Investigating the genetic diversity of sugar beet half-sib families under natural infection conditions to cyst nematode and rhizomania diseases

Plant breeding is based on genetic diversity. Genetic diversity originates from natural evolution and is the most important component in the stability of biological systems and ensures long-term adaptation and population survival . Conventional agriculture has caused a drastic reduction in the diversity of crop plants. Among the 30,000 identified edible plant species, only 30 species are the main sources of nutrition for the world's people. Considering that the existence of genetic diversity is necessary for success in plant breeding, therefore, the selection of superior genotypes from among the modified populations depends on the existence of genetic diversity. The purpose of this research is to evaluate the genetic diversity of sugar beet half-sib families in the conditions of natural infection with rhizomania and cyst nematode and to determine the relationships of different traits using multivariate statistical methods.

This experiment was studied the half-sib families of sugar beet (90 lines) in a field naturally infected with cyst nematode and rhizomania at Torogh Agricultural Research Station (Mashhad) in 2020 using Augmented design with four controls, Aria, Fernando, Pauletta and Sharif.

The results of analysis of variance showed that there was a significant genetic diversity among the half-sib families studied in terms of root yield, sugar yield and white sugar yield. The highest amount of heritability among the evaluated traits was related to white sugar yield with 86.87% heritability, which indicates that this trait is less influenced by environmental factors. In this research, white sugar yield had a positive and significant correlation with all traits except molasses sugar percentage at the probability level of 1%. Stepwise regression showed that the two attributes of sugar yield and extraction coefficient of sugar cause more than 99% of changes in white sugar yield. Path analysis results showed that sugar yield had the most direct and positive effect on white sugar yield. Based on cluster analysis, the experimental genotypes were classified into three distinct groups; So that the first group included half-sib families that had high root yield and sugar.

Due to the existence of considerable diversity between the traits and experimental half-sib families, half-sibs with desirable traits can be selected based on breeding goals and used in future breeding programs in order to prepare cultivars resistant to cyst nematode and rhizomania diseases.