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United States Department of Agriculture

Agricultural Research Service

Title: Screening Citrus Germplasm for Resistance to Xanthomonas Anonopodis Pv. Citri

Authors
item MCCOLLUM, THOMAS
item BOWMAN, KIM
item GOTTWALD, TIMOTHY

Submitted to: Hortscience Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 15, 2006
Publication Date: July 15, 2006
Citation: Mccollum, T.G., Bowman, K.D., Gottwald, T.R. 2006. Screening citrus germplasm for resistance to xanthomonas anonopodis pv. citri. Hortscience Proceedings.41:1048-1049

Interpretive Summary: Citrus bacterial canker is a serious threat to the citrus industry and currently there are no effective means to control this disease. Developing breeding citrus cultivars resistant to bacterial canker would be the best method for dealing with the disease. Our objective in this work was to determine the resistance of selected citrus species, citrus hybrids, and citrus relatives to citrus canker with the ultimate goal of incorporating resistance into new cultivars. Our first experiment focused on determining if differences in resistance exist among 20 mandarin genotypes and along with three other citrus species and citrus relatives Glycosmis pentaphylla and Clausena hardimandiana. Our second experiment included 10 members of the genus Citrus and Poncirus trifoliata representing a total of 31 different selections. In both experiments the plants were inoculated with the bacterium which causes canker and the incidence of disease was recorded. We found highly significant differences among genotypes in response to inoculation with the bacterium. Our results expand on previous studies on resistance of citrus and citrus relatives to canker and indicate that there may be potential for increasing resistance by breeding using selected parents.

Technical Abstract: Citrus bacterial canker (causal agent Xanthomonas axonopodis pv. citri (Xac)) is a serious threat to the citrus industry. Currently there are no effective means to control citrus canker. Our objective was to determine the resistance of selected Citrus species, citrus hybrids, and citrus relatives to Xac. Our first experiment focused on determining if differences in resistance exist among 20 C. reticulata genotypes and included three other citrus species and citrus relatives Glycosmis pentaphylla and Clausena hardimandiana. Plants were inoculated with Xac strain A either by injection infiltration or needle-prick. Our second experiment included 10 members of the genus Citrus and Poncirus trifoliata representing a total of 31 different selections. Plants were needle-prick inoculated with both Xac strain A and Xac strain A Wellington (AW). All inoculations were done using suspensions of Xac at a concentration of 104 cfu/mL. In both experiments there were highly significant differences among genotypes in response to inoculation with Xac. In the first experiment, regardless of inoculation method, G. pentaphylla and C. hardimandiana were found to be highly resistant to Xac whereas C. paradisi was least resistant. In the second experiment for both Xac strain A and AW, Chinotto sour orange, Carrizo citrange, Eustis limequat, and P. trifoliata were the most resistant. Thornless key lime x Meiwa kumquat hybrids showed a range of resistance from among the most susceptible to among the most resistant. Our results expand on previous studies on resistance of citrus and citrus relatives to Xac and indicate that there may be potential for increasing resistance by breeding using selected parents.

Last Modified: 7/25/2014
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