Infected Bushes Research Articles

Acerola shoot proliferation induced by a phytoplasma enclosed in the subgroup 16SrIII-F

Acerola bushes were observed showing symptoms of shoot proliferation, generalized stunting, yellowing and decline. Since these symptoms are typically induced by phytoplasmas, this survey was carried out with the aim of detecting, identifying and classifying the supposed phytoplasma present in symptomatic bushes. Total DNA was extracted from symptomatic and asymptomatic samples and used in nested PCR conducted by the primer pairs R16mF2/mR1 followed by R16F2n/R2. Amplifications of expected genomic fragments of 1.2 kb revealed the presence of phytoplasma in 73 % of the symptomatic samples. Molecular analyses, using computer-simulated RFLP patterns, similarity coefficient calculation and phylogenetic analysis allowed for classifying the bacterium as a ‘Candidatus Phytoplasma pruni’ – related strain (subgroup 16SrIII-F). The phytoplasma induced the same symptoms in healthy acerola plants inoculated by grafting and showed molecular identity with the strain identified in naturally infected bushes. Although various strains belonging to distinct subgroups within the 16SrIII group have been previously identified in Brazil, this is the first report of the presence of a representative of the 16SrIII-F subgroup in the Brazilian agroecosystem. Considering that phytoplasmas can be systemically distributed throughout the plant and acerola plants are vegetatively propagated, it is recommended that propagation material be obtained from mother plants free of the pathogen.

Blueberry fruit drop-associated virus: A New Member of the Family Caulimoviridae Isolated From Blueberry Exhibiting Fruit-Drop Symptoms.

This study describes the nucleotide sequence and genome organization of a new DNA virus isolated from 'Bluecrop' blueberry plants exhibiting fruit-drop symptoms and named Blueberry fruit drop-associated virus (BFDaV). Blueberry fruit drop disease was first detected in blueberry plants in British Columbia, Canada in the late 1990s, and in a single field in northern Washington state in the United States in 2012. Infected bushes abort nearly 100% of their fruit about three weeks prior to harvest, when the berries are about 3 to 5 mm in diameter. At harvest, the affected plants appear taller than healthy ones as there is no fruit weighing down the branches. The virus was amplified from diseased material using rolling circle amplification, followed by enzyme digestion, cloning, and sequencing. The full genome of BFDaV is 9,850 bp in length and contains a single open reading frame, encoding for a polyprotein, and a large noncoding region. Based on the genome size and organization and phylogenetics, BFDaV is proposed as a new and the largest member of family Caulimoviridae. Finally, in mapping part of a field with fruit-drop symptoms, there was a nearly perfect correlation between the presence of the virus and fruit-drop symptoms.

Preliminary host specificity testing of Endophyllum osteospermi (Uredinales, Pucciniaceae), a biological control agent against Chrysanthemoides monilifera ssp. monilifera

Chrysanthemoides monilifera ssp. monilifera, indigenous to the Western Cape Province of South Africa, is a serious invader of native vegetation in south-eastern Australia. The rust fungus Endophyllum osteospermi causes witches’ brooms on C. monilifera ssp. monilifera in South Africa, and is associated with a reduction in growth and seed production of its host under natural conditions, as well as mortality of severely infected bushes. This rust fungus is considered to be a potential biological control agent for use against C. monilifera ssp. monilifera in Australia. Endophyllum osteospermi has a long latent period, typically between 6 and 24 months between infection and the initiation of witches’ brooms. This long latent period makes the logistics of doing traditional host specificity testing, in which all test plant species are inoculated and observed for symptom development, unfeasible for this rust fungus. Germination of aecidioid teliospores and penetration by basidiospores were observed on the surface of excised leaves of 32 test plant species at 4 days after inoculation, and compared to that on C. monilifera ssp. monilifera. Germinating aecidioid teliospores aborted on 14 test plant species, whilst no penetration was attempted on a further 12 test plant species. Penetration only occurred on nine of the 32 test plant species, in addition to C. monilifera ssp. monilifera. Inoculating whole plants of nine selected test plant species confirmed the above results. Therefore, only the test plant species in which penetration occurred, or at least was attempted, need to undergo comprehensive host specificity testing. Pending these results, E. osteospermi may be suitable for release in Australia for the biological control of C. monilifera ssp. monilifera.

Occurrence, symptom variation and yield loss caused by full blossom disease in red and white currants in the Czech Republic

Full blossom disease (FBD) was found at 11 of 19 monitored locations in the Czech Republic. Six cultivars of white currant and 26 cultivars of red currant with characteristic symptoms of the disease were found in germplasm collections, propagation material and commercial plantations. The incidence of the disease varied from 1% to 70% of infected bushes in different cultivars and locations. Similarly, the intensity of symptoms in the field observed between 1999 and 2004 varied from a few malformed flowers up to a massive occurrence of such flowers on whole branches. Yield losses of up to 70% were recorded in severely infected bushes of red currant Vitan and fruit quality was poor. Infected seedlings seem to have been the major source of spread of the disease in the last two decades. The presence of both phytoplasma and BRV was confirmed in FBD infected bushes.

Infection of Chrysanthemoides monilifera ssp. monilifera by the rust fungus Endophyllum osteospermi is associated with a reduction in�vegetative growth and reproduction

The perennial shrub Chrysanthemoides monilifera ssp. monilifera (Asteraceae: Calendulae), indigenous to South Africa, has become a serious weed of native vegetation in cool-temperate, winter-rainfall areas in southeastern Australia. The microcyclic, autoecious, rust fungus Endophyllum osteospermi induces the production of witches’ brooms on C. monilifera ssp. monilifera. Field observations indicate that the presence of witches’ brooms may reduce the growth and reproduction of the remaining symptomless parts of the host bushes and, therefore, this rust fungus is currently being considered as a biocontrol agent for use against C. monilifera ssp. monilifera in Australia. The vegetative growth and reproductive output of symptomless branches on bushes with different levels of E. osteospermi infections were measured at three South African sites with naturally infected populations of C. monilifera ssp. monilifera. The growth of symptomless branches on infected bushes was 26–81% less than that of symptomless branches on uninfected bushes. The number of buds, flowering capitulae, fruiting capitulae and drupes on individual symptomless branches of infected bushes was 35–75%, 45–90%, 15–99%, and 15–90% less, respectively, than those on uninfected bushes. The presence of witches’ brooms was consistently associated with reduced growth and reproductive output of bushes. Very little flowering and drupe production occurred on witches’ brooms themselves.

Septoria lavandulae . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Septoria lavandulae . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Disease of living and withering leaves. The fungus causes small necrotic spots on the lower leaves of young plants (BOUNAURIO et al. , 1996). Further development of S. lavandulae retards growth of the whole infected plant and promotes premature defoliation (ZHUKOVA, 1977). HOSTS: Lavandula angustifolia (syn. : L. spica ), L. dentata, L. latifolia, L. officinalis, L. pyrenaica, L. stoechas, L. vera (Lamiaceae). [Type host- L. vera .] GEOGRAPHICAL DISTRIBUTION: Africa: Madeira. Europe: Bulgaria, Belgium, Czech Republic, Denmark, France, Germany, Italy, Latvia, Lithuania, Moldova, Netherlands, Portugal, Romania, Russia, Sweden, UK, Ukraine. North America: USA (Ohio, Oklahoma). TRANSMISSION: By air-borne or splash dispersed conidia from infected bushes (WORMALD, 1925); also from infected plant débris.

Strain Variation and Oxalic Acid Production byCytospora leucostomasolated from Saskatoon (A melanchier alnifolia)

Leucostoma persoonii (anamorph = Cytospora leucostoma) is a pathogen that causes early dieback and canker disease on a variety of fruit trees in North America. It has recently been recognized as an economically important disease of saskatoon (Amelanchier spp.) in Alberta, Canada. Isolates from infected bushes from five locations in Alberta were studied to determine the extent of strain variability and to investigate mechanisms of pathogenesis. Differences among isolates were found to be significant with respect to cultural characteristics on various media, and growth responses of the isolates to a range of temperatures also varied significantly. Oxalic acid production was observed in cultures of C. leucostoma [...]

Control of the live-wood tea termite Glyptotermes dilatatus using Heterorhabditis Sp. (Nemat.)

Glyptotermes dilatatus is the main pest of the lowland-grown tea in Sri Lanka, affecting some 42 000 ha. Infested bushes suffer debilitation of their structure, loss of yield and death. The concealed habit of Glyptotermes and its social organization makes it difficult to control by chemical, classical biological and other conventional methods. It was recently found that the nematode Heterorhabditis sp. (isolated in Darwin, Australia, and mass-produced by CSIRO entomologists) infests Glyptotermes and is able to kill the termite and breed in the cadaver both in the laboratory (22°C; 100% relative humidity) and under extreme climatic conditions experienced in the field (mean temp.: 28.3°C; range, 19.5–38.4°C; only 7 days low rainfall between 20 December 1981 and 28 February 1982). Within each cadaver, up to about 3500 juveniles were produced which are able to infect healthy termites in the laboratory as well as in the field, creating a chain of infection that leads to complete annihilation of a colony. In the laboratory, the dosage mortality equation predicted an LD 50 of 3670±564 worms/ml, suggesting that a very high rate of application is needed to obtain 99.9% kill. In the field, experimental application of infectives at rates of 4000 and 8000 worms/ml in doses of 40 and 30 ml per bush, respectively, gave complete control within 60–95 days. The cost of control is US$2.39 (50.20 Sri Lankan rupees) per 1000 infected bushes (1987 values).

Blueberry Shoestring Virus in Natural Populations of Highbush and Lowbush Blueberry

Abstract Blueberry shoestring virus (BBSSV) is the most serious disease in Michigan, and it has been reported in New Jersey, Washington, North Carolina, and Nova Scotia (4, 8). Shoestring is particularly difficult to eradicate, since there is no known control other than removing diseased bushes, and infected bushes do not show external symptoms for up to 4 years. Also, no cultivars of highbush blueberry are immune to the disease (2).

Epidemiology of three viruses infecting the rose in the United Kingdom

SUMMARYStudies on the epidemiology of arabis mosaic (AMV), prunus necrotic ringspot (PNRSV) and strawberry latent ringspot (SLRV) viruses were made in relation to commercial production of standard and bush roses. AMV or SLRV apparently induced either symptomless infection in rose cultivars and Rosa spp., or leaf symptoms ranging from small chlorotic flecks to severe chlorotic mosaic and, occasionally, plant death. Infection of R. canina ‘inermis’ or R. corymbifera by an isolate of SLRV from R. corymbifera also severely depressed flowering and hip formation. In addition, whereas this isolate could be graft‐transmitted to all Rosa spp. tested, isolates from R. rugosa and R. multiflora failed to be graft‐transmitted to R. canina ‘inermis’ or R. corymbifera. No difference was detected in graft‐transmission tests of Rosa spp. with several isolates of AMV or PNRSV.In plantings of up to 7 yr none of the viruses was transmitted through pollen to healthy roses grown in nematode‐free soil, and only SLRV was readily seed‐transmitted, particularly in R. rugosa. Nevertheless, in soil containing viruliferous nematodes, AMV and/or SLRV were transmitted to c. 80% of healthy plants.AMV and particularly SLRV were each damaging to field‐grown maiden rose bushes cv. Fragrant Cloud. SLRV delayed the onset of flowering, and reduced the number and size of blooms. Diseased bushes were less vigorous, and half or none of the AMV‐ or SLRV‐ infected bushes respectively, conformed to the British Standards Institution specifications for maiden bush roses.These results are discussed in relation to the commercial production of field‐grown roses in the UK.

The effect of gooseberry vein banding virus on the growth and yield of gooseberry and red currant

SummaryA meristem clone of gooseberry cv Careless consistently outyielded otherwise comparable bushes infected with gooseberry vein banding virus (GVBV). In each of two seasons the yield increase exceeded 15%. Cuttings from uninfected bushes grew faster and survived better than those from infected bushes. Only five of 496 bushes became infected with GVBV within six years when grown in seven commercial plantings in Kent and Cambridgeshire. Red currant bushes cv Jonkheer van Tets infected with GVBV yielded less than GVBV-free controls but variability was great, and half of the control bushes became infected within six years. Cuttings from uninfected bushes grew more vigorously than those from infected ones.

Hawthorn powdery mildew: Diurnal and seasonal distribution of conidia in air near infected plants

Conidia of Podosphaera clandestine Lev. were trapped near powdery mildew infected bushes of hawthorn, Crataegus monogyna Jacq., in Leeds, Yorkshire, U.K., during 1972. The highest numbers of conidia were trapped between 11.00 and 16.00 h each day. None were trapped between 24.00 and 06.00 h, with very few being airborne from 18.00 to 24.00 h. First mildew primary infections were observed developing from a few infected buds on 26 April. First conidia were trapped on 18 May, with high numbers being airborne during the first half of June and again (with even higher catches) in the first half of July. The greatest increase in secondary leaf infections occurred also in two peaks, at the end of June and at the beginning of August. Both the early July peak of conidia in the air and the early August increase in mildew infections were related to clipping the infected bushes at the end of June and the infection of newly induced lateral shoots.

Field experiments on the chemical control of blackcurrant reversion virus and its gall‐mite vector (Phytoptus ribis Nal.)

SUMMARYHealthy blackcurrant bushes and others infected with reversion virus were exposed equally to infestation by the gall‐mite vector (Phytoptus ribis Nal.) spreading from unsprayed sources planted nearby. Four applications of 1·0% lime sulphur at fortnightly intervals during the dispersal period were less effective than 0·05% endosulfan in preventing the infestation of healthy bushes, whereas endrin at 0·04% gave almost complete control. All spray treatments were much less effective when applied to the virus‐infected bushes, although endosulfan remained superior to lime sulphur and inferior to endrin. Infected bushes sprayed with lime sulphur developed more galls than unsprayed healthy bushes.In another experiment, four applications of endrin or lime sulphur decreased the spread of mites and reversion virus from infested bushes to adjacent sprayed and unsprayed bushes. Lime sulphur was much less effective than endrin in preventing infestation with mites, but more effective in decreasing the incidence of virus.These results are discussed in relation to commercial spray programmes and to the design of experiments on the effectiveness and mode of action of spray materials against mites and virus.

Increased susceptibility of black‐currant bushes to the gall‐mite vector (Phytoptusribis Nal.) following infection with reversion virus

SUMMARYHealthy black‐currant bushes (var. Wellington XXX) and others infected systemically with a virulent strain of reversion virus were exposed equally to infestation by the gall‐mite vector (Phytoptus ribis Nal.). Shoots with malformed leaves caused by mites feeding at the stem apices were virtually restricted to the virus‐infected bushes. Buds infested with mites became rounded galls, which were far fewer and more localized on shoots of healthy bushes than on infected ones.Similar results were obtained in further experiments with Wellington XXX and seven other varieties. Bushes infected systemically with an avirulent strain of reversion virus developed more galls than healthy bushes, but fewer galls than bushes infected with a virulent strain.The young buds of virus‐infected bushes were 170 times more susceptible to dispersing mites than those of healthy bushes. The axillary buds of healthy bushes resisted infestation and the apical meristems were virtually inaccessible to mites, whereas the axillary and apical buds of virus‐infected bushes were invaded readily.An experiment with bushes var. Cotswold Cross that were either healthy or partially or completely infected with reversion virus was retained for two years. Each year there was a relationship between symptom expression and mite infestation; only shoots with chronic virus symptoms developed mite‐affected leaves and numerous galls.Virus infection increased the vulnerability and accessibility of the apical and axillary buds by decreasing the density of hairs on the stems and leaves. Infected bushes also presented a greater catchment area to dispersing mites and more shoots and buds were available for colonization than on healthy bushes.The interactions between virus, host and vector are discussed, together with their implications in nature, in experimental design and in disease control.