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A novel virus that infecting hypovirulent strain XG36-1 of plant fungal pathogen Sclerotinia sclerotiorum.

Zhang L, Fu Y, Xie J, Jiang D, Li G, Yi X - Virol. J. (2009)

Bottom Line: Hypovirulence is a phenomenon where the virulence of fungal pathogens is decreased, even lost, due to mycovirus infection.Furthermore, the viral particles could be co-transmitted with the hypovirulence traits through hyphal anastomosis.Currently, we could not know the characteristic of this virus, but it likely represent a new type of mycovirus in S. sclerotiorum, and possibly in fungi.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, Hubei Province, PR China. zhangliyan@webmail.hzau.edu.cn

ABSTRACT

Background: Sclerotinia sclerotiorum is a notorious plant fungal pathogen which spreads across the world. Hypovirulence is a phenomenon where the virulence of fungal pathogens is decreased, even lost, due to mycovirus infection. The potential of hypoviruses for biological control of the chestnut blight fungus (Cryphonectria parasitica) has attracted much interest, and has led to discovery of new hypovirulent strains in other fungi.

Results: A hypovirulent strain, strain XG36-1, was isolated from a typical lesion on the stem of rapeseed (Brassica napus) caused by Sclerotinia sclerotiorum. Strain XG36-1 grew on PDA very slowly (average 2.5 +/- 0.1 mm/d) with sectoring, and developed abnormal colony morphology with few sclerotia. Unlike health strains (such as wildtype strain XG-13), it was unable to induce lesions on detached leaves of rapeseed. Sclerotia of strain XG36-1 produced apothecia rarely. A sexual progeny test showed that the phenotypes of all 104 sexual progeny were not different from wildtype strain XG-13 which shows normal phenotype of S. sclerotiorum, and protoplast regeneration tests showed that 25.5% of the regenerants of strain XG36-1 were recovered fully. Furthermore, the hypovirulence and its associated traits could be transmitted to XG36-1A34R, a hygromycin-resistance gene labelled sexual progeny of strain XG36-1, by hyphal anastomosis. Transmission electron microscope (TEM) observation showed that the cytoplasm of strain XG36-1 was destroyed and granulated; the membranes of nuclei and mitochondria were disintegrated; and mitochondrial cristae were cavitated. Viral particles (about 40 nm) in hyphae of strain XG36-1, but not in its sexual progeny and wildtype strain XG-13, could be observed with TEM, and several virus-like particles were uniquely enveloped by single layer membrane in the cells of strain XG36-1. Furthermore, the viral particles could be co-transmitted with the hypovirulence traits through hyphal anastomosis.

Conclusion: Hypovirulence and its associated traits of strain XG36-1 could be mediated by a fungal virus. Currently, we could not know the characteristic of this virus, but it likely represent a new type of mycovirus in S. sclerotiorum, and possibly in fungi.

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Diverse phenotypes of protoplast regenarants of S. sclerotiorum hypovirulent strain XG36-1. A, three types of colony morphologies, namely Type I, Type IIand Type III, were developed on PDA plate at 20–22 C for 15 days. Regenarants in Type Iwere not significantly different from wildtype strain XG-13, while regenarants in Type III were similar to strain XG36-1 (see Figure 1), Type II were intermediate type between Type Iand Type III. B and C, comparison of the hyphal growth rate on PDA plate and virulence on detached rapeseed leaves among three types of regenarants. The growth and virulence of regenarants in TypeI were fully recovered, and that in Type II were partially recovered; the growth and virulence of regenarants in Type III was not significantly different from strain XG36-1.
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Figure 2: Diverse phenotypes of protoplast regenarants of S. sclerotiorum hypovirulent strain XG36-1. A, three types of colony morphologies, namely Type I, Type IIand Type III, were developed on PDA plate at 20–22 C for 15 days. Regenarants in Type Iwere not significantly different from wildtype strain XG-13, while regenarants in Type III were similar to strain XG36-1 (see Figure 1), Type II were intermediate type between Type Iand Type III. B and C, comparison of the hyphal growth rate on PDA plate and virulence on detached rapeseed leaves among three types of regenarants. The growth and virulence of regenarants in TypeI were fully recovered, and that in Type II were partially recovered; the growth and virulence of regenarants in Type III was not significantly different from strain XG36-1.

Mentions: Fifty-five protoplast regenerants of strain XG36-1 were obtained. Their growth rates, colony morphology and pathogenicity were tested, and the results showed that the phenotypes of these regenerants were significantly diverse. Based on growth rate and colony morphology, these regenerants could divide into three groups, namely TypeI, TypeII and Type III. Type I regenerants grew on PDA just like wildtype strain XG-13, developing normal colony morphology of S. sclerotiorum, and capable of inducing typical lesions on detached leaves of rapeseed (Fig 2). Approximately 25.5% of the regenerants (14/55) belonged to Type I. Type II regenerants grew on PDA much faster than hypovirulent parental strain XG36-1, but slower than wildtype strain XG-13. These regenerants could cover an entire 9-cm-diam. PDA plate by 14 days with an average growth rate of 9.7 mm/d. These regenerants could induce small lesions on detached leaves with an average size of 1.0 cm across (Fig 2). Approximately 23.8% of the regenerants (13/55) belonged to type II. Type III regenerants were not significantly different from hypovirulent parental strain XG36-1 (Fig 2), comprising 51.7% of the regenerants (28/55).


A novel virus that infecting hypovirulent strain XG36-1 of plant fungal pathogen Sclerotinia sclerotiorum.

Zhang L, Fu Y, Xie J, Jiang D, Li G, Yi X - Virol. J. (2009)

Diverse phenotypes of protoplast regenarants of S. sclerotiorum hypovirulent strain XG36-1. A, three types of colony morphologies, namely Type I, Type IIand Type III, were developed on PDA plate at 20–22 C for 15 days. Regenarants in Type Iwere not significantly different from wildtype strain XG-13, while regenarants in Type III were similar to strain XG36-1 (see Figure 1), Type II were intermediate type between Type Iand Type III. B and C, comparison of the hyphal growth rate on PDA plate and virulence on detached rapeseed leaves among three types of regenarants. The growth and virulence of regenarants in TypeI were fully recovered, and that in Type II were partially recovered; the growth and virulence of regenarants in Type III was not significantly different from strain XG36-1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2714488&req=5

Figure 2: Diverse phenotypes of protoplast regenarants of S. sclerotiorum hypovirulent strain XG36-1. A, three types of colony morphologies, namely Type I, Type IIand Type III, were developed on PDA plate at 20–22 C for 15 days. Regenarants in Type Iwere not significantly different from wildtype strain XG-13, while regenarants in Type III were similar to strain XG36-1 (see Figure 1), Type II were intermediate type between Type Iand Type III. B and C, comparison of the hyphal growth rate on PDA plate and virulence on detached rapeseed leaves among three types of regenarants. The growth and virulence of regenarants in TypeI were fully recovered, and that in Type II were partially recovered; the growth and virulence of regenarants in Type III was not significantly different from strain XG36-1.
Mentions: Fifty-five protoplast regenerants of strain XG36-1 were obtained. Their growth rates, colony morphology and pathogenicity were tested, and the results showed that the phenotypes of these regenerants were significantly diverse. Based on growth rate and colony morphology, these regenerants could divide into three groups, namely TypeI, TypeII and Type III. Type I regenerants grew on PDA just like wildtype strain XG-13, developing normal colony morphology of S. sclerotiorum, and capable of inducing typical lesions on detached leaves of rapeseed (Fig 2). Approximately 25.5% of the regenerants (14/55) belonged to Type I. Type II regenerants grew on PDA much faster than hypovirulent parental strain XG36-1, but slower than wildtype strain XG-13. These regenerants could cover an entire 9-cm-diam. PDA plate by 14 days with an average growth rate of 9.7 mm/d. These regenerants could induce small lesions on detached leaves with an average size of 1.0 cm across (Fig 2). Approximately 23.8% of the regenerants (13/55) belonged to type II. Type III regenerants were not significantly different from hypovirulent parental strain XG36-1 (Fig 2), comprising 51.7% of the regenerants (28/55).

Bottom Line: Hypovirulence is a phenomenon where the virulence of fungal pathogens is decreased, even lost, due to mycovirus infection.Furthermore, the viral particles could be co-transmitted with the hypovirulence traits through hyphal anastomosis.Currently, we could not know the characteristic of this virus, but it likely represent a new type of mycovirus in S. sclerotiorum, and possibly in fungi.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, Hubei Province, PR China. zhangliyan@webmail.hzau.edu.cn

ABSTRACT

Background: Sclerotinia sclerotiorum is a notorious plant fungal pathogen which spreads across the world. Hypovirulence is a phenomenon where the virulence of fungal pathogens is decreased, even lost, due to mycovirus infection. The potential of hypoviruses for biological control of the chestnut blight fungus (Cryphonectria parasitica) has attracted much interest, and has led to discovery of new hypovirulent strains in other fungi.

Results: A hypovirulent strain, strain XG36-1, was isolated from a typical lesion on the stem of rapeseed (Brassica napus) caused by Sclerotinia sclerotiorum. Strain XG36-1 grew on PDA very slowly (average 2.5 +/- 0.1 mm/d) with sectoring, and developed abnormal colony morphology with few sclerotia. Unlike health strains (such as wildtype strain XG-13), it was unable to induce lesions on detached leaves of rapeseed. Sclerotia of strain XG36-1 produced apothecia rarely. A sexual progeny test showed that the phenotypes of all 104 sexual progeny were not different from wildtype strain XG-13 which shows normal phenotype of S. sclerotiorum, and protoplast regeneration tests showed that 25.5% of the regenerants of strain XG36-1 were recovered fully. Furthermore, the hypovirulence and its associated traits could be transmitted to XG36-1A34R, a hygromycin-resistance gene labelled sexual progeny of strain XG36-1, by hyphal anastomosis. Transmission electron microscope (TEM) observation showed that the cytoplasm of strain XG36-1 was destroyed and granulated; the membranes of nuclei and mitochondria were disintegrated; and mitochondrial cristae were cavitated. Viral particles (about 40 nm) in hyphae of strain XG36-1, but not in its sexual progeny and wildtype strain XG-13, could be observed with TEM, and several virus-like particles were uniquely enveloped by single layer membrane in the cells of strain XG36-1. Furthermore, the viral particles could be co-transmitted with the hypovirulence traits through hyphal anastomosis.

Conclusion: Hypovirulence and its associated traits of strain XG36-1 could be mediated by a fungal virus. Currently, we could not know the characteristic of this virus, but it likely represent a new type of mycovirus in S. sclerotiorum, and possibly in fungi.

Show MeSH
Related in: MedlinePlus