Cytogenetic Analysis and Molecular Marker Development for a New Wheat–Thinopyrum ponticum 1Js (1D) Disomic Substitution Line With Resistance to Stripe Rust and Powdery Mildew

Abstract

<i>Thinopyrum ponticum</i> (2<i>n</i> = 10<i>x</i> = 70), a member of the tertiary gene pool of wheat (<i>Triticum aestivum</i> L.), harbors many biotic and abiotic stress resistance genes. CH10A5, a novel disomic substitution line from a cross of <i>T. aestivum</i> cv. 7182 and <i>Th. ponticum</i>, was characterized by cytogenetic identification, <i>in situ</i> hybridization, molecular marker analysis, and morphological investigation of agronomic traits and disease resistance. Cytological observations showed that CH10A5 contained 42 chromosomes and formed 21 bivalents at meiotic metaphase I. Genome <i>in situ</i> hybridization (GISH) analysis indicated that two of its chromosomes came from the J^s genome of <i>Th. ponticum</i>, and wheat 15K array mapping and fluorescence <i>in situ</i> hybridization (FISH) revealed that chromosome 1D was absent from CH10A5. Polymorphic analysis of molecular markers indicated that the pair of alien chromosomes belonged to homoeologous group one, designated as 1J^s. Thus, CH10A5 was a wheat-<i>Th. ponticum</i> 1J^s (1D) disomic substitution line. Field disease resistance trials demonstrated that the introduced <i>Th. ponticum</i> chromosome 1J^s was probably responsible for resistance to both stripe rust and powdery mildew at the adult stage. Based on specific-locus amplified fragment sequencing (SLAF-seq), 507 STS molecular markers were developed to distinguish chromosome 1J^s genetic material from that of wheat. Of these, 49 STS markers could be used to specifically identify the genetic material of <i>Th. ponticum</i>. CH10A5 will increase the resistance gene diversity of wheat breeding materials, and the markers developed here will permit further tracing of heterosomal chromosome fragments in the future.