Progress 09/15/03 to 09/14/06
Outputs
Dodder (Cuscuta spp.) is a ubiquitous parasitic plant infesting many field and horticultural crops in the United States and throughout the Caribbean. Cuscuta americana and C. pentagona occur widely as an economical parasitic weed problem of fruit, timber and ornamentals in the Caribbean. Alternaria destruens has been developed as a registered bioherbicide for Cuscuta species. A host-range study using 30 plants of economic importance belonging to 8 families (Asteraceae, Convolvulaceae, Fabaceae, Malvaceae, Meliaceae, Poaceae, Rutaceae and Solanaceae) indicated that A. destruens is pathogenic only to Cuscuta spp. In greenhouse trials of efficacy in citrus, seven treatments were applied: an untreated control; oil (PCC 588); A. destruens (Smolder WP); a mixture of A. destruens + oil; ammonium sulfate at 0.125% w/v in water; glyphosate at 0.02 kg (ae)/L of Roundup Pro; and a mixture of A. destruens + oil, glyphosate at 0.02 kg (ae)/L of Roundup Pro, and ammonium sulfate at
0.125%. By 35 days after treatment, all C. pentagona plants treated with the last treatment were dead but not the citrus host plant. However, no treatment was found effective in controlling with C. americana. Efficacy of A. destruens was further assessed in field trials. Four treatments consisting of an untreated control, oil, A. destruens + oil and A. destruens were tested, but the levels of control did not differ among the treatments. To determine if this lack of difference was due to pathogen's dispersal, Alternaria isolates from randomly chosen Cuscuta pentagona tissue samples were collected from field and greenhouse trials and studied using nuclear rDNA internal transcribed spacer (ITS) region, including ITS1, ITS2 and the 5.8S rDNA. Neighbor-joining analysis revealed that all 47 unknown isolates and the reference A. destruens isolate were 100% identical. The results indicated a high degree of conservation of the ITS region in A. destruens which made it impossible to conclude
that the isolates from field and greenhouse samples were the same as the reference isolate used in these trials. Overall, this study has confirmed the effectiveness of an integrated system consisting of A. destruens, glyphosate and ammonium sulfate to control C. pentagona.
Impacts
Cuscuta species are difficult to control parasitic plants that cause serious weed problems in many economic and ornamental crops. Current control methods are inadequate. The results indicates that Cuscuta pentagona can be completely killed by using a mixture of a fungal pathogen, Alternaria destruens Simmons, sp. nov., used as a bioherbicide, glyphosate at 23.14 g ae/L of Roundup Pro and ammonium sulfate at 0.125% w/v in water. The information contributes to the agricultural industry by providing an integrated method of controlling C. pentagona.
Publications
- Cook, J., R. Charudattan, E. Rosskopf, T. Zimmerman, G. MacDonald and W. Stall. 2004. Integrated control of dodder (Cuscuta pentagona) using glyphosate, ammonium sulphate and the biological control agent Alternaria destruens. Proc. 40th Caribbean Food Crops Society 40:102-104.
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Progress 01/01/05 to 12/31/05
Outputs
Dodder, C. pentagona stems and flowers were collected from three previous studies conducted at the University of Florida in Gainesville, FL. The Cuscuta collected were inoculated with 7 treatments consisting of: A. destruens (Smolder WP), A destruens + oil, ammonium sulfate at 0.125% w/v in water, glyphosate (N-(phosphonomethyl)glycine) at 0.065% concentration of Roundup Pro, oil, a mixture of A. destruens + oil, glyphosate, and ammonium sulfate, and an untreated control. For morphological identification of the species and to obtain single-spore cultures, the fungi were grown to produce spores in culture. In addition to the unknown 47 isolates, 4 known Alternaria spp., Alternaria cassiae Jurair and Khan, A. eichhorniae Nag Raj and Ponnappa, A.macrospora Zimmermann and A. tenuis Nees were used for comparison. The nuclear rDNA internal transcribed spacer region,including ITS 1 and ITS 2 and the 5.8S rDNA, was amplified with primer pairs ITS4 and ITS5 by polymerase chain
reaction(PCR). The forward primer ITS5 was 5'-GGA AGT AAA AGT CGT AAC AAG G-3' and the reverse primer was ITS4 5'-TCC TCC GCT TAT TGA TAT GC-3'. Bands were resolved by electrophoresis. Phylogenetic analyses were performed with programs contained in PAUP Phylogenetic Software. Alternaria cassiae, A. eichhorniae, A. macrospora, and A. tenuis were designated as outgroups. Phylogenetic trees were constructed using distance methods because heuristic searches for the parsimony analysis yielded too many trees. Distance-based trees were generated with neighbor-joining using the Jukes-Cantor one-parameter algorithm. The sequence alignment revealed that the outgroups, A. cassiae and A. macrospora, were distinct from the other species and formed one clade, which was supported with a bootstrap value of 100%. The second and third clade contained A. tenuis and A. eichhorniae with a bootstrap value of 99 % and 86%, respectively. The last and largest clade contained A. destruens and all 47 unknown
Alternaria isolates. Neighbor-joining analysis revealed all of these isolates, which were recovered from greenhouse and outdoor studies, and my reference A. destruens were identical.
Impacts
Smolder WP has been released for control of dodder and is available for farmers and home owners to use in controlling this parasitic plant.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/30/04
Outputs
Studies have been conducted on the volatile emitted from dodder during parasitization. Citrus plants were inoculated with dodder in glass chambers that were sealed and volatiles were recorded over time. Greenhouse studies include treating plants with Alternaria, glyphosate and ammonium sulfate as separate treatments and as a combined treatment.
Impacts
Control of parasitic plants as dodder has been difficult with damaging the host plant. Using a naturally occurring biological control agent Alternaria destruens provides growers with a cost effective control.
Publications
- Cook, J., R. Charudattan, E. Rosskopf, T. Zimmerman, G. MacDonald and W. Stall. 2004. Integrated control of dodder (Cuscuta pentagona) using glyphosate, ammonium sulphate and the biological control agent Alternaria destruens. Proc. 40th Caribbean Food Crops Society 40: (in press).
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Progress 01/01/03 to 12/31/03
Outputs
The use of Alternaria destruens (Smolder), a commercial bioherbicide, was found to be effective in controlling dodder species found in Florida Cuscuta gronovii and C. pentagona, however the Smolder was not effective on C. americana, the dodder species found in the Virgin Islands. The spray application of glyphosate (Roundup) at low rate of 0.1% controlled all three species of dodder on certain host plants. Higher concentrations of glyphosate resulted in host plant damage and/or death.
Impacts
Three successful methods to control dodder from chemical herbicide to a biological control system are available for residence of Florida to choose from.
Publications
- No publications reported this period
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