Honors Program


Document Type


Date of this Version



Benes, M. 2022. Source of Off-Type Frequencies in Winter Wheat Varieties. Undergraduate Honors Thesis. University of Nebraska-Lincoln.


Copyright Michaela Benes 2022.


The enzyme polyphenol oxidase (PPO) is undesirable in most wheat products due to the discoloration it causes. Purifying wheat varieties through selective breeding is the best way at getting rid of PPO in a variety. The variety NW15443 was planted in both a field in McCook, NE, and in a greenhouse in Lincoln, NE. Individual heads were snapped from the field and the greenhouse seed was harvested in bulk. After completing a PPO test of the seed, it was determined that the percentages of off-type frequencies from the field seed and the greenhouse seed were 11% and 3.6%, respectively. Using this data, the off-type frequencies of the seed were compared to the expected frequencies due to combine mixing, genetic segregation, and out-crossing via chi-squared tests. It was determined that the off-type frequencies from both the field and greenhouse were best explained by outcrossing. The off-types from the greenhouse seed could also be explained by combine mixing, but this mixing method was less likely. The off-typing in the field likely also was affected by existing off-types in the previous generation which increased in frequency. Mitigation methods such as increasing the space between plots and increasing the field size could help reduce out-crossing.