Analysis of aneuploid lines of bread wheat to map chromosomal locations of genes controlling root hair length.

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Long root hairs enable the efficient uptake of poorly mobile nutrients such as phosphorus. Mapping the chromosomal locations of genes that control root hair length can help exploit the natural variation within crops to develop improved cultivars. Genetic stocks of the wheat cultivar 'Chinese Spring' were used to map genes that control root hair length. Aneuploid stocks of 'Chinese Spring' were screened using a rapid method based on rhizosheath size and then selected lines were assayed for root hair length to identify chromosomes harbouring genes controlling root hair length. A series of lines with various fractional deletions of candidate chromosomes were then screened to map the root hair loci more accurately. A line with a deletion in chromosome 5A was analysed with a 90 000 single nucleotide polymorphism (SNP) array. The phosphorus acquisition efficiency (PAE) of one deletion line was compared with that of euploid 'Chinese Spring' by growing the seedlings in pots at low and luxury phosphorus supplies. Chromosomes 1A, 1D and 5A were found to harbour genes controlling root hair length. The 90 000 SNP array identified two candidate genes controlling root hair length located on chromosome 5A. The line with a deletion in chromosome 5A had root hairs that were approx. 20% shorter than euploid 'Chinese Spring', but this was insufficient to reduce its PAE. A rapid screen for rhizosheath size enabled chromosomal regions controlling root hair length to be mapped in the wheat cultivar 'Chinese Spring' and subsequent analysis with an SNP array identified candidate genes controlling root hair length. The difference in root hair length between euploid 'Chinese Spring' and a deletion line identified in the rapid screen was still apparent, albeit attenuated, when the seedlings were grown on a fully fertilized soil.