Identification of Genetic Markers Associated with Chronic Moderate Hyperosmotic Stress Responses in Spring Varieties of Triticum aestivum

Triticum aestivum (bread wheat) contributes approximately a fifth of global daily protein and calorie intake, and annually is cultivated on an area of 220 million ha, being at present the most extensively grown stable food crop worldwide (Shiferaw, 2013; FAO, 2017). Abiotic stresses such as drought and heat can dramatically reduce bread wheat productivity by impeding photosynthetic and metabolic processes necessary for optimal growth and development (Gregorová, 2015; Zhang, 2017). Wheat yields have been shown to be suffering greater decreases as a result of drought and heat stress incidents over the last decade, compared to several of the last previous decades (Lesk, 2016). Associative Transcriptomics (AT) is a statistical genomics method which identifies associations between phenotypic trait data, and sequence variation (single nucleotide polymorphisms) and transcript abundance (gene expression markers) data. Here, 135 Triticum aestivum landraces, belonging to the YoGI biodiversity panel (Harper and Bancroft, unpublished data), were phenotyped for traits measuring biomass accumulation in response to hyperosmotic stress. Samples were cultured hydroponically, and treated with 7.5% polyethylene glycol (PEG) 8000. An AT analysis was conducted utilising RNA-seq derived transcriptomic data taken from the YoGI panel, and the phenotypic trait data generated in this study. The AT analysis identified 21 gene expression markers, and sequence variation of one genomic region, as significantly associating with measured variation in fresh root biomass. TraesCS4B01G319100.1, identified by NCBI pBLAST searches and the latest IWGSC annotation information as a putative heat shock protein 40 (HSP40) gene. AT findings were validated through a morphological analysis experiment of a Triticum durum mutant (Kronos4610) purported to have a stop codon mutation within a TraesCS4B01G319100.1 homolog. Future work, utilising genetic markers identified by the AT analysis, is suggested. Associative Transcriptomics is here demonstrated as a novel method for the investigation of plant abiotic stress responses such as hyperosmotic stress.