|BALDWIN, ELIZABETH - Retired ARS Employee|
|JONES, JEFFREY - University Of Florida|
Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2019
Publication Date: 11/22/2019
Citation: Ference, C.M., Baldwin, E.A., Manthey, J.A., Jones, J. 2019. Inhibitory extracts of calamondin leaves associated with precipitous decline of Xanthomonas citri subsp. citri populations. European Journal of Plant Pathology. 156:451-461. https://doi.org/10.1007/s10658-019-01894-w.
Interpretive Summary: Leaf extracts of calamondin and kumquot are observed to contain compound(s) that prevent in vitro growth of the citrus canker-causing bacteria. Other varieties of citrus did not show this antibacterial property. Potentially, constitutively produced inhibitory compounds in calamondin and kumquat may result in less severe citrus canker symptoms as a result of the rapid decline in the bacterial populations.
Technical Abstract: The relative susceptibility of six Rutaceae family genotypes to bacterial citrus canker (CC) caused by Xanthomonas citri subsp. citri (Xcc) was assessed by measuring and comparing in planta bacterial populations over time following inoculation using a minimally destructive inoculation. These genotypes included lime (Citrus aurantifolia), grapefruit (C. paradisi), sweet orange (C. sinensis), calamondin (C. reticulata X C. japonica), kumquat (C. japonica), and orange jessamine (Murraya paniculata). Internal Xcc populations in orange jessamine plateaued early and remained significantly lower than other genotypes. Xcc populations increased rapidly in all other genotypes, decreasing precipitously and significantly over time in kumquat and calamondin as compared to the more susceptible genotypes sweet orange, grapefruit, and lime. Xcc populations in calamondin peaked by 7 DPI then began to fall significantly relative to the more susceptible genotypes sweet orange, grapefruit, and lime. Given the steep decline in populations in calamondin and kumquat, we compared water-soluble extracts from healthy leaf tissue from all previously investigated Citrus genotypes to determine if the extracts had any inhibitory effect on Xcc, implicating them in this abrupt population declinelate in the infection process. Only extracts from calamondin leaf tissue significantly inhibited Xcc growth within 24 h. Potentially, constitutively produced inhibitory compounds in calamondin may result in less severe CC symptoms as a result of the rapid decline in Xcc populations.