1^st transgenic crop plant was . . . . . . . . , developed in 1983.

1^st transgenic crop plant was tobacco developed in 1983.
The first transgenic plants were produced in tobacco plants (Nicotiana tabacum) which expressed antibiotic resistance. L-phosphinothricin, a gene resistant to PPT, Basta (the active ingredient of herbicide) was isolated in Medicago sativa.
In a transgenic plant, a segment of its DNA into the plant's nuclear DNA using a plasmid-integration system - one of the earliest discoveries of a natural DNA-transfer mechanism. In May 1983, the Van Montagu and Schell lab deployed this system as a gene-expression vector and the first transgenic plants.