QTL mapping of shoot and seed traits impacted by drought in barley using a recombinant inbred line population

Authors: Ajayi, Oyeyemi; Bregitzer, Paul; Esvelt Klos, Kathy; Hu, Gongshe; Walling, Jason; Mahalingam, Ramamurthy

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2023
Publication Date: 5/27/2023
Citation: Ajayi, O.O., Bregitzer, P.P., Esvelt Klos, K.L., Hu, G., Walling, J.G., Mahalingam, R. 2023. QTL mapping of shoot and seed traits impacted by drought in barley using a recombinant inbred line population. BMC Plant Biology. 23. Article 283. https://doi.org/10.1186/s12870-023-04292-x.
DOI: https://doi.org/10.1186/s12870-023-04292-x

Interpretive Summary: Water deficit or drought poses a significant threat to barley production and seed quality. If drought occurs during the flowering stages of the plant it is detrimental to seed yields. Otis is a drought tolerant feed barley variety and Golden Promise is a drought sensitive malting variety. A cross was made between these two varieties to develop a population of barley lines. By the process of naturally occurring recombination events genes for drought tolerance from Otis could be introgressed in lines with good malting traits found in Golden Promise. This population of 192 recombinant inbred lines were subjected to water stress for 5-6 days during flowering under greenhouse conditions. Seed yields, shoot weight and seed protein content were evaluated. This population was also grown in field in Aberdeen under irrigated and rainfed conditions. Gene regions associated with the three traits were mapped to the barley genome based on the genotype information from 50,000 sites across the genome in this population. Regions of Chromosomes 2 and 5 harbored genes that were contributing to seed yields and shoot weight traits in this population. Genes involved in abiotic stress tolerance in these regions could be useful for marker assisted selection to breed drought tolerant barley varieties.

Technical Abstract: With ongoing climate change, drought events are severely limiting barley production worldwide and pose a significant risk to the malting, brewing and food industry. The genetic diversity inherent in the barley germplasm offers an important resource to develop stress resiliency. The purpose of this study was to identify novel, stable, and adaptive Quantitative Trait Loci (QTL), and candidate genes associated with drought tolerance. A recombinant inbred line (RIL) population (n=192) developed from a cross between the drought tolerant ‘Otis’ barley variety, and susceptible ‘Golden Promise’(GP) was subjected to short-term progressive drought during heading in the Biotron. This population was also evaluated under irrigated and rainfed conditions in the field for yields and seed protein content. Barley 50k iSelect SNP Array was used to genotype the RIL population to elucidate drought-adaptive QTL. Twenty-three QTL (eleven for seed weight, eight for shoot dry weight and four for protein content) were identified across several barley chromosomes. QTL analysis identified genomic regions on chromosome 2H and 5H that appear to be stable across both environments and accounted for nearly 60% variation in shoot weight and 17.6% variation in seed protein content. QTL at approximately 29 Mbp on chromosome 2H and 488 Mbp on chromosome 5H are in very close proximity to ascorbate peroxidase (APX) and in the coding sequence of the Dirigent (DIR) gene, respectively. Both APX and DIR are well-known key players in abiotic stress tolerance in several plants. In the quest to identify key recombinants with improved tolerance to drought (like Otis) and good malting profiles (like GP), five drought tolerant RILs were selected for malt quality analysis. The selected drought tolerant RILs exhibited one or more traits that were outside the realms of the suggested limits for acceptable commercial malting quality. The candidate genes can be used for marker assisted selection and/or genetic manipulation to develop barley cultivars with improved tolerance to drought. RILs with genetic network reshuffling necessary to generate drought tolerance of Otis and favorable malting quality attributes of GP may be realized by screening a larger population.