Improvement of nitrogen fixation capacity of Rhizobium

The biofertilizers have a great perspective of application in the agricultural fields in Mexico because they are environmentally friendly, have a low cost and they are easily transported and applied. On the other hand, the nitrogen chemical fertilization represents high economic costs for the farmers, but the most serious effects of the massive fertilization in the world are environmental: industrial production contaminates the air, soils are deteriorated by the salinity, as well as the water-bearing mantles. Studying the
transcriptional regulation of the reiterated sequences of the nitrogenase in R. etli and the carbon flow modification, we obtained modified strains that overexpress the enzyme and have very important effects in their association with common bean (a main staple in Mexico): increases in seed production (up to 50%) and in its nutritious value (up to 100%).
The increase in the nitrogen fixation ability of Rhizobium , obtained with modifications without transgenes, are the highest reported to the date.

Additionally, we done metabolic and genetic characterization of rhizobia strains from Costa Rica with high nitrogen fixation ability in order to define the key factors influencing their performance. After four year-tests in the field, we promoted the use of all these strains
as biofertilizers. In regard to the genetic modification, a national (PA/2002/003920) and international (PCT MX 03/00033) patent was requested and the strains were transferred by means of an Agreement to the company Asesoría Integral Agropecuaria y Administrativa ( ASIA ).
In order to use the biofertilizer in the field, the procedure is very simple: add a small amount of water to the seed, add an adherent and the content of a 400 gram-bag, mix thoroughly and it is ready to hand- or machine-sowing. The biofertilizer costs 10 times less than the chemical fertilizer.

In Northern Mexico , in the state of Durango , the biofertilizer was applied at commercial level and obtained satisfactory results in production increase. If farmers accept to use the
biofertilizer, the whole population also will receive benefits such as lesser environmental contamination and greater nutritious quality of the seed.