True breeding transgenics from plants heterozygous for transgene insertions

Abstract

The invention provides a method for biasing a crop plant which is heterozygous for a transgene towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene coding for resistance to a specific phytotoxin with the specific phytotoxin one or more times during the life of the crop plant. The method achieves this through selective inhibition of phytotoxin-sensitive plant ovules, embryos and pollen. The method has particular application to the production of open pollinated and synthetic varieties of crop plants, such as alfalfa synthetic varieties.

What is claimed is:  
     
         1 . A method for biasing a crop plant which is heterozygous for a transgene coding for resistance to a specific phytotoxin towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene with the specific phytotoxin one or more times during the life of the crop plant, wherein the crop plant is part of an open-pollinated population or a synthetic variety.  
     
     
         2 . A method of selectively inhibiting phytotoxin-sensitive plant ovules, embryos and/or pollen in order to bias a crop plant which is heterozygous for a transgene coding for resistance to a specific phytotoxin towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene with the specific phytotoxin one or more times during the life of the crop plant, wherein the crop plant is part of an open-pollinated population or a synthetic variety.  
     
     
         3 . A method of selectively inhibiting phytotoxin-sensitive plant ovules in order to bias a crop plant which is heterozygous for a transgene coding for resistance to a specific phytotoxin towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene with the specific phytotoxin one or more times during the life of the crop plant, wherein the crop plant is part of an open-pollinated population or a synthetic variety.  
     
     
         4 . A method of selectively aborting phytotoxin-sensitive plant embryos in order to bias a crop plant which is heterozygous for a transgene coding for resistance to a specific phytotoxin towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene with the specific phytotoxin one or more times during the life of the crop plant, wherein the crop plant is part of an open-pollinated population or a synthetic variety.  
     
     
         5 . A method of selectively inhibiting phytotoxin-sensitive pollen in order to bias a crop plant which is heterozygous for a transgene coding for resistance to a specific phytotoxin towards the production of seeds which carry the transgene comprising the step of contacting the crop plant containing a gene construct comprising the transgene with the specific phytotoxin one or more times during the life of the crop plant, wherein the crop plant is part of an open-pollinated population or a synthetic variety.  
     
     
         6 . The method of  claim 1  wherein the phytotoxin is contacted with said crop plant during the vegetative or reproductive growth phase of the crop plant.  
     
     
         7 . The method of  claim 1  wherein the crop plant is alfalfa or clover.  
     
     
         8 . The method of  claim 1  wherein the gene construct consists of a transgene coding for resistance to a specific phytotoxin operably linked to one or more additional transgene(s), such that the crop plant is biased towards the production of seeds which carry all of the transgenes.  
     
     
         9 . The method of  claim 1  wherein the phytotoxin is a herbicide.  
     
     
         10 . The method of  claim 9  wherein the herbicide is one which translocates throughout the plant upon application.  
     
     
         11 . The method of  claim 12  wherein the herbicide is chlorsulfuron.  
     
     
         12 . The method of  claim 1  wherein the phytotoxin is an antibiotic.  
     
     
         13 . The method of  claim 1  wherein the crop plant is a forage crop, a tree, a vegetable or a flowering plant.  
     
     
         14 . The method as claimed in  claim 13  wherein the forage crop is a forage brassica, a forage legume, a grass, or a mixture of two or more of these forage crops.  
     
     
         15 . The method of  claim 1  which includes the subsequent step of collecting the seed produced by the plant and confirming the presence of the transgene.  
     
     
         16 . The method of  claim 1  which includes the preliminary step of introducing the gene construct into the crop plant or into the seed from which the crop plant is grown.  
     
     
         17 . The method as claimed in  claim 16  wherein the gene construct consists of a transgene coding for resistance to a specific phytotoxin and wherein the construct is introduced into the genome of the crop plant at an integration site immediately adjacent a desirable homologous gene, such that when the crop plant is contacted with said phytotoxin the crop plant is biased towards the production of seeds which carry both the transgene and the homologous gene.  
     
     
         18 . A seed which carries a gene construct which is produced by the method as claimed in  claim 1 .  
     
     
         19 . An open-pollinated population or synthetic variety of a crop plant which is produced by the method as claimed in  claim 1 .  
     
     
         20 . A method of producing a transgenic synthetic alfalfa variety comprising the steps of: 
 1) producing a transgenic alfalfa plant, wherein the transgenic alfalfa plant comprises an introduced gene construct which comprises a heterologous gene coding for phytotoxin resistance operably linked to a heterologous gene of interest;    2) using the transgenic alfalfa plant produced by step 1) as a pollen parent and crossing the transgenic alfalfa plant to one or more alfalfa plants which do not contain the phytotoxin gene operably linked to the heterologous gene of interest;    3) applying the phytotoxin one or more times during the life cycle of the plants in step 2); and,    4) harvesting and bulking the resultant seed to produce a new synthetic alfalfa variety which contains the phytotoxin gene operably linked to the gene of interest.    
     
     
         21 . The method of  claim 20  further comprising the following steps: 
 5) intermating the plants grown from the bulked seed obtained in step 4);  
 6) applying the phytotoxin one or more times during the life cycle of the plants in step 5); and,  
 7) harvesting and bulking the resultant seed, wherein such seed contains the phytotoxin gene operably linked to the gene of interest.