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Poster: Biology & Disease Mgmt: Biological Control


Isolation of endophytic bacteria associated with roots from citrus infected with Phytophthora nicotianae
A. OLIVARES (1), J. Hernandez-Mendoza (1), S. Nelson (2), V. Ancona (1) (1) Texas A&M Kingsville Citrus Center, U.S.A.; (2) Texas A&M Kingsville Citrus Center, U.S.A.

Citrus orchards in Texas are greatly affected by Phytophthora foot and root rot. Because the presence of antagonistic bacteria associated with plant roots may play a crucial role in root health and disease development we decided to study the effect of Phytophthora infection on endophytic bacterial communities associated with citrus roots. Roots from three Phytophthora infected and three uninfected grapefruit trees were randomly selected to isolate culturable bacteria. Roots were collected from soil samples taken from each tree at four quadrants, 1 meter away from the trunk at a depth of 15 centimeters. Serial dilutions of macerated root tissues were plated onto nutrient agar, tryptone yeast, King’s B and actinomycetes isolation mediums and incubated at three different temperatures. A significantly higher number of cultivable bacteria were present in roots from infected trees versus uninfected trees. In addition, a total of 140 and 119 morphologically distinct bacterial colonies were recovered and isolated from Phytophthora infected and uninfected trees respectively. These initial results indicate that citrus trees infected with Phytophthora spp. are more prone to develop bacteria-root associations. Characterization of the bacterial species associated with Phytophthora infection will lead to the identification of beneficial or antagonistic bacteria against Phytophthora spp.