Sustained organic amendments utilization enhances ratoon crop growth and soil quality by enriching beneficial metabolites and suppressing pathogenic bacteria.

Introduction: Organic soil amendments such as filter mud (FM) and biochar (BC) can potentially influence the abundance and composition of metabolites. However, our current understanding of the stimulatory effects of FM and BC's long-term impact on stress-regulating metabolites, such as abscisic acid (ABA), jasmonic acid (JA), melatonin, and phenyllactic acid (PLA), and these substrates regulatory effects on disease-causing bacteria in sugarcane ratooning field, which is susceptible to nutrients depletion, diseases, etc., remain poorly understood. Additionally, little is known about how the long-term interaction of these substrates and compounds influences sugarcane ratooning soil enzyme activities, nutrient cycling, and crop growth performance. Methods: To answer these questions, we adopted metabolomics tools combined with high-throughput sequencing to explore the stimulatory effects of the long-term addition of FM and BC on metabolites (e.g., PLA and abscisic aldehyde) and quantify these substrates' regulatory effects on disease-causing bacteria, soil enzyme activities, nutrient cycling, and crop growth performance. Results: The result revealed that ratoon crop weight, stem diameter, sugar content, as well as soil physico-chemical properties, including soil nitrate (NH3 +-N), organic matter (OM), total nitrogen (TN), total carbon (TC), and ß-glucosidase, marked a significant increase under the BC and FM-amended soils. Whereas soil available potassium (AK), NO3 -N, cellulase activity, and phosphatase peaked under the BC-amended soil, primarily due to the enduring effects of these substrates and metabolites. Furthermore, BC and FM-amended soils enriched specific stress-regulating metabolites, including JA, melatonin, abscisic aldehyde, etc. The sustained effects of both BC and FM-amended soils suppressed disease-causing bacteria, eventually promoting ratooning soil growth conditions. A number of key bioactive compounds had distinct associations with several beneficial bacteria and soil physico-chemical properties. Discussion: This study proves that long-term BC and FM application is one of the eco-friendly strategies to promote ratoon crop growth and soil quality through the enrichment of stress-regulating metabolites and the suppression of disease-causing bacteria.

Plant growth and stress-regulating metabolite response to biochar utilization boost crop traits and soil health.

Introduction: The utilization of biochar (BC) as a soil amendment in agriculture has gained significant traction among many farmers and researchers, primarily due to its eco-friendly role in boosting crop output. However, the performance of specific metabolites (e.g., zeatin, melatonin, sucrose, and phenyllactic acid) in the various tissues of sugarcane plant (leaf, stem, and root) and rhizosphere soil-deemed plant growth and stress regulators in a long-term BC-amended field remains poorly understood. Additionally, literature on the shift in soil attributes and crop growth triggered by the strong response of these bioactive compounds to longterm BC utilization remains undocumented. Methods: Metabolome integrated with highthroughput sequencing analyses were conducted to identify and quantify the performance of plant growth and stress-regulating metabolites in a long-term BC-amended field. Additionally, we investigated how the response of these compounds to BC-treated soil influences crop traits and soil biochemical properties. Results: We also identified and quantified the performance of pathogenic bacteria and unraveled the association between these compounds and potential plant growth-promoting bacteria. The BC-supplemented soil significantly boosted the crop traits, including brix, sucrose content, and chlorophyll, as well as soil nutrients, such as soil total nitrogen (TN), ammonium (NH4 +-N), and nitrate (NO3 --N). We also noticed that metabolite-deemed plant growth and stress regulators, including melatonin and phenyllactic acid, were enriched considerably in the stem and root tissues of the BC-amended soil. Zeatin in the leaf, stem, and root tissues exhibited the same trend, followed by sucrose in the leaf tissue of the BC-treated soil, implying that the strong response of these compounds to BC utilization contributed to the promotion of crop traits and soil quality. Pathogenic bacteria belonging to Proteobacteria and Acidobacteria were suppressed under the BC-supplemented soil, especially in the root tissue and rhizosphere soil, whereas plant growth-regulating bacteria, mainly Bradyrhizobium, responded strongly and positively to several metabolites. Discussion: Our finding provides valuable information for agronomists, farmers, and environmentalists to make informed decisions about crop production, land use, and soil management practices. Proper soil assessment and understanding of the interaction between the attributes of soil, BC, and metabolites are essential for promoting sustainable agriculture practices and land conservation.

Identification of ARF transcription factor gene family and its defense responses to bacterial infection and salicylic acid treatment in sugarcane.

Auxin response factor (ARF) is a critical regulator in the auxin signaling pathway, involved in a variety of plant biological processes. Here, gene members of 24 SpapARFs and 39 SpnpARFs were identified in two genomes of Saccharum spontaneum clones AP85-441 and Np-X, respectively. Phylogenetic analysis showed that all ARF genes were clustered into four clades, which is identical to those ARF genes in maize (Zea mays) and sorghum (Sorghum bicolor). The gene structure and domain composition of this ARF family are conserved to a large degree across plant species. The SpapARF and SpnpARF genes were unevenly distributed on chromosomes 1-8 and 1-10 in the two genomes of AP85-441 and Np-X, respectively. Segmental duplication events may also contribute to this gene family expansion in S. spontaneum. The post-transcriptional regulation of ARF genes likely involves sugarcane against various stressors through a miRNA-medicated pathway. Expression levels of six representative ShARF genes were analyzed by qRT-PCR assays on two sugarcane cultivars [LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald)] triggered by Acidovorax avenae subsp. avenae (Aaa) and Xanthomonas albilineans (Xa) infections and salicylic acid (SA) treatment. ShARF04 functioned as a positive regulator under Xa and Aaa stress, whereas it was a negative regulator under SA treatment. ShARF07/17 genes played positive roles against both pathogenic bacteria and SA stresses. Additionally, ShARF22 was negatively modulated by Xa and Aaa stimuli in both cultivars, particularly LCP85-384. These findings imply that sugarcane ARFs exhibit functional redundancy and divergence against stressful conditions. This work lays the foundation for further research on ARF gene functions in sugarcane against diverse environmental stressors.