Integrating high-throughput phenotyping with multiple complementary GWAS models reduces method-dependent bias and enables reliable identification of novel loci and elite germplasm for durable yellow and leaf rust resistance in wheat. The causal agents of yellow and leaf rust in wheat, Puccinia striiformis f. sp. tritici and Puccinia triticina, pose a serious threat to grain yield and quality worldwide. Growing durable resistant wheat cultivars is an effective protection measure contributing to sustainable agriculture. Many of the known resistance genes, however, have been overcome due to the high genetic diversity and adaptability of pathogen populations. Therefore, the present study aimed to identify novel loci associated with yellow rust and leaf rust in a genome-wide association study using 1984 spring wheat accessions from the German Federal ex situ Genebank. Phenotypic data obtained from a detached-leaf assay were combined with 90,283 genotyping-by-sequencing genome-wide markers. Six significant peak marker-trait associations were identified for yellow rust and leaf rust, respectively. These are located on chromosomes 1D, 2B, 3B, 4A, 4B, 4D, 5A, 6B, and 7D. Six candidate genes were identified close to the identified loci. These findings may be valuable for identifying and deploying genetic resources to broaden the genetic basis of resistance and safeguard durability of resistance against yellow and leaf rust.
Behnaz Soleimani, Anne-Kathrin Pfrieme, Ulrike Beukert et al.· Theoretical and Applied Gene...· 0 citations
The barley yellow mosaic virus disease is one of the most important threats of barley production in Europe and Asia. Transmitted by the soil-borne plasmodiophorid Polymyxa graminis, there are no direct control options against the causal bymoviruses Barley Yellow Mosaic Virus (BaYMV) and Barley Mild Mosaic Virus (BaMMV). Resistance breeding is thus the only viable approach and has been very successful in the past, with the resistance-conferring alleles rym4 and rym5 of the EUKARYOTIC TRANSLATION INITIATION FACTOR 4E being used extensively in European winter barley breeding. However, virus strains have meanwhile overcome this resistance. Therefore, there is an urgent need for new sources of resistance. Genome editing with Cas endonucleases is a timely and promising approach in this respect. However, the small insertions and deletions that frequently arise during site-directed mutagenesis usually lead to the knockout of the target genes. In the case of EIF4E, loss-of-function is accompanied by significant yield reduction. Consequently, more precisely edited alleles with retained function are necessary for crop improvement. The present study represents the first application of base editing in barley plants, using the EIF4E gene as an example. Base exchanges were made at two positions in this gene using an nCas9-cytidine deaminase fusion, resulting in a total of 10 novel EIF4E alleles in addition to the introduction of a single nucleotide polymorphism that is part of rym4. Two of these newly generated alleles led to resistance upon BaMMV inoculation without adverse effects on yield, proving this approach promising to generate new material for resistance breeding.
R. Hoffie, A. Habekuss, D. Perović et al.· bioRxiv· 0 citations
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