تحلیل تنوع برخی از صفات زراعی و کیفی مرتبط با قند در برخی از ژنوتیپ‌های چغندرقند

Extended Abstract
Introduction
Sugar beet (Beta vulgaris L.) is produced worldwide due to its economic importance in sugar production. Evaluation of different traits in sugar beet plays an important role in understanding the interaction between hybrids and their related characteristics. To achieve this goal, researchers use various statistical multivariate methods, which enables a comprehensive interpretation of the interactions of hybrids and traits. As sugar beet production expands beyond conventional areas, breeding is necessary to develop new cultivars and evaluate imported foreign cultivars. Quantitative traits pose challenges in selection programs because heritable variation is often masked by non-heritable variation. This study was conducted with the aim of investigating variety of agronomic and morphological traits of 20 sugar beet hybrids in the cold, semi-arid conditions of northwest Iran (Miandoab) to determine hybrids with high root yield and high sugar percentage.
Materials and Methods
After the usual autumn tillage operation, the plant materials were cultivated in randomized complete block design with six replications. The rows were set to be eight m long with 60 cm the distance between rows. The seeds were planted in rows with 17 cm distance and 3-4 cm depth. Initial seed placement exceeded the optimal final density and thinning performed at 2-4 leaf stage. Weed control in the field included manual weeding at different stages as well as herbicide usage. Harvest was done at the end of October and harvested roots were weighed in each plot. Roots were transferred to the laboratory and various traits such as sugar content (SC), sodium content (Na), potassium amount (K), alpha-amino nitrogen (AN), alkalinity coefficient (ALC), white sugar content (WSC), extraction coefficient of sugar (ECS), molasses sugar (MS), root yield (RY) and tuber size (TS) were measured according to the recommended standard guidelines. Data distribution was tested using Ryan-Joiner's normality test, and several descriptive indices such as average, minimum, maximum and coefficient of variation were calculated for traits to show the hybrids status in the studied traits. The principal components analysis was used to reduce the traits to a limited number of components, and the coefficients of the first two components were drawn in a two-dimensional graph to visually show the relationship between traits. In order to simultaneously display hybrids and traits in a single graph, a two-dimensional biplot was created.
Results and Discussion
The highest and the lowest coefficient of variation (CV) was observed in root yield (10.21%) and extraction coefficient of sugar (0.52%), respectively. The coefficient of variation of sodium content and root size traits was relatively high, while the coefficient of variation of sugar content and white sugar content were low. For other traits, the coefficient of variation was moderate. Principal components analysis showed that four components had eigenvalues above unity and were extracted, which explained about 88% of the variations. These components were named impurity factors, crystallized sucrose inhibitor, yield and, quantity and quality inhibitor, respectively. The graph of the first two components showed a positive relationship between the amount of sodium and alpha-amino nitrogen, as well as between root yield and tuber size. Also, there was a positive correlation between sugar extraction coefficient, sugar grade and white sugar content due to closed angles between vectors. The graph of the first two main components of sugar beet hybrids separated them into four different groups, the fourth group includes 5 hybrids (1, 6, 8, 12 and 13) and in terms of characteristics such as sugar extraction coefficient, white sugar amount, root yield and the size of the tuber was significant. The amount of potassium, alkalinity coefficient and molasses sugar of this group was low, so these hybrids can be introduced to regional performance tests for further investigation to be evaluated in terms of performance and quality. Although, most cultivated varieties of sugar beet in Iran are imported from European countries and have high yield and sugar content, but their environmental adaptability has not been well established, so their evaluation is important to meet the necessary condition. Evaluation of different traits in sugar beet showed that root size was related to root performance, while quality traits (sugar and minerals) were less related to root yield, while qualitative traits (sugar and minerals) were less related to root yield and alkalinity coefficient also had a negative effect. The use of multivariate statistical methods facilitated the valuation of hybrids and traits and can be valuable for selecting the best sugar beet hybrid and providing some basic information for the genetic improvement of sugar beet hybrid and providing some initial information for genetic improvement of sugar beet in future projects.
Conclusion
Five hybrids (1, 6, 8, 12 and 13) were identified as the best hybrids in terms of sugar extraction coefficient, white sugar content, root yield, and tuber size. The biplot graphical method was suitable for understanding the pattern of combination and trait interaction in sugar beet.
Keywords: Biplot, Principal Components analysis, Root yield
References
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