International Journal of Horticulture, 2025, Vol.15, No.2, 80-90 http://hortherbpublisher.com/index.php/ijh 81 2 Genetic Factors Influencing Grapevine Yield 2.1 Varietal differences and cultivar selection Varietal differences and the selection of appropriate cultivars play a crucial role in determining grapevine yield. Studies have shown that different grapevine cultivars exhibit significant genetic variation in traits such as bunch weight, berry weight, and fruit yield per vine, which are critical for high yield production. For instance, high estimates of genotypic and phenotypic coefficients of variation for these traits indicate the presence of adequate genetic variation among grapevine genotypes, making them suitable for improvement through selection (Gupta et al., 2015). Additionally, the selection of cultivars with specific traits, such as loose cluster architecture, can enhance resilience to diseases and improve overall yield (Rossmann et al., 2020). 2.2 Genetic improvement and breeding programs Genetic improvement and breeding programs have been pivotal in developing grapevine varieties with enhanced yield performance. Traditional breeding methods, combined with modern biotechnological approaches, have led to the creation of new grapevine varieties that are more productive and resilient to environmental stresses. For example, advancements in plant regeneration and genetic transformation techniques have enabled the development of transgenic grape lines with improved yield, quality, and stress tolerance (Zhang et al., 2021). Moreover, the integration of polyploidization and genomic selection has been proposed as a powerful tool to accelerate the breeding of superior grapevine genotypes with desirable traits (Bharati et al., 2023). 2.3 Genetic markers and genomic selection The use of genetic markers and genomic selection has revolutionized grapevine breeding by allowing for the precise identification and selection of desirable traits. Molecular marker-based methods, such as single nucleotide polymorphisms (SNPs), have been employed to map traits related to fruit set and yield components (Zhu et al., 2024). For instance, a study identified 164 SNPs associated with fruit set-related traits, suggesting a complex polygenic determinism and the potential for pyramiding advantageous alleles to generate superior cultivars (Zinelabidine et al., 2021). Additionally, next-generation sequencing (NGS) technologies have facilitated high-throughput genotyping, trait mapping, and genomic selection, further enhancing the efficiency of grapevine breeding programs (Butiuc-Keul and Coste, 2023). 3 Nutritional Management for High Yield 3.1 Soil fertility and nutrient requirements Soil fertility is foundational to grapevine health and productivity. Grapevines require a balanced supply of macronutrients (N, P, K) and micronutrients to support their physiological growth and fruit development. Deficiencies in essential nutrients can lead to chlorosis, necrosis, and overall poor vine health, which negatively impacts yield and grape quality (Brunetto et al., 2015; James et al., 2022). Long-term studies have shown that maintaining soil fertility through appropriate fertilization practices can significantly enhance grape yield and quality by improving soil organic matter and microbial activity (Zhu et al., 2022). 3.2 Fertilizer application strategies Fertilizer application strategies must be tailored to the specific nutrient requirements of grapevines and the existing soil nutrient status. Integrated approaches that combine organic and inorganic fertilizers have been shown to be effective. For instance, using a mix of mineral nitrogen (60%-80%) and organic or bio-fertilizers (20%-40%) can improve growth characteristics and yield while minimizing the negative impacts of excessive mineral nitrogen use (Muhammed et al., 2023). Additionally, the method of fertilizer application, such as fertigation, can influence nutrient uptake efficiency and soil nutrient status. Studies have demonstrated that combining soil and fertigation methods can optimize nutrient availability and improve grapevine performance (Pushpavathi et al., 2021). 3.3 Role of organic amendments Organic amendments play a vital role in sustainable grapevine nutrition management. The use of organic fertilizers, such as chicken manure, humic acids, and fulvic acids, can enhance soil fertility by increasing organic carbon content and promoting beneficial microbial activity (James et al., 2022; El-Salhy et al., 2023). Organic amendments not only improve soil structure and nutrient availability but also contribute to better water retention
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