Genetically modified grass varieties that carry genes for disease and drought resistance are now available. they were produced by recombinant dna technology. however, the government has still not approved the sale of most of them, due to cautionary factors. what is the main reason for this concern?

These grasses can act as uncontrolled invasive species and can harm other useful species of plants.

Explanation:

The genetically modified grass are generated with the help of genetic engineering methods that comprise genes for disease and drought resistance. Due to the presence of these genes, these varieties of grasses exhibit greater chances to thrive in stressful situations and they disperse with a tremendous frequency.  

The majority of the genetically modified varieties of grass are still didn't received approval by the government, as these species may function as uncontrolled invasive species and may result in harm to other useful species of plants, which can disperse fast and are tough to eradicate because of the presence of resistance against the stress conditions.  

this transfer is call conjunction

that is wrong, its not thymus.