Development of Triticum turgidum subsp. durum--Aegilops longissima amphiploids with high iron and zinc content through unreduced gamete formation in F1 hybrids.

Four different interspecific hybrids involving three different accessions of Aegilops longissima Schweinf. & Muschl. with high grain iron and zinc content and three Triticum turgidum L. subsp. durum (Desf.) Husn. cultivars with low micronutrient content were made for durum wheat biofortification and investigated for chromosome pairing, fertility, putative amphiploidy, and micronutrient content. The chromosome pairing in the 21-chromosome F1 hybrids (ABSl) consisted of 0-6 rod bivalents and occasionally 1 trivalent. All the F1 hybrids, however, unexpectedly showed partial but variable fertility. The detailed meiotic investigation indicated the simultaneous occurrence of two types of aberrant meiotic divisions, namely first-division restitution and single-division meiosis, leading to regular dyads and unreduced gamete formation and fertility. The F2 seeds, being putative amphiploids (AABBSlSl), had nearly double the chromosome number (40-42) and regular meiosis and fertility. The F1 hybrids were intermediate between the two parents for different morphological traits. The putative amphiploids with bold seed size had higher grain ash content and ash iron and zinc content than durum wheat cultivars, suggesting that Ae. longissima possesses a better genetic system(s) for uptake and seed sequestration of iron and zinc, which could be transferred to elite durum and bread wheat cultivars and exploited.