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Australian National University (2002)

Physiology and genetics of salt tolerance in durum wheat

Husain, Shazia

Titre : Physiology and genetics of salt tolerance in durum wheat

Auteur : Husain, Shazia

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2002

Résumé partiel
Responses of plants to saline environments have indicated that Na+ exclusion is an important mechanism of salt tolerance. Current durum wheat cultivars lack the character of Na+ exclusion, which makes them more salt sensitive than bread wheat cultivars, which have the character. The aim of the present study was to understand the physiology and genetics of the character of Na+ exclusion that was recently discovered in some durum wheat landraces, in order to advance the introduction of the character into cultivated durum wheat. Three ancestral durumlandraces with very low Na+ levels in leaf blades at high salinity (150 mM NaCl) were compared with the current Australian durum cultivar Wollaroi and a durum landrace with very high Na+ levels. Performance of the low Na+ uptake genotypes was evaluated over a wide range of salinity levels, on the basis of shoot and root ion contents, growth rates, ion transport rates and ion selectivity. Low Na+ uptake genotypes had much lower shoot Na+ concentration at all external salinity levels ( 10- 150 mM NaCl) than the cultivar and the high Na+ uptake genotype. This was due to low rates of transport from root to shoot, not to higher growth rates or higher shoot:root ratios. Low Na+ uptake genotypes also had much higher K+ shoot concentrations, hence higher K+ IN a+ discrimination. Root Na+ concentrations were similar for all genotypes, indicating that the genetic differences in the control of Na+·transport were at the loading of the xylem in the root. There was little difference in er concentration between genotypes, in roots or shoots. Root concentrations of Na+ and er for all genotypes were controlled well, showing little increase above 50 mM with increasing salinity. This study showed clear genetic differences in K+/Na+ discrimination in durum landraces that could be used to increase the salt tolerance of current durum varieties.

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