Development and genetic analysis of wheat double substitution lines carrying Hordeum vulgare 2H and Thinopyrum intermedium 2Ai#2 chromosomes

Abstract

Thinopyrum intermedium and barley are two close relatives of wheat and carry many genes that are potentially valuable for the improvement of various wheat traits. In this study we created wheat double substitution lines by hybridizing different wheat–Th. intermedium and wheat–barley disomic alien substitution lines, with the aim of using genes in Th. intermedium and barley for wheat breeding and investigating the genetic behavior of alien chromosomes and their wheat homoeologs. As expected, we obtained two types of wheat double substitution lines, 2D2Ai#2(2B)2H(2A) and 2A2Ai#2(2B)2H(2D), in which different group 2 wheat chromosomes were replaced by barley chromosome 2H and Th. intermedium chromosome 2Ai#2. The new materials were characterized using molecular markers, genomic in situ hybridization (GISH), and fluorescent in situ hybridization (FISH). GISH and FISH experiments revealed that the double substitution lines harbor 42 chromosomes including 38 wheat chromosomes, a pair of barley chromosomes, and a pair of Th. intermedium chromosomes. Analysis using specific DNA markers showed that two pairs of wheat homoeologous group 2 chromosomes in the new lines were substituted by a pair of 2H and a pair of 2Ai#2 chromosomes. Chromosome 2H showed a higher transmission rate than 2Ai#2, and both chromosomes were preferentially transmitted between generations via female gametes. Evaluation of botanic and agronomic traits demonstrated that, compared with their parents, the new lines showed similar growth habits and plant type but differences in plant height, flowering date, and self-fertility. Cytological observations using different probes suggested that the double substitution lines showed nearly normal genetic behavior before and during meiosis. The novel substitution lines can potentially be used in wheat meiosis research and breeding programs. Keywords: Wheat, Double substitution lines, Molecular markers, Transmission rate of alien chromosomes, Genomic in situ hybridization