ABSTRACT
Wheat is the domesticated form of many of the grasses from Poaceae and tribe Triticeae. These annual and perennial grasses comprising of approximately 325 species also include the diploid ancestors of wheat known as its wild relatives. These relatives exhibit more genetic diversity as compared to their cultivated form, hence are a potent means of allelic enrichment of wheat via intergeneric, interspecific or intraspecific hybridization. Wheat relatives include many grasses like Aegilops, Thinopyrum, Triticum, Elymus, Leymus, Elytrigia, Lophopyrum, Secale, Heteranthelium, Taeniantherum, Haynaldia, and Hordeum from the tribe Hordeae that are distributed across the three gene pools (primary, secondary, and tertiary) based upon their genetic distance attribute. Due to the allelic variation that is present, these relatives have been utilized in wheat research and production for over a century commencing in 1904 with wheat/barley combinations or as early as 1872 if X Triticale is considered. During these many decades via basic, strategic, and applied research efforts genes have been exploited for introgressing resistances/tolerances to several biotic and abiotic stresses of global significance. The trait coverage has increased progressively and currently targets include insect/virus resistance, micronutrients with growing focus on cereal quality parameters towards which these alien resources are contributing new diversity. Wild relative variation is not restricted to bread 396wheats alone and the tetraploid durums are also recipients of their practical benefits for crop yield maximization. Potential of the wild resource also exists for inducing sterility; crucial for hybrid wheat development. In addition, within the strategic research scenario wild species have emerged as a significant base for producing user-friendly wheat genomic genetic stocks for future usage practicality. We in this review have targeted major facets of wild relative utilization for wheat improvement since 1904 and in addition have provided an in-depth overview of the germplasm holdings that global researchers could tap upon.
