Evaluation of commercial biocontrol agents for Botrytis cinerea control in strawberry
Killian C. Brady1,2 , Martin Downes2 and Liam Staunton3
1Institute of Bioengineering and Agroecology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland, 2Teagasc, Oak Park Research Centre, Carlow, Co. Carlow, Ireland, 3Teagasc, Kinsealy Research Centre, Malahide Road, Co. Dublin, Ireland
Grey mould disease of fruit (Botrytis cinerea) is the most important fungal pathogen of strawberry in Ireland. Typically, control of B. cinerea is achieved with the use of chemical fungicides. However, consumer sensitivity to pesticide use and tolerance of B. cinerea to chemical fungicides has prompted the need to develop alternative methods for disease control. One such alternative is the use of biological control agents (BCAs), which have the potential to reduce or possibly remove, chemical fungicides from disease management programs. The effects of weekly applications of five commercial BCAs (Trichodex, Trichospray, Trianum-P, Serenade, Messenger) and the chemical fungicide Rovral (iprodione) on disease incidence and marketable yield of strawberry (cv. Elsanta) were evaluated in polythene-covered tunnels. Three days after BCA application, plants were challenge-inoculated with B. cinerea. Results showed that Botrytis fruit rot accounted for 10-15% loss in total yield in each treatment. Weekly applications of iprodione gave best disease control. Messenger gave poorest control, with up to 20% of total yield being lost. Control of Botrytis fruit rot was achieved using BCAs (except Messenger) and this level of control was not statistically different to that of the iprodione treatment (P > 0.05). Of the BCAs, disease control was best in the Trichodex treatment. Marketable yield was not adversely affected by the use of BCAs. Highest yields were obtained from plants treated with iprodione, although this was not statistically greater than any of the BCA treatments. It was concluded that BCAs have the potential to replace chemical fungicide usage in strawberry grown under protection.
L-FORM BACTERIA: ENDOSYMBIONTS AND PLANT PROTECTION AGENTS
Allan, EJ., Daulagala, PWHKP., Glover, LA., Gooday, GW., Seddon, B., Tsomlexoglou, E. and Walker, R.
College of Life Sciences and Medicine, University of Aberdeen, Aberdeen, Scotland. Email: firstname.lastname@example.org.
Many cell-walled bacteria can be induced, either naturally or artificially, into a phase of growth where the cell wall is either absent or modified, in this state they are called L-phase or L-form bacteria. Successful artificial induction has been obtained from both Gram positive, including filamentous actinomycetes, and Gram negative bacteria. A wide range of different plants can be treated with L-form bacteria to form plant-bacterial symbioses. This poster will present results validating the plant-microbe association, show that the symbiosis results in the plants becoming protected against microbial pathogens and suggest a mechanism for this outcome. Stable L-form bacteria derived from Bacillus subtilis were genetically modified to express the gus gene (encoding -glucuronidase) and were associated with Chinese cabbage. Histochemical staining of associated plants showed -glucuronidase activity (X-gluc) while PCR detected the gusA gene. Leaves from plants treated with B. subtilis L-forms 12, 21 and 35d, after association at the seed germination stage, showed that Botrytis cinerea (grey mould) conidial germination was reduced significantly compared to untreated plants. plant pathogen, Pseudomonas syringae pv. phaseolicola. In these studies induction of chitinases was investigated using a fluorometric assay with 4-methylumbelliferyl substrates. Maximum chitinase activity was found 31 days after seed treatment with L-form bacteria and showed 4-fold and 1.5-fold endochitinase activities with 4-Methylumbelliferyl -D-N-triacetylchitotrioside and 4-Methylumbelliferyl -D-N-tetraacetylchitotetraoside respectively. Plant/L-form association was detected using a range of methods including a slide agglutination assay, ELISA and by re-isolation of bacteria from seedlings. L-form bacteria were also observed in root hairs using light microscopy. Re-isolation showed that L-forms were systemically distributed throughout the plant, with the highest population in roots. These Chinese cabbage seedlings, treated with the Ps. syringae pv. phaseolicola L-form bacteria, also had enhanced resistance to grey mould as determined using a whole plant bioassay. This indicates that L-form bacteria induce systemic resistance in the host. Since L-form bacteria act as endosymbionts and can persist within the plant throughout its development this system has potential for targeted biological control of phytopathogens.
Sympatric Subpopolations of Botrytis cinerea Per.:Fr. in Strawberries and Grapevine and their connection to Resistance to Dichlofluanid
Topolovec-Pintarić S.*, Miličević T., Cvjetković B.
Faculty of Agriculture, Dept of Plant Pathology, Zagreb, Croatia
During a survey in Croatia in 2002, samples were taken of strawberry and grapevine naturally infected with Botrytis cinerea. The 37 isolates were isolated and their sensitivity to dichlofluanid (fenilsulfamid) was tested in mycelial growth assays. The three phenotypes of B.cinerea can be distinguished according to their response toward dichlofluanid and their EC50 and CMI values. The sensitive phenotype has EC50 1-3 ppm and CMI 6-10 ppm; the phenotype with a low level of resistance has EC50 3-10 ppm and CMI > 100 ppm and the higher resistant phenotype has EC50 10-30 ppm and CMI > 100 ppm. Based on the content of transposable elements the subpopulations Transposa and Vacuma were found among collected isolates. The Transposa strains were prevalent among isolates originated from grapevine bunches. Also, the isolates having only the transposon Boty or only the transposon Flipper were found among isolates from strawberry.