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Stem-end rot disease has been causing damage to the production of pomelos in Vietnam. The cur-rent study aimed to (i) isolate fungal pathogens causing pomelo stem-end rot disease (PSERD) and (ii) discover Trichoderma spp. that had an antagonistic ability against pathogens under in vitro conditions. Fungi causing PSERD were isolated from pomelo fruits with symptoms of stem-end rot disease and collected from pomelo farms in Ben Tre province, Vietnam. Moreover, 50 fungal strains of Trichoderma spp. also originated from soils of these pomelo farms in Ben Tre province and were dual-tested with the fungal pathogen on the PDA medium. The results demonstrated that 11 pathogenic fungi causing PSERD were isolated from the fruit and showed mycelial growth of roughly 5.33–8.77 cm diameter at 72 h after inoculation. The two fungi that exhibited the fast-est growth, namely, S-P06 and S-P07, were selected. ITS sequencing of the S-P06 and S-P07 fungi resulted in Lasiodiplodia theobromae. All the 50 Trichoderma spp. strains were allowed to antago-nize against the S-P06 and S-P07 strains under in vitro conditions. The greatest antagonistic effi-ciency was found in Trichoderma spp. T-SP19 at 85.4–86.2% and T-SP32 at 84.7–85.4%. The two antagonists were identified as Trichoderma asperellum T-SP19 and T-SP32. The selected strains of Trichoderma asperellum were potent as a biological control for fruit plants. [ABSTRACT FROM AUTHOR]

Meloidogyne enterolobii Yang & Eisenback, 1983 is amongst the most aggressive root-knot nematodes, causing significant annual losses worldwide to many crops and emerging in many countries recently. Although plants belonging to the citrus family such as grapefruit and citrus have been reported as non-hosts or poor hosts for M. enterolobii, our study recorded the heavy infection of a root-knot nematode that resembles M. enterolobii on pomelo, a species in the citrus family. The molecular data of D2-D3 of 28S rRNA region, morphometrics, and morphological features of second-stage juveniles, males, and females in the present study have confirmed that the root-knot nematode recovered from pomelo in Vietnam belongs to M. enterolobii. To the best of our knowledge, this represents the first report of M. enterolobii infecting pomelo, providing new insight into the host status of this important pest. [ABSTRACT FROM AUTHOR]

Volatile compounds of citrus essential oil are responsible for its flavor and functional properties. In this study, chemical compositions, antioxidant and antibacterial activities of peels' essential oils extracted from different pomelo varieties grown in the south of Vietnam were investigated. The compositions of volatile compounds of pomelo essential oils varied with different pomelo varieties. The essential oils of DaXanh in DongThap (DX-DT) and DuongCam in DongNai (DC-DN) were mostly limonene (90.1% and 95.7% of total relative concentrations, respectively), whereas NamRoi in VinhLong (NR-VL) and BuoiLong in DongThap (BL-DT) had high amounts of γ-terpinene, α-pinene, α- and β-phellandrene. The results also indicate that the essential oils of NR-VL and BL-DT exhibited the highest antioxidant and antibacterial activities against S. iniae and P. aeruginosa as compared to the essential oils of other pomelo varieties. Thus, the high amounts of γ-terpinene, α-pinene, α- and β-phellandrene in the essential oils of NR-VL and BL-DT were responsible for the high antibacterial activities of these essential oils, whereas the high amounts of limonene and myrcene had less effect on the tested bacteria. As a result, the different pomelo varieties and growing locations significantly affect the chemical compositions, antioxidant and antimicrobial activities of the peels' essential oils. [ABSTRACT FROM AUTHOR]