Thinopyrum species as a genetic resource: enhancing salt tolerance in wheat and forage crops for sustainable agriculture

<i>Thinopyrum</i> species are native to coastal regions and have evolved notable salt tolerance mechanisms, including efficient Na⁺ exclusion and K⁺ retention, enhanced antioxidant capacity, and the accumulation of compatible solutes for osmoregulation. Among the <i>Thinopyrum</i> species, <i>Th. ponticum</i> has long been used as saline pasture and energy plant, which was recently suggested for the construction of a "Coastal Grass Belt" around the Bohai Sea. The salt tolerance in some <i>Thinopyrum</i> species, such as <i>Th. ponticum</i>, <i>Th. elongatum</i>, <i>Th. bessarabicum</i>, and <i>Th. distichum</i> have been transferred into wheat as (partial) amphiploid, addition, substitution, translocation, and introgression lines. The introgression lines with enhanced salt tolerance, derived from wheat × <i>Th. ponticum</i> had been utilized as salt-tolerant wheat varieties. In addition, amphiploids and perennial wheat have been developed as salt-tolerant forage crops. Salt tolerance in <i>Thinopyrum</i> species is governed by multiple genes, which have been mapped principally to homologous chromosomes group 3 and group 5. Transcriptomic and proteomic analyses have revealed a number of differentially expressed genes (proteins) involved in the salt tolerance response in <i>Thinopyrum</i> species; however, few of these have been functionally characterized. Therefore, further work is needed to investigate gene networks underlying salt tolerance in <i>Thinopyrum</i>, which may serve as molecular targets for the genetic improvement of salt-tolerant forage crops such as <i>Tritipyrum</i> and staple crops like wheat.