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Salvatore Moricca – One of the best experts on this subject based on the ideXlab platform.

  • antagonism of the two needle pine stem rust fungi cronartium flaccidum and peridermium pini by cladosporium tenuissimum in vitro and in planta
    Phytopathology, 2001
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Gemma Assante
    Abstract:

    Selected isolates of Cladosporium tenuissimum were tested for their ability to inhibit in vitro Aeciospore germination of the two-needle pine stem rusts Cronartium flaccidum and Peridermium pini and to suppress disease development in planta. The antagonistic fungus displayed a number of disease-suppressive mechanisms. Aeciospore germination on water agar slides was reduced at 12, 18, and 24 h when a conidial suspension (1.5 x 10(7) conidia per ml) of the Cladosporium tenuissimum isolates was added. When the Aeciospores were incubated in same-strength conidial suspensions for 1, 11, 21, and 31 days, viability was reduced at 20 and 4 degreesC. Light and scanning electron microscopy showed that rust spores were directly parasitized by Cladosporium tenuissimum and that the antagonist had evolved several strategies to breach the spore wail and gain access to the underlying tissues. Penetration occurred with or without appressoria. The hyperparasite exerted a mechanical force to destroy the spore structures (spinules, cell wall) by direct contact, penetrated the Aeciospores and subsequently proliferated within them. However, an enzymatic action could also be involved. This was shown by the dissolution of the host tell wall that comes in contact with the mycelium of the mycoparasite, by the lack of indentation in the host wall at the contact site, and by the minimal swelling at the infecting hyphal tip. Culture filtrates of the hyperparasite inhibited germination of rust propagules. A compound purified from the filtrates was characterized by chemical and spectroscopic analysis as cladosporol, a known beta -1,3-glucan biosynthesis inhibitor. Conidia of Cladosporium tenuissimum reduced rust development on new infected pine seedlings over 2 years under greenhouse conditions. Because the fungus is an aggressive mycoparasite, produces fungicidal metabolites, and can survive and multiply in forest ecosystems without rusts, it seems a promising agent for the biological control of pine stem rusts in Europe.

  • Heterogeneity in intergenic regions of the ribosomal repeat of the pine-blister rusts Cronartium flaccidum and Peridermium pini
    Current genetics, 1996
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Takao Kasuga, Stephanos Diamandis
    Abstract:

    Mixed Aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed Aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini.

  • Heterogeneity in intergenic regions of the ribosomal repeat of the pine-blister rustsCronartium flaccidum andPeridermium pini
    Current Genetics, 1996
    Co-Authors: Salvatore Moricca, Keith Mitchelson, Takao Kasuga, Alessandro Ragazzi, Stephanos Diamandis
    Abstract:

    Mixed Aeciospore isolates of Cronartium flaccidum and Peridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8 s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar between C. flaccidum and P. pini . Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed Aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms of C. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual form C. flaccidum , than in the monoaecious form P. pini .

Roland W.s. Weber – One of the best experts on this subject based on the ideXlab platform.

  • Identification and quantification of carotenoid pigments in Aeciospores of the daisy rust fungus, Puccinia distincta.
    Phytochemistry, 2002
    Co-Authors: Paolo Davoli, Roland W.s. Weber
    Abstract:

    Abstract The yellow-orange colour of Aeciospores of the daisy rust fungus, Puccinia distincta , was found to be due to the carotenoid pigments β,ψ-carotene (γ-carotene) and β,β-carotene (β-carotene), which were identified by means of HPLC–APCI-MS. The combined concentration of β- and γ-carotene in the Aeciospores was 3.3×10 −15 mol spore −1 or 6 mol% mol −1 total fatty acids. This concentration is sufficient for a postulated antioxidant role of carotenoids as free radical scavengers.

  • Autophagocytosis of carotenoid-rich lipid droplets into vacuoles during Aeciospore ageing in Puccinia distincta
    New Phytologist, 2002
    Co-Authors: Roland W.s. Weber, Paolo Davoli
    Abstract:

    Summary •  Aeciospores of rust fungfungi contain numerous lipid droplets (LDs) which are stained yellow due to the presence of β-and γ-carotene, thereby facilitating observations of their fate during developmental processes. •  The ageing process of Aeciospores of Puccinia distincta was examined by light and transmission elecelectron microscopy. •  The cytoplasm of freshly harvested spores was filled with LDs but devoid of vacuoles. Within 12 h, numerous small vacuoles developed, and the LDs became associated with their cytoplasmic tonoplast surface. The vacuoles enlarged and fused together; they were also the destination of endocytotic uptake of the vital dye, Neutral Red. Within 36 h, LDs entered these vacuoles by autophagocytosis and were degraded in the vacuolar lumen. After 96 h, most lipid reserves had been used up and the highly vacuolated spores lost viability as indicated by their failure to germinate or take up Neutral Red. •  Spore maturation by vacuolation thus seems to occur at the direct expense of metabolic energy stored as LDs and is an extremely rapid process in Aeciospores of P. distincta.

  • Puccinia distincta, cause of the current daisy rust epidemic in Britain, in comparison with other rusts recorded on daisies, P. obscura and P. lagenophorae
    Mycological Research, 1998
    Co-Authors: Roland W.s. Weber, John Webster, Dunia H. Al-gharabally
    Abstract:

    Three British rust fungfungi reported to form aecia on daisy ( Bellis perennis ) are compared. A recently discovered species, possibly introduced from Australia, is identified as Puccinia distincta. It is a short-cycled – opsis form lacking uredinia, with aecia and telia confined to Bellis and its Aeciospores capable of reinfecting the same host. This rust is compared with a macrocyclic heteroecious eu -form, P. obscura , which produces pycnia and aecia on Bellis and uredinia and telia on Luzula. Puccinia distincta is probably derived from and correlated with P. obscura because both species have the same aecial host, and because their teliospores are closely similar in morphology and dimensions. Comparison is extended to P. lagenophorae , a common rust with aecia and telia on Senecio spp., which has been reported to form aecia on Bellis following inoculation with Aeciospores from Senecio. The repeated failure of our own reciprocal inoculation experiments using Aeciospores from the two different hosts and differences in teliospore morphology between P. distincta and P. lagenophorae lead us to conclude that the current rust epidemic on daisies is caused by P. distincta which is distinct from P. lagenophorae.

Keith Mitchelson – One of the best experts on this subject based on the ideXlab platform.

  • antagonism of the two needle pine stem rust fungi cronartium flaccidum and peridermium pini by cladosporium tenuissimum in vitro and in planta
    Phytopathology, 2001
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Gemma Assante
    Abstract:

    Selected isolates of Cladosporium tenuissimum were tested for their ability to inhibit in vitro Aeciospore germination of the two-needle pine stem rusts Cronartium flaccidum and Peridermium pini and to suppress disease development in planta. The antagonistic fungus displayed a number of disease-suppressive mechanisms. Aeciospore germination on water agar slides was reduced at 12, 18, and 24 h when a conidial suspension (1.5 x 10(7) conidia per ml) of the Cladosporium tenuissimum isolates was added. When the Aeciospores were incubated in same-strength conidial suspensions for 1, 11, 21, and 31 days, viability was reduced at 20 and 4 degreesC. Light and scanning electron microscopy showed that rust spores were directly parasitized by Cladosporium tenuissimum and that the antagonist had evolved several strategies to breach the spore wail and gain access to the underlying tissues. Penetration occurred with or without appressoria. The hyperparasite exerted a mechanical force to destroy the spore structures (spinules, cell wall) by direct contact, penetrated the Aeciospores and subsequently proliferated within them. However, an enzymatic action could also be involved. This was shown by the dissolution of the host tell wall that comes in contact with the mycelium of the mycoparasite, by the lack of indentation in the host wall at the contact site, and by the minimal swelling at the infecting hyphal tip. Culture filtrates of the hyperparasite inhibited germination of rust propagules. A compound purified from the filtrates was characterized by chemical and spectroscopic analysis as cladosporol, a known beta -1,3-glucan biosynthesis inhibitor. Conidia of Cladosporium tenuissimum reduced rust development on new infected pine seedlings over 2 years under greenhouse conditions. Because the fungus is an aggressive mycoparasite, produces fungicidal metabolites, and can survive and multiply in forest ecosystems without rusts, it seems a promising agent for the biological control of pine stem rusts in Europe.

  • Heterogeneity in intergenic regions of the ribosomal repeat of the pine-blister rusts Cronartium flaccidum and Peridermium pini
    Current genetics, 1996
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Takao Kasuga, Stephanos Diamandis
    Abstract:

    Mixed Aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed Aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini.

  • Heterogeneity in intergenic regions of the ribosomal repeat of the pine-blister rustsCronartium flaccidum andPeridermium pini
    Current Genetics, 1996
    Co-Authors: Salvatore Moricca, Keith Mitchelson, Takao Kasuga, Alessandro Ragazzi, Stephanos Diamandis
    Abstract:

    Mixed Aeciospore isolates of Cronartium flaccidum and Peridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8 s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar between C. flaccidum and P. pini . Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed Aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms of C. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual form C. flaccidum , than in the monoaecious form P. pini .

A Ragazzi – One of the best experts on this subject based on the ideXlab platform.

  • antagonism of the two needle pine stem rust fungi cronartium flaccidum and peridermium pini by cladosporium tenuissimum in vitro and in planta
    Phytopathology, 2001
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Gemma Assante
    Abstract:

    Selected isolates of Cladosporium tenuissimum were tested for their ability to inhibit in vitro Aeciospore germination of the two-needle pine stem rusts Cronartium flaccidum and Peridermium pini and to suppress disease development in planta. The antagonistic fungus displayed a number of disease-suppressive mechanisms. Aeciospore germination on water agar slides was reduced at 12, 18, and 24 h when a conidial suspension (1.5 x 10(7) conidia per ml) of the Cladosporium tenuissimum isolates was added. When the Aeciospores were incubated in same-strength conidial suspensions for 1, 11, 21, and 31 days, viability was reduced at 20 and 4 degreesC. Light and scanning electron microscopy showed that rust spores were directly parasitized by Cladosporium tenuissimum and that the antagonist had evolved several strategies to breach the spore wail and gain access to the underlying tissues. Penetration occurred with or without appressoria. The hyperparasite exerted a mechanical force to destroy the spore structures (spinules, cell wall) by direct contact, penetrated the Aeciospores and subsequently proliferated within them. However, an enzymatic action could also be involved. This was shown by the dissolution of the host tell wall that comes in contact with the mycelium of the mycoparasite, by the lack of indentation in the host wall at the contact site, and by the minimal swelling at the infecting hyphal tip. Culture filtrates of the hyperparasite inhibited germination of rust propagules. A compound purified from the filtrates was characterized by chemical and spectroscopic analysis as cladosporol, a known beta -1,3-glucan biosynthesis inhibitor. Conidia of Cladosporium tenuissimum reduced rust development on new infected pine seedlings over 2 years under greenhouse conditions. Because the fungus is an aggressive mycoparasite, produces fungicidal metabolites, and can survive and multiply in forest ecosystems without rusts, it seems a promising agent for the biological control of pine stem rusts in Europe.

  • Heterogeneity in intergenic regions of the ribosomal repeat of the pine-blister rusts Cronartium flaccidum and Peridermium pini
    Current genetics, 1996
    Co-Authors: Salvatore Moricca, A Ragazzi, Keith Mitchelson, Takao Kasuga, Stephanos Diamandis
    Abstract:

    Mixed Aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed Aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini.

  • axenic culture of the aecial state of cronartium flaccidum from italy
    Fungal Biology, 1994
    Co-Authors: Salvatore Moricca, A Ragazzi
    Abstract:

    Axenic cultures of Cronartium flaccidum were obtained for the first time by seeding Aeciospores on modified Schenk and Hildebrandt’s and Harvey and Grasham’s media. Aeciospores came from foci at four locations in Italy. Colonies developed more readily on thickly seeded plates. High variation was observed in hyphal length and morphology, and in colony appearance, margin and morphology. The appearance and morphology of individual colonies also varied greatly over the five-month incubation period.

Peterg. Ayres – One of the best experts on this subject based on the ideXlab platform.

  • Changes in tissue freezing in Senecio vulgaris infected by Rust (Puccinia lagenophorae)
    Annals of Botany, 1991
    Co-Authors: Nigel D Paul, Peterg. Ayres
    Abstract:

    Freezing of healthy and rust (Puccinia lagenophorae) infected leaves of Senecio vulgaris was compared calorimetrically by thermal analysis. In fully expanded leaves the threshold freezing temperature was in the range −6.8 to −8.4 °C in controls but −3.0 to −5.1 °C in leaves with sporulating rust sori. Comparable values in expanding leaves were −5.0 to −8.9 °C and −3.9 to −6.7 °C for healthy and rusted tissues, respectively. The bulk tissue freezing point was between −1.0 and −4.0 °C in both fully expanded and expanding healthy leaves, and was increased by infection by between +0.2 and 2.5 °C. Whereas healthy leaves supercooled by 3.1−5.8 °C, rusted leaves supercooled by only 1.8−4.9 °C Supercooling of control leaves was reduced by dusting with Aeciospores, particularly when leaves were wounded to simulate the rupture of the surface caused by sporulation, but wounding alone had no significant effect. Supercooling of distilled water was also significantly reduced by Aeciospores, suspended at a concentration of 105 spores ml−1. It is concluded that rust-induced changes in leaf freezing in S. vulgaris grown in controlled environments were due to an increase in the number of sites for ice nucleation, caused by the presence of the Aeciospores, and increased penetration of ice into internal tissues, resulting from damage to the cuticle and epidermis. Although data for frost resistance obtained in the growth-room are similar to previous field observations, the role of the above mechanisms under field conditions remains unproven.