Effect of apple fermentation liquid on rice growth and stress responses in saline-alkali soil under pot conditions

Saline-alkali soil is a major constraint in agricultural production worldwide; environmentally sustainable amendment is being adopted. This study systematically investigated the effects of different concentrations of apple fermentation liquid (AFL). On rice growth under saline-alkali soil using a controlled greenhouse pot experiment. Rice plants were treated with four AFL dilutions (1:25, 1:50, 1:100 and 1:200, v/v), and the plant growth traits, development, physiological responses, biochemical characteristics, rhizosphere fungal community composition, and root transcriptome profiles were assessed. The results showed that: (1) AFL application significantly enhanced growth of rice, with the JS25 (1:25) treatment increasing plant height, stem and root length by 70.7%, 111.4% and 72.9% respectively, compared with the saline-alkali control. It also increased the antioxidant enzyme activities CAT (114.7%-232.2%) and SOD (52.5%-119.1%), and chlorophyll content (127.1%-189.6%), while indicating alleviation of saline-alkali stress by reducing proline accumulation (53.0%-74.9%); (2) High-throughput sequencing (ITS region) revealed that AFL treatment significantly altered the structure of rhizosphere fungal community, markedly increasing the relative abundance of genera such as Plectosphaerella, and Acremonium while changes in Fusarium abundance were interpreted cautiously due to its taxonomic diversity; (3) Transcriptome analysis showed that AFL treatment (JS100) induced large-scale gene expression reprograming in rice roots, including genes associated with ion transport, antioxidant defense, and stress signaling pathways. Because of the post-treatment soil physiochemical parameters and qRT-PCR validation were not conducted, the proposed mechanism should be considered exploratory and hypothesis generating. Overall, this study suggests that AFL treatment may enhance rice stress tolerance under saline-alkali conditions, as reflected in the observed physiochemical, fungal, and transcriptomic responses. However, due to the absence of post-treatment soil analysis and qRT-PCR validation, these findings should be considered exploratory and hypothesis-generating.