NEWS FROM THE SMALL GRAINS SPECIALIST

SMALL GRAINS FOCUS

Can You Select Varieties For Weather Extremes?

By Jochum Wiersma
U of M Small Grains Specialist
wiers002@umn.edu

It appears by all accounts that weather across the globe is becoming more extreme: snow in Portugal (near the Mediterranean); no rain during the month of February in the usually-moisture-plentiful Netherlands; bone-dry conditions in the Plains; cloudburst deluges in the Red River Valley.  Some blame global warming and ozone depletion, others El Nino/La Nina.

I’m not going to get into what’s causing these weather aberrations. But I do know that even small changes in average temperatures and rainfall will have huge impacts on small grain production. So a key question is: can you select varieties that can handle these extremes?

Observations from last year allow us to expand upon that question. Torrential downpours last June and July caused temporary flooding and drown-outs.  I was invited to scout a field of spring wheat after a downpour.  The water had been knee deep for more than two days by the time I looked at the field, and it didn’t seem very likely that the water would recede soon. The rule of the thumb I had is that wheat could handle fully saturated soil/standing soils water no longer than three or at the most four days if the temperatures were cool.  I told the farmer that I doubted the field would survive, and I didn’t think a fungicide application in this case would be a wise investment.

I “waded” into the field and pulled up some plants to inspect the root system and the crown. At two days the crown looked quite healthy.  Some of the roots didn’t.  However, I did notice that this particular variety was growing new roots. Not from the crown but from the first node, just above the soil surface but well below water.  The roots were just starting to “sprout” from the node and looked very similar to the roots in corn.

I had never seen this before.  I submitted a photo and a question to an Internet listserve whether any other researcher had ever seen adventitious roots from the first node. I received answers almost immediately. Although not frequently observed, some wheat varieties do have the ability to produce such roots. 

CIMMYT (the international wheat and maize improvement center in Mexico) actually studied this ability and the genetic background of it.  The research showed that varieties differ in their ability to survive waterlogged soils, and some varieties also showed these adventitious roots under flooded conditions. 

The other extreme is drought.  Again, varieties do differ in their ability to withstand drought. The general rule is that tall wheat varieties perform better under drought conditions than semi-dwarf wheat varieties. The explanation is that the taller wheat varieties also have a larger root system, while semi-dwarf varieties have a smaller and shallower root system.

Where does this amazing ability of wheat come from, to grow from desert to rice paddy conditions?  It has to do with its “roots” —as in ancestry.  The species evolved in an area known as the Fertile Crescent, where agriculture and civilization began, roughly from the delta of the Euphrates and Tigris Rivers (including Iraq) to the high plains of Turkey and the eastern coast of the Mediterranean Sea.  This is a very diverse geographic area with sweltering deserts, cold mountain plateaus, and fertile river deltas.  Wheat evolved and adapted to withstand and survive all these different stresses.  So even after 10,000 years of domestication and more than 100 years of modern plant breeding, wheat still can surprise you.  It has the ability to adapt to a temporary flooding situation by producing auxiliary roots from the first crown, and can withstand drought stress better than other crops.

Wheat breeders could select for traits that would improve the plant’s ability to withstand drought or flooding even better.  However, these are still incidental and infrequent stresses, probably not worth the investment in time and money to warrant a whole selection or screening nursery.

Thus, there is no variety to prescribe for extremely dry or wet conditions.  That doesn’t mean you can’t manage at all for those conditions, however. Compare the performance of wheat varieties at different locations in multiple years. It’s a good bet that the varieties which have performed well at Dickinson and Williston will have a better chance in dry conditions than the varieties which have performed well in Crookston and Fargo.  And those varieties which perform better out west might not be the best fit in the Red River Valley.

Keep other agronomic characteristics in mind too, such as plant height and disease ratings. And if planting is delayed, consider switching to earlier maturing wheat varieties.