Screening of Diverse Ethiopian Durum Wheat Accessions for Aluminum Tolerance

Abstract

Acid soils and associated Al3+ toxicity are prevalent in Ethiopia where normally Al3+-sensitive durum wheat (Triticum turgidum ssp durum Desf.) is an important crop. To identify a source of Al3+ tolerance, we screened diverse Ethiopian durum germplasm. As a center of diversity for durum wheat coupled with the strong selection pressure imposed by extensive acid soils, it was conceivable that Al3+ tolerance had evolved in Ethiopian germplasm. We used a rapid method on seedlings to rate Al3+ tolerance according to the length of seminal roots. From 595 accessions screened using the rapid method, we identified 21 tolerant, 180 intermediate, and 394 sensitive accessions. When assessed in the field the accessions had tolerance rankings consistent with the rapid screen. However, a molecular marker specific for the D-genome showed that all accessions rated as Al3+-tolerant or of intermediate tolerance were hexaploid wheat (Triticum aestivum L.) that had contaminated the durum grain stocks. The absence of Al3+ tolerance in durum has implications for how Al3+ tolerance evolved in bread wheat. There remains a need for a source of Al3+-tolerance genes for durum wheat and previous work that introgressed genes from bread wheat into durum wheat is discussed as a potential source for enhancing the Al3+ tolerance of durum germplasm.