Colonyzation of Lycopersicon esculentum by Burkholderia tropica

CARELLA N. V.; VAZQUEZ R. F.; APREA J.; GALAR M. L.; BOIARDI J. L.; LUNA M. F.

Rosario

Congreso; V Congreso Argentino de Microbiología General; 2008

Sociedad Argentina de Microbiología General (SAMIGE)

As agricultural production is intensified over the past few decades, producers became more dependent on agrochemicals as a relatively reliable method of crop protection helping with economic stability of their operations. However, increasing use of chemical inputs causes several negative effects, i.e., development of pathogen resistance to the applied agents and their nontarget environmental impacts. Furthermore, the growing costs of pesticides, particularly in less-affluent regions of the world, and consumer demand for pesticide-free food has led to a search for substitutes for these products. The use of biofertilizer and biocontrol organisms is thus being considered as an alternative or a supplemental way of reducing the use of chemicals in agriculture. These beneficial bacteria are usually referred as PGPB (plant growth-promoting bacteria). These organisms are able to colonize roots and, some of them, are also able to colonize plant tissues (endophytes). Despite their different ecological niches, have been described different mechanism to promote plant growth and control of phytopathogens. The degree of tissue colonization shows the capacity of these bacteria to adapt to that specific environment and to establish a non pathogenic association. Several techniques have been employed for the isolation of endophytic bacteria. The most common procedure are based on surface disinfection of plant tissues and further bacteria enumeration in specific media. These techniques, although able to estimate the colonization degree of plants do not provide information on colonization sites or type of tissue that have been infected. To obtain such an information methods that allow a direct in situ identification and localization of endophytes have been developed. In the present study microscopic in situ localization of Burkholderia tropica (labeled with a gus reporter gene) has been performed in tomato plants (Lycopersicon esculentum, cv. platense italiano) inoculated with this organism. Our results can be summarized as follows: emerging roots and root hairs were heavily colonized (>10^5 CFU.gram fresh tissue^-1); stem tissues were also colonized (~10^4-10^5 CFU.gram fresh tissue^-1).