| Summary: | <p>Abstract</p> <p>Background</p> <p>The yellow colour of pasta products is one of the main criteria used by consumers to assess pasta quality. This character is due to the presence of carotenoid pigments in semolina. During pasta processing, oxidative degradation of carotenoid pigments occurs mainly due to lipoxygenase (LOX). In durum wheat (<it>Triticum durum </it>Desf.), two <it>Lpx-1 </it>genes have been identified on chromosome 4B, <it>Lpx-B1.1 </it>and <it>Lpx-B1.2</it>, and evidences have been reported that the deletion of <it>Lpx-B1.1 </it>is associated with a strong reduction in LOX activity in semolina. In the present study, we characterised the <it>Lpx-B1 </it>gene family identified in a durum wheat germplasm collection and related the distribution and expression of the <it>Lpx-B1 </it>genes and alleles to variations in LOX activity in the mature grains.</p> <p>Results</p> <p>In addition to the already known <it>Lpx-B1.1 </it>and <it>Lpx-B1.2 </it>genes, a new gene was identified, <it>Lpx-B1.3</it>, along with three different <it>Lpx-B1.1 </it>alleles, <it>Lpx-B1.1a</it>, <it>Lpx-B1.1b </it>and the partially deleted <it>Lpx-B1.1c</it>. Screening of the germplasm collection showed that all of the genotypes have one of the three <it>Lpx-B1.1 </it>alleles, associated with either <it>Lpx-B1.2 </it>or <it>Lpx-B1.3</it>, thus showing that in this collection the two genes are alternatives. Therefore, based on <it>Lpx-B1 </it>distribution, three different haplotypes were distinguished: haplotype I, carrying <it>Lpx-B1.3 </it>and the <it>Lpx-B1.1b </it>allele; haplotype II carrying <it>Lpx-B1.2 </it>and the <it>Lpx-B1.1a </it>allele; and haplotype III carrying <it>Lpx-B1.2 </it>and the <it>Lpx-B1.1c </it>allele. Determination of <it>Lpx-B1 </it>transcript abundance and total LOX activity in mature grains revealed differences among these three haplotypes: haplotypes I, II and III showed high, intermediate and low levels, respectively, of functional <it>Lpx-B1 </it>transcripts and enzymatic activity.</p> <p>Conclusions</p> <p>In this germplasm collection, the <it>Lpx-B1 </it>gene family accounts for most of the total LOX activity in the mature grains. Information on these <it>Lpx-B1 </it>haplotypes provides significant improvement for prediction of LOX-1 activity levels in mature grains, and will therefore help in breeding programmes aimed at selection of new durum wheat genotypes with higher carotenoid contents in their end products.</p>
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