Molecular dissection of Secale africanum chromosome 6Rafr in wheat enabled localization of genes for resistance to powdery mildew and stripe rust

Abstract

Background: Introgression of chromatin from Secale species into common wheat has for decades been a successful strategy for controlling the wheat diseases. The wild Secale species, Secale africanum Stapf., is a valuable source for resistance to foliar disease of wheat. A wheat-S. africanum chromosome 6R afr substitution line displayed resistance to both powdery mildew and stripe rust at the adult-plant stage. Results: Wheat-S. africanum chromosome 6R afr deletion and translocation lines were produced and identified by sequential non-denaturing fluorescence in situ hybridization (ND-FISH) using multiple Oligo-based probes. Different ND-FISH patterns were observed between S. cereale 6R and S. africanum 6R afr. With reference to the physical map of the draft genome sequence of rye inbred line Lo7, a comprehensive PCR marker analysis indicated that insertions and deletions had occurred by random exchange between chromosomes 6R and 6R afr. A survey of the wheat-S. africanum 6R afr lines for disease resistance indicated that a powdery mildew resistance gene(s) was present on the long arm of 6R afr at FL0.85-1.00, and that a stripe rust resistance gene(s) was located in the terminal region of 6R afr S at FL0.95-1.00. The wheat-S. africanum 6R afr introgression lines also displayed superior agronomic traits, indicating that the chromosome 6R afr may have little linkage drag in the wheat background. Conclusions: The combination of molecular and cytogenetic methods allowed to precisely identify the chromosome rearrangements in wheat-S. africanum 6R afr substitution, deletion and translocation lines, and compare the structural difference between chromosomes 6R and 6R afr. The wheat-S. africanum 6R afr lines containing gene(s) for powdery mildew and stripe rust resistance could be used as novel germplasm for wheat breeding by chromosome engineering.

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Addition Line and Physical Localization of Its Powdery Mildew Resistance Gene

“…Some powdery mildew resistance genes have been reported from chromosome 6RL of rye cultivars including Prolific, Jingzhouheimai, and Kustro, among which the resistance gene from Kustro was localized in the region from the site between 2.3 and 2.5 to the telomere ( Friebe et al, 1994 ; Wang et al, 2010 ; Li et al, 2016 ; Du et al, 2018 ). A powdery mildew APR gene(s) from the wild species Secale africanum was mapped on the long arm of 6R afr at FL0.85–1.00 ( Li G.R. et al, 2020 ).…”

An efficient Oligo‐FISH painting system for revealing chromosome rearrangements and polyploidization in Triticeae

“…Similarly, based on the breakpoints revealed by Synt2, Synt6, and sequential ND-FISH, we found that the FL 0.85-1.00 segments of chromosomes 6R a L and 6R s L of S. africanum and S. sylvestre, respectively, most likely belonged to linkage group 2. Li et al (2020a) physically localized a Pm gene in that region, and thus it is likely that the gene may be traced to the linkage group 2L region of S. africanum. Therefore, we propose that the bulked probes could assist in locating breakpoints of non-homologous regions for physical dissection of rearranged regions carrying useful genes transferred from Secale to wheat.…”

Rapid Creation of Interspecific Hybrid Progeny to Broaden Genetic Distance through Double Haploid (DH) Inducer in Brassica napus

“…The seeds were placed in a sterilized germination box and cultured in the dark at 25 °C for 24 h in an incubator. At 9 a.m. the next day, the germination box was placed in an incubator at 15 °C for 12 h in the dark, and at 9 p.m., the germination box was placed in an incubator at 25 °C for 12 h in the dark according to the method of Li [ 37 ] and Lang [ 38 ]. At 9 a.m. on the third day, we took a 1–2 cm root tip from the ultra-clean workbench and put the moist root tip into a 1.5 mL centrifuge tube (the cap was pierced with a red-hot dissecting needle) and put it in nitrous oxide for 2 h. Afterward, we added acetic acid to the centrifuge tube and fixed it for 5 min.…”