BUCTRIL^® (bromoxynil) is a widely used post-emergence herbicide that controls many broadleaf weeds. Calgene's patented BROMOTOL(TM) gene encodes an enzyme that detoxifies the herbicide within an engineered cotton plant. In this third year of study, yield and related agronomic and fiber properties of 45 transgenic cotton strains having the BROMOTOL(TM) gene are compared, with 5 commercial cotton cultivars.

The study was conducted under normal field conditions in the Stoneville Research breeding nurseries at 3 locations: Hartsville, SC, Leland, MS, and Maricopa, AZ. The 50 entry test at each location was planted in May, 1992; harvest in AZ occurred in October, and the SC and MS sites were harvested in November, 1992. At each location 4 reps per entry were planted with plot size being two 40'rows with 38" spacing between rows, and with plant population being about 40,000 plants/acre. Standard cultural practices were used throughout the season with insect control as required by local conditions. No BUCTRIL^® was applied to the plots since this would have destroyed the commercial checks in the test. Transgenic strains tolerance to BUCTRILO was confirmed in a separate planting. Harvest was done with a conventional 2-row plot harvester, with seed-cotton weights taken in the field and two reps per entry taken to a lab research gin for lint % determinations. Two fiber samples per entry at each location were submitted to the LSIT Fiber Lab for tests, the cultivar Stoneville 506 lint yield was 1148 lb/ac (LSD.05 = 257) with 5 transgenic strains yielding 1152 to 1303 lb/ac. In the AZ tests, the cultivar Stoneville 506 lint yield was 1416 lb/ac (LSD.05 = 158) with one transgenic strain yielding 1443 lb/ac. Concerning fiber quality of the transgenic strains using a mean of the MS/AZ data, Stoneville 453 had fiber length of 1.12 inches, micronaire of 4.5, and strength of 27 gm/tex; the mean of all transgenic strains using the MS/AZ data was fiber length of 1.14 inches, micronaire of 4.2 and strength of 27 gm/tex. The data did suggest that variation among strains within transgenic events may exist, and that potential exists to select for strains superior to the parent transgenic event.

In summary, the initial year of yield testing of the BUCTRIL^® resistant transgenic cotton strains suggests that several entries have yield / fiber / agronomic properties at least equivalent to present leading commercial cotton cultivars. Those transgenic strains with the best performance are now in 1992-93 winter increase. In 1993, testing on a wider scale is planned for the major or cotton production areas of the United States; purification and increase is also planned by the Stoneville Parent Seed staff at Leland, MS.

In the SC tests, the cultivar Stoneville 453 lint yield was 762 lb/ac (LSD(.05)=136) with 12 of the 45 transgenic strains yielding 772 to 899 lb/ac. In the MS