Evaluation of genetic diversity in sugar beet (Sugar beet L.) hybrids in terms of yield, qualitative and germination traits

The study of phenotypic diversity is highly recommended as a first step before conducting in-depth biochemical or molecular studies. Hence, morphological description is the most important issue in the process of studying and preserving plant genetic diversity. The use of different traits to study phenotypic diversity reveals the genetic structure and degree of diversity of the study population, which forms the basis of genetic breeding. In breeding programs with the aim of improving the crop and increasing productivity, recognizing the genetic diversity associated with important agronomic traits and also determining the relationship between them is of particular importance.

In this regard, 155 sugar beet hybrids were planted in five incomplete blocks in Khoy Agricultural Research Station during 2020 in the augmented randomized complete block design with five controls of Sina, Novodoro, Modex, Lorquite and Pirula. Germination uniformity and growth uniformity were recorded during the growing season. Experimental harvesting operation was performed by counting and weighing the roots of experimental plots. The roots were then transferred to the sugar technology laboratory of Khoy Agricultural Research Station to wash and prepare a random sample of pulp. To estimate sugar yield, first the root yield of each hybrid was generalized per ton per hectare and by multiplying the percentage of sugar and root yield, sugar yield was obtained. Phenotypic, genetic and environmental variances, phenotypic, genetic and environmental variation coefficients, general heritability and genetic advance were calculated. After calculating Pearson correlation coefficients between the studied traits, stepwise regression analysis was performed for sugar yield characteristics; Then, according to the traits entered in the regression equation, path analysis for sugar yield was performed. Experimental genotypes were grouped based on the Ward method and the optimal number of clusters was determined based on k means.

The results of analysis of variance of the studied traits indicated that there was significant genetic diversity among experimental hybrids in terms of germination uniformity, root yield, sugar content and sugar yield. In all studied traits, due to the influence of environmental factors on them, the phenotypic diversity coefficient was estimated to be higher than the genetic diversity coefficient. Four traits of germination uniformity, root yield, sugar yield and sugar content showed high inheritance. Among the different studied traits, sugar yield and root yield had a positive and a very significant correlation at the probability level of 0.1%. The results of stepwise regression analysis confirmed that the three traits of root yield, sugar content and germination uniformity cause more than 99% change in sugar yield. The results of path analysis confirmed the results of correlation analysis and stepwise regression and showed that the most direct and positive effect is related to the root yield. Based on cluster analysis, experimental hybrids were classified into four distinct groups; So that in the first group was hybrids that had high uniformity in germination and good yield in terms of roots and sugar.

Genetic diversity is now accepted as a special field that can contribute to food security and nutrition. Genetic diversity of crops is the basis of sustainable development. Therefore, there is a need to identify diverse genetic resources using various statistical tools and use them in breeding programs. In the present study, genetic diversity in terms of different traits among sugar beet hybrids was investigated using statistical methods. The results showed that there was considerable genetic diversity among the experimental hybrids in terms of the majority of traits, which confirms the extensive genetic variation in breeding hybrids and provided the paternal basis of this rich diversity in the studied germplasm; Experimental hybrids were divided into four heterotic groups for all traits. Given the diversity of traits and experimental hybrids, hybrids with desirable traits can be selected based on breeding goals and used in future breeding programs to achieve the goals.