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Universidade de Tras os Montes E Alto Douro (2020)

Enhancement of wheat establishment and drought stress resistance through seed priming and foliar fertilisation

Pavia, Ivo Miguel Meneses

Titre : Enhancement of wheat establishment and drought stress resistance through seed priming and foliar fertilisation

Auteur : Pavia, Ivo Miguel Meneses

Université de soutenance : Universidade de Tras os Montes E Alto Douro

Grade : Tese de Doutoramento 2020

Résumé
Wheat (Triticum spp.) is one of the most important crops worldwide. Drought is a critical factor in world food security and one of the most critical limiting factors for cereal productivity. In the context of global climate change is expected the increase of mean temperature and drought severity in major wheat growing regions, compromising wheat production. Considering the importance of wheat, improving this crop establishment and drought stress resistance is a challenge on a global scale. Exogenously application of microminerals and antioxidants by seed priming or foliar application is considered an effective strategy to enhanced stress resistance and plants nutritional content. This thesis focuses mainly on the consequences of seed priming and foliar application of zinc (Zn) and ascorbic acid (AsA) and, secondary, on the effects of iron (Fe) and pyridoxine (Pyr). We have shown that ancient wheat cultivars, may have key features that allow them to germinate and withstand drought stress. Still, for this study we selected a modern cultivar – ‘Jordão’ – with high and stable yield, and good germination characteristics across water potentials. Zn priming induced early growth inhibition, cytogenetic instabilities and modulated nucleolar activity, being these effects exacerbated under drought stress. The combination of Zn and Fe in the priming solution proven efficient in reducing the cytogenetic anomalies caused by Zn alone. This combination leads to a decrease in cytogenetic anomalies and long-term beneficial effects such as improved tillering and yield. Priming with AsA and Pyr also promoted a long-term improvement by enhancing wheat growth, from joining until heading. Considering that climate change is expected to change sowing time and decrease wheat’s growing season, this improvement might be valuable. We also showed that severe drought stress induces a non-regulated energy dissipation which most likely produced photo-damage and long lasting damaged to the photosystems. Priming alone and/or coupled with the foliar application of either Zn or AsA were able to enhance photoprotection during drought by increasing regulated dissipation of excess energy and promoting a better recovery of wheat plants after stress relief.

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Page publiée le 22 mars 2021