Effects of rice-crayfish integrated model on root exudates and microorganisms of rice during grain filling

The traditional rice-crayfish coculture systems may develop a novel sustainable agriculture by clarifying whether crayfish is serving as a stimulus for rice growth. In order to investigate this mechanism, the experiment selected Cherax quadricarinatus as the cultured species and compared rice root exudates (organic acids, amino acids and phenolic acids) and microbial community structure in integrated rice-crayfish farming (RSC)and rice monoculture (RMC). Gas chromatography/mass spectrometry (GC–MS) and Illumina MiSeq sequencers were adopted as the research method. The results showed that the secretions of malic acid, tartaric acid, maleic acid, isoleucine, serine, total organic acids and total amino acids in rice roots were increased significantly in coculture system during the grain filling stage, with the gap reaching 29.07% ,61.84%,10.8%, 136.11%, 218.54%, 21.50% and 12.69% respectively compared to the control group; The total amount of p-hydroxybenzoic acid, coumaric acid and phenolic acid decreased by 20.38%, 25.5% and 9.48%. In the hard dough stage, the abundance of Methylomirabilota and Latescibacterota were increased in integrated farming system by 101.11% and 48.86%, respectively; At the genus level, the rice-crayfish integrated model significantly increased the abundance of Vicinamibacteria-norank and Latescibacterota-norank by 22.96% and 48.23%. Correlation analysis showed that the total amount of organic acids and phenolic acids secreted by roots were negatively correlated with Chloroflexi and Actinobacteriota. Similarly, tartaric acid, isoleucine, serine and total organic acids were negatively correlated with Actinobacteriota. In contrast, tartaric acid and serine were positively correlated with Vicinabacteria-norank. In conclusion integrated rice-crayfish farming could significantly enhance the secretion of organic acids and amino acids in rice roots and tap sufficient carbon source for the microorganisms of Methylomirabilota, Latescibacterota, Latescibacterota-norank and Vicinamibacteria-norank, thus to stimulate their accumulation in rice rhizosphere and accelerate the release of soil nutrients. These findings provide unique insights into how positive interactions between crayfish and rice root properties in terms of efficient nutrient absorption and how modern agricultural systems might be improved by boosting grain yield and quality.