Abstract
Leymus mollis (2n = 4x = 28, NsNsXmXm) possesses novel and important genes for resistance against multi-fungal diseases. The development of new wheat—L. mollis introgression lines is of great significance for wheat disease resistance breeding. M11003-3-1-15-8, a novel disomic substitution line of common wheat cv. 7182 –L. mollis, developed and selected from the BC1F5 progeny between wheat cv. 7182 and octoploid Tritileymus M47 (2n = 8x = 56, AABBDDNsNs), was characterized by morphological and cytogenetic identification, analysis of functional molecular markers, genomic in situ hybridization (GISH), sequential fluorescence in situ hybridization (FISH)—genomic in situ hybridization (GISH) and disease resistance evaluation. Cytological observations suggested that M11003-3-1-15-8 contained 42 chromosomes and formed 21 bivalents at meiotic metaphase I. The GISH investigations showed that line contained 40 wheat chromosomes and a pair of L. mollis chromosomes. EST-STS multiple loci markers and PLUG (PCR-based Landmark Unique Gene) markers confirmed that the introduced L. mollis chromosomes belonged to homoeologous group 7, it was designated as Lm#7Ns. While nulli-tetrasomic and sequential FISH-GISH analysis using the oligonucleotide Oligo-pSc119.2 and Oligo-pTa535 as probes revealed that the wheat 7D chromosomes were absent in M11003-3-1-15-8. Therefore, it was deduced that M11003-3-1-15-8 was a wheat–L. mollis Lm#7Ns (7D) disomic substitution line. Field disease resistance demonstrated that the introduced L. mollis chromosomes Lm#7Ns were responsible for the stripe rust resistance at the adult stage. Moreover, M11003-3-1-15-8 had a superior numbers of florets. The novel disomic substitution line M11003-3-1-15-8, could be exploited as an important genetic material in wheat resistance breeding programs and genetic resources.
Highlights
Leymus mollis (Trin.) pilger (2n = 4x = 28, NsNsXmXm) is an important tetraploid species in Leymus (Poaceae: Triticeae) and a useful genetic resource for wheat breeding as a tertiary gene pool [1]
Plant type, spike length, long awns of M11003-3-1-15-8 closely resembled those of wheat parent 7182, and exhibiting high seed set as wheat cv. 7182
The mitotic and meiotic observations of line M11003-3-1-15-8 indicated that root tip cells (RTCs) had a chromosome number of 42 (Fig 2a), pollen mother cells (PMCs) formed a pairing configuration of 21 II (Fig 2b), and the average chromosome configuration at MI was 0.17 univalent, 1.21 rod, 19.62 ring bivalents, no trivalents or quadrivalents were observed at metaphase I, no chromosomes was lagged at anaphase I (Table 2, Fig 2c)
Summary
Many different derivatives have been developed, especially octoploid Tritileymus [17,18,19,20], which were extensively backcrossed with common wheat as a novel and useful bridge materials for wheat breeding. A translocation line Shannong0096 with resistance to stripe rust was developed from interspecific hybridization between common wheat cv. The multiple alien substitution line 05DM6 with resistance to stripe rust at the adult stage, which had three pairs of Ns chromosomes from L. mollis, was selected from the progeny of octoploid Tritileymus M842-12 and T. durum cv. In order to further transfer excellent resistance genes of M47 line into common wheat, the development of wheat- L. mollis chromosome addition line, substitution line or translocation line may be a novel step. We characterized a novel wheat- L. mollis disomic substitution line via morphological observation, cytogenetic identification, functional molecular markers analysis, genomic in situ hybridization (GISH), sequential FISH-GISH and disease resistance evaluation
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