Final answer:
Hybrid corn not 'coming true' refers to the genetic variability in the offspring of hybrid plants, resulting in inconsistent traits compared to the hybrid parent generation. This variability can lead to the loss of desirable characteristics and uniformity that were present in the first hybrid generation.
Step-by-step explanation:
When we say that hybrid corn does not "come true", it means that the offspring of hybrid plants do not consistently exhibit the desirable traits found in the parent generation.
This happens because hybrids are produced by cross-pollinating two different inbred lines to create an F1 generation that possesses a combination of traits from both parent plants. These F1 hybrids often demonstrate increased vigor or yield due to a phenomenon known as heterosis or hybrid vigor.
However, when these hybrids self-pollinate or are further cross-pollinated, their offspring (the F2 generation) exhibit a wide range of genetic combinations, as the genes segregate and assort independently, following Mendelian inheritance patterns.
As a result, the uniformity in characteristics appreciated in the F1 generation is not maintained, which is what is meant by not coming true to type.
The example of the southern leaf blight highlights the risks associated with uniformity in hybrid crops. Because the hybrids used had the same genetic susceptibility to the pathogen, the lack of genetic diversity in these plants led to widespread crop failure.