Changes in rheological properties and endosperm peroxidase activity associated with breeding for an osmoregulation gene in bread wheat

Backcross lines which had been bred for an osmoregulation gene to improve the drought tolerance of 3 commercial bread wheat cultivars were tested for standard grain, dough, and baking characteristics. Three field sites were used to provide a range of protein contents of 10-14%. It was found that backcross lines with high osmoregulation had alterations in dough strength which could only be understood in terms of genetic linkage. Evidence of a linkage effect was found by comparing lines with recurrent parents in a season of low water stress, i.e. where yields and hence protein contents of each group were the same. On average, lines which had been bred for high osmoregulation had significantly shorter development times and significantly lower maximum resistances to extension than recurrent parents. Other parameters were not significantly different. A probable explanation of the dough strength effect lay in a difference in peroxidase activity due to linkage between the endosperm peroxidase, Per-A4, locus, and the osmoregulation, or, locus. There was an expectation, from published work, that dough strength could be affected by peroxidase. The hypothesis was confirmed by measurements of peroxidase activity. On average, lines with high osmoregulation (lower dough strength) had lower peroxidase activities than recurrent parents (higher dough strength). This effect, however, depended on protein content and genotype. Significance for plant breeding is discussed.