Conventional and alien genetic diversity for salt tolerant wheats: focus on current status and new germplasm development

Abstract

Abiotic stresses are static mechanisms that tend to be more durable due to the absence of pathogen influence. Three abiotic stresses of significance deal with heat, drought and salinity tolerance. Focusing on salinity with wheat as the crop, the current status of some available salt tolerant germplasm is emphasized, and further is presented a detail of germplasms that may be assembled/developed in the near future. Conventional genetic diversity for salinity and significant practical outputs as measured over tons/ha in farmers fields remain limited so far. Unique genetic diversity in the wheat family resides in three gene pools; primary, secondary, and tertiary. Harnessing this resource has a simple to complex range based upon the species genetic distance as compared to the three bread wheat genomes; 2n=6x=42, AABBDD. The primary gene pool species are relatively simple to exploit, and of these Aegilops tauschii (2n=2x=14, DD) has a priority. The synthetic hexaploid germplasm developed from combinations of this grasses several accessions with Triticum turgidum L., provides a resource that possesses superb potential for transferring salt tolerance genes into wheat cultivars. The homologous association of the D genome provides a rapid output for breeding, and whean combined with doubled haploidy protocols end-products emerge even more swiftly, Data are presented to substantitate the salt tolerance potential of some of these D genome synthetic hexaploid wheats. More futuristic and complex because of genomic distance; but highly potent; is the diversity of some tertirary gene pool species, of which Thinopyrum bessabaribum and Th. elongatum (2n=2x=14, JJ and EE respectively) are prime candidates. A cytogenetic manipulation strategy promising multiple wheat/alien chromosomal exchanges, mediated by the ph gene action and facilitated by PCR molecular diagnostics has been under study. This strategy is presented, in the anticipation that complex genetic transfer protocols associated with distant gene pools may get simplified. A holistic approach will be to foster gene pyramiding across all gene pools, an aspect that has a distinct advantage in crop improvement. Consequently, the conventional germplasm of the primary gene pool is the base to build upon, A tester set of reportedly tolerant cultivars and land races is in our resource. This has been globally distributed for testing and genetic usage. It is our contention that greater success may result if to this tester set of cultivars is added the novel diversity from other gene pool species, complimented with homozygosity and stringent global multilocational testing.