Showing papers by "Angelo Garibaldi published in 2015"
TL;DR: A wide range of secondary metabolites are involved in plant defense against pathogens and phytoalexin synthesis could be an important factor for rice resistance against bakanae disease, according to a quantitative method developed by using HPLC-MS/MS.
Abstract: Fusarium fujikuroi, the causal agent of bakanae disease, is the main seedborne pathogen on rice To understand the basis of rice resistance, a quantitative method to simultaneously detect phytohormones and phytoalexins was developed by using HPLC–MS/MS With this method dynamic profiles and possible interactions of defense-related phytohormones and phytoalexins were investigated on two rice cultivars, inoculated or not with F fujikuroi In the resistant cultivar Selenio, the presence of pathogen induced high production of phytoalexins, mainly sakuranetin, and symptoms of bakanae were not observed On the contrary, in the susceptible genotype Dorella, the pathogen induced the production of gibberellin and abscisic acid and inhibited jasmonic acid production, phytoalexins were very low, and bakanae symptoms were observed The results suggested that a wide range of secondary metabolites are involved in plant defense against pathogens and phytoalexin synthesis could be an important factor for rice resistance
55 citations
TL;DR: This work shows that the chitinase MfChi could be developed as a postharvest treatment with antimicrobial activity for fruit undergoing a short shelf life, and confirms that P. pastoris KM71 is a suitable microorganism for cost-effective large-scale production of recombinant chitInase.
51 citations
TL;DR: The following review was designed to highlight management studies that have advanced knowledge of how to minimize Fusarium diseases and to indicate areas where additional research and technological development are needed.
35 citations
TL;DR: Commercial products, and products under development, were evaluated over 2 years to assess their ability to control bacterial canker on kiwifruit under controlled conditions and copper hydroxide significantly reduced the foliar symptoms, and showed low phytotoxicity.
Abstract: The recent outbreak of bacterial canker on kiwifruit, caused by Pseudomonas syringae pv. actinidiae, has caused considerable damage to the international kiwifruit industry. Commercial products, and products under development, were evaluated over 2 years to assess their ability to control bacterial canker on kiwifruit under controlled conditions. The results were compared with two trials carried out in a kiwifruit orchard located in northern Italy during 2011 and 2012, to test the preventative efficacy of different copper formulations against P. syringae pv. actinidiae. In the greenhouse and orchard trials, copper hydroxide and the mixtures of copper hydroxide and copper oxychloride, significantly reduced the foliar symptoms by 70–80 % compared with the control, and showed low phytotoxicity. Similar efficacy was provided by acibenzolar-S-methyl, whose use has been temporarily extended to kiwifruit in Italy, with a maximum of four treatments per year. However, the product showed phytotoxicity on one-year old plants. The efficacy of fosetyl-Al was lower, particularly in the first orchard trials of 2012 and 2013. The efficacy of the other products tested never exceeded 30–40 %, and some products were not significantly different from the control. Kiwifruit plants grown in a steamed peat substrate mixed with compost obtained from digested organic matrices of municipal solid waste showed significantly fewer leaf spots compared with untreated controls. Copper compounds alternated with resistance inducers could be used in combination with compost, in order to develop new integrated control strategies to reduce the disease development and spread.
32 citations
TL;DR: In vitro assay is a useful tool to predict the possible mycotoxin contamination under field and greenhouse conditions and good correlation between in vitro and in vivo production was observed.
Abstract: Fungi belonging to the genus Alternaria are common pathogens of fruit and vegetables with some species able to produce secondary metabolites dangerous to human health. Twenty-eight Alternaria isolates from rocket and cabbage were investigated for their mycotoxin production. Five different Alternaria toxins were extracted from synthetic liquid media and from plant material (cabbage, cultivated rocket, cauliflower). A modified Czapek-Dox medium was used for the in vitro assay. Under these conditions, more than 80% of the isolates showed the ability to produce at least one mycotoxin, generally with higher levels for tenuazonic acid. However, the same isolates analyzed in vivo seemed to lose their ability to produce tenuazonic acid. For the other mycotoxins; alternariol, alternariol monomethyl ether, altenuene and tentoxin a good correlation between in vitro and in vivo production was observed. In vitro assay is a useful tool to predict the possible mycotoxin contamination under field and greenhouse conditions.
29 citations
TL;DR: The integrated analysis confirmed the presence of virulence variation and genetic diversity among the F. oxysporum f.
Abstract: Twenty-seven isolates of Fusarium oxysporum f. sp. eustomae obtained from diseased Eustoma grandiflorum (lisianthus) plants in north Italy, showing typical fusarium wilt symptoms, were studied for genetic diversity, pathogenicity, and vegetative compatibility (VC). The strains were examined for differences in the nucleotide sequence of translation elongation factor 1-α (tef) and two endopolygalacturonase genes (pg1 and pg5). The phylogenetic analysis performed on the isolates enabled the identification of three main groups, named I, II, and III, and two subgroups (Ia and Ib). In pg1 and pg5 sequences, most of nucleotide variations resulted in aminoacid variations, while in tef most of SNPs are in the introns or are silent. By considering the virulence of the strains included in Group I, a low virulence could be observed, Group II and III showed a reduced virulence at 30 °C compared to 20 °C. Some cultivars showed higher tolerance at 30 °C. Principal component analysis (PCA) performed on pathogenicity values, confirmed the three molecular clusters. VC identified two VCGs (vegetative compatibility groups) in Group II, one VCG in Group III, and vegetatively incompatible isolates grouped together in Group I. The integrated analysis confirmed the presence of virulence variation and genetic diversity among the F. oxysporum f. sp. eustomae isolates studied.
27 citations
TL;DR: The results show that global climate changes could influence disease incidence, probably through plant-mediated effects, caused by soilborne pathogens.
Abstract: The severity of F. oxysporum f.sp. conglutinans on rocket plants grown under simulated climate change conditions has been studied. The rocket plants were cultivated on an infested substrate (4 log CFU g-1) and a non-infested substrate over three cycles. Pots were placed in six phytotrons in order to simulate different environmental conditions: 1) 400–450 ppm CO2, 18–22°C; 2) 800–850 ppm CO2, 18–22°C; 3) 400–450 ppm CO2, 22–26°C, 4) 800–850 ppm CO2, 22–26°C, 5) 400–450 ppm CO2, 26–30°C; 6) 800–850 ppm CO2, 26–30°C. Substrates from the infested and control samples were collected from each phytotron at 0, 60 and 120 days after transplanting. The disease index, microbial abundance, leaf physiological performances, root exudates and variability in the fungal profiles were monitored. The disease index was found to be significantly influenced by higher levels of temperature and CO2. Plate counts showed that fungal and bacterial development was not affected by the different CO2 and temperature levels, but a significant decreasing trend was observed from 0 up to 120 days. Conversely, the F. oxysporum f.sp. conglutinans plate counts did not show any significantly decrease from 0 up to 120 days. The fungal profiles, evaluated by means of polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE), showed a relationship to temperature and CO2 on fungal diversity profiles. Different exudation patterns were observed when the controls and infested plants were compared, and it was found that both CO2 and temperature can influence the release of compounds from the roots of rocket plants. In short, the results show that global climate changes could influence disease incidence, probably through plant-mediated effects, caused by soilborne pathogens.
27 citations
01 Jan 2015
TL;DR: The use of Brassica species as green manure is considered a type of biofumigation that involves the release of volatile and toxic compounds as discussed by the authors, which can help to control soilborne pathogens in vegetable and ornamental crops.
Abstract: Organic amendments are an important tool for the management of diseases of vegetable and ornamental crops. They include manure, crop and food residues, compost and organic fertilisers. Their use can help to control soilborne pathogens in vegetable and ornamental crops, especially when applied in conjunction with other management practices and considering a system approach. Composts and Brassica pellets are considered those more promising. The use of Brassica species as green manure is considered a type of biofumigation that involves the release of volatile and toxic compounds. Compost involves different modes of actions, mainly correlated to its microbial community and the presence of biological control agents. Organic amendments can be successfully integrated with other control strategies, like soil solarisation and grafting on resistant rootstocks, to control soilborne pathogens affecting vegetable crops in field conditions. Another possibility is their application mixed in potting soils, which is of particular interest for ornamental crops.
19 citations
TL;DR: In vitro evaluation was carried out on seed samples of wild and cultivated rocket cultivars, most frequently grown in Italy, and obtained from farms affected by the leaf spot caused by Alternaria japonica in Piedmont and Lombardy during the fall of 2010, finding that A. japonica obtained from seeds were pathogenic on both wild and cultivating rocket.
Abstract: In vitro evaluation was carried out on seed samples of wild and cultivated rocket cultivars, most frequently grown in Italy, and obtained from farms affected by the leaf spot caused by Alternaria japonica in Piedmont and Lombardy during the fall of 2010 Twelve seed samples were collected and assayed for the presence of A japonica The pathogen was isolated only from not disinfected seeds Among the two seed samples of cultivated rocket (Eruca vesicaria), only one was infected by A japonica at a level of one infected seed out of 800 Four out of ten samples of wild (Diplotaxis tenuifolia) rocket seeds were contaminated by A japonica with the highest level of infection detected in a single sample of 3 out of 800 All tested isolates of A japonica obtained from seeds were pathogenic on both wild and cultivated rocket
15 citations
TL;DR: Considering the difficulty in reaching a complete disease management level against P. cucumerina, an integrated approach should be considered, and the most effective treatment in terms of disease severity reduction did not always provide a better response in plant biomass.
11 citations
TL;DR: Seed dressing represents the starting point of a full integrated approach for downy mildew management and thiram is also effective against other pathogens affecting basil and the thermal treatment and potassium phosphite are fully compatible with the rules of organic farming.
Abstract: Four experimental trials were carried out in order to evaluate the efficacy of different products (chemicals, resistance inducers and natural products) as well as heat air when applied to basil seeds naturally infested by Peronospora belbahrii, the causal agent of downy mildew of basil, a pathogen which is seed transmitted. Seed quality, as vigour index, was also evaluated. In general, seed treatment had a positive effect on the reduction of disease incidence and on plant biomass at the end of each trial, with very satisfactory results when disease incidence was lower than 10% and still satisfactory results with a higher disease incidence. Although many of the fungicides, resistance inducers and thyme oil treatments tested showed a significant disease reduction compared with the untreated control, the protection offered was only partial. Moreover, the effectiveness of the tested seed treatments varied considerably between the trials. The seeds treatment with heat air (65°C for 10 min) significantly reduced the number of infected plants per container. The interaction effect between the fungicides (at the lowest dosage tested, with the exception of acibenzolar-S-methyl, and dimethomorph), thyme oil and the heat air treatment was also significant. In terms of biomass, most treatments not significantly improved the fresh weight in comparison with the untreated control. The highest biomass was observed in the plots where seeds were dressed with mancozeb combined with heat air. Interestingly, thiram is also effective against other pathogens affecting basil and the thermal treatment and potassium phosphite are fully compatible with the rules of organic farming. Seed dressing represents the starting point of a full integrated approach for downy mildew management.
TL;DR: The phylogenetic analysis and positive pathogenicity tests permits us to introduce a new forma specialis named F. oxysporum f.
Abstract: Symptoms of a new vascular wilt were observed on several plants of Papaver nudicaule cultivated at the Regional Institute for Floriculture in Sanremo and in a nursery near Ventimiglia, Liguria region, Northern Italy. Morphology and ITS sequence analysis characterize the pathogen as Fusarium oxysporum . To identify the forma specialis , eight isolates obtained from infected tissues were used for a phylogenetic analysis based on translation elongation factor 1-α ( EF-1α ) gene and four polygalacturonase genes ( Pg1 , Pg5 , Pgx1 and Pgx4 ). After amplification by PCR, the gene sequences were aligned with corresponding sequences from other formae speciales of Fusarium oxysporum obtained from GenBank databases in order to build phylogenetic trees. Results obtained for each genomic region showed that the isolates derived from P. nudicaule form a unique group well separated from other formae speciales . To our knowledge, this is the first report of F. oxysporum on P. nudicaule and together with the phylogenetic analysis and positive pathogenicity tests permits us to introduce a new forma specialis named F. oxysporum f. sp. papaveris.
TL;DR: A new forma specialis is suggested, here named F. oxysporum f.
Abstract: analysis based on the ITS region confirmed the pathogen as Fusarium oxysporum . In order to identify the forma specialis , thirteen isolates obtained from infected tissues were used for phylogenetic analysis based on four polygalacturonase genes ( Pg1 , Pg5 , Pgx1 and Pgx4 ) together with the translation elongation factor 1-alpha ( EF-1alpha ) gene. Sequences generated in this study were aligned with other formae speciales of Fusarium oxysporum from GenBank to construct phylogenetic trees. Eleven isolates of a new forma specialis, Fusarium oxysporum f. sp. crassulae described on C rassula ovata , were added to the analysis based on Pg5 and Pgx1 genes. The results obtained for each genomic region showed that the isolates derived from E. agavoides are in a unique group well separated from other formae speciales already described. The first report of F. oxysporum on E. agavoides together with the results obtained in this study suggest a new forma specialis , here named F. oxysporum f. sp. echeveriae.
TL;DR: In 2011, a new Fusarium wilt of Papaver nudicaule was observed in a commercial nursery near Ventimiglia as well as in the Regional Institute of Floriculture of Sanremo (Imperia province, northern Italy) and molecular analysis enabled identification of the causal agent as a new forma specialis called FUSarium oxysporum f.
Abstract: In 2011, a new Fusarium wilt of Papaver nudicaule was observed in a commercial nursery near Ventimiglia (Imperia province, northern Italy) as well as in the Regional Institute of Floriculture (I.R.F.) of Sanremo (Imperia province, northern Italy). Molecular analysis enabled identification of the causal agent as a new forma specialis called Fusarium oxysporum f. sp. papaveris. The origin of the infection was found on P. nudicaule seeds. However, disinfection with sodium hypochlorite was able to eliminate the pathogen infection. Virulence of ten isolates obtained from seeds was evaluated by pathogenicity assay. The more virulent strains were analyzed by phylogenetic analysis on the basis of the EF-1α, pg1 and pgx4 genes. Sequences obtained by PCR amplification were aligned with other formae speciales of Fusarium oxysporum from the GenBank and used in the construction of the phylogenetic trees. Seed infections have been observed in the case of many vegetable crops; however, this phenomenon has been less studied in the case of ornamental crops. As a consequence of seed exchanges or transmission via infected seeds, new and old pathogenic species of Fusarium are continuously introduced into new areas and production systems.
TL;DR: In the autumn of 2014, in a commercial farm at Albenga (northern Italy), a new disease was observed on 5-month-old potted plants of butterfly lavander (Lavandula stoechas).
Abstract: In the autumn of 2014, in a commercial farm at Albenga (northern Italy), a new disease was observed on 5-month-old potted plants of butterfly lavander (Lavandula stoechas). Initial symptoms consisted of stem necrosis, darkening and withering of the leaves followed by wiltinig of the plants. In the presence of high relative humidity, the lesions became covered with a whitish mycelium which produced irregular dark grey sclerotia 2.0-7.5×1.5-4.0 mm in size. From infected stem pieces placed on potato dextrose agar (PDA) whitish fungal colonies developed, which produced sclerotia measuring 0.6-3.0×0.6-2.7 mm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced (GenBank accession No. KP792750). BLAST analysis (Altschul et al., 1997) of the 492 bp amplified sequence showed a 99% homology with the sequence of Sclerotinia sclerotiorum (JX442064). The pathogenicity of one fungal isolate was tested by placing mycelium and sclerotia grown on autoclaved wheat kernels at the base of three healthy plants of L. stoechas. Control plants were inoculated with autoclaved wheat kernels alone. All the plants were covered with plastic bags and maintained at 25±1°C. First symptoms, consisting of stem necrosis and leaf withering, appeared on inoculated plants five days post inoculation Whereas S. sclerotiorum was constantly reisolated from symptomatic plants, controls remained symptomless. To the best of our knowledge, this is the first report of S. sclerotiorum on L. stoechas in Italy as well as worldwide.