Comprehensive analysis of oil sunflower traits in salinized coastal soils in Hebei Province

Because of soil salinization, economic benefits of agricultural lands are low in saline coastal soils. It is therefore important to improve agricultural productivity of saline coastal soils. Though oil sunflower (Helianthus annuus L.) has long been considered as economic oil crop with considerable tolerance to saline-alkaline soils, salinization-driven abiotic stress is a major natural environmental factor that adversely affects oil sunflower production and quality in saline coastal soils. To select salt tolerant oil sunflower variety with optimal traits, and provide reference for salt-tolerant germplasm resources and genetic breeding of oil sunflower, we conducted a controlled chamber test for evaluation of salt tolerance at seedling stage, and a field test for comprehensive assessment of agronomic traits of oil sunflower. In the chamber test, 9 oil sunflower accessions were cultivated in saline-alkali soil and loamy soil. The saline-alkali soil was coastal saline soil with 6 g·kg^-1 salt content adjusted by using weighting method. The loamy soil was a tillage layer of farmland with salt content of 1 g·kg^-1, used as the control. The emergence rate and index were analyzed every 3 days after sowing, and plant height, leaf area, biomass weight of oil sunflower seedlings were measured after 20 days of sowing. In the field experiment, 9 oil sunflower accessions were planted in coastal saline soil with > 4 g·kg^-1 salt content. Growth stage, growth and fruit traits were investigated. Salt tolerance of different oil sunflower accessions was evaluated using the fuzzy membership function. Correlation analysis, principal component analysis and cluster analysis were used to explore properties of accessions and select suitable accessions for coastal saline soil cultivation. The results showed that while the investigated indexes of seedlings of 9 oil sunflower accessions decreased under 6 g·kg^-1 salt content soil, change degrees of 9 oil sunflower accessions were different. The fuzzy membership function analysis of salt tolerance of 9 oil sunflower accessions showed that 'Binkui 1' and 'T562' were strongly tolerant to salt stress, 'Xianrui 1' was the most sensitive to salt stress. The field experiment results showed that one trait was correlated (or extremely correlated) with at least two other traits. Growth period was extremely negatively correlated with production factors, indicating that suffering severe saline environments longer induced lower oil sunflower yield. Cluster analysis of agronomic traits divided 9 oil sunflower accessions into 3 groups. Group Ⅰ included 5 accessions which were high in oil content with medium yield and late maturity. Group Ⅱ included 3 accessions which were early maturing with medium yield and low oil content. Group Ⅲ included 1 accession with high yield, medium maturity and medium oil content. Principal component analysis showed that the three eigenvalues of cumulative variance proportions was 69%, which were growth period, yield factors and quality factors. The comprehensive score of 'Binkui 1' was highest in 9 oil sunflower accessions. Combined with the results of salt tolerance at seedling stage, comprehensive analysis suggested that 'Binkui 1' and 'T562' were excellent varieties of oil sunflower for salt tolerance breeding and cultivation in saline coastal soils.