the pathogen and planted with sweet Buddha’s Hand citron orange in groves. As another research project, we further evaluated the sources of natural could play role in canker resistance in Buddha’s Hand citron (Citrus medica var. sarcodactylis). This resistance breeding small ornamental tree is characterized by the human finger-like appearance of mature fruit. The rind of the fruit By Naveen Kumar, R.C. Ebel and P.D. Roberts is highly fragrant, and fruit size varies from 7 to 12 inches. Fruit lack pulp and are dominated by thick albedo. itrus canker became endemic Education Center (SWFREC) lab was In China, Buddha’s Hand is popularly in Florida after several intro- actively engaged in identifying natural known as Fo Shou and is used as a ductions and eradication resistance to citrus canker. An article symbol of long life and happiness. Cprograms dating back to 1915. from Citrus Industry in February The citrus industry struggles for an 2013 reported the mechanisms of AFTER ARTIFICIAL effective, permanent program. Canker natural canker (Xanthomonas citri INOCULATION is an expensive disease due to the need subsp. citri; Xcc) resistance in kum- Earlier disease development of to increase the number of sprays and quat. However, certain physiological canker in Buddha’s Hand is similar to products applied. Canker also causes limitations prevent its use in current other genotypes following artificial enormous economic losses due to fruit breeding programs. Kumquat pres- inoculation of Xcc. Characteristics drop and reduction in export quality. ents an avoidance mechanism (leaf include water soaking and raised Generally, citrus growers spray defoliation) for canker resistance. epidermis, which were evident at copper compounds to control this Canker-infected leaves defoliate after four and six days after inoculation WE CARRY THE disease. Copper is a trace element, artificial inoculation within one week, (DAI) (Figure 1). However, the most micronutrient and potential envi- curtailing photosynthate availability to striking and conserved features were POWERSPORTS PARTS YOU NEED ronmental pollutant. In due course, developing fruits and bacteria may develop resistance against concomitant decline in this metallic pesticide. fruit yield. In addition, there are reports that NATURAL RESISTANCE showed kumquat also BRAKE ELECTRICAL FILTERS BELTS powersport To identify other canker man- exhibits typical canker PADS agement options in citrus groves, symptoms when arti- BRAKE ELECTRICAL the Southwest Florida Research and ficially inoculated with PADS

Figure 2. Microscopic view of the epidermis of an Xcc-infected leaf of Buddha’s Hand.

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Figure 1. Visual symptoms of canker development in Buddha’s Hand. The number at the bottom represents the number of days after Figure 3. Bacterial population (colony forming units/cm2) in FUEL BALL inoculation (DAI). Buddha’s Hand leaves. SOLENOIDS U-JOINTS CV BOOTS FILTERS JOINTS

Citrus Industry February 2017 20 OReillyAuto.com ADV 1107

ADV 1107 Citrus FL 8.375x11.indd 1 12/1/16 2:12 PM observed at eight DAI: 1) the devel- of a necrotic zone acts as a barrier manifests these positive responses. opment of small necrotic zones that restricting the movement of Xcc to Following artificial inoculation, later transformed into large necrotic non-infected parts of the leaf (figures Xcc populations transiently increased areas (figures 1 and 2, page 20), 2) 1 and 2, page 20), 2) an intact epider- and then declined by a factor of 108 the epidermis remained intact, which mis prevents the spread of inoculum in Buddha’s Hand leaves at 8 DAI is notably ruptured in other citrus through wind-driven rain and wounds (Figure 3, page 20). Data showed active genotypes (Figure 2, page 20) and 3) on citrus and 3) delayed abscission resistance against citrus canker. Such a infected leaves were retained on the means that leaves are still supporting drastic decline in Xcc populations was infected plant between 20 to 30 DAI. the photosynthates supply to fruits. not observed in kumquat. Kumquat These characteristics are of ecologi- Buddha’s Hand is unique from other only showed a 103 factor decline in cal significance because: 1) formation commercial varieties of citrus because it Xcc populations, which is followed by excessive defoliation.

BIOCHEMICAL BASIS ® We also studied the biochemical SOAR Bloom Spray basis behind this significant decline in Xcc populations in terms of hydro- improves flowering, gen peroxide production and lipid peroxidation of membranes. Both fruit set and tree health. of these indices have been shown to cause adverse effects on the host, as well as on pathogen populations. In our work, a higher concentration of hydrogen peroxide and lipid peroxi- dation coincided with active decline in Xcc populations. Several reports have shown that lipid peroxidation of membranes generate intermediate metabolites that act as a precursor for defense hormones like jasmonic acid. Jasmonic acid is a defense hormone and can initiate cell death program. These active canker resistance responses identified in Buddha’s Hand are just the first steps in understanding the full potential and mechanisms of canker resistance for eventual use in canker resistance breeding programs.

Acknowledgment: The authors thank E.A. Hanlon (Soil and Water Science Department, SWFREC) for his critical reading of this article. Replicated university-level-protocol research shows that SOAR Grow your investment ® Bloom Spray can improve flowering and fruit set. SOAR Bloom Spray can Protect your young trees with Extinguish Plus. make a real dollars and sense difference in marketable yields and Naveen Kumar (previously a postdoc- Extinguish® Plus Fire Ant Bait gives non-bearing trees a fighting chance overall tree health and disease resistance. toral research associate at the Citrus against fire ants. Extinguish® Plus Fire Ant Bait combines the killing Contact us today for more information and put SOAR to work for you... Research and Education Center at speed of an adulticide and the long-lasting control of an insect growth ® the time this article was submitted) is regulator (IGR). With its two-way action, Extinguish Plus Fire Ant Bait assistant professor of horticulture and is economical to use with a great price per acre. Our Business Is To Help You Grow Extension specialist at the University To learn more about Extinguish® Plus and a special rebate offer, Order SOAR Bloom Sparay from your favorite supplier or call... of Maryland Eastern Shore. R.C. Ebel visit CentralAntControl.com/rebate or call 1.800.248.7763. 800-277-4950 is a consultant and P.D. Roberts is a 4206 Business Lane • Plant City, Florida 33566 • ChemicalDynamics.com professor of plant pathology, both at the Always read and follow label directions. Extinguish is a registered trademark of Wellmark International. Always read and follow label directions carefully.®SOAR is a registered trademark of Chemical Dynamics, Inc. University of Florida/Institute of Food ©2017 Wellmark International. and Agricultural Sciences SWFREC. 22 Citrus Industry February 2017