Identification of F1 hybrid and assessment of cold resistance in grape interspecific hybridization

• Integrates field morphology with SSR markers for reliable hybrid authentication. • Employs Low Temperature Exotherm analysis on dormant buds to assess cold hardiness. • Provides valuable germplasm resources for cold-resistant grape rootstock breeding. European grape varieties are extensively grown in northern China, necessitating burial in soil to endure severe winter conditions. While effective for cold protection, this method elevates production costs, damages the vines, and ultimately impedes the development of the grape sector by diminishing the competitiveness of Chinese grapes in domestic and international markets. Breeding new grape varieties with natural overwintering capabilities is crucial to address cold resistance challenges. Three interspecific hybrid combinations — V. amurensis ‘Zuoshan-2′ × V. riparia ‘Hean-2′, V. amurensis ‘Zuoshan-2′ × V. riparia ‘Hean-1′ , and V. riparia ‘Hean-1′ × V. adstricta ‘Taishan-2′ — were developed through conventional hybridization to incorporate cold-resistant germplasm. Identification of true hybrids from each cross combination was achieved through a combination of Simple Sequence Repeat (SSR) molecular markers and morphological traits, yielding hybrid rates of 57.14 %, 23.53 %, and 75.00 %, respectively. The cold resistance of these verified hybrids was determined using low-temperature exotherm (LTE) analysis. The rootstock 15–1–49, from the V. amurensis ‘Zuoshan-2′ × V. riparia ‘Hean-2′ cross, demonstrated the highest cold resistance with an LTE value of –26.96 °C. In the V. amurensis ‘Zuoshan-2′ × V. riparia ‘Hean-1′ combination, rootstocks 15–2–4 and 15–2–23 exhibited the most cold resistance, with LTE values of –23.98 °C and –22.59 °C, respectively. Within the V. riparia ‘Hean-1′ × V. adstricta ‘Taishan-2’ population, rootstocks 15–6–12, 15–6–34, and 15–6–45 displayed the strongest cold resistance, with LTE values of –27.09 °C, –27.15 °C, and –27.65 °C, respectively. These findings offer valuable germplasm resources for breeding novel high-quality cold-resistant grape varieties. They also have significant implications for utilizing and promoting grape genetic resources, developing cold-resistant rootstocks, and enhancing China's grape industry competitiveness.