Spanish spelt is unique germplasm for improvement of root hair length in hexaploid wheat

Aims Longer root hair length (RHL) increases root surface area, thereby contributing to increased phosphorous uptake. This study aimed to identify useful germplasms and quantitative trait loci (QTL) for RHL improvement in wheat. Methods The genetic variation in RHL was examined using hydroponic culture in 117 hexaploid wheat strains. Rhizosheath size and phosphorous uptake ability were also examined using high P-fixing soils with extremely low phosphorous availability (Andisols). QTL analysis was performed using backcross inbred lines from a cross between a Spanish spelt strain and a bread wheat variety. Results A wide range in genetic variation was found, especially in spelt wheat and landraces of bread wheat, whereas modern bread wheat varieties tended to show shorter RHL. Interestingly, remarkably longer RHL were observed in Spanish spelt strains than in strains from other countries. RHL exhibited a significant positive correlation with rhizosheath size and phosphorous uptake in soils. A QTL on chromosome 2A ( QRhl.obu-2A ) conferring longer RHL by the allele of a Spanish spelt strain was identified. It was co-located with TaRSL4-2AS , a key regulator of root hair elongation. Conclusions Spanish spelt wheat strains could be unique germplasms that provide a useful allele for increasing RHL to enhance phosphorous uptake ability.