Evaluation of genetic parameters and relationships between physiological and yield traits of sugar beet under normal and salinity stress condition

In order to determine the genetic parameters and heritability of different traits of sugar beet and also the relationship between traits, full-sib and hybrid genotypes were evaluated in separate trials at Miandoab Agricultural Research Station under salinity and normal conditions in 2017. In full-sib trial performed under salinity condition, root yield, sugar yield, white sugar yield, leaf relative water content, root dry weight, and root/shoot ratio, and under normal condition, root yield, sugar yield, root/shoot ratio and specific leaf weight had higher genetic variance than environmental variance and consequently had higher broad-sense heritability. In hybrid trial performed under salinity condition, for white sugar yield, potassium content, potassium/sodium ratio, nitrogen content, and leaf area, and under normal condition, for root yield, sodium content, potassium/sodium ratio and nitrogen content, genetic variance was high and as a result, broad-sense heritability was above 0.5. Therefore, these traits can be considered in breeding and selection programs. Under salinity condition, the narrow-sense heritability ranged from 0.16 to 0.66. The highest narrow-sense heritability was related to molasses sugar with 0.66, nitrogen content with 0.43, sugar yield with 0.38 and leaf relative water content with 0.38, respectively. Therefore, it can be concluded that these traits are partially controlled by additive effects and can be used for selection of different degrees. Under normal condition, the narrow-sense heritability ranged from 0.01 to 0.29 and the relative water content with 0.29 showed the highest heritability. Under salinity stress, heritability of root yield and sugar yield was moderate; so yield could be improved by long-term selection and hybrid production. The results of regression and path analysis showed that under salinity and normal conditions, when the root yield was considered as dependent variable, specific leaf weight, leaf area, and relative water content explained the variation among which the leaf area had the highest positive direct effect on root yield.