Crop breeding has increased the productivity and leaf wax n-alkane concentration in a series of five winter wheat cultivars developed over the last 60 years

Plant wax n-alkanes are a major constituent of the leaf and grain surface. In this study, we explored what can be learned from the abundance and carbon isotopic composition (delta C-13) of n-alkanes in historical winter wheat cultivars. We investigated leaf and grain wax n-alkane concentration (Sigma(alkL)and Sigma(alkG)) and carbon isotopes (delta C-13(alkL) and delta C-13(alkG)) on C-29 as well as bulk leaf and grain carbon isotopes (delta C-13(bulkL) and delta C-13(bulkG)) to assess if these wax components changed across five wheat cultivars released from the 1950s to the early 2010s. Results showed that Sigma(alkL) and grain yield increased, while delta C-13(alkL) and delta C-13(bulkL) decreased across the historical wheat cultivars. We found a significant correlation between Sigma(alkL) and shoot biomass at the early growth stage, and a strong correlation between Sigma(alkL) at the grain-filling stage and grain yield. Grain measures, including Sigma(alkG), delta C-13(alkG), and delta C-13(bulkG) did not correlate with crop production. Although delta C-13(alkL) and grain yield were not correlated at the flowering stage, they were correlated at the grain-filling stage under dry conditions. Our results indicate that increased Sigma(alkL) has been indirectly selected in breeding efforts to improve crop production in winter wheat, suggesting that greater leaf waxiness confers advantages for crop growth.