Allelopathic rice ‘PI312777’ (PI) and non-allelopathic rice ‘Lemont’ (Le) were used to assess phenolic acids and terpenoids in the soils of different circles using inhibitory-circle method. The rhizosphere soils of rice (inner circle) and barnyard grass at a 12 cm distance from rice (outer circle) were collected for analyses. The results showed total content of phenolic acids in outer circle of PI was significantly higher than that of Le, while the outer soil of PI contained a higher total content of benzoic acid derivatives and a lower total content of cinnamic acid derivatives than the inner soil. Total terpenoid and monoterpene contents in inner and outer circle soils of PI were significantly higher than that of Le, and the ratio of oxygenated monoterpenes in outer soil of PI was higher than that of Le. Furthermore, phenolic acid mixtures showed a more obvious inhibitory effect on root length than on shoot length of the receptor, while oxygenated monoterpenes were opposite, and a low concentration of oxygenated monoterpenes enhanced inhibitory effect of phenolic acids mixtures on shoot length of the receptor. All results suggested oxygenated monoterpenes participated in the weed-suppressive effect together with phenolic acids of allelopathic rice.

Two main adenoviral diseases have been described in pigeons: pigeon adenovirus type 1 (PiAdV-1) and pigeon adenovirus type 2 (PiAdV-2), which belong to the genus Aviadenovirus under the family Adenoviridae. PiAdV-1 and PiAdV-2 are highly pathogenic to pigeons, leading to considerable losses worldwide. To date, there is little information on the epidemiological distribution of PiAdV-1 and PiAdV-2 in pigeons due to the lack of detection and differentiation platforms for these two viruses. High-resolution melting technology (HRM) has been widely used for developing detection and differentiation platforms, with the melting profile based on the GC content in the real-time PCR (qPCR-HRM) system. This study designed and synthesized a pair of specific primers on the basis of the characteristic variations of the 52K genes of PiAdV-1 and PiAdV-2, then the detection and differentiation qPCR-HRM platform was established after conditional optimization. The results showed that this method had good specificity; it could only specifically detect PiAdV-1 and PiAdV-2, with no cross-reaction with other pigeon-origin pathogens that occur in pigeons. This method had high sensitivity, with the lowest detection limits at 57 copies/µL (for PiAdV-1) and 56 copies/µL (for PiAdV-2). This method had good intra-group and inter-group coefficients of variation, both of which were less than 1.5%. Field samples for the epidemiological surveillance and investigation data of PiAdV-1 and PiAdV-2 were checked. We found only PiAdV-2-positive samples in meat pigeons, but the percentages of PiAdV-1-positive, PiAdV-2-positive, and coinfection-positive samples among the racing pigeons were 5.71%, 14.29%, and 2.86%, respectively. To our knowledge, this is the first report for the simultaneous detection and differentiation of PiAdV-1 and PiAdV-2 using the qPCR-HRM platform. Our study also provided evidence of PiAdV-1 and PiAdV-2 coinfection in racing pigeons, but further studies are needed.

Duck adenovirus 3 (DAdV-3) was firstly identified in Muscovy ducklings exhibiting slight pericardial effusion, swelling, and hemorrhaging in the kidneys, which is a poorly characterized duck virus. This study established a CRISPR/Cas12a coupled with a Lateral flow dipstick (RAA-CRISPR/Cas12a-LFD) detection platform for DAdV-3. The core mechanism of this platform involves a three-step cascade reaction pathway. First, the target sequence of the DAdV-3100 k gene is amplified via RAA isothermal amplification. Second, the amplified products activate the trans-cleavage activity of Cas12a. Finally, signal output is achieved by cleaving probes on the Lateral flow dipstick. This method exhibits high sensitivity, with a minimum detection limit of 2.87 × 10 ² copies/μL for the DAdV-3 positive plasmid. It also demonstrates high specificity for DAdV-3, showing no cross-reactivity with other common duck-origin viruses such as avian influenza virus (AIV), Newcastle disease virus (NDV), duck Tembusu virus (DTMUV), duck plague virus (DPV), Muscovy duck parvovirus (MDPV), duck hepatitis A virus type 1 (DHAV-1), and duck reovirus (DRV). The method enables on-site detection of DAdV-3 within 1 h and 20 min. It does not rely on standardized molecular laboratories or professional operation, provides visualized detection results, allows rapid detection at the grassroots level, and has low detection costs, making it suitable for promotion in small-scale farms. This approach provides a technical means for the detection and epidemiological investigation of DAdV-3.

Background: Increasing the induced-allelopathic potential of rice at the seedling stage by chemical induction is an important strategy in weed management. More in-depth work is needed to find inducing agents for effectively improving the weed-suppressive activity of allelopathic and non-allelopathic rice accessions via the modulation of root morphology and allelochemicals production. Methods: Grown in Hoagland’s solution, two rice cultivars—allelopathic PI312777 (PI) and non-allelopathic Lemont (LE)—were treated using various phytohormones to evaluate root growth and allelopathic potential. Optimal phytohormones (ABA and EBL) were selected based on root growth responses. Extraction of rice leaf and root exudates, subsequently assessed on lettuce seedlings, revealed induced allelopathy. WinRHIZO software was used to investigate root morphologies; HPLC and GC-MS evaluated phenolic acids and terpenoids in rice tissues. The transcription of genes related to phenolic acid and terpenoid biosynthesis was measured by qPCR. ANOVA and correlation analysis were applied in data analysis. Results: The results showed that the optimal induction conditions were abscisic acid (ABA, three µmol/L) or 24-epibrassinolide (EBL, 0.5 nmol/L) for 3 days. Under these conditions, the induced-allelopathy (IA) values of rice root exudates induced by three µmol/L ABA were 9.62% in PI31277, and 13.76% in Lemont, while the IA values of PI31277 and Lemont after 0.5 nmol/L EBL treatment were 7.83% and 11.51%, respectively. ABA mainly affected the root length and volume at 0–0.2 mm diameter, while EBL mostly affected root length and volume at 0–1.0 mm diameter. The total content of phenolic acids in root-exudates of PI31277 and Lemont induced by EBL were 1.16 and 2.33 times greater, respectively, while ABA induction also increased the phenolic acid content by 1.48 and 1.87 times, respectively. Most genes related to phenolic acid and terpenoid synthesis, such as PAL, C4H, F5H, MK, SQS, and PS, were upregulated after EBL induction, while most genes were downregulated after ABA treatment. Moreover, correlation analysis confirmed that root morphology, allelochemicals production, and related gene expression levels were significantly correlated with induced-allelopathy caused by ABA or EBL treatment.

Despite our preliminary research about the inductive effect of exogenous abscisic acid (ABA) on the weed-suppressive activity of rice in a hydroponic system, there is a lack of knowledge regarding the induction mechanism for ABA application to enhance the ability for weed control underground. Here, two pot experiments using rice–barnyard grass mixed culture were conducted to investigate the effects of exogenous ABA treatment on weed inhibition strategies in both allelopathic rice PI312777 (PI) and non-allelopathic rice Lemont (Le). The largest observed weed inhibition changes in the two rice accessions both occurred with the 9 μmol/L ABA treatment. ABA induction on PI significantly increases the inhibitory effect on the plant height of barnyard grass with root contact and root segregation by 25.7% and 19.1%, respectively, with 23.5% increases observed in Le rice with root contact and no significant increases in plants with root segregation with nylon mesh. ABA induction also significantly increased the root distribution in the soil of Le. Compared with the uninduced group, ABA treatment significantly elevated the total amounts of reversibly adsorbed phenolic acids in the two soil layers of PI and the irreversibly adsorbed phenolic acids in Le soil layers. Furthermore, exogenous ABA could change the bacterial composition in rhizosphere soil of the two rice accessions, with the change in the species composition in the rhizosphere soil of the allelopathic rice PI being greater. Importantly, the bacterial compositions (Anaerolineales, Bacteroidales, and Myxococcale) in the PI rhizosphere soil of rice induced by ABA were more related to the contents of reversibly adsorbed phenolic acids in the soil. However, the core bacterial compositions that promote plant growth (Sphingomonadales, Cyanobacteriales, and Rhizobiales) in the Le rhizosphere soil were more related to the contents of irreversibly adsorbed phenolic acids in the soil. These findings suggested that the ABA induction mainly changed root distribution and core bacterial compositions in Le to enhance resource competition, whereas it stimulated the release of reversibly adsorbed phenolic acids to modulate the specific bacterial compositions in rhizosphere soil of PI and to strengthen allelopathic effects.

Rice allelopathy is a natural method of weed control that is regarded as an eco-friendly practice in agroecology. The root growth of allelopathic rice at the seedling stage plays an important role in its weed control. Our study characterizes a plant hormone that promotes root growth, abscisic acid (ABA), to explore its role in the induction of rice allelopathy. Increasing the root morphology traits (root length, root tip number, and root biomass) in rice using different concentrations of exogenous ABA resulted in increased inhibitory ratios against barnyard grass (Echinochloa crus-galli), both in a hydroponic experiment and pot test. In particular, the relative proportion of induced allelopathy to total allelopathy in non-allelopathic rice Lemont (Le) was higher than that in allelopathic rice PI31277 (PI). The total content of phenolic acid, which is an important allelochemical in rice, as previously reported, was significantly elevated in the root exudates of both PI and LE. The gene expression levels of OsPAL, OsC4H, and OsCOL related to phenolic acid synthesis were also up-regulated, with a higher regulatory fold in PI. ABA also increased the expression of OsKSL4 and CYP75B4 involved in the biosynthesis of momilactone B and tricin. Moreover, low concentrations of exogenous ABA mainly positively regulate the expression of OsIAA11, an AUX/IAA transcription factor gene, in the root of PI and Le. These findings suggest that the application of ABA could significantly enhance the weed-suppressive activity of both rice cultivars through regulating root growth and the synthesis of allelochemicals secreted by rice roots, providing an option for the improvement of rice allelopathy through chemical induction.