An integrated approach to stabilising Hagberg Falling Number in wheat: screens, genes and understanding

Abstract

Hagberg Falling Number (HFN) is the wheat quality characteristic which is least amenable to agronomic or post-harvest manipulation and thus almost totally reliant on breeding for improvement. It is, however, difficult to breed for stable HFN and also difficult to assess HFN stability in the Recommended List variety trials due to the highly weather-dependent variation in HFN inductive conditions from year to year.

The main aim of this LINK project was to provide the information to the breeding companies to enable the technique of marker-assisted breeding to be implemented for HFN. A secondary aim was to establish the genetic and molecular mechanisms underlying the two principal causes of low HFN: pre-harvest sprouting (PHS) and pre-maturity amylase (PMA).

At the heart of the project was a series of field trials with mapping lines derived from several crosses between resistant parent varieties and susceptible parent varieties for PHS and for PMA. Some of these trials were overhead-irrigated to ensure PHS induction, and some were unirrigated to assess PMA if inductive weather occurred for PMA and not PHS.

The position of genes controlling PHS and PMA (mainly quantitative trait loci [QTLs], each having a small effect) were located along the length of specific chromosomes by mathematical analysis following HFN measurement of grain from the mapping lines. The QTL locations were validated through the development of controlled environmental screening procedures for PHS and PMA and their use with selected mapping lines.

The foundation for further developments in breeding for stable HFN was laid by identifying and mapping genes regulating hormones involved in amylase production in the grain. Understanding of PMA was enhanced by several cell biology and molecular techniques, which demonstrated that different varieties may develop PMA in different locations within the grain.

This project has provided, for the first time, a comprehensive understanding of the genetics of HFN in UK breeding material and this will enable varieties with more stable HFN to be commercially available within the next five to ten years.