What is Typical Spelt and How Do We Distinguish it From Modern Wheat-Spelt Intercrosses in Switzerland?

Spelt (Triticum aestivum ssp. spelta) is in increasing demand from consumers and bakeries. Linking phenotypic traits to the underlying genetic information of each variety helps us to better categorise the spelt varieties in Switzerland.

The Swiss spelt market is currently dominated by two varieties – ‘Ostro’ and ‘Oberkulmer Rotkorn’ – considered to be references for Swiss typical spelt (‘PureSpelt’). However, these varieties are fairly low-yielding and susceptible to diseases and lodging. There is therefore a need for improved spelt varieties with higher agronomic potential which should nevertheless retain the essential characteristics of typical spelt.

Modern spelt varieties are often intercrosses of traditional spelt and wheat

As spelt (Triticum aestivum ssp. spelta) is closely related to bread wheat (Triticum aestivum ssp. aestivum), the two subspecies can be intercrossed. Many modern spelt varieties have therefore emerged from crosses between traditional spelt and modern bread wheat. To this day, it remains difficult to distinguish between typical spelt (‘PureSpelt’) and modern wheat-spelt intercrosses, which has led to a degree of uncertainty on the spelt market.

50 typical and modern spelt varieties from Switzerland and Central Europe tested

The ‘SpeltBase21’ project attempts to clarify the phenotypic distinction between typical spelt and modern wheat-spelt intercrosses in the Swiss context. To this end, we tested 50 spelt accessions from Switzerland and Central Europe. These accessions were cultivated in field trials for two seasons on three different Swiss sites. Agronomic, rheological and nutritional parameters were measured for each accession. In addition, the accessions were genotyped using a 25K Illumina Wheat SNP array. The genotyping enabled us to see the location of the varieties on a ‘wheat-spelt’ axis obtained by combining the results of additional spelt and wheat accessions and calculating the genetic proximity of each accession to a reference wheat. In Figure 1 we can see that the bread wheat accessions are clustered on the left-hand side of the graph (in grey), while the spelt accessions are on the right (in orange). Within the spelt cluster, we can further distinguish the accessions according to their genetic proximity to the reference wheat: ‘Ostro’ and ‘Oberkulmer Rotkorn’ are located on the far right of the graph and are hence the most genetically distant from the reference wheat. Near them we also find ‘Tellenbacher Rotkorn’, ‘Rubiota’ and ‘Schwabenkorn’. On the other side of the spelt cluster are ‘Hubel’ and ‘Zürcher Oberländer’, which are the closest genetically to the reference wheat.

Seven significant parameters found for spelt typicity

By linking the genetic results with the phenotypic parameters measured in the field trials for each variety, we were able to determine which phenotypic parameters were associated with genetic proximity to typical spelt. Seventeen phenotypic parameters were measured, including agronomic (plant height, harvest index, precocity, grain yield, protein content etc.), rheological (dough extensibility, resistance, etc.) and nutritional traits (fatty-acid composition, amylose content). Of the 17 variables studied, seven proved to be significant for the description of spelt typicity: typical spelt accessions were characterised by a highly extensible dough, later phenological development, low harvest index, high thousand-kernel weights, a lower Zeleny/protein ratio, a lower dough extensibility/resistance ratio and high plant length (Fig. 2).

Spelt and wheat gluten differ from one another and give different dough properties

The dough properties are therefore typical of spelt. Spelt gluten is more extensible and less elastic than the gluten of soft-wheat varieties, resulting in weaker doughs and a lower baking volume. Typical spelt varieties also have a higher oleic/palmitic acid ratio, a higher monounsaturated fatty-acid content and a higher omega-6/omega-3 ratio.