Assessment of the phosphorus acquisition related root traits of two wheat cultivars differing on efficiency: towards phosphorus sustainability
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Universidad de Granada
DepartamentoUniversidad de Granada. Programa de Doctorado en Biología Fundamental y de Sistemas
Raíces (Botánica)SostenibilidadProductividad agrícolaFósforo
Montesano de Souza Campos, Pedro. Assessment of the phosphorus acquisition related root traits of two wheat cultivars differing on efficiency: towards phosphorus sustainability. Granada: Universidad de Granada, 2020. [http://hdl.handle.net/10481/62885]
SponsorshipTesis Univ. Granada.; Fondo Nacional de Desarrollo Científico Tecnológico, a través del Proyecto FONDECYT 11160385; Programa de Formación de Capital Humano Avanzado de la Comisión Nacional de Investigación Científica y Tecnológica (CONICYT), por la beca CONICYT Nº 21161474; Programa de Atracción e Inserción de Capital Humano Avanzado (PAI-CONICYT) a través del Concurso Nacional Tesis de Doctorado en el Sector Productivo por el Proyecto Nº T7817120011; Campex Baer Proyecto Nº T7817120011
This Doctoral Thesis was focused on the study of the root morphology, organic acid and phosphatase exudation, expression of phosphate transporters, and root mycorrhizal colonization as the main mechanisms involved in the PAE of wheat genotypes growing under P-limiting conditions, and the underlying SL modulation behind those traits. In chapter I, a general overview on the topic was presented, describing the state of the art and showing the hypothesis and aims of this study. In chapter II, plant adaptations related to P acquisition root traits, with emphasis on AM symbiosis and its possible effects on plant’ P-related root traits were deeply reviewed. A summary of results from 1980-2018 regarding AM growth responses and P uptake in wheat plants was presented to discuss the generally accepted lack of positive responses in this plant species. The importance of considering AM functional diversity on future studies and the need to improve PAE definition considering carbon trade between all the directly related PAE traits and its benefits to the host plant were also discussed. In chapter III, the effects of two indigenous AM fungal isolates (Claroideoglomus claroideum and Rhizophagus intraradices) on nutrient uptake and root traits of two commercial Chilean wheat genotypes with contrasting P-acquisition efficiency were evaluated in order to determine if the responses were dependent on the interaction between host plant genotype and AM ecotype and if the symbiosis can effectively enhance P acquisition on these cultivars (specific objective 1). The results showed that biomass production and root morphological responses to AM colonization significantly varied between genotypes and AM isolate, being the most P-efficient genotype – cv. Crac iv – not affected by the symbiosis in these parameters, while the less efficient – cv. Tukan – showed a higher mycorrhizal dependency. Moreover, P and Ca accumulation were increased in both cultivars when colonized by C. claroideum and R. intraradices, respectively. It was demonstrated that AM growth responses vary at intra-specific level, depending on the basal efficiency of each cultivar and that the nutritional benefits were specific to each AM isolate. Therefore, AM symbiosis could contribute to increase agricultural sustainability; however, genotype and environmental-specific combinations should be considered to maximize the benefits from the symbiosis. The chapter IV is related to the specific objective 2, where the P acquisitionrelated root traits (root morphology, organic acid and phosphatase exudation, and root mycorrhizal colonization) of the wheat genotypes under study were evaluated to determine those that mainly contributed to P accumulation. To that, a pot and rhizobox experiments were performed using a high P-fixing volcanic soil, either fertilized or not with P. Crac plants showed higher P accumulation regardless of P treatment and experiment, being root morphological traits the most correlated with P acquisition, both in the presence and in absence of Pi fertilization. Also, the results suggest that AM symbiosis and oxalate exudation could be other important mechanisms to enhance P acquisition under P-limiting conditions. Finally, the traits evaluated in this study can become important targets for future breeding programs oriented to generate cultivars adapted to both high- and low-P input systems. In chapter V, the SL production among the studied wheat cultivars and its effects on Pi-starvation responses (PSRs) and P acquisition (specific objective 3) were assessed. To accomplish this goal, plants were grown hydroponically, and P-starvation was applied to evaluate the main PSRs at the transcriptional level – especially related to the modulation of the P signaling and homeostasis pathway (IPS1-mir399-PHO2) and Pi v transporters expressions. Here, a higher expression of the Pi transporters TaPht1;2 and TaPht1;10 and a faster and higher modulation of the IPS1–miR399–PHO2 pathway was observed in Crac plants. Remarkably, Crac presented higher levels of SLs, suggesting a direct relationship with the responses mentioned above. Finally, an improved model for the regulation of the P homeostasis module was proposed. Taking together, the higher PAE in Crac was associated with a faster and improved P signaling through a fine-tuning regulation of PHO2, which seems to be regulated by SLs. This knowledge could help to develop new strategies for improved plant performance under P stress limitation. All the results obtained here are discussed comprehensively in chapter VI of this Thesis.