Development of a cost-effective method for assessing varietal purity of barley and malt using molecular genotyping

Abstract

This study demonstrates that it is possible to accurately estimate the level of varietal admixture in a sample of grain - specifically barley - using DNA microsatellite markers without having to analyse grains individually.

The analytical laboratory results obtained are analysed using a Bayesian statistical approach applied to attribute data from counted batches of grain. The attributes in question are 'contains no admixture' and 'contains at least one grain of admixture'.

The advantage of this approach is that it offers the potential to reduce the cost of molecular genotyping since expensive per grain extraction and amplification of DNA can be replaced by extraction from a composite bulk of grains. For example, 100 grains could be analysed as 10 batches, each of 10 grains - a reduction of 90% in some aspects of input cost.

The use of this approach is limited by two factors 1) that where polymorphism exists that off-type alleles can be detected above a background of alleles which are as expected. 2) That the number of grains examined does not exceed that number in which one off-type grain can be detected i.e. the limit of detection.  Methodologies for the detection of off-type alleles and determination of limits of detection for a suite of microsatellite markers are reported.