Heterofertilization exhibited by trifluralin-induced bicellular pollen on diploid and tetraploid maize crosses

The heterofertilization rates and fertility of trifluralin-induced bicellular pollen were investigated in maize (Zea mays L.). A diploid inbred line, Oh43 (r1/r1), and a tetraploid line, Q28-1 (r1/r1/r1/r1), were pollinated with a trifluralin treated diploid stock heterozygous for R1-scm2. The gene R1-scm2 conditions purple pigmentation in both the embryo and the aleurone layer. Heterofertilized kernels were detected as discordant kernels, i.e., yellow kernel with purple embryo or purple kernel with white embryo. The diploid-diploid crosses treated with 0.2-0.3% Trefanocide solution (0.09-0.13% trifluralin) resulted in incidences of discordant kernels (3.7-4.8%) that were significantly higher than the control (2.3%). Most of the seedlings (86%) of the discordant kernels in the 0.3% treatment were triploids or triploid-class aneuploids. In tetraploid-diploid crosses, trifluralin treatments increased the number of plump kernels on the tetraploid ears. In the 0.3% treatment, 5.2% of ovaries produced plump kernels on the ears and most of the seedlings (92%) were tetraploids or tetraploid-class aneuploids, whereas in the control, only 1.5% ovaries produced plump kernels and most of the seedlings (98%) were triploids or triploid-class aneuploids. A high rate of discordance was observed among the plump kernels both in the treated plots (36.1-48.0%) and in the control (33.3%). Consequently, almost all of the plump kernels from the tetraploid-diploid crosses were considered to be the results of heterofertilization.