Date of Award

2021

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Shannon ABC

First Advisor

Dr. Oscar Goñi

Second Advisor

Dr. Shane O’Connell

Abstract

Salinity is one of the major abiotic stresses affecting crop production, especially in arid and semi-arid areas. Most of the vegetable crops are salt sensitive, growing inadequately in salinised soils due to the accumulation of toxic ions from prolonged, inadequate irrigation programs. A meaningful approach to counteract salinity stress and increase crop yield is the use of protein hydrolysate biostimulants (PHBs). The main objectives of this study were to generate legume-derived PHBs by enzymatic hydrolysis, evaluate their ability to induce salinity stress tolerance in plants, and understand their mode of action. A full compositional and structural analysis of the generated PHBs was firstly conducted to gain an insight of their molecular properties. The biostimulant activity of one legumederived PHB produced under optimised conditions (namely PHB5) was first screened at different dosage rates using Arabidopsis thaliana in a high-throughput root microphenotyping system. Then, the bioactivity of PHB5 was assessed by foliar application on tomato plants (cv. Micro-Tom) subjected to controlled salinity stress conditions. The results confirmed its ability to improve phenotypical, physiological, biochemical, and molecular stress tolerance markers, providing relevant fruit yield gains. After determining the most effective dosage rate of PHB5 in tomato, the implementation of metabolic and transcriptome studies was carried out in different tomato plant tissues. PHB5 provided long-term protective effects on salinity stressed tomato plants through enhanced osmotic adjustment, improved tissue ion partitioning and also stimulated other metabolic mechanisms. Finally, different protein and oligopeptide fractions from PHB5 were isolated and their bioactivity was evaluated in Arabidopsis thaliana and tomato plants. The results suggest that a role is played by low molecular weight oligopeptides in salinity stress tolerance. Taken together, it can be concluded that a legume-derived PHBs generated efficiently by enzymatic hydrolysis in this study can represent a valuable agronomic tool for growers to enhance salinity stress tolerance in crops through a well-defined physiological mode of action.

Access Level

info:eu-repo/semantics/openAccess

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