Week In Science

Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants is a PNAS paper detailing research findings that may account for reduced agricultural output. The cause may be the use of pesticides and agrichemicals that interfere with a vital plant function known as nitrogen fixation by inhibiting interaction between rhizobia bacteria and plant roots. As the authors note: "The vast majority of biologically fixed N is attributable to symbiosis between leguminous plants (soybeans, alfalfa etc.) and species of Rhizobium bacteria..." The importance of the symbiotic relationship to agricultural yield indicates that adjustments in agricultural practices will be forthcoming.

Another article entitled Food safety begins as vegetables grow reveals a finding that comes as as surprise for those thinking that food contamination is likely to occur at the processing or retail part of the process. According to Jeri D. Barak, a research microbiologist working with the the U.S. Department of Agriculture's Agricultural Research Service, contamination is most likely to occur while plants are growing in the field. It therefore makes sense to take preventative measures prior to, rather than after harvest. Barak's research indicated that there is interaction on the plant surface involving pathogens like Salmonella and genes that aid in plant colonization. The interaction is so significant that it is almost as if the vegetable and pathogen become one.

A 'Nature' article 'Transgenic crops relatively kind to insects' by Heidi Ledford,(doi:10.1038/news070604-9) provides some good news about a particular type of insecticide which had caused concern because of fears that it would adversely affect insects not targeted as pests. The insecticide in question is a toxin produced by the Bacillus thuringiensis bacterium. It is intended for use against specific targets like corn borers and cotton bollworms. Research results indicate that harmful effects of the toxin may be limited to the intended targets. The issue addressed by the finding is a controversial one as previous findings had been the object of criticism. Environmental concerns signify that the controversy may yet persist.