Effects and side effects of penicillin injection in huanglongbing affected grapefruit trees. (December 2016)

• Record Type: Journal Article
• Authors: Shin, Keumchul; Ascunce, Marina S.; Narouei-Khandan, Hossein A.; Sun, Xiaoan; Jones, Debra; Kolawole, Oluwaseun Olawale; Goss, Erica M.; van Bruggen, Ariena H.C.
• Is Part Of: Crop protection. Volume 90(2016)
• Page Start: 106
• Page End: 116
• Publication Date: 2016-12
• Subjects: Candidatus Liberibacter asiaticus -- Colony forming units (CFU) -- qPCR -- Penicillin resistance -- Glyphosate resistance -- Phytophthora nicotianae; Plants, Protection of -- Periodicals; 632.05
• DOI: 10.1016/j.cropro.2016.08.025
• Languages: English
• ISSNs: 0261-2194

Abstract

Abstract: Trunk injection with penicillin has been tested to control citrus huanglongbing (HLB), but side effects and environmental safety must be assured before approval of penicillin injection can be considered. We investigated effects of penicillin injection on densities of Candidatus Liberibacter asiaticus (Las) in leaves, as well as culturable bacterial populations in rhizospheres and petioles of grapefruit trees in field and greenhouse experiments. Trees were injected with penicillin G, and leaf and root concentrations were assessed in bioassays with Bacillus subtilis . Las densities were determined by qPCR, and bacteria were isolated on a low carbon medium from roots plus rhizosphere and surface-sterilized petioles at various times after penicillin injection. Selected bacterial isolates were tested for penicillin resistance (20 μg/mL) and glyphosate resistance (7000 μg/mL), because glyphosate is widely used and cross-resistance against antibiotics had been documented. One month after penicillin injection half of the greenhouse trees were inoculated with Phytophthora nicotianae . Cycle threshold (Ct) values of Las in old and young leaves significantly increased 90 days after trunk injection with penicillin. Bacterial populations in petioles and root-rhizospheres initially increased after penicillin injections, probably due to nutrient release, then returned to control levels after one week. Penicillin resistance was common in isolates from penicillin-injected and control trees (30–94%). Significantly more glyphosate resistant than sensitive isolates were penicillin resistant (81% versus 52%). Phytophthora root rot was not increased after penicillin injection. Thus, side effects of penicillin injection tested here were minimal, while Las titers were reduced after three months. Highlights: Bacterial populations temporarily increase after penicillin injection in citrus trees. Penicillin resistance is common in penicillin-injected and control trees. Penicillin resistance is associated with glyphosate resistance. Phytophthora root rot does not increase after penicillin injection. Side effects of penicillin injection are minimal, while Las titers are reduced.