'Kuharske' is a selection of 'Carrizo' that is supposed to be more tolerant to burrowing nematode but similar in other respects (Castle et al, 1993; Castle and Tucker, 1998). "The limited data available so far show that this rootstock...has good potential especially for oranges on the Ridge. It has excellent tolerance to the burrowing nematode, but otherwise is just like Carrizo except its tolerance to blight has not been determined. Earygold trees have grown and yielded well on this rootstock http://edis.ifas.ufl.edu/HS173" (Castle, 2003b). 'Kuharske' is not used in California (proabably due to the lack of burrowing nematode) but is currently the second most widely used rootstock in Florida, after 'Swingle' citrumelo, according to the Florida Bureau of Budwood Registration. According to Bill Castle (personal communication, 2009), the early history of 'Kuharske' is somewhat unclear. Here is his version (Castle, 2003a):
"The somewhat mysterious history of Carrizo and Troyer citranges apparently is connected to the Kuharske citrange, according to the rootstock's namesake, Cleveland M. "Mac" Kuharske.
"Kuharske's father came to the Bay Lake area south of Groveland in the 1920s. The Kuharskes were Illinois farmers and exchanged land there for land in Florida, which eventually grew to 1,000 acres. Much of the land was eventually planted to citrus and included a nursery. The family also produced and ginned cotton for many years in central Florida.
"The history of Kuharske citrange traces to Winter Haven, Tex., where seedlings were sent of what was later named Carrizo citrange after the nearby town of Carrizo Springs. Seed trees were subsequently established at the U.S. Department of Agriculture facility in Orlando.
"Frank Gardner, the former rootstock scientist and director of the USDA lab in Orlando, visited the Kuharske nursery one day with a bag of seeds from those trees. He asked his friend Mac Kuharske to plant them. Kuharske was working in the family farming operations after having served in World War II as a tactical fighter pilot in Africa and Europe.
"Kuharske arbitrarily selected "interesting" seedlings from among the stand and propagated them in Row 1 of the nursery. Later, Dave Kaplan, a nematologist formerly of the USDA, Orlando, collected seed from each of those plants and screened them. He found two plants that had exceptional tolerance to burrowing nematodes. Thos plants are now known as the Kuharske citrange."
Although Bill's account does not include dates, a very rough timeline can be inferred from the fact that Frank Gardner was active in the 1950's through 1970's, and Dave Kaplan's results were reported in the late 1980's and early 1990's (Kaplan, 1986, 1992). What is now 'Kuharske' citrange can be inferred to be the seedling lines '01-10' and '01-18' reported in Kaplan (1986, 1992).
(RR Krueger, 05/08/2009)