Morphological diversity of Western Balkan durum wheat landraces

Wheat (Triticum spp.) is a vital food source for a substantial portion of the global population, with durum wheat (Triticum turgidum L. subsp. durum Desf) particularly significant in warmer regions like the Mediterranean. However, the aggressive introduction, spread and adoption of elite germplasm has led to crop genetic diversity loss, prompting efforts to preserve local durum wheat landraces. This study investigates the phenotypic diversity of 80 durum wheat landraces originating from the Western Balkan region, including accessions from Montenegro, Bosnia and Herzegovina, and Croatia. These landraces, locally known under traditional names such as 'Rogosija', 'Grbljanka', or 'Velja pšenica', represent a historical gene pool of durum wheat once widely cultivated until 1972 but subsequently abandoned. Historically, these landraces were valued for productivity, disease resistance, and resilience to drought and heat-traits well suited to Mediterranean conditions. Phenotypic traits were assessed across 17 morphological descriptors following International Union for the Protection of New Varieties of Plants (UPOV) guidelines. We observed wide trait variability, with high variation in ear and plant length, and limited variation in straw pith thickness and ear density. Strong correlations among certain traits suggest coordinated selection patterns or shared developmental pathways, while others may reflect distinct genetic or environmental influences. Our study identified 370 differentiated morphological types across 80 accessions, with most accessions displaying between four and six phenotypes. This demonstrates the extensive genetic variability within the collection. The normalized Shannon-Weaver index (H') across 17 traits averaged 0.59, indicating moderate to high diversity. Maximum H' values exceeded 0.80 for traits such as beak length, shoulder width of the lower glume, ear awn distribution, and recurved flag leaf frequency. Low variation in traits like straw pith thickness (H' = 0.05) and ear density (H' = 0.22) may indicate fixation or selection pressure. These findings provide valuable insights into Western Balkan durum wheat diversity, emphasizing the importance of considering both morphological traits and geographical origins in crop diversity studies. Overall, our study provides a foundation for future breeding efforts aimed at enhancing the agronomic performance and resilience of durum wheat cultivars.