During this reporting time period, we have conducted the following studies. 1) To use genome editing technologies to produce gene-edited and transgene-free plants derived from mature citrus tissues, one challenge is to reduce chimeric plants that are composed of both edited and non-edited cells. We have been working to develop an endogenous chemical resistance to reduce chimeras. We have identified a citrus candidate gene and constructed a vector for the resistance to reduce chimeric plants. We have used Agrobacterium cells hosting these genes to infect mature and juvenile citrus tissues. Our first set experiment for creating the chemical resistance in citrus cells has not been completed because the chemical resistant cells from the infected citrus tissues have not been obvious. We may need to wait for additional weeks to see any resistance. We have also been continuing to repeat some previously observed results using the proposed genes because we have observed some inconsistent results regarding their effects when used in mature citrus tissues. We have also continued to test the effects of some chemicals on transient and stable expression activities and also regeneration efficiencies in mature citrus tissues. We have observed some improvement of shoot regenerated from calli derived from mature tissues of citrus. We are also using fresh young shoot tissues propagated from mature citrus shoots for regeneration and transformation studies. However, we need more tissues for testing because the effects are not always consistent from one experiments to another when mature citrus tissues are used. In addition to improving the efficiencies of traditional methods for mature citrus tissues, we have been working to develop an �in planta� transformation method for mature citrus tissues. In-planta transformation means that genetic transformation of can be achieved without going through tissue culture-based regeneration of shoots or embryos. In-planta transformation methods have been successfully developed for a small number of higher plants that are difficult to transform using traditional tissue culture-based methods. We have successfully used an �in �planta� transformation method to produce transgenic and gene-edited plants using juvenile tissues of citrus. For mature citrus tissue transformation, we have done two testing so far but encountered some problems. One problem is that we need lots of shoots from mature citrus trees to work out important parameters of the method. We have worked with Mr. Phillip Rucks and Ms. Beth Lamb (Phillip Rucks Citrus Nursery in Frostproof, FL) who have kindly provided and will provide us significant amounts of mature citrus shoots for our experiments.