مروری بر یافته های ژنتیکی مرتبط با ساقه روی در چغندرقند

Extended Abstract
 
Introduction
Sugar beet (Beta vulgaris L.) is a biennial crop that accumulates sucrose in its storage root during the first growing season. However, under specific environmental and genetic conditions, premature bolting may occur in the first year, leading to significant reductions in root yield and sugar content. Bolting tolerance is thus a key breeding objective, especially for autumn-sown cultivars in regions with mild winters. This study aimed to review and elucidate the genetic mechanisms governing bolting and flowering in sugar beet, with a focus on the role of major and minor genes, regulatory pathways, and molecular markers associated with this trait.
 
Materials and Methods
A comprehensive review and synthesis of published research on the inheritance and molecular genetics of bolting tolerance in sugar beet were conducted. Studies involving classical breeding, genetic mapping, QTL analysis, gene expression profiling, and molecular marker development were critically examined. Particular attention was given to the function of B, BTC1, BvFT1, BvFT2, and related genes, as well as the interaction of environmental cues (vernalization and photoperiod) with genetic regulators of the bolting process.
 
Results and discussion
Bolting tolerance in sugar beet is a polygenic trait influenced by both genetic and environmental factors. Early research identified the B gene as a dominant locus controlling annual habit, while subsequent mapping studies revealed additional loci (B2, B3, B4) contributing to flowering regulation. The BTC1 gene plays a central role by coordinating the expression of BvFT1 and BvFT2  under photoperiodic and vernalization control. Vernalization suppresses BvFT1 expression, allowing BvFT2 activation and transition to reproductive growth. Moreover, epigenetic mechanisms such as DNA methylation in shoot apical meristems are associated with differential bolting responses between tolerant and susceptible genotypes.
Molecular marker studies demonstrated strong associations with bolting tendency and offer valuable tools for marker-assisted selection (MAS). Breeding programs in Iran and other countries have successfully developed bolting-tolerant genotypes suitable for autumn planting without adverse effects on root yield or sugar productivity.
 
Conclusion
The transition from vegetative to reproductive growth in sugar beet is governed by complex genetic, epigenetic, and environmental interactions. Advances in molecular genetics and genomics have significantly improved the understanding of bolting control, enabling targeted breeding strategies for bolting tolerance. Integrating traditional selection with molecular tools such as QTL mapping and marker-assisted selection will accelerate the development of stable, high-yielding cultivars adapted to diverse agro-climatic regions. Enhanced knowledge of the genetic basis of bolting not only contributes to crop improvement but also provides a model for studying flowering regulation in biennial plants.
 
Keywords
Bolting tolerance, Photoperiod, Vernalization
 
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