Monday, December 30, 2013

Evaluating new pecan cultivars: A look inside the shell

     2013 turned out to be a good year for evaluating new pecan cultivars. The above average rainfall we received this past summer meant that soil moisture would not be a limiting factor in terms of kernel fill. However, the 2013 growing season was significantly shorter and cooler than normal. Lets take a closer look at the kernels inside the shells of three cultivars to see how cooler temperatures can impact nut quality.

    Let's start by looking at an open-pollinated Giles seedling we originally planted in the Chetopa City Park.  On the outside, this nut is large and attractive. City Park is larger than its Giles parent but smaller than Mohawk (the possible male parent). At first glance the kernels look OK but on closer inspection I note a lack of plumpness and some shriveling towards the tip of each kernel half. I also spot some kernel fuzz on surface of the kernels.

    USDA 75-8-5 and USDA 75-8-9 are sibling cultivars that resulted from a cross of Osage and Creek. Both cultivars produced medium-sized pecans this year. The kernels are bright and attractive but upon closer inspection, both cultivars have a significant amount of fuzz on the surface of the nut meats. In a previous post, I found the USDA 75-8-9 had more scab on the shucks than USDA 75-8-5.  With more scab on the shucks, USDA 75-8-9 had poorer kernel fill than its sister clone. Note that USDA 75-8-9 has flatter, less-plump kernels.

     All three of the cultivars pictured in this post show kernel symptoms that point to a shortage of summer heat during the growing season. Even though all three cultivars split their shucks well before the first fall freeze, nut development was delayed by cool mid-summer temperatures and kernel filling process simply ran out of time as fall approached.