Alien introgressions represent a rich source of genes for crop improvement

Abstract

O ur major crop species represent the relatively few species that were selected by our ancestors from a multitude of extant species, and the resulting narrow germplasm forms the basis of modern monoculture in many areas of the world. Crop monoculture over vast areas inevitably leads to boom and bust cycles alternating between susceptible and resistance genotypes, disease epidemics, and loss of productivity after the appearance of new virulent races of pathogens. Breeders and geneticists have increasingly sought new sources of resistance in diverse germplasm, often involving distant wild relatives. Often, such alien introgressions are accompanied by linkage drag where recombination is suppressed in the target gene region, and standard recombinationbased approaches cannot be used in the molecular dissection of the target genes. In PNAS, Cao et al. (1), however, circumvent the problems and report the isolation of a resistance gene from an alien introgression in wheat using a combination of cytology and gene expression analysis.As a rule, polyploids containing more than two sets of chromosomes have highly buffered genotypes, are more tolerant, and are more likely to benefit from alien introgression than diploids. Common bread wheat (Triticum aestivum L.; 2n = 6x = 42, genomes AABBDD) is hexaploid, consisting of A, B, and D progenitor genomes. Most of the highest yielding wheat cultivars carry portions of alien chromosomal introgression from related weedy species. The process of alien introgression is illustrated in Fig.

Molecular cytogenetic characterization of novel wheat-Thinopyrum bessarabicum recombinant lines carrying intercalary translocations

“…Lines are obtained relatively easy by backcrossing an amphiploid hybrid derivative to the wheat parent, and such lines are available as cytogenetic stocks for a number of alien species; addition lines may also be selected from these crosses ( Molnár-Láng et al 2000. As noted in the BIntroduction,^linkage drag means such lines are not normally grown as varieties (Falke et al 2009;Feuillet et al 2008;Gill et al 2011), and further crosses are needed to reduce the size of the alien chromosome fragment. Spontaneous whole arm translocations can occur, such as the 1RS.1BL translocation found in many biscuit or feed wheat varieties ( Heslop-Harrison et al 1990, including the Prinia variety studied here), and occasional recombinants with small alien chromosome segments have been reported, e.g., the Danish wheat variety 'Viking' (Schlegel et al 1993) or the Portuguese wheat landrace 'Barbela' ( Ribeiro-Carvalho et al 1997) including a small terminal rye chromosome segments on chromosome 4B and 2D, respectively.…”

Production and Molecular Cytogenetic Characterization of a Durum Wheat-<b><i>Thinopyrum elongatum</i></b> 7E Disomic Addition Line with Resistance to Fusarium Head Blight

“…intermedium or Th. ponticum , with resistance to FHB [Gill et al, 2011]. So intergeneric hybridization combined with chromosome engineering may help to incorporate FHB resistance from wild relatives in durum wheat background [Jauhar, 2014].…”

High throughput transformation of a Sorghum cDNA library for rice improvement

“…Alien introgressions provide a rich gene resource for crop improvement (Gill et al 2011), and alien gene expression by transformation is a popular and practical approach to improve crop plants (Hu and Lubberstedt 2015). In order to improve rice using alien genes from other plants especially the grass family of C4 plants, a Sorghum cDNA library was constructed using the young inflorescences (about 8-12 cm length) of Sorghum.…”