First Report of Pseudomonas aeruginosa Causing Soft Rot of Ginger in China

Le résumé fourni par la source

Tongling white ginger (Zingiber officinale), a geographically protected crop renowned for its medicinal and culinary value, has been cultivated for over 2,500 years in Yi'an District, Tongling City (30°45'N, 117°43'E) (Hua et al. 2024). In August 2024, soft rot disease was detected in major production areas, with approximately 30% disease incidence. The disease symptoms manifested as soft rot of rhizomes, accompanied by withering and yellowing of leaves. To identify the pathogens causing the soft rot disease, stem and rhizome tissues were collected from 12 diseased plants across different locations. The samples were subjected to sterilization using 1.0% sodium hypochlorite solution for 5 minutes, followed by triple rinsing with sterile water. The sterilized samples were homogenized in 0.9% saline solution. Serial dilutions of the homogenate were then plated onto nutrient agar (NA) and incubated at 28°C for 48 hours. Representative colonies were purified by sub-culturing on NA medium. Several of the purified colonies on the NA medium displayed smooth and round shapes. Subsequent liquid culture in nutrient broth (NB) revealed their capacity for producing greenish-blue pigments. To confirm the species identity of the bacteria, the 16S rRNA gene, rpoB, atpD, gyrA, gyrB, purH, ilvD and tpiA were amplified from three randomly chosen isolates (Weisburg et al. 1991, Spilker et al. 2012). The gene sequences of 16S rRNA (PV523522, PV523523 and PV523524), rpoB (PV535331, PV535332 and PV535333), atpD (PV544162, PV544163 and PV544164), gyrA (PV808914, PV808900 and PV808901), gyrB (PV808902, PV808903 and PV808904), purH (PV808905, PV808906 and PV808907), ilvD (PV808908, PV808909 and PV808910) and tpiA (PV808911, PV808912 and PV808913) for the three strains, namely AH02, AH14 and AH140, were submitted to the GenBank database. The BLASTn analysis of the 16S rRNA and seven housekeeping gene sequences of the three strains showed more than 98% identity with P. aeruginosa strain F005, respectively. A phylogenetic tree was constructed using MEGA11.0 software based on the multilocus sequences (Tamura et al., 2021). Phylogenetic analysis revealed that strains AH02, AH14 and AH140 were most closely related to P. aeruginosa strain F005. Based on both morphological characteristics and sequence analysis, the three strains were identified as P. aeruginosa. To fulfill Koch's postulates, pathogenicity tests were performed on five two-month-old ginger plants with three replicates per treatment. Bacterial suspensions were prepared in sterile water to achieve a final concentration of 10⁸ CFU/mL. Then, 10 μL of the bacterial suspensions was injected into the stem base of ginger plants, and sterile water was used as a control (Zhang et al. 2024). These plants were then placed in a greenhouse at 30°C and a relative humidity of 80%. After 7 days of inoculation, soft rot disease symptoms developed, resembling those seen on diseased plants in the field. Additionally, in vitro assays revealed tissue discoloration and sponginess in the inoculated rhizome slices. In contrast, the control plants showed no symptoms. The bacterial pathogen was successfully re-isolated from the diseased plants, confirming through morphological examination and sequence analysis. To our knowledge, this is the first report of P. aeruginosa causing soft rot disease of Tongling white ginger in China. This finding is of significant importance for the management and protection of this crop.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.