Generation of spontaneous Triticum durum ×Aegilops tauschii wheat synthetic amphiploids and their characterization

Abstract

Aegilops tauschii (2n=2x=14), the D-genome donor is the closest progenitor to modern wheat representing a large proportion of unexplored genetic variation. Flourishing in the adverse climatic conditions it can be utilized in the wheat improvement programmes. We targeted to develop and characterize the primary synthetics amphiploids from nine different accessions of Ae. tauschii and one Triticum durum cv. PBW114 through spontaneous chromosomal doubling. Being fertile with ~50% survival rate, the amphiploids were selfed for five generations without any selection and 38 F6 amphiploids were obtained. They were evaluated for chromosome number and pairing behaviour, different agro-morphological traits and diseases of leaf rust, yellow rust and powdery mildew. Nineteen amphiploids had 2n = 42 chromosomes, four had 2n=28, two had 41 chromosomes. While in the remaining 12 amphiploids, the chromosome number varied from 24 to 42, some with abnormal pairing. Large variations were observed in agromorphological traits with 32 amphiploids showing better thousand grain weight than the hexaploid check varieties and PBW114. Response to the three targeted diseases varied widely across the panel. Twenty-four D-genome specific SSRs used to assess the genetic diversity showed that the amphiploids from same cross combinations were grouped differently. We observed that development of a new species is a complex event, and combining divergent genomes into one nucleus with chromosome doubling inflicts considerable stress on a newly emerged species with rapid genomic instability in nascent allopolyploid individuals to enable their immediate survival. However, this is an effective and novel means of creating new diversity for wheat improvement programmes.