PRELIMINARY RESULTS ON THE IN VITRO INHIBITION OF GROWTH AND SPORANGIA PRODUCTION OF PHYTOPHTHORA NICOTIANAE BY BIOLOGICAL TREATMENTS

LUCERO G.; PIZZUOLO P.H.; FRANCESCHINI S.

ROMA

Congreso; 13th Congress of the Mediterranean Phytopatological Union MPU; 2010

Phytophthora nicotianae Breda de Haan (= P. parasitica Dastur) is one of the most widespread and destructive soilborne plant pathogens associated to 301 host species (Erwin and Ribeiro 1996). It causes root rots, stem necroses and crown decline, as well as fruit and foliar blights on many agronomic and horticultural plants in seed beds, nurseries, fields, and landscape plantings. Pathogen propagules spread through soil particles and infected plants. Strategies of disease control focus on the reduction of the inoculum in soil. Biological treatments may be a viable strategy to control soilborne pathogens. Examples of the effectiveness of formulated plant extracts are already available in literature for a number of soil-inhabiting microbial group such as Fusarium spp., Verticillium spp. and Phytophthora spp. (Bowers and Locke, 1998, 2000, 2004). If natural plant products can reduce populations of soilborne plant pathogens and control disease development, then these plant extracts have potential as environmentally safe alternatives and as components in integrated pest management programs. The objective of the present research was to evaluate oregano, thyme and rosmarine essential oils, chicken manure and potassium phosphite in reducing P. nicotianae growth and sporangia production. To evaluate their effectiveness two isolates of the pathogen were used. The influence on P. nicotianae growth of increasing concentration of potassium phosphite, chicken manure and three essential oils was assessed through in vitro assays. Essential oils significantly reduced the growth if applied at the highest concentrations (P<0.05). Chicken manure, although effective in the mycelial growth inhibition lead to an increase in the number of sporangia produced. Phosphite showed the most efficiency in the inhibition of either the mycelial development or the sporangia production. The role of those biological substances as potential alternatives in the management of P. nicotianae is discussed.