Publicação
Rhizobiome dynamics in Pinus spp.-Fusarium circinatum interaction: host susceptibility and priming
| Resumo: | The rhizobiome (i.e. the rhizosphere microbiome) may play an important role in plant growth and defence against pathogens. Pitch canker, caused by the fungus Fusarium circinatum, infects a wide range of Pine species with different degrees of susceptibility, Pinus radiata is highly sensitive while Pinus pinea is resistant. To date, there are no suitable approaches available to control this threat, being associated with elevated economic losses to the forestry sector. Priming by chemical compounds such as phosphite, a priming agent with antifungal activity, is pointed as environmental-friendly approach to boost plant immune system. However, the relation between microbiome and host behaviour and priming was never studied in this pathosystem. Therefore, the aim of this study is to unveil the dynamics of the rhizobiome in Pinus spp. -F. circinatum interaction. Specific aims are to elucidate rhizobiome dynamics: 1) in a susceptible and in a resistant Pine species in response to F. circinatum inoculation; and 2) after phosphite application (foliarly or irrigation) in of the susceptible species. To attain these aims, two experiments were set up using 8 month-old Pinus seedlings of both species. Plants were artificially stem inoculated with 1x106 spores of the fungus. A non-inoculated control group was set up. The effect of phosphite (3%) was analyzed in P. radiata, testing two application modes (foliarly and irrigation) and included inoculated and noninoculated plants (control). For both experiments, plant symptoms were monitorized over time and sampled after 10 days, then physiological performance was assessed in needle by gasexchange parameters and antioxidant capacity. DNA was purified from the rhizosphere and used to evaluate the rhizobiome structure by 16S rRNA gene PCR-DGGE and massive parallel sequencing. The functional diversity of the community was inferred using the Piphillin software. When the two species were compared, visible symptoms were observed only in P. radiata, in parallel with significant alteration of gas-exchange parameters. Looking at species level, both rhizobiomes were significantly different, with a higher relative abundance of families known for their specific plant growth promoting traits (e.g. Nocardioidaceae, Burkholderiaceae, Xanthomonadaceae) in P. pinea. In P. pinea rhizobiome a higher abundance of genes related to the synthesis of monoterpenes, compounds with antimicrobial activity, was also estimated. However, F. circinatum inoculation had low impact on both species rhizobiome. Yet in P. radiata a higher abundance of Kofleriaceae, a family associated with plant necrotic tissues was evident after inoculation. The use of phosphite resulted in a priming effect resulting in a clear reduction in of symptomatic plants after 10 days, particularly when applied by irrigation (30%) in comparison to foliar application mode (50%). Moreover, a slight alleviation of the negative impacts on gas exchange parameters comparing to non- priming inoculated plants were observed. At rhizobiome level, phosphite significantly affected the abundance of several families, especially when applied through irrigation. This response is probably related to soil pH decrease, selecting bacteria adapted to acidic soils such as Acidimicrobiaceae, while Polyangiaceae abundance may be related to an increase in phosphorus bioavailability. In conclusion, our study compared for the first time the P. radiata and P. pinea rhizobiome, detecting significant differences that may play a role in the differential host susceptibility to F. circinatum infection. Despite the observed priming effect of phosphite, the strong impact on the plants’ rhizobiome may has further implications on plant development, which deserve further investigation. |
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| Autores principais: | Leitão, Frederico Tiago Sobral |
| Assunto: | Rhizobiome Pine Fusarium Priming Phosphite Infection trials Structure of bacterial communities Phytopathogen resistance |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | The rhizobiome (i.e. the rhizosphere microbiome) may play an important role in plant growth and defence against pathogens. Pitch canker, caused by the fungus Fusarium circinatum, infects a wide range of Pine species with different degrees of susceptibility, Pinus radiata is highly sensitive while Pinus pinea is resistant. To date, there are no suitable approaches available to control this threat, being associated with elevated economic losses to the forestry sector. Priming by chemical compounds such as phosphite, a priming agent with antifungal activity, is pointed as environmental-friendly approach to boost plant immune system. However, the relation between microbiome and host behaviour and priming was never studied in this pathosystem. Therefore, the aim of this study is to unveil the dynamics of the rhizobiome in Pinus spp. -F. circinatum interaction. Specific aims are to elucidate rhizobiome dynamics: 1) in a susceptible and in a resistant Pine species in response to F. circinatum inoculation; and 2) after phosphite application (foliarly or irrigation) in of the susceptible species. To attain these aims, two experiments were set up using 8 month-old Pinus seedlings of both species. Plants were artificially stem inoculated with 1x106 spores of the fungus. A non-inoculated control group was set up. The effect of phosphite (3%) was analyzed in P. radiata, testing two application modes (foliarly and irrigation) and included inoculated and noninoculated plants (control). For both experiments, plant symptoms were monitorized over time and sampled after 10 days, then physiological performance was assessed in needle by gasexchange parameters and antioxidant capacity. DNA was purified from the rhizosphere and used to evaluate the rhizobiome structure by 16S rRNA gene PCR-DGGE and massive parallel sequencing. The functional diversity of the community was inferred using the Piphillin software. When the two species were compared, visible symptoms were observed only in P. radiata, in parallel with significant alteration of gas-exchange parameters. Looking at species level, both rhizobiomes were significantly different, with a higher relative abundance of families known for their specific plant growth promoting traits (e.g. Nocardioidaceae, Burkholderiaceae, Xanthomonadaceae) in P. pinea. In P. pinea rhizobiome a higher abundance of genes related to the synthesis of monoterpenes, compounds with antimicrobial activity, was also estimated. However, F. circinatum inoculation had low impact on both species rhizobiome. Yet in P. radiata a higher abundance of Kofleriaceae, a family associated with plant necrotic tissues was evident after inoculation. The use of phosphite resulted in a priming effect resulting in a clear reduction in of symptomatic plants after 10 days, particularly when applied by irrigation (30%) in comparison to foliar application mode (50%). Moreover, a slight alleviation of the negative impacts on gas exchange parameters comparing to non- priming inoculated plants were observed. At rhizobiome level, phosphite significantly affected the abundance of several families, especially when applied through irrigation. This response is probably related to soil pH decrease, selecting bacteria adapted to acidic soils such as Acidimicrobiaceae, while Polyangiaceae abundance may be related to an increase in phosphorus bioavailability. In conclusion, our study compared for the first time the P. radiata and P. pinea rhizobiome, detecting significant differences that may play a role in the differential host susceptibility to F. circinatum infection. Despite the observed priming effect of phosphite, the strong impact on the plants’ rhizobiome may has further implications on plant development, which deserve further investigation. |
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