ABSTRACT
In a maize polyploidy series, there is a decline in stature with increasing ploidy when the genome is homozygous. In contrast, when heterozygosity is maximized, the stature of plants increases with higher ploidy. Double cross tetraploids are more vigorous than double cross diploids. However, this increased vigor is difficult to capture for agricultural practices (grain yield) because the quadrivalent pairing of chromosomes and the phenomenon of double reduction lead to some sterility and variability in the progeny. These barriers to tetraploid corn production could in theory be overcome by introducing mechanisms of apomixis and/or chromosome level diploidization, but all attempts to do so in vivo have so far met with very limited success.
