But there is a flip side to the temperature dilemma. Peaches also need warm temperatures at the right time. An early spring warmup followed by a plummeting cold snap can bring disaster.
This is what happened in 2007 when the entire state crop was wiped out, said Bielenberg. Before the buds open they are more frost resistant. The ideal system would be a chilling requirement that matches local winter conditions combined with a higher heat requirement to keep buds closed longer and protect them from possible sharp freezes.
"The work we are doing not only involves understanding the chilling requirement, but also should help us breed for increased heat requirement to help protect the industry from late freezes," he said. The challenge is that heat requirement is not very well understood and is difficult to study since the timing of chilling and heat requirements overlap.
The temperature needs to be around 45 degrees or lower to meet the chill requirement for peaches. Different varieties need varied chilling times ranging from a couple of hundred hours to more than a thousand. Peach trees can "count" the chilling hours and suspend the count if there is a warm spell, then continue where they stopped when the chilling hours begin again.
Much remains unknown, Bielenberg said. How does a peach tree "sense" the temperature? How does it keep track of the number of chilling hours? How does it blend chilling hours with warming temperatures to control blossoming and growth?
"You can think of what we don't know as a 'black box,' and we haven't figured out how to see what's going on inside," he said.
Bielenberg and colleagues Gregory Reighard and Ksenija Gasic in Clemson's School of Agriculture, Forestry and Life Sciences are analyzing the peach genome looking for "DNA road signs" markers that can locate genes involved in chilling requirements, dormancy and growth.
"What we are learning is that there is
|Contact: Douglas Bielenberg|