Objective We studied the fungal community composition in the rhizosphere soil of sorghum parental lines with different salt tolerance grown in light saline-alkali soil, aiming to understand the relationship between fungal communities and salt tolerance and provide a technical support for screening high quality seed resources.

Methods Ten sorghum parental lines were selected for a pot experiment, including 2 highly salt-sensitive lines (366 and 1012), 4 salt-sensitive lines (67, 68, 473, and 135), 1 moderately sensitive line (622), 1 salt-tolerant line (342), and 2 highly salt-tolerant lines (1187 and 1090). The plants were grown in light saline-alkali soil with an electrical conductivity (EC) of 1214 mS/cm. After 15 days of growth, rhizosphere soil samples were collected for high-throughput sequencing of the ITS region using Illumina Miseq platform. Mothur software was used for OTU clusting and for analyzing α-diversity, β-diversity and community composition.

Results A total of 619544 valid sequences were obtained from rhizosphere soil of 10 sorghum parent materials, with an average length of 371.94−392.93 bp. A total of 2145 OTUs were identified, 38 of them were common in the 10 rhizosphere soils. and more OTUs were identified from the rhizosphere soil of the two high salt-tolerant materials 1187 and 1090 than from the others. The Chao1, ACE and Shannon indices of the fungal communities in the rhizosphere soils of salt-tolerant sorghum parent materials were higher while the Simpson were lower than those in the other materials. While in rhizosphere soil of salt-sensitive materials, the Chao1, ACE and Shannon indices were lower and the Simpson were higher than the other materials. The β-diversity of fungal communities were significantly different in rhizosphere soils between salt-tolerant and salt-sensitive sorghum parent materials. At the genus level, the dominant fungal communities in rizhosphere soil of salt-tolerant sorghum materials were Phlyctochytrium, Podospora, unclassified Glomerales and unclassified Psathyrellaceae, while in the rizhosphere soil of salt-sensitive sorghum materials were unclassified Xylariaceae, Actinomucor and Fusarium. Correlation analysis indicated that the correlations among most traits reached significant or extremely significant levels. The correlation coefficient between Psathyrellaceae and bud length was 0.98**, between Phlyctochytrium and root length was 0.94**, and between Podospora and root length was 0.86**. In contrast, unclassified Xylariaceae, Actinomucor, and Fusarium showed significant negative correlations with both root length and bud length.

Conclusions When grown in light saline-alkali soil, the rhizosphere soil of salt-tolerant sorghum parental lines contained more fungal community species (mainly AMF) and had higher diversity indices than those of salt sensitive lines. The abundances of the fungal communities, that are positively correlated with the development and growth of roots, are higher in rhizosphere soil of salt-tolerant materials than in that of the salt-sensitive lines, indicating the suitable micro-environment created by the salt-tolerant sorghum lines, which helps to stimulate the nutrient absorption of root, thus increasing the salt -tolerance.