A genetic strategy generating wheat with very high amylose content

Summary Resistant starch ( RS ), a type of dietary fibre, plays an important role in human health; however, the content of RS in most modern processed starchy foods is low. Cereal starch, when structurally manipulated through a modified starch biosynthetic pathway to greatly increase the amylose content, could be an important food source of RS . Transgenic studies have previously revealed the requirement of simultaneous down‐regulation of two starch branching enzyme ( SBE ) II isoforms both located on the long arm of chromosome 2, namely SBEII a and SBEII b , to elevate the amylose content in wheat from ~25% to ~75%. The current study revealed close proximity of genes encoding SBEII a and SBEII b isoforms in wheat with a genetic distance of 0.5 cM on chromosome 2B. A series of deletion and single nucleotide polymorphism ( SNP ) loss of function alleles in SBEII a , SBEII b or both was isolated from two different wheat populations. A breeding strategy to combine deletions and SNP s generated wheat genotypes with altered expression levels of SBEII a and SBEII b, elevating the amylose content to an unprecedented ~85%, with a marked concomitant increase in RS content. Biochemical assays were used to confirm the complete absence in the grain of expression of SBEII a from all three genomes in combination with the absence of SBEII b from one of the genomes.