Sunday, August 10, 2008
P71

Isolation and Selection of Grass Fungal Pathogens for Their Use as Bioherbicides and Phytotoxin Producers for Weed Control In Sugarcane Fields

L. C. Silva - Villanueva, M.M. Hernández - Arroyo, A. Guzmán-Alonso, A. Ruiz-Font, and S. R. Trejo - Estrada. Centro de Investigación en Biotecnología Aplicada del Instituto Politécnico Nacional, CIBA-IPN Tlaxcala, Carretera Estatal Santa Ines Tecuexcomac - Tepetitla Km. 1.5, Exhacienda San Juan Molinos, Tepetitla de Lardizabal, Mexico

Sugarcane is one of the most important biomass producers in tropical countries. Mexico´s sugar industry comprises 60 sugar factories. Extensive cane cultivation in marginal lands includes the use of sustainable non-synthetic substitutes of currently used agrochemicals. Based on value, herbicides are the most important product used in sugarcane production. In order to provide for new alternatives for both sustainable production of biomass, and for the production of organic sugar, fungal pathogens of grasses have been isolated and tested as preemergence herbicides for the selective control of weeds widely present in sugarcane cultivars. The main weeds in Mexico´s sugarcane plantations are: furry grass (Panicum hirticaule); white flower (Eupatorium adenophorum); and yellow flower (Bidens biternata)  Strains of Pythium spp and Fusarium spp strains were isolated from four different soil samples, obtained from agricultural fields were fungal plant diseases have been recently recorded. Baiting and selective plating media were used for the isolation of Pythium strains (P10VP medium) and Fusarium strains (Nash & Snyder medium). An in vitro plate method was developed to screen for diffusible products with differential activity on the inhibition of seed germination towards either sugarcane seeds or weed seeds.  Two selected strains, tested in soil, under laboratory conditions, showed a consistently inhibitory activity of weed seeds germination, while no significant inhibition was recorded for sugarcane plantlet development or growth. The use of the fungal bioherbicides or their phytotoxic compounds in agricultural fields is now subject to intensive experimentation. 

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