Production Blog
Pam Smith DTN\Progressive Farmer Crops Technology Editor

Thursday 07/17/14

Four-Leaf Soy Surprise

DECATUR, Ill. (DTN) -- I've always been lucky. Well ... I rarely go through a yard or a patch of clover without finding a four-leaf clover. Around one out of 10,000 clovers have four leaves, so I count it as a gift. I also find five-leaf versions routinely and have found up to seven leaves on clovers.

The camera tells the tale. Four-leaf soybeans do exist, although they are rarer than four-leaf clovers. (DTN photo by Pamela Smith)

So I was a little surprised, but not astonished, to spot several four-leaf soybean leaflets at a Southern Illinois University agronomy plot near Belleville, Ill., last summer. Soybeans are typically trifoliate (have three leaves).

However, when I mentioned this find to soybean breeders, I began to realize how rare these soybeans might be.

"There are noncommercial soybean lines with more than three leaflets," said Roger Boerma, Georgia Seed Development executive director and former University of Georgia soybean plant breeder. "There is a mutant type with mostly five leaflets and another mutant type with varying number of leaflets per plant. It is likely that the variety you saw in the field has a weak mutation that allows a low degree of four-leaflet plants. This is uncommon."

Randy Nelson, curator of USDA's Soybean Germplasm Collection at the University of Illinois knows of soybean lines with five, seven and nine leaflets for which the genetics are known. "For the five-leaflet plants, every leaf will have five leaflets," he said.

"We have a few lines in our collection that are described as having four leaflets, but the fourth leaflet is usually small and seems out of place," said Nelson. "The expression is also inconsistent. Not all plants will have four leaflets and not all leaves on any plant will have four leaflets."

My lucky find had leaflets of near like size and I found four of them -- each on different plants. I have no idea how many were in the row. The tour was leaving and dallying would have resulted in the unlucky situation of being left in a soybean field in the heat of the day.

Nelson did note (by viewing a photo I took) that the fourth leaf had a very short petiolule (stalk holding up the leaflets). "We have not studied the genetics of four leaflets and the inconsistency of expression makes standard Mendelian studies a big challenge," Nelson said.

Lucky or not? Boerma said that part of the question can only be answered at harvest.

Pamela Smith can be reached at

Posted at 6:54AM CDT 07/17/14 by Pam Smith
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