Comprehensive evaluation of 158 strawberry germplasm resources cultivated in weakly alkaline soil

【Objective】In order to investigate the impact of weakly alkaline condition on cultivated strawberry (Fragaria × ananassa Duch.) germplasm resources, the present experiment was carried out. The shallow root system of cultivated strawberry makes it particularly susceptible to abiotic stresses such as drought and saline-alkali conditions. The aim of this research is to identify promising strawberry genotypes suitable for cultivation in weakly alkaline soils.【Methods】A total of 158 strawberry resources served as the experimental materials. Twenty- one descriptive traits and 11 quantitative traits were evaluated, including plant height, fruit size, as well as leaf and petiole characteristics. For fruit size measurement, 5-6 strawberry fruits were cut longitudinally, and the cross-section area and length were analyzed by a scanner. The 21 descriptive traits were classified according to the Descriptors and Data Standard for Strawberry (Fragaria spp.). The Shannon’s diversity index (H′) was calculated for each descriptive trait. Statistical analysis, including mean, standard deviation, minimum, maximum and coefficient of variation, were conducted for the 11 quantitative traits. Person correlation analysis, principal component analysis (PCA), and cluster analysis were performed by using R package PerformanceAnalytics, FactoMineR and cluster, respectively. Comprehensive scores were based on principal components, and relative proximity degree was evaluated using the DOPSIS method.【Results】The Shannon’ s diversity index (H') for the 21 descriptive traits of cultivated strawberries ranged from 0.218 5 to 1.418 0. The highest diversity was observed in seed-bearing condition, followed by fruit texture (H′ = 1.294 5), while the lowest diversity was found in calyx color. The H′ value for seed color was 0.760 1, with 76.58% of the resources exhibiting both yellow and red seed colors. Descriptive statistics of 11 quantitative traits, including plant height, fruit size and quality, and other agronomic characteristics, revealed substantial phenotypic variation among the accessions, with coefficients of variation (CV) ranging from 12.84% to 54.35%. The highest CV was observed in fruit weight, while the fruit length-to-diameter ratio (L/D) showed the lowest variability. Fruit weight ranged from 2.58 g to 27.20 g, and the L/ D ratio varied between 1.03 and 1.72. The average fruit diameter and length were 30.82 mm and 37.85 mm, respectively. Fruit hardness ranged from 0.41 to 3.11 kg · cm- 2 , with a coefficient of variation of 44.36%. The number of branch crowns ranged from no branching (n = 1) to multiple branching (n = 4.60), with a coefficient of variation of 28.36%. The stolon thickness exhibited considerable variation, ranging from 0.36 mm to 2.59 mm. Correlation analysis revealed a significant positive association between plant height (PH) and fruit-related traits such as fruit size and weight. In contrast, soluble solids content (SSC) showed no significant correlation with the other eight quantitative traits, including fruit diameter (D), length (L), L/D, area (A), perimeter (P), weight (W), hardness (H) and crown number (C). A weak association was observed between SSC and the width of runners (WR). To effectively preserve the information from 11 traits while reducing data redundancy, PCA was performed. The contribution rates of PC 1, PC 2, PC 3 and PC 4 were 51.78%, 12.09%, 10.65% and 9.44%, respectively, with a cumulative contribution rate being 83.97%, which could explain most of the information of the 11 trait indicators. PC 1, with an eigenvalue of 5.70, primarily represented factors related to fruit yield. PC 2 was closely associated with plant height, L/D ratio, and soluble solid content. Cluster analysis classified the germplasms into three distinct groups, each showing distinct differences in quantitative traits. Group 1 comprised 57 germplasms, accounting for 36.08% of the total resources. Group 2 included 34 resources, which exhibited superior performance, characterized by taller plants, larger fruits, and robust stolons. Group 3 contained 67 resources that were identified as alkali-sensitive. While there was little difference in SSC among the three groups, major differences were observed in fruit size, fruit weight, and plant height, which were basically consistent with the results of principal component analysis. Based on the principal component, a comprehensive score was derived for each germplasm, with a higher ranking indicating better overall performance under alkaline soil conditions. Among the top 15 germplasms, six were of foreign origin and nine were Chinese varieties, all demonstrating strong adaptability to alkaline soils. The relative proximity of each resource was further evaluated using the TOPSIS method. Among the top 15 strawberry germplasms identified by TOPSIS, four varieties, Charlotte, Jiatianbao, Kinuama, and Jijiu, were newly introduced resources that ranked highly using this approach.【Conclusion】A total of 11 germplasms were ranked within the top 15 by both evaluation methods, among which six were Chinese varieties. Yanli and Dongxiang were identified as particularly suitable for cultivation in alkaline soil, while C4 and Zhongmei No. 5 demonstrated strong potential as bridging parents for breeding alkaline-tolerant strawberry varieties. These findings establish a solid germplasm resource foundation for the targeted introduction and breeding of Fragaria varieties, as well as for uncovering the molecular regulatory mechanisms underlying alkaline tolerance in cultivated strawberry.