title: Genetic analysis of potassium use efficiency in Brassica oleracea.
abstract: OBJECTIVE
  Potassium (K) fertilizers are used in intensive and extensive agricultural systems to maximize production. However, there are both financial and environmental costs to K-fertilization. It is therefore important to optimize the efficiency with which K-fertilizers are used. Cultivating crops that acquire and/or utilize K more effectively can reduce the use of K-fertilizers. The aim of the present study was to determine the genetic factors affecting K utilization efficiency (KUtE), defined as the reciprocal of shoot K concentration (1/[K](shoot)), and K acquisition efficiency (KUpE), defined as shoot K content, in Brassica oleracea.
  
  
  METHODS
  Genetic variation in [K](shoot) was estimated using a structured diversity foundation set (DFS) of 376 accessions and in 74 commercial genotypes grown in glasshouse and field experiments that included phosphorus (P) supply as a treatment factor. Chromosomal quantitative trait loci (QTL) associated with [K](shoot) and KUpE were identified using a genetic mapping population grown in the glasshouse and field. Putative QTL were tested using recurrent backcross substitution lines in the glasshouse.
  
  
  RESULTS
  More than two-fold variation in [K](shoot) was observed among DFS accessions grown in the glasshouse, a significant proportion of which could be attributed to genetic factors. Several QTL associated with [K](shoot) were identified, which, despite a significant correlation in [K](shoot) among genotypes grown in the glasshouse and field, differed between these two environments. A QTL associated with [K](shoot) in glasshouse-grown plants (chromosome C7 at 62.2 cM) was confirmed using substitution lines. This QTL corresponds to a segment of arabidopsis chromosome 4 containing genes encoding the K+ transporters AtKUP9, AtAKT2, AtKAT2 and AtTPK3.
  
  
  CONCLUSIONS
  There is sufficient genetic variation in B. oleracea to breed for both KUtE and KUpE. However, as QTL associated with these traits differ between glasshouse and field environments, marker-assisted breeding programmes must consider carefully the conditions under which the crop will be grown.
authors.affiliation: Scottish Crop Research Institute, Invergowrie, Dundee DD25DA, UK. philip.white@scri.ac.uk
authors.forename: P J
authors.initials: PJ
authors.lastname: White
authors.forename: J P
authors.initials: JP
authors.lastname: Hammond
authors.forename: G J
authors.initials: GJ
authors.lastname: King
authors.forename: H C
authors.initials: HC
authors.lastname: Bowen
authors.forename: R M
authors.initials: RM
authors.lastname: Hayden
authors.forename: M C
authors.initials: MC
authors.lastname: Meacham
authors.forename: W P
authors.initials: WP
authors.lastname: Spracklen
authors.forename: M R
authors.initials: MR
authors.lastname: Broadley
mesh_terms: D001937:Brassica / Q000235:genetics* / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D040641:Quantitative Trait Loci / Q000235:genetics
chemical_list: D011188:Potassium