1,720,971 research outputs found
Effects of essential oils, Bacillus amiloliquefaciens and acibenzolar-s-methyl on bacterial wilt incidence and Ralstonia solanacearum populations in tomato plants.
No full textThe efficacy of 5 Sardinian essential oils (Helichrysum sp., Mentha piperita, M. pulegium, Myrtus communis, Thymus herbabarona), thymol (Fluka) and Bacillus amyloliquefaciens and a SAR inducer acibenzolar-S-methyl in vitro and on tomatoes plants grown in greenhouse for control bacterial wilt was evaluated. The soil was first infested with a mixture of an equal amounts of two virulent Rs strains. After 1h of incubation, essential oils and thymol were incorporated into soils. In order to evaluate antagonistic activity of B. amyloliquefaciens, the suspensions of Rs were incorporated into soil 24 h after the antagonist. Acibenzolar-S-methyl was applied on tomato plantlets as a foliar spray at a concentration of 25 mg/l before transplanting and increased to 50 mg/l after transplanting. The trials were repeated twice. Seven days after essential oils treatments, Rs populations density were determined on SMSA. Wilted plants and latent infection, detected by direct isolation and ELISA, were determined one month after transplanting. Bacterial wilt incidence and Rs concentration, compared with control, were reduced considerably on tomato plants transplanted in soil treated with 1g/l of essential oils, thymol and B. amyloliquefaciens. However, the effectiveness of oils and thymol was reduced when application rates were lowered (0,5g/l). At two concentrations (0,5 and 1g/l), significantly more wilt occurred in tomato plants grown in soil treated with M. piperita oil. Plants treated with acibenzolar-S-methyl were apparently healthy. Tests revealed that all plants were systematically infected by Rs. The possibility to test essential oils, together with antagonists and SAR inducers are now in progress
Studies on susceptibility of pruning wounds to infection by fungi involved in grapevine wood diseases in Italy
No full textThe susceptibility of grapevine annual pruning wounds to Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and Diplodia seriata was investigated over three years (2005–2007) in a 15 year-old vineyard, cv. Sauvignon blanc. Vines were pruned each year in January, February and March and the wounds were inoculated weekly with conidial suspensions, and with sterile water as a control. Penetration of the fungi into the wood was assessed after 4 weeks by plating pieces of host tissue on agar medium. The susceptibility of annual pruning wounds, expressed as the infection percentages of inoculated spurs, varied with both the trial year and the fungus inoculated. Average infection percentages of inoculated spurs in the three years were respectively 14.7, 38.5 and 50.9% for Pa. chlamydospora, 31.7, 32.2 and 49.4% for Pm. aleophilum and 84.2, 43.8 and 40.9% for D. seriata. The period of pruning was significant for the infection percentages of all fungi in 2005, and for D. seriata in 2006. Natural infection of control spurs by Pa. chlamydospora (2, 4.4, and 11.7% of spurs in the three years respectively) and by Pm. Aleophilum (0.3, 1.8, and 6.4%) began when average weekly temperatures stabilized around 10°C, while infection by D. seriata (12.2, 12 and 18.3% in the same period) occurred even below that threshold. Higher infection percentages of both artificially and naturally infected spurs in 2007 were probably due to the higher temperatures recorded in February and March (besides the use of a more efficient selective medium for the isolation of Pa. chlamydospora and Pm. aleophilum). Only artificial infections with D. seriata showed an opposite trend that cannot be explained by the weather data. Infection of one-year-old wood appeared to be an important factor in disease spread. Spurs remained liable to infections with any of the fungi for up to 4 months after pruning, and isolation percentages could be fairly high also in late spring. As a consequence, the planning of pruning does not seem to be an effective means to counteract the wood diseases caused by these fungi
Identification and characterization of Burkholderia isolates obtained from bacterial rot of saffron (Crocus sativus L.) grown in Italy
No full textIncidenza di mal dell'esca su Cannonau, Sauvignon blanc e Cabernet sauvignon in Sardegna
No full textCHARACTERIZATION OF PSEUDOMONAS SPP. STRAINS, CAUSAL AGENTS OF CANKERS AND WILT ON STONE FRUITS IN SARDINIA.
No full textIsolations made from apricot, nectarine, peach and plum plants showing cankers on twigs, stems and branches, gum exudates, buds’ necrosis, shoots wilted, and spots on leaves allowed us to collect 94 bacterial strains. 13 of them, selected on the basis of morphology on NSA and hypersensitivity reaction on tobacco leaves, were able to infect cherry plum GF31, watermelon and marrow plantlets; two of them pepper and tomato plantlets and five of them lilac and lemon fruits. On the basis of the results obtained by Gram, catalase, Poly--hydroxybutyrate, fluorescence on KB and LOPAT tests, five strains were ascribed to Pseudomonas syringae (Ps); three to P. viridiflava (Pv); four to P. fluorescens; one was not identified. Biolog and serological agglutination tests partially confirmed the results above reported, allowing us even to ascribe three strains of Pseudomonas syringae to the pv. syringae (Pss). The fatty acid analysis of five out of thirteen isolates ascribed one of them to Ps (S.I., 0.967); one to Pv (S.I., 0.979); one to P. putida (S.I., 0.847); while two were not identified. The analysis of the thirteen strains with BOX-PCR produced 5 reaction profiles. One of them was characteristic of the type strain Pss CFBP 700. SyrB gene amplification produced the specific band of 752 bp for the three Pss strains as the type strain Pss CFBP 700, confirming their identification. In conclusion while Pss is already present in Italy in all plant species analyzed, Pv was not yet reported in Europe on apricots and nectarine
Occurrence of Phaeomoniella chlamydospora on grapevine planting material in Sardinia and effect of combined hot water and cyproconazole treatments on its control
No full textThe occurrence of Phaeomoniella chlamydospora was investigated during vine propagation in an Italian nursery, and combined hot water (HWT) and cyproconazole treatments were carried out to limit the spread of the fungus in nursery vines. In the three-year period 2005–07, cutting and graft samples (scion cv. Sangiovese, rootstock cv. 140Ru in 2005 and 1103P in 2006–07) were taken during propagation at several infection risk stages, and the occurrence of P. chlamydospora was assessed by nested PCR. In 2005 and 2006, cuttings from esca-symptomatic grapevines (scion cv. Sauvignon blanc, rootstock cv. 140Ru in 2005 and 1103P in 2006) were treated at different stages of the propagation process. In 2007, artificially infected 1103P cuttings were treated with HWT and cyproconazole after being inoculated with P. chlamydospora, and the fungus was detected by isolation on agar medium. The effect of HWT on the growth of 1103P, 779P, Sangiovese and Cabernet franc cuttings was also assessed. Despite extended wood discoloration, P. chlamydospora was scarce in nursery vines during the three-year period. The contamination of planting material may have resulted from already infected mother plants (0.0 to 6.7% of infected cuttings) or may have started during the propagation, particularly after grafting (0.0 to 23.3% of infected grafts). Canes from esca-diseased mother plants were always infected, but the incidence of infection of the cuttings varied widely (about 30% in 2005, from 1.9 to 4.1% in the other years). However, no final conclusions could be drawn about the stage or stages at which the nursery vines mainly became infected, because the infection frequencies detected in the propagation process were too low and irregular. As regards control of P. chlamydospora, HWT of cuttings performed before or after cold storage influenced plant growth, depending on both the cultivar and the growing conditions, but HWT was harmful to callused graftlings. Natural contamination of nursery material in 2005 and 2006 was insufficient to allow the effectiveness of treatments to be assessed. In 2007, HWT and cyproconzole alone did not reduce the percentage of infection in artificially inoculated cuttings. Only cyproconazole immediately followed by HWT significantly reduced the number of infected cuttings, but this procedure did not eradicate the pathogen
Spread of an atypical population of Pseudomonas savastanoi on Myrtus sp.in Sardinia.
No full textVirulent strains of the phytopathogenic bacterium Pseudomonas savastanoi induce parenchymatous galls (knots) at the site of bacterial infection. Knots are mostly seen on the young stems, branches and twigs of different plants belonging to Oleaceae (Olea, Jasminum, Forsythia, Phillyrea, Ligustrum), Fabaceae (Retama), Rhamnaceae (Rhamnus), Myrtaceae (Myrtus) or to Apocinaceae (Nerium, Mandevilla). On ash (Fraxinus spp.) P. savastanoi causes wart like excrescences.
During surveys carried out in the spring of 2010 in six locations of north-western Sardinia (Italy) on different selections of myrtle (Myrtus communis) and also on spontaneous plants, canker-like lesions of about 1 cm long were observed on branches and twigs.
From the tissues below the bark, which appeared dark brown, dried and cracked, was constantly isolated a bacterium that, on the basis of the results of biochemical tests and molecular typing methods, was identified as Pseudomonas savastanoi. Pathogenicity tests were performed with 2 isolates by placing a bacterial suspension containing 108 cfu/ml on wounds made in the bark of twigs of Myrtus communis var. tarentina. After 4 to 6 weeks the centre of the wound was surrounded by an irregular mound of new tissue. Occasionally after 2-3 months these new formed tissues had joined together over the surface of the wound. Typical “knots” were never observed. Further characterization is now in progress to better evaluate the differences that exist between the myrtle population of P. savastanoi found in Sardinia and knot inducing strains isolated from Myrtus sp. in other countries of the Mediterranean basin
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