Drought-Tolerant Hybrid Technology Ramping Up
PHOTO COURTESY OF SYNGENTASyngenta’s Agrisure Artesian hybrids (to the right), developed using the gene marker approach, showed less drought stress in 2012 field trials in New Paris, Ohio. "We selected for native traits related to drought tolerance as we do for other hybrid traits," said Jerry Harrington, DuPont Pioneer. "Mechanisms identified included stomata control, maintenance of photosynthesis and preservation of leaf area. Some of the traits are still being investigated; however overall, Optimum AQUAmax hybrids tend to stay green, have more root mass and are more closely synchronized in pollination and silking."
In Syngenta's case, that identification process led to identification of 13 different genes that were then validated by crossing them into hybrid lines and comparing their effect against identical material without the genes. Those showing a significant effect under drought conditions were then brought forward in elite hybrids. Fithian noted that combinations of genes assured multiple modes of action to address drought stress throughout the season, as different response mechanisms deal better with stress pre-pollination versus pollination to mid-grain fill and mid-grain fill to maturity.
Addressing drought response in those multiple stages is one reason Mycogen has continued to rely on traditional breeding for drought tolerance, selecting high yielding hybrids that respond.
"The key is to find hybrid lines that perform well in well-watered situations as well as in drought," suggested Lyndall Dallas, product development agronomist, Mycogen Seeds. "It is difficult to expect a single gene to improve tolerance at all three stages, and adding multiple genes adds complexity. We focus on the flowering stage, where stress is most devastating. Tolerant hybrids at that stage tend to develop more consistent ears with more kernels and less kernel abortion."
PLANNING FOR DROUGHT?
Evaluating drought tolerance by appearance at any stage, or eventual impact at one stage versus another, can be difficult, noted Dallas. "While some see leaf rolling as a bad sign, others say it is simply a protective feature. The jury is still out," he said. "If a hybrid handles flowering stress better, it can mask the effect of stress earlier in the season because flowering stress is so important."
He pointed to areas in Illinois that received only one rain in July, but made 190 to 200 bushel yields. He argued that reducing the impact of drought gets down to yield potential. A successful hybrid under drought conditions has to produce optimum yields under optimum conditions as well, he added.