Breeding for improving yield and grain quality of durum wheat in Southern Italy through the identification of ideal allelic combination of adaptation genes

This thesis investigates the genetic and environmental factors influencing key agronomic and quality traits in durum wheat, focusing on the roles of vernalization (Vrn), photoperiod (Ppd), and reduced height (Rht) genes across different genotype groups—landraces, old cultivars, and modern cultivars. The study spans three main research areas: phenology and plant height, yield components, and grain quality and physical properties, using a panel of 186 durum wheat genotypes evaluated over three consecutive years in southern Italy under rainfed conditions and various sowing-by-season combinations. The first study examines allelic diversity at Vrn, Ppd, and Rht loci and their effects on phenological stages and plant height. Results highlight distinct allele combinations (ACs) within genotypes that adapt to early, optimal, and delayed sowing dates. Modern cultivars exhibited shorter heading and flowering times and reduced height, largely due to the presence of Vrn-A1c, photoperiod-insensitive Ppd-A1a alleles, and the semi-dwarf allele Rht- B1b. Landraces and old cultivars, with fixed photoperiod-sensitive alleles and tall alleles at Rht loci, generally displayed longer phenological stages and greater plant height, underscoring the impact of specific ACs on adaptability and growth. The second study explores the effect of these adaptation genes on yield components such as spike length, grain number per spike, and grain weight. The presence of Vrn-A1c and Rht-B1b in modern cultivars was strongly correlated with increased grain number and weight, suggesting that these alleles optimize yield under Mediterranean climates, especially in earlier sowing conditions. In contrast, delayed sowing negatively impacted yield components across all genotypes, with the adaptation genes at Vrn-A1 and Rht-B1 loci modulating environmental responses and promoting yield stability in select genotypes. The third study assesses grain quality traits—including protein, starch, carotenoid content, and physical properties like grain size and weight—across genotypes and sowing conditions. Modern cultivars exhibited higher starch and carotenoid levels due to photoperiod-insensitive Ppd-A1 alleles and semi-dwarf Rht-B1b alleles, which accelerated maturity stages. Meanwhile, delayed sowing was associated with increased grain protein and reduced carotenoid levels. These findings emphasize the combined influence of genetic and environmental factors on durum wheat grain quality, with implications for targeted breeding strategies. Together, these studies illustrate the potential of integrating key alleles into breeding programs to enhance durum wheat's adaptability, yield, and quality under climate variability, offering valuable insights for developing resilient crop varieties.