Volatile organic compounds (VOCs), a bouquet of chemical compounds released by all life forms, play essential roles in trophic interactions. VOCs can facilitate a large number of interactions with different organisms belowground. VOCs-regulated plant-plant or plant-insect interaction both below and aboveground has been reported extensively. Nevertheless, there is little information about the role of VOCs derived from soilborne pathogenic fungi and beneficial fungi, particularly mycorrhizae, in influencing plant performance. In this review, we show how plant VOCs regulate plant-soilborne pathogenic fungi and beneficial fungi (mycorrhizae) interactions. How fungal VOCs mediate plant–soilborne pathogenic and beneficial fungi interactions are presented and the most common methods to collect and analyze belowground volatiles are evaluated. Furthermore, we suggest a promising method for future research on belowground VOCs.

Halophytes are found in high-salt environments naturally, and their roots may be associated with promising microbial candidates for promoting crop growth and salt tolerance. In this study, halotolerant bacteria were isolated from soil and root samples of Rhizophora apiculate (R. apiculate), Avicennia ofcinalis (A. ofcinalis), Thespesia populnea (T. populnea), Acanthus ilicifolius (A. ilicifolius) and Trichophorum cespitosum (T. cespitosum), five native halophytes of southeast seaside of Vietnam. Isolates were tested for maximum salt tolerant and screened for the ability of phosphate solubilization and indole acetic acid (IAA) production. Colony morphology, pigmentation, and Gram staining of each IAA production halotolerant isolate were determined. The bacterial isolates showed the highest salt tolerance and IAA production were identifed by sequencing the 16S rRNA gene. A total of 54 isolates which were able to grow in the presence of up to NaCl 3M were isolated. Twenty-three halotolerant bacterial isolates had the capacity of IAA production, 60.9% from which were Gram positive with a cocci shape, colony in opaque/transparent yellow or opaque/off white, 1 - 2 mm or 2 - 3 mm in diameter with the convex surface. Three isolates VTDD1, VTTD2, and KGOR1 were able to solubilize insoluble phosphorus. The highest IAA production was observed in VTDR1 (93.77 µg/mL) followed by VTMR1 (75.23 µg/mL) and VTDR2 (60.00 µg/mL), while the smallest IAA production was observed in CGOD1 (0.50 µg/mL). The isolates VTDR1 and VTDR2 were identifed as Salinicola tamaricis (99.58% and 99.67% identity respectively), while VTMR1 was found to be Salinicola peritrichatus (98.37% identity).

Tien Giang is one of the Mekong Delta's largest jackfruit-growing provinces, with a total cultivation area of jackfruit of approximately 13,141.09 ha. Bronzing of jackfruit appeared on Thai jackfruit and caused significant damage to growers, however, the information about the disease is still limited. In this study, we assessed the status of bronzing diseases on Thai jackfruit in Tien Giang province via direct interviews with farmers, mapped the disease distribution by Google Earth, and recorded the disease appearance on Thai jackfruit during the year's two main seasons. Bronzing of Thai jackfruit occurred in all growing areas in Tien Giang during both rainy and sunny seasons, causing damage with an average disease prevalence in inquired regions from 5.29% to 10.19% in sunny season, and from 25.43% to 33.05% in rainy season. The disease prevalence was higher in the rainy season. Most farmers showed that bronzing of jackfruit could be identified by external symptoms of the fruit, such as abnormalities in the left stalk, fruit color, shape, and spines, and confirmed by the result of appearance investigation of bronzing on Thai jackfruit during rainy and sunny seasons of the year 2022. Fungicide application and fruit selection at the early stage of fruit development could prevent the disease. According to the disease progress, bronzing of jackfruit appeared from fruit set to harvest and the disease prevalence reached 55.56% in sunny season and 88.89% in rainy season at 20 days after fruit set.