Breeding Organic Corn varieties to resist GMO contamination
Backcross generation three (BC3) of adapted elite white and yellow grain parental lines of corn with the cross-sterility gene GA1-S were self-pollinated in a winter nursery in Florida. BC3 lines were expected to have the heterozygous genotype GA1-S/ga1-S. These self-pollinated ears formed the BC3S1 generation of parental lines T175 and T177 (white grain) and T274 and T276 (yellow grain). Individual kernels on the ears of these plants will be either homozygous or heterozygous for the GA1-S allele. One row was planted in the summer nursery in Knoxville from each BC3S1 ear. Plants in these rows were outcrossed to a line with purple seeds by hand pollination, then self-pollinated the following day. Ears that have no purple seed at harvest are homozygous GA1-S/GA1-S, forming the BC3S2 generation, and were selected for further evaluation. Ears with purple seeds at harvest were discarded (Figure 1).
BC3 lines heterozygous for the cross sterility allele GA1-S, and with 93.75 % recurrent parent DNA, were self- pollinated to produce BC3S1 seed in a winter nursery. The following BC3S1 ears were harvested:
(T175/MO511GA1-S) BC3S1 10 ears
(T177/MO501GA1-S) BC3S1 4 ears
(T177/MO506GA1-S) BC3S1 2 ears
(T177/MO508GA1-S) BC3S1 8 ears
(T274/MO506GA1-S) BC3S1 6 ears
(T274/MO508GA1-S) BC3S1 6 ears
(T276/MO502GA1-S) BC3S1 2 ears
In the summer nursery in Knoxville, TN, seed from each of the above ears was used to plant one row, giving a total of 38 rows with 20 plants per row. Individual plants within each row were hand pollinated by a line with purple seed. The following day, these plants were self-pollinated. Ears that produced purple seed were discarded at harvest. Ears with no purple seed are homozygous for the GA1-S allele, and were selected for further testing (Figure 1). The following plants, homozygous for GA1-S were selected at harvest:
(T175/MO511GA1-S) BC3S2 7 plants
(T177/MO501GA1-S) BC3S2 4 plants
(T177/MO506GA1-S) BC3S1 3 plants
(T177/MO508GA1-S) BC3S2 14 plants
(T274/MO506GA1-S) BC3S2 9 plants
(T276/MO502GA1-S) BC3S2 8 plants
Additionally, the following experimental hybrid was produced:
(T175/MO511GA1-S) BC3S1 X (T177/MO501GA1-S) BC3S1
Seed from these BC3S2 plants will be grown in the 2015 summer nursery. Individual plants in each line will be hand pollinated with pollen from a purple seeded tester that does not contain the GA1-S allele. These plants will be self-pollinated the following day. Within each row, one plant will also be pollinated with pollen from a commercial GMO hybrid to demonstrate that these lines are cross sterile to pollen from GMO hybrids. At harvest, ears which produce purple seeds (we expect this number to be zero) will be discarded, and ears that are either completely white (elite lines T175 and T177) or completely yellow (elite lines T274 and T276) will be selected for advance. Seed from these self-pollinations will possess 93.75 % of the DNA of the recurrent parent and will be homozygous for the GA1-S allele. We will produce sufficient quantities of the new GMO resistant parent lines, T175GA1-S, T177GA1-S, T274GA1-S, and T276GA1-S to allow sharing with a limited number of organic corn producers for demonstration planting on their farm in 2016. Additionally we will enter the experimental hybrid, (T175/MO511GA1-S) BC3S1 X (T177/MO501GA1-S) BC3S1in yield trials for comparison with the original hybrid T175 X T177.
We have achieved our goal of producing elite white and yellow grain parent lines of corn that are homozygous for the cross sterility allele GA1-S.
Impacts and Contributions/Outcomes
This research has produced white and yellow grained parent lines of corn that will be used to produce hybrids that cannot be pollinated by genetically modified (GMO) maize hybrids grown in adjacent or the same field. This will prevent loss of income from “adventitious presence” of GMO grain in fields planted to non-GMO cross sterility maize hybrids.
252 Ellington Hall
2431 Joe Johnson Drive
Knoxville, TN 37996-4561
Office Phone: 8659748826