tihomir.cupic@poljinos.hr, spetrovic@fazos.hr, suncica.kujundzic@fazos.hr, vlado.guberac@unios.hr, sonja.vila@unios.hr

Genetic variability and functional roles of the Rht8 and Ppd-D1 genes have been crucial in the evolution of Croatian wheat cultivars, impacting important agronomic traits. This study aimed to investigate the association of Rht8 and Ppd-D1 alleles with key agronomic characteristics in Croatian wheat genetic resources over time.

A total of 40 winter bread wheat cultivars registered in Croatia from 1931 to 2008 were evaluated for seven agronomic traits. These cultivars originated from Croatia, Austria, France, Italy, and Russia, reflecting a diverse set of genetic resources used in Croatian wheat breeding programs. Significant genetic variability was found for alleles of Rht8 and Ppd-D1 genes.

The analysis found that certain alleles of these genes have a statistically significant influence on agronomic traits such as plant height, spike length, number of spikelets, thousand grain weight and grain yield. Among the researched accessions, the most represented allele was Rht8 with a length of 192 base pairs (bp), which contributed to the development of cultivars with lower plant height, faster spike development and higher grain yield.

On the other hand, the Ppd-D1 allele also showed an influence on these characteristics, particularly accelerating spikelet development and shortening the plant's life cycle. These results highlight the important role of Rht8 and Ppd-D1 genes in wheat breeding and provide valuable insights for further selection programs aimed at improving agronomic characteristics in Croatian wheat cultivars.

Understanding the genetic variability of these genes allows better management of wheat genetic resources to achieve higher productivity and adaptability under different growing conditions. In addition, research has shown that the combination of certain alleles of the Rht and Ppd group genes can influence the optimization of agronomic properties in new wheat cultivars that are more resistant to extreme conditions and adapted to changing climatic conditions.