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MACHADO, Andréia Q. et al. Potential of water restriction use in cotton seed health testing. Fitopatol. bras. [online]. 2007, vol.32, n.5, pp.408-414. ISSN 0100-4158. http://dx.doi.org/10.1590/S0100-41582007000500006.
The fast germination of cotton seeds that occurs in blotter and agar seed health tests may become a difficulty in the identification of fungi, thus affecting the efficiency of these tests. The available alternative to impede or to reduce seed germination of dicotyledoneous species is the incorporation of 2.4-D (sodium salt formulation) solution to the substrate. Nevertheless, some questions about 2,4-D use may be raised for several reasons, including the toxicity of this compound. The aim of this work was to investigate the viability of the use of water restriction technique in place of the 2,4-D method to reduce seed germination in incubation seed health testing. The effects of water restriction produced by mannitol and sodium chloride at -0,6, -0,8, -1,0 and -1,2 MPa osmotic potentials were evaluated on seed germination, seedling elongation and in vitro mycelial growth of some fungi occurring on cotton seeds and on their development in the blotter test. The water restriction provided by the solutes at the osmotic potentials tested was proved to reduce germination and seedling elongation to satisfactory levels for cotton seed health analysis, allowing recovery of the main fungi on those seeds under blotter test conditions. This method was seen to be an efficient alternative to the use of 2,4-D. The mycelial growth of fungi was reduced on agar medium at osmotic potentials higher than -0,6 MPa. The recovery of pathogenic fungi under blotter test was not affected by the water restriction technique.
Keywords : seed health testing; fungi.