Only a small number of the F. redotens and F. sambucinum isolates were pathogenic and most C. destructans isolates were weakly pathogenic. Isolation frequencies were relatively stable from year to year, but P. cryptogea was isolated more frequently in autumn than in spring. No clear relationships were found between pathogen prevalence and disease severity index of surveyed field plants, between pathogen prevalence and plant developmental stage, or between prevalence of the different pathogens isolated.     

Phytophthora root and crown rot of raspberry in Bulgaria

Root and crown rot of raspberry (Rubus idaeus L.) was observed in a plantation at the experimental station of small fruits in Kostinbrod, Bulgaria. Isolates ofPhytophthora spp. were obtained from diseased plants. Colony morphology, growth rates, features of asexual and sexual structures were studied and as a result twoPhytophthora species were identified:Phytophthora citricola Saw. andPhytophora citrophthora (R.E. Sm. & E.H. Sm.) Leonian. Their pathogenicity was confirmed in artificial inoculation experiments. The isozyme (-esterase) patterns ofP. citrophthora andP. citricola isolates from raspberry and from the collection of the CBS, Baarn the Netherlands were compared, using micro-gel electrophoresis. Both species are reported for the first time as pathogens of raspberry in Bulgaria. This is only the second report in phytopathological literature ofP. citrophthora on raspberry, the first being from Chile [Latorre and Munoz, 1993].     

Occurrence and distribution of Raspberry bushy dwarf virus in commercial Rubus plantations in England and Wales

Serological surveys for Raspberry bushy dwarf virus (RBDV) made between 1995 and 1997 and covering ≈ 10% of the commercial farms growing Rubus (red raspberry and hybrid berries) in England and Wales showed that this virus was present on approximately one-quarter of all farms and in approximately one-sixth of all plots tested. RBDV was found in all of the four main raspberry cultivars being grown at that time (Autumn Bliss, Glen Moy, Glen Prosen and Leo), in Loganberry and in Tayberry. Fifteen RBDV genotypes (including two that appeared to be mixed) were identified using RT-PCR/RFLPs, but the majority of genotypes were found only rarely. Of the RBDV isolates tested, two genotypes each comprised 12·5% and another 46·4%. None of the three most common genotypes was associated solely with single Rubus cultivars and vice versa . It is suggested that two separate outbreaks of RBDV are occurring in England and Wales. One outbreak comprises the most frequent genotype combined with one of the moderately frequent genotypes; this outbreak is largely confined to the main growing areas and is either spreading between farms or coming from multiple local sources. Circumstantial evidence suggests that these isolates (and hence this first outbreak) are of the RB pathotype. The second outbreak consists of the other moderately frequent genotype and those genotypes which are less common. These genotypes appear to be more scattered across England and Wales and seem more likely to be coming from local sources and not to be spreading naturally between commercial farms.     

Control of Phytophthora cryptogea in the hydroponic forcing of witloof chicory with the rhamnolipid-based biosurfactant formulation PRO1

Rhamnolipids, extracellular metabolites of Pseudomonas aeruginosa with surfactant properties, proved to be very effective in controlling the spread of brown root rot disease caused by Phytophthora cryptogea in the hydroponic forcing system of witloof chicory ( Cichorium intybus var. foliosum ). The biosurfactant was applied as the product PRO1, a formulation of 25% rhamnolipids in oil. Both an in vitro screening and in vivo experiments in a mini-hydroponic system demonstrated the ability of PRO1 to control brown root rot. A 25  µ g mL⁻¹ rhamnolipids nutrient solution was enough to obtain good control of an artificial infection with a zoospore suspension of P. cryptogea . The biosurfactant PRO1 performed well in a semicommercial system under growers' conditions. A treatment of 25  µ g mL⁻¹ rhamnolipids (100  µ g mL⁻¹ PRO1) reduced the disease incidence significantly in two independent experiments. However, PRO1 was not effective when a mycelial suspension was used as inoculum. Rhamnolipids have good potential to limit the spread of P. cryptogea in the hydroponic forcing system of witloof chicory, and can be used as a preventive measure against brown root rot.     

Changes in phenolic content induced by infection with Didymella applanata and Leptosphaeria coniothyrium,the causal agents of raspberry spur and cane blight

The phenolic profile of healthy and infected raspberry canes was investigated in three raspberry cultivars: Autumn Bliss, Himbo Top and Polka. The content of total phenols and tannins was determined using spectrophotometric methods, whilst individual phenolic acids, flavan‐3‐ols, ellagic acid derivatives and glycosides of quercetin were analysed using HPLC/MS analysis. The content of secondary metabolites varied considerably among the analysed raspberry cultivars. Moreover, Didymella applanata and Leptosphaeria coniothyrium infection significantly altered the metabolism of phenolic compounds. Flavanols represented the greatest share of all identified phenolics in raspberry canes (90%), followed by glycosides of quercetin (6%), derivatives of ellagic acid (3%) and traces of hydroxycinnamic acid derivatives. Spur and cane blight diseases caused an increase of flavan‐3‐ols and tannins but the levels of hydroxycinnamic acid derivatives, conjugates of ellagic acid and quercetin glycosides were significantly reduced. Cultivars Himbo Top and Polka contained higher levels of hydroxycinnamic acid and ellagic acid derivatives in healthy and infected canes compared to cv. Autumn Bliss. Cultivar Polka also contained the highest level of flavanols and tannins. However, despite high levels of flavanols and total phenols measured in cv. Polka, the canes were highly diseased following infection with D. applanata and L. coniothyrium. The results of the study provide evidence that the level of phenolic compounds in the canes could be causally linked to the differences in disease susceptibility.     

First report of raspberry yellows disease caused by raspberry bushy dwarf virus in Japan

Severe yellowing of leaves was observed on red raspberry in Akita Prefecture. When inoculated with sap from symptomatic raspberry leaves, Chenopodium quinoa plants developed chlorotic ringspot and mottling that are typical of raspberry bushy dwarf virus (RBDV) infection. In western blot analysis, an antibody to the coat protein (CP) of RBDV reacted against ca. 30-kDa protein specific to the diseased trees. In RT-PCR testing for RBDV, single DNA fragments were amplified from total RNA samples of the diseased trees. The nucleotide sequences of the DNA fragments covering the entire CP region revealed 87–97?% identities with those of RBDV isolates.     

Etiology of a newly described root rot of guar (Cyamopsis tetragonoloba) in Australia caused by Phytophthora cryptogea

An isolate of Phytophthora obtained from diseased roots and stems of guar ( Cyamopsis tetragonoloba ) growing in waterlogged soil from Dalby. Queensland. was identified as Phytophothora cryptogea ( P. drechsleri ). Sex organs were not observed, Pathogenicity to guar seedlings was established under glasshouse conditions either by using a hypocotyl-wound inoculation technique, or adding motile zoospores to seedlings growing under saturated conditions. This appears to be the first report of this disease. Seven isolates of P. drechsleri from hosts other than guar were shown to be pathogenic to guar following hypocotyls-wound inoculation.
The host range of the guar isolate was studied using both hypocotyl-wound inoculation and zoospores. After hypocotyl inoculation, the following species were found to be susceptible^: cantaloupe. cowpea, cucumber, mungbean, pea. pigeon-pea, safflower. sunflower, tomato and watermelon. Slight symptoms were observed on bean and chickpea. When zoospores were used as the inoculum, only pea. pigeon-pea, sunflower and safflower were highly susceptible. A range of guar cultivars and breeding lines were screened for resistance using zoospore inoculum, and although no genotypes were highly resistant, there were significant differences between disease reactions.     

Phylogenetic history of Phytophthora cryptogea and P. drechsleri isolates from floriculture crops in North Carolina greenhouses

The evolutionary history of Phytophthora cryptogea and P. drechsleri isolates previously collected from floriculture crops in North Carolina commercial greenhouses was explored with coalescent- and parsimony-based analyses. Initially, 68 isolates representing 13 location-host groups were sequenced at multiple loci. Sequences of all isolates within a group were identical. A subset of isolates were selected, cloned to resolve heterozygous sites, and analyzed with SNAP Workbench. The internal transcribed spacer (ITS) region of the ribosomal DNA and cytochrome oxidase II gene genealogies were congruent and indicated that P. cryptogea and P. drechsleri are sister species diverged from a common ancestor with no evidence of gene flow. In contrast, genealogies inferred from β-tubulin (β-tub) and translation elongation factor 1α (EF-1α) genes were in conflict with these loci. Coalescent analysis based on a nonrecombining partition in β-tub and EF-1α showed an initial (older) split between P. cryptogea and P. drechsleri, with a later (recent) event separating the remaining P. cryptogea haplotypes from P. drechsleri. A parsimony-based minimal ancestral recombination graph inferred recombination between P. cryptogea and P. drechsleri isolates in the ITS region and β-tub, suggesting genetic exchange between species. Also, putative recombination between A1 and A2 mating types of P. cryptogea suggests that sexual reproduction has occurred in the history of these P. cryptogea isolates.     

Comparison of a baiting method and PCR for the detection of Phytophthora fragariae var. rubi in certified raspberry stocks*

In winter 2002/2003, a total of 136 root samples from 57 different raspberry stocks in Scotland were examined for the presence of raspberry root rot caused by the fungus‐like pathogen Phytophthora fragariae var. rubi. All stocks had been planted as propagation material entered at different grades in the Scottish certification scheme or had applied for plant passports. For detection, a modified ‘Duncan bait test’ was compared to a nested PCR method. The two tests identified the same infected stocks: PCR detected 10 positive samples from four different stocks, while the bait test picked up two additional positive samples coming from the same four stocks. The two tests had a similar level of reliability in this examination and a recommendation for one or the other depends mainly on the technical equipment and skills available in the laboratory.     

Examination of latent infection in raspberry canes with Phytophthora rubi and P. idaei and transmission in micropropagation

Buds of raspberry canes from naturally and artificially infected root stocks were tested by nested PCR for the latent presence of Phytophthora rubi and P. idaei to establish the risk of introducing these pathogens into micropropagation. Fifteen out of 201 buds tested positive for P. rubi and only 1 out of 176 for P. idaei. These infections were not restricted to buds in the lower part of the cane and mostly do not appear to spread systemically up from the rootstock but seem to be caused by secondary infections of the canes. Buds from symptomless canes from infected root stocks were used for micropropagation and P. rubi could be detected in 5.8% of the obtained microplants after ten generations in one of the two trials. This indicates that micropropagation procedures are not absolutely infallible in eliminating infection and underlines the necessity of a zero tolerance towards diseases in the starting material.     

云南树莓病虫害调查初报

为了解经济植物树莓栽培中的病虫害危害情况,2005-2007年在云南省农业科学院高山经济植物研究所基地对树莓病虫害进行了系统调查．发现危害树莓的病虫害共有9种,分别是叶斑病、炭疽病、茎枯病、茎腐病、灰霉病、稻绿蝽、小长蝽、拟小黄卷叶蛾和果蝇。树莓病虫害总体发生数量少、危害程度轻,是一种优良的新型果树,可进一步扩大种植。本文对其主要病虫害发生情况及其相应的防治技术措施作了概述。     

Prevention of Phytophthora Root Rot in Gerbera by increasing copper ion concentration in the nutrient solution

Increased copper concentration in the nutrient solution was used as a means for reducing the severity of root rot caused by Phytophthora cryptogea in Gerbera jamesonii in three experiments. Plants were grown in pots on ebb-and-flow benches with separate systems for recirculating nutrient solutions. Eight nutrient solutions with two concentrations of copper ions (0.07 and 0.28 ppm), two electrical conductivity values (1.5 and 2.2 mScm^-1), and two iron sources (FeHEEDTA or FeSO₄) were combined in a factorial design. Plants were inoculated with zoospores of P. cryptogea via the recirculating nutrient solution. Disease incidence was significantly reduced in inoculated plants grown on nutrient solution with 0.28 ppm copper compared with 0.07 ppm copper, when FeSO₄was introduced as the iron source. No effects of increased copper concentration was observed when iron was added as FeHEEDTA. The change in electrical conductivity from 1.5 to 2.2 mScm^-1 without changing the Cu²⁺ concentration did not influence the disease severity in these experiments. The results suggest that increased copper ion concentration in the nutrient solution could be a component of disease management strategy for ebb-and-flow systems. Possible management of the cupric ion concentration in the nutrient solutions is discussed.