Tesi etd-03302024-123812
Link copiato negli appunti
Tipo di tesi
Dottorato
Autore
MARRASSINI, VALENTINA
URN
etd-03302024-123812
Titolo
Drivers of cereal productivity: plant genotype, environment, diversity of arbuscular mycorrhizal fungal inoculum and organic amendment
Settore scientifico disciplinare
AGR/02
Corso di studi
Istituto di Scienze della Vita - PHD IN AGROBIOSCIENZE
Commissione
relatore Prof.ssa MENSUALI, ANNA
Parole chiave
- arbuscular mycorrhizal symbiosis
- biochar
- compost
- fungal diversity
- fungal infectivity
- intraspecific functional diversity
- nutrient uptake
- plant benefits
Data inizio appello
09/07/2024;
Disponibilità
parziale
Riassunto analitico
Long-term heavy application of mineral fertilizers in combination with low crop nutrient use efficiency results in severe environmental and economic issues such as decreases in soil quality and biodiversity. Organic amendments such as biochar and compost and arbuscular mycorrhizal fungi (AMF) have been applied in cereal to improve soil fertility and crop productivity in climatic vulnerable areas, such as the Mediterranean. However, the outcome of the field application of AMF with compost and/or biochar is still poorly studied. Moreover, variability in AM root colonization and crop productivity were observed among crop genotypes and according to AM genotype and environment. Characterizing and selecting AMF taxa to design inocula tailored to meet a spectrum of needs is a crucial first step to achieving specific beneficial agronomic functions. Commonly, commercial microbial inocula are based on generalist single AM fungal taxa, having low genetic variability and not offering efficiency and stability when applied in agroecosystems. In this context, inoculants with indigenous AMF could represent an efficient solution where intensive agriculture negatively impacted soil AM fungal abundance and diversity. The whole research aimed to understand the drivers of cereal productivity, specifically, the effect of crop genotype, environment, diversity of AM fungal inoculum, and organic amendment and their interactions, throughout a laboratory study and three field studies, considering different agronomic aspects of the symbiosis.
In the first study, the AMF functional variability at inter- and intra-species levels was investigated by characterizing colonization traits, host growth, and mineral uptake of single-spore AM fungi isolated from soils with a fertility gradient. Nineteen single-spore cultures, showing high spore density and AMF colonization, were phylogenetically assigned to different isolates of three AM fungal species (i.e. Entrophospora claroidea, Funneliformis mosseae and Archaeospora trappei). A higher functional variability in infectivity and effectiveness was detected among isolates within AMF species (25% of total variance) than among AMF species. Most AM fungal isolates of F. mosseae have a better outcome in terms of plant growth, although with a performance gradient. Overall, isolates originating from the soil of the conventional arable field with higher pH and phosphorous availability promoted the uptake of plant nutrients, while those originating from soils with higher SOM and plant diversity promoted plant growth. On the contrary, the infectivity traits of the AM fungi were more conserved, as they were not affected by the environmental parameters of the soils of origin. Finally, we highlighted that soil pH played an important role in shaping the pattern of AMF functionality. Boosting the isolation and cultivation of AMF taxa, originating from agricultural and natural soils, is shown to be a key step in exploiting AMF diversity and designing a new generation of microbial inoculants.
In the second study, three isolates of F. mosseae (FmMix) and A. trappei (ArMix), biochar, and compost were applied to maize for studying crop productivity and soil fertility as a direct effect on maize and residual effect on wheat. FmMix alone or in combination with organic amendments (Amend) improved maize and wheat yield in comparison to control, although no synergistic effects were reported. On maize, the application of compost with or without biochar and AMF strongly promoted soil fungal biomass, whereas the residual effect was detected only with Amend and ArMix treatments. Moreover, under both crops, a positive effect on soil organic C was observed with biochar in comparison with control (+67%). Finally, the direct effect of Amend was predominant on soil enzymes, whereas the residual effect was driven mainly by AMF inoculation. In both years, AM fungal colonization traits, soil enzymatic activities, and microbial biomass were significantly related to crop productivity and soil chemical parameters, and arbuscules and urease were the best predictors of the mechanism. Thus, green restoration processes based on compost alone or AM inocula, mainly composed of F. mosseae, can be valid options for promoting soil health and crop productivity in the Mediterranean.
The third study was aimed at testing the hypotheses that wheat response to AM inoculation is more affected by genotype than environment and that this response is driven by increases in AM abundance and community structure changes, and not by modification of composition. To do that we inoculated an indigenous AM consortium on four old genotypes (Bianco Nostrale, Andriolo, Abbondanza, Sieve) and one modern variety (Bologna) of bread wheat for two years. The effect was evaluated by assessing grain yield, nutrients, and quality of processed products (flour and breadsticks), while the AM root abundance and the community diversity were characterized using morphological and molecular tools. The functional traits of AMF and plant were better explained by inoculation than by genotype or environment (33%, 17%, 4% of total explained variance), although significant interactions between environment x genotype and genotype x inoculation were highlighted. Consistent increases in AM abundance in Sieve and Bologna were associated with positive changes in productivity, supporting the good responsiveness of these genotypes with inoculated AMF, while the plant response of other genotypes was shaped by air temperature and rainfall. After inoculation, AM community composition was similar in all wheat genotypes, but the structure greatly differed among genotypes in interaction with inoculation and plant growth stage. These changes were significantly related to wheat productivity. The characterization of the community structure at early crop development and maturity allowed the identification of fast and latest active AM colonizers. Our results showed for the first time that AM inoculation affects the rheological parameters and nutraceuticals of processed products, although the response was modulated by genotype. The positive effects on wheat productivity and field persistence of the inoculated AMF support the use of indigenous consortia that have low impacts on resident AMF. Our findings advance the understanding of the facilitative mechanisms that underlie compatibility between AMF and wheat genotypes.
In the fourth study, we tested the agro-ecological effect of field inoculation with an indigenous AM fungal consortium on three varieties of barley (Atlante, Atomo, and Concerto) for two years. In 2020, when the soil was clay loam with very low P availability and no drought stress, Atomo and Concerto varieties positively responded to inoculation in terms of AM fungal traits. In contrast, in 2021, with silty clay loam soil, low P availability, and drought stress, only Concerto was responsive. In 2020, inoculation promoted grain yield by 64% and 37% in Atomo and Concerto, and in 2021 by 78% and 134% in Concerto and Atlante. Accordingly, the multivariate analysis highlighted a strong effect of environment on barley productivity and a third-order significant interaction among AMF, genotype, and environment (65% and 7% of explained variance). Moreover, the inoculation strongly modified, together with plant growth stage, the AM fungal community structures, and in particular some taxa , members of the local AM inoculum, were detected as key players in barley response. The general positive barley outcome supports the use of indigenous AMF for building efficient inoculants in sustainable agriculture. Nevertheless, the selection of genotypes with stable AM fungal response in specific climatic conditions is crucial in biofertilization programs.
Overall, these findings represent a great advancement in disentangling the key drivers of cereal productivity under sustainable agriculture. Indeed, our study gives innovative solutions in response to the accessibility and affordability of mineral fertilizers and in building resilient farming and food systems through smart circular economy approaches to safeguard food security and address climate objectives. The solutions focus on the efficient use of local resources, reducing input requirements for crop production, and recycling agricultural by-products. The proposed farming system, if applied at a larger scale, could create great benefits for the rural economy, ensuring a transition towards a more sustainable way of food production.
In the first study, the AMF functional variability at inter- and intra-species levels was investigated by characterizing colonization traits, host growth, and mineral uptake of single-spore AM fungi isolated from soils with a fertility gradient. Nineteen single-spore cultures, showing high spore density and AMF colonization, were phylogenetically assigned to different isolates of three AM fungal species (i.e. Entrophospora claroidea, Funneliformis mosseae and Archaeospora trappei). A higher functional variability in infectivity and effectiveness was detected among isolates within AMF species (25% of total variance) than among AMF species. Most AM fungal isolates of F. mosseae have a better outcome in terms of plant growth, although with a performance gradient. Overall, isolates originating from the soil of the conventional arable field with higher pH and phosphorous availability promoted the uptake of plant nutrients, while those originating from soils with higher SOM and plant diversity promoted plant growth. On the contrary, the infectivity traits of the AM fungi were more conserved, as they were not affected by the environmental parameters of the soils of origin. Finally, we highlighted that soil pH played an important role in shaping the pattern of AMF functionality. Boosting the isolation and cultivation of AMF taxa, originating from agricultural and natural soils, is shown to be a key step in exploiting AMF diversity and designing a new generation of microbial inoculants.
In the second study, three isolates of F. mosseae (FmMix) and A. trappei (ArMix), biochar, and compost were applied to maize for studying crop productivity and soil fertility as a direct effect on maize and residual effect on wheat. FmMix alone or in combination with organic amendments (Amend) improved maize and wheat yield in comparison to control, although no synergistic effects were reported. On maize, the application of compost with or without biochar and AMF strongly promoted soil fungal biomass, whereas the residual effect was detected only with Amend and ArMix treatments. Moreover, under both crops, a positive effect on soil organic C was observed with biochar in comparison with control (+67%). Finally, the direct effect of Amend was predominant on soil enzymes, whereas the residual effect was driven mainly by AMF inoculation. In both years, AM fungal colonization traits, soil enzymatic activities, and microbial biomass were significantly related to crop productivity and soil chemical parameters, and arbuscules and urease were the best predictors of the mechanism. Thus, green restoration processes based on compost alone or AM inocula, mainly composed of F. mosseae, can be valid options for promoting soil health and crop productivity in the Mediterranean.
The third study was aimed at testing the hypotheses that wheat response to AM inoculation is more affected by genotype than environment and that this response is driven by increases in AM abundance and community structure changes, and not by modification of composition. To do that we inoculated an indigenous AM consortium on four old genotypes (Bianco Nostrale, Andriolo, Abbondanza, Sieve) and one modern variety (Bologna) of bread wheat for two years. The effect was evaluated by assessing grain yield, nutrients, and quality of processed products (flour and breadsticks), while the AM root abundance and the community diversity were characterized using morphological and molecular tools. The functional traits of AMF and plant were better explained by inoculation than by genotype or environment (33%, 17%, 4% of total explained variance), although significant interactions between environment x genotype and genotype x inoculation were highlighted. Consistent increases in AM abundance in Sieve and Bologna were associated with positive changes in productivity, supporting the good responsiveness of these genotypes with inoculated AMF, while the plant response of other genotypes was shaped by air temperature and rainfall. After inoculation, AM community composition was similar in all wheat genotypes, but the structure greatly differed among genotypes in interaction with inoculation and plant growth stage. These changes were significantly related to wheat productivity. The characterization of the community structure at early crop development and maturity allowed the identification of fast and latest active AM colonizers. Our results showed for the first time that AM inoculation affects the rheological parameters and nutraceuticals of processed products, although the response was modulated by genotype. The positive effects on wheat productivity and field persistence of the inoculated AMF support the use of indigenous consortia that have low impacts on resident AMF. Our findings advance the understanding of the facilitative mechanisms that underlie compatibility between AMF and wheat genotypes.
In the fourth study, we tested the agro-ecological effect of field inoculation with an indigenous AM fungal consortium on three varieties of barley (Atlante, Atomo, and Concerto) for two years. In 2020, when the soil was clay loam with very low P availability and no drought stress, Atomo and Concerto varieties positively responded to inoculation in terms of AM fungal traits. In contrast, in 2021, with silty clay loam soil, low P availability, and drought stress, only Concerto was responsive. In 2020, inoculation promoted grain yield by 64% and 37% in Atomo and Concerto, and in 2021 by 78% and 134% in Concerto and Atlante. Accordingly, the multivariate analysis highlighted a strong effect of environment on barley productivity and a third-order significant interaction among AMF, genotype, and environment (65% and 7% of explained variance). Moreover, the inoculation strongly modified, together with plant growth stage, the AM fungal community structures, and in particular some taxa , members of the local AM inoculum, were detected as key players in barley response. The general positive barley outcome supports the use of indigenous AMF for building efficient inoculants in sustainable agriculture. Nevertheless, the selection of genotypes with stable AM fungal response in specific climatic conditions is crucial in biofertilization programs.
Overall, these findings represent a great advancement in disentangling the key drivers of cereal productivity under sustainable agriculture. Indeed, our study gives innovative solutions in response to the accessibility and affordability of mineral fertilizers and in building resilient farming and food systems through smart circular economy approaches to safeguard food security and address climate objectives. The solutions focus on the efficient use of local resources, reducing input requirements for crop production, and recycling agricultural by-products. The proposed farming system, if applied at a larger scale, could create great benefits for the rural economy, ensuring a transition towards a more sustainable way of food production.
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