Causes and control of gape, splitting and skinning in grains of malting spring barley

Abstract

Malting barley grain that is damaged by gape, splitting or skinning presents product and processing problems and puts a grower's malting quality premium at risk. Split grain may be rejected for use in both the UK and for export. Gape, splitting and skinning were defined to assist in the development of assessment procedures within the malting industry and in variety testing.

Significant regional differences in splitting and skinning have been noted in the UK indicating that environmental factors, probably due to certain weather patterns, are triggers for splitting and skinning. At locations where there are likely to be a number of high-risk factors, e.g. weather or other seasonal conditions, it is desirable to choose low risk varieties. There is also a significant genetic component to gape, splitting and skinning as varieties and breeding lines vary in their susceptibility to these conditions. Surveys of National List and Recommended List trials would allow the industry to rank varieties according to their risk.

The influence of agronomic practice is not the same in varieties of high or low susceptibility. In susceptible varieties, treatments that enhance excessive grain-filling or prolong canopy greenness have the disadvantageous side effects in that they may increase the risk of splitting or skinning. Crop management in terms of fungicide and nitrogen fertiliser usage must be considered in relation to the relative risks predisposing the crop to grain damage or loss of yield and quality due to disease. In varieties that are predisposed to skinning it is best to avoid the more abrasive combine settings and mechanical damage associated with some post-harvest processing.

Growth and physiological changes during husk and grain development were associated with incidence of gape, splitting and skinning. However, there was no strong evidence to suggest that gape per se leads to splitting. Splitting and skinning are examples of traits that are determined by a number of genes whose expression is under considerable environmental influence but associations have been identified between genetic markers and a number of loci affecting the grain traits; gape, splitting and skinning.

This project offers the prospect of developing molecular markers of real value in marker-assisted selection. Variety improvement depends on successful selection that is best attained in traits with a high proportion of genetic variation and low environment or genetic x environment influences. In respect to splitting there would appear to be sufficient genetic variability to permit progress using a combination of marker-assisted selection and phenotypic screening.