The high glanding trait (i.e. presence of gossypol glands on the lobes or crown of the cotton flower bud calyx) confers a significant level of resistance to bollworm and tobacco budworm. Until recently, all cultivated upland cotton cultivars were normal glanding (i.e. lacked glands in this area of the calyx). Three new cultivars, Hartz H1215, H1220, and H1244, express the high glanding trait, transferred from Socorro Island (a wild Gossypium hirsutum) via a breeding line, XG-15. In 1994, an effort was begun at the Delta Res. and Ext. Ctr. to determine the inheritance of the high glanding trait present in XG-15.

One of the parents used in the study was a monomeric line, XG-15gl₂Gl₃, developed by Dr. Joshua Lee. This line had glandless alleles (gl₂gl₂) at the Gl₂ locus, and dominant Gl₃ alleles from XG-15. The line was high glanding, which led to the hypothesis that the high glanding trait was conferred by a special Gl₃ allele derived from the Socorro Island cotton and passed on to the high glanding Hartz cultivars.

Crosses of high glanding x normal glanding parents resulted in high glanding F₁'s and F₂ populations that segregated 3 high glanding:1 normal glanding; crosses of XG-15gl₂Gl₃ x normal glanding produced similar results. The cross of XG-15 gl₂Gl₃ x high glanding did not segregate for calyx crown glanding type. The cross of XG-15gl₂Gl₃ x glandless parents resulted in glandless squares in the F₁ and a ratio of 3 glandless (squares): 1 high glanding in the F₂.

Data available to date are consistent with the hypothesis of a special Gl₃ allele (tentatively identified as Gl₃s) derived from Socorro Island cotton. Based on the phenotype of XG-15gl₂Gl₃, it should be possible to develop cultivars that express the high glanding trait, but have reduced seed gossypol by using recessive alleles at the Gl₂ locus which has been identified as more potent in affecting seed gossypol.