Genomes, chromosomes and genes of the wheatgrass genus thinopyrum: The value oftheir transfer into wheat for gains in cytogenomic knowledge and sustainable breeding

Abstract

Perennial wheatgrass species of the genus Thinopyrum possess several appealing attributes for wheat improvement, contributing to tolerance to biotic and abiotic stresses, as well as to quality and even to yield increase. Major genes or QTLs underlying such traits have been identified on numerous chromosomes of both diploid (Th. elongatum and Th. bessarabicum) and polyploid (mainly Th. intermedium and Th. ponticum) representatives of the genus, having different genome origin (E, J, St/S) and involving several homoeologous groups. Thinopyrum chromosomes sharing homoeology with wheat group 7 chromosomes turned to be particularly rich in beneficial genes; among them, a Th. ponticum group 7 chromosome referred to as 7Ag or 7el has been extensively targeted in various successful attempts of harnessing its attractive gene content. A survey of the several wheat translocation/recombinant lines involving this chromosome in the background of both bread and durum wheat is given. Such lines are described as highly valuable tools for a variety of studies, from development of integrated genetic and physical maps, to the analysis of structural and functional characteristics associated with defined alien chromosome subregions. The validity of Th. ponticum group 7 transfers as breeding materials (notable genes and traits including Lr19, Sr25, Fusarium head blight resistance, yellow pigment content, and even yield) is also highlighted. Finally, examples are given of pyramiding of group 7 Thinopyrum genes through ‘precision’breeding strategies of chromosome engineering, which, efficiently aided by current genetic, cytogenetic and genomic (or, collectively, ‘cytogenomic’) technologies, enable a multifaceted and sustainable improvement of the wheat crop based on the use of the wealth of natural genetic resources of its related gene pools.