The Impact of Weather Conditions and Storage Duration on the Germination of Croatian Winter Wheat (Triticum aestivum L.) Varieties

Seed germination is a key determinant of wheat seed quality, strongly affected by genetic potential, weather conditions during production, and storage duration. Although numerous studies have investigated seed viability, little is known about how the interaction between annual climatic variability and storage length affects long-term germination performance of winter wheat. The objective of this study was therefore to assess the influence of weather conditions and storage period on germination energy and germination of 50 Croatian winter wheat (Triticum aestivum L.) cultivars released between 1947 and 2010. The experiment was conducted over five consecutive production years (2013/2014–2017/2018). Seeds of each cultivar were reproduced under standardized field conditions, harvested annually, and stored under identical controlled conditions (5 °C, 30–35% RH). Germination energy (first count, day 4) and total germination (final count, day 8) were evaluated according to ISTA protocols. The results revealed significant effects of both production year and cultivar on germination performance. Seeds produced in 2016/2017 exhibited the highest germination (96.21%), which was ~15% higher than the lowest rate observed in 2013/2014 (80.48%). Germination energy of 2013/2014 seeds was 23% lower compared to 2015/2016 and 2016/2017. Unexpectedly, seeds stored for only one year (2017/2018 production) showed lower germination (90.92%) than those stored for two (96.21%) or three years (95.01%), likely due to excessive rainfall (>100% above average) during seed maturation in 2018 that impaired seed quality. Several cultivars, including Una, Tonka, Žitarka, and Kuna, consistently maintained high germination rates (>94%) even after five years of storage, demonstrating strong physiological stability and long-term viability. These findings underline the combined importance of weather conditions during seed production and storage duration for seed longevity. In practical terms, cultivars with proven stability may be recommended for long-term storage and reliable field performance. Future research should extend germination assessment to additional vigor indices (e.g., germination synchrony, vigor index, abnormal seedlings) and explore genetic mechanisms underlying superior seed longevity in modern wheat breeding.