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sur le développement des zones arides et semi-arides

Titre : Identificación y caracterización de los hongos micorrícicos arbusculares autóctonos en simbiosis con prosopis alba y los mecanismos fisiológicos/bioquímicos relacionados con la tolerancia a sequia

Auteur : Sagadín, Mónica Beatriz

Université de soutenance : Universidad Nacional de Córdoba

Grade : Doctor en Ciencias Agropecuarias 2019

Résumé
Prosopis alba Grisebach (algarrobo blanco) is one of the most important species in the natural ecosystem of the Semi-arid Western Chaco of Argentina. Among the strategies to ensure the establishment and proper development of implanted forests, the production of good quality seedlings is an indispensable requirement. The objective of this thesis was to select and characterize mixed inoculums of native arbuscular mycorrhizal fungi (AMF) that confer greater tolerance to drought stress in P. alba seedlings with special emphasis on the regulation of oxidative damage. Two mixed native HMA inocula were isolated from the sites of Colonia Benítez (CB, wet) and Padre Lozano (PL, semi-arid) in the provinces of Chaco and Salta respectively. In the CB site, HMAs that adapt to different environmental conditions were identified, while in the trap plants of PL, Diversispora spurca was identified in soils with high organic content and drought tolerant. Likewise, an experimental system was developed under controlled conditions of irrigation and moderate and severe drought, at 50 and 10% of soil water content. In the symbiosis with P.alba, under normal irrigation conditions, both inoculums showed a similar ability to increase the early mycorrhizal response (MR). However, under irrigation conditions, and for longer treatment time (from 60 days onwards) the inoculum of CB, presented greater formation of hyphae and arbuscules compared to the inoculum of PL, which was accompanied by an increase in the MR for growth and nutrient content such as P and N in P.alba. On the contrary, the inoculum of PL isolated from a semi-arid region, was promising in the mitigation of drought, compared with the inoculum of CB and the mixture of both (MIX) which did not show a synergistic effect under irrigation and / or drought. The symbiosis P. alba-HMA (PL), was characterized by a greater capacity in the formation of arbuscules, nutrient content such as P and N, larger stem diameter and mitigation of oxidative damage. In addition, the inoculum of PL was the most efficient in nursery and greenhouse conditions, when it was subjected to severe drought, suggesting that its greater capacity to benefit P. alba is related to the site of origin of the inoculum, being improved its effect by the application of low fertilization rates.

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