Telling hybrids apart in the field
October 1, 2020
“Final yield is very important, but farmers also need hybrids with other favorable characteristics and it helps to know which characteristics distinguish one hybrid from another,” said Dave Nanda, Ph.D., Seed Genetics Direct director of genetics, who is also a plant breeder. “Hybrids have many different characteristics that you can determine in the field.”
Nanda recently pointed out a number of differences between two hybrids planted side-by-side in the Corn Watch ’20 plot, a project sponsored by Seed Genetics Direct to observe and share plant progress throughout a growing season. Below are nine characteristics that helped Nanda distinguish between the two hybrids:
1. Plant height. There was an obvious difference in overall plant height between the hybrids once they tasseled out and reached their final height. Nanda looks for hybrid height to become shorter in the future, as breeders turn out genetics that yield well at high populations. However, today, there are still taller hybrids that yield well.
2. Tassel structure. The architecture of the tassel, which sheds pollen, varies by hybrid. Often, there is a difference in the number of branches per tassel. In the Corn Watch ’20 plot, one hybrid had eight branches on each tassel; the other had nine or more on each tassel.
3. Maturity. Once ears form, maturity can be determined based on progression of the milk line within kernels. In the Corn Watch ’20 plot, one hybrid was maturing a few days ahead of the other.
4. Leaf count. “Many years ago, I was involved in helping establish that there is a correlation between maturity and number of leaves,” Nanda said. “Earlier-maturing hybrids tend to have fewer leaves.” In the Corn Watch ’20 plot, the taller hybrid with ears slightly behind on maturity had 18 to 19 leaves per plant; the slightly earlier-maturing hybrid had 16 to 17 leaves per plant.
5. Ear placement. Between the Corn Watch ’20 hybrids, there was at least a six-inch difference in height of ear placement above the ground; ears on the shorter hybrid were placed slightly lower on the plant.
6. Rows of kernels and ear length. Genetics primarily determines the number of kernel rows per ear. Environmental factors and weather stress can also impact row number. In the Corn Watch ’20 plot, the later-maturing hybrid tended to have 18 rows per ear, and the earlier hybrid 16 rows. Ear length is also somewhat determined by genetics and impacted by weather conditions.
7. Kernel depth. Here is where the rubber meets the road for yield. Kernels on the earlier-maturing hybrid appeared deeper, but the cob diameter was also larger. Conditions during grain fill have a large impact on final kernel size.
8. Roots and brace roots. Without digging plants up, differences can often be seen in roots. In this case, one hybrid had more aggressive brace roots on the surface than the other hybrid.
9. Disease tolerance and resistance. Gray leaf spot was intense on lower leaves when Nanda inspected the Corn Watch ’20 field, particularly on the earlier hybrid. “It was on both hybrids, but was more intense on one than the other,” Nanda says. “It reaffirms the need to ask about tolerance to various diseases.”