Characterization of T5DL·5DS-2RS, a wheat-rye chromosomal translocation with enhanced grain hardness and pre-harvest sprouting resistance.

The breakpoint and segment size of wheat-rye T5DL·5DS-2RS translocation and differentially expressed genes for enhancing grain hardness and pre-harvest sprouting resistance were determined. Wheat (Triticum aestivum L.) is increasingly challenged by pre-harvest sprouting and other various biotic and abiotic stresses due to increasing effects of climate change. Here, by utilizing oligonucleotide probe multiplex #6 FISH (fluorescence in situ hybridization), GISH (genomic in situ hybridization), molecular markers, RNA-seq, and phenotyping analyses, a wheat-rye (Secale cereale L.) segmental T5DL·5DS-2RS translocation was precisely characterized. This translocation chromosome has a 4.05-Mb deletion of 5DS harboring grain hardness genes Pina-D1, Pinb-D1 and soft-protein gene Gsp-D1 that is replaced by a 218-Mb rye 2RS segment carrying Secalin-2, a gene encoding a 75kγ-secalin subunit. This translocation line has markedly enhanced grain hardness and pre-harvest sprouting resistance, but showed small adverse effect on thousand-kernel weight and grain width. The translocation line has significantly changed gene expression profiles whereby down-regulation of genes Pina, Pinb, Gsp-1 contributed to enhanced grain hardness. Differentially expressed genes in the ABA (abscisic acid) and GAs (gibberellins) signaling pathways of both rye and wheat chromosomes appear to be key factors for PHS resistance.