Jones Farms - Micropropagation

Growing Micropropagated Sweetpotatoes

We have a separate greenhouse for each variety that we get from the NC State University Micropropagation Unit. A wood-frame greenhouse-- 20'X80' - 1/3 center area is screened in for mother plants.

Each greenhouse features electricity on thermostats and automatic timers for water and fertilizing.

Before entering each greenhouse, everyone goes though a double entry area for sterilization with a fogging system that complete covers the body to eliminate insects and diseases getting into the greenhouse. We don't feel it's enough to just step in a clorox-filled tub.

At the start of each growing season, we sterilize everything with a Clorox/
Oxidate/fungicide/
spore killer mixture to make sure everything is spic 'n' span and ready for new mother plants to be micropropagated.

Around the 1st week of Feb. we pick up plants in 4" clay pots from the NC State MPU. We get 50 plants of four different varieties with a color-coded label for each variety.

We immediately re-pot the mother plants into 3-gallon pots or hanging baskets that were previously fillled with special potting soil and watered thoroughly. We want to make sure our new plants can grow and not be root bound.

As the mother plant grows runners, we spray alcohol on clippers before making each cut at the second node joint to make sure we are not transmitting any viruses.

Jessica places 7 to 8 second-node cuttings in a hanging basket, which are hung in the greenhouse just outside the caged mother plant room

These first daughter cuttings, with each pot labeled to show what mother plant it came from, continue to grow .


As they grow, Jim and Jimmy take 2 node cuttings from each first daughter plant, which will be planted in another greenhouse with the same variety.

Each of our greenhouses has ground cover and gravel on the floor for drainage, as well as drain lines that run underground to remove any standing water.

Jim and Jimmy punch holes in the soil ready for second daughter cuts.

Jim and Jessica spacing and planting second daughter cuts in 6" rows, with each plant about 4" apart. We have about 18-20,000 plant capacity in each greenhouse.

Jim adjusts irrigation pipes to water second daughter plants.

Second daughter plants are now ready for transplanting and making seed stock in the field.

Prior to planting, we sample and meter the soil in all our sweet potato fields to determine what nutrients are needed to grow a good crop.


Starting about the first or second week of May, plants are cut every 8-9 days for 7-10 weeks for transplanting in our fields, We practice select cutting, using clippers to get the biggest plants to grow. We give the smaller plants time to get bigger before weekly cuttings and transplanting in the field.

Irrigation is key to growing quality plants and assuring a good stand. To get a good, uniform stand, a grower must irrigate if there has been no rainfall.

Applying sidedress fertilizer four weeks after transplanting will help ensure us of a good high yield of uniform #1 sweet potatoes.

Moving vines 8-10 days before digging with plow.

Digging with 2-row plow


Potatoes upturned by digger.

Bins and buckets are sterilized before harvest time. Harvesting crew separates seeds from #1's, carefully handling them as they're placed in bins for storage.

Curing boxes
(each holds 40 bushels)
of sweetpotatoes on truck.

In the curing shed, sweet potatoes are cured and stored over winter. They are kept for 4 to 5 days at 85 degrees and 85 percent humidity and then down to 55 degrees at 85 percent humidity for the duration of the time in the curing barn.

With the right micropropagated seeds or plants and, God willing, mother nature's cooperation we will have the very best crop of sweetpotatoes under our rows.

We grow our micropropagated 1st generation seed potatoes in field beds to make 2nd generation plants, which become our commercial potatoes and 2nd generation seed for sale to other growers. We start by placing the seed potatoes as close as we can without stacking.

We place 2 lines of drip tape for irrigation as we cover seed beds with soil.

The beds are covered with plastic

Jim's wife, Barbara, punches holes in the plastic to allow air to circulate on the plant bed. Along with water, we add nutrients once a week through irrigation drip tape.


	G-2 plants come from our G-1 field seed beds. They are hand selected to ensure uniform, healthy plants that will produce high yielding good quality G-2 sweet potatoes.

Micropropagation Brings Sweet results
to North Carolina Growers

With farmers in dire need of something to generate bank deposits after tobacco’s lean years and the damage from the 1999 hurricane season, micropropagated sweetpotatoes just might be the crop to boost cash flow in years to come.

The sweetpotato, North Carolina’s official vegetable, brought in $60 million in cash receipts last year from the more than 37,000 acres grown on the western edge of our state’s coastal plains, home to much of the nation’s crop.

Due mostly to seed stock improved by the College of Agriculture and Life Sciences’ Micropropagation Unit (MPU) at N.C. State University, a total of about 40,000 coastal plains acres probably will go to sweetpotatoes this year, says Dr. Zvezdana Pesic-van Esbroeck, MPU director.

Micropropagation is the carefully controlled generation of plants from a few cells of an original plant, which allows massive plant regeneration from originals that have been checked for disease and other problems.

The MPU meets the increasing demands of North Carolina’s fruit and vegetable industries for pathogen-free, virus-indexed, true-to-variety, asexually propagated stock plants.

N.C. State researchers, Cooperative Extension specialists and county agents, who in 1988 introduced the first micropropagated sweetpotatoes into North Carolina fields, strive to hold and improve the plant’s national market share. That share already is a healthy 40 percent, say statistics from the North Carolina Sweetpotato Commission Inc.

To produce micropropagated plants, researchers such as Pesic-van Esbroeck and Dr. Marilyn Daykin, a tissue culture specialist, grow tiny groups of meri-stematic cells — located at the leading edge of the plant’s growth — under controlled laboratory conditions at the MPU, generating small plants called mericlones.

Mericlone production in the lab bears no relation to the process that creates transgenic, or genetically modified, organisms.

"No sweetpotato mericlone genes are altered or transferred from one plant to another," Pesic-van Esbroeck says.

Researchers check the clones, and pathogen-free mericlones are multiplied — "increased," in growers’ language —through in-vitro techniques.

Later, scientists make cuttings to further increase the mericlones in isolated, insect-free greenhouses at the Sandhills Research Station in Montgomery County.

The MPU’s sweetpotato research is part of a continuing College effort to assist growers. College departments such as Plant Pathology, Horticultural Science and Entomology have cooperated with Extension and growers to help the sweetpotato buck stiff competition from other states.

Extension workers and researchers also help protect the crop from diseases such as the russet crack strain of the feathery mottle virus and against genetic drift, which happens if several generations of the same mother plant’s roots — not the preferred vines — are used for seed stock and replanted in the same field.

"The MPU avoids that problem through cloning the sweetpotato’s vine at the spot where it’s growing, the meri-stem," says Pesic-van Esbroeck. "A virus and other plant pathogens can be present everywhere in an infected plant but only rarely in the meristematic tissue."

Since the cleanest stock comes directly from the MPU, North Carolina Foundation Seed Producer growers must refresh their stock from the N.C. State greenhouse annually. Only that stock guarantees commercial sweet potato growers hill-selected, tissue-culture-generated, field-evaluated stock. But one such plant can translate into millions of sweetpotato plants in the field in a year.

The field is yet another place where researchers exercise quality control. Breeders Dr. Craig Yencho of the Vernon James Research and Extension Center in Plymouth, Kenneth Pecota of the College’s Horticultural Science Department, growers and others walk through harvested plantings yearly, while roots still are attached. They examine hundreds of plants, looking for the best. They also evaluate the lab’s existing mericlones in several fields to test for evidence of disease and genetic drift.

Dr. Charles Averre, a retired plant pathologist, helped develop the micropropagation system at N.C. State. Averre; Dr. Robert Milholland, retired plant pathology professor; Dr. Jonathan Schultheis, Extension horticulture specialist; and Bill Jester, an Extension area specialist, developed and demonstrated micropropagation procedures compatible with existing North Carolina Foundation and Certificate programs. These procedures ensured that sweetpotatoes stayed disease-free and stopped genetic drifts.

"But the most important thing about this program," says Averre, "is to give our growers quality roots. Then they will have a comparative edge, and that’s what pays off."

NC MPU Lauren Hix came out to inspect our plants. Protocol of NC Crop Improvement and Micropropagation Unit, inspected regularly once per month. During these unscheduled visits, they inspect greenhouses, look at plants, check for cleanliness, good housekeeping, etc.