Building Resilience and Flexibility into Midwest Organic Potato Production: Participatory Breeding and Seed Potato Production

Objective 1: Evaluate the practical and economic feasibility of on-farm production of high quality seed potatoes from minitubers and foundation class seed potatoes. 

a. Field production of seed potatoes from minitubers and saved seed tubers

Two participants planted minitubers into rows in a larger field setting. At both sites, weed pressure impacted the trials. At Stoney Acres Farm, weed density was greater in minituber plots than in neighboring plots. Although this trial was not designed to compare yields from minitubers and certified seed potatoes, it was noticeable that yields from minituber plots were much lower than yields in neighboring rows that had been planted with certified seed potatoes. At LCOCC Farm, weed pressure overwhelmed minituber plantings. Harvests from these plots were very low, and the farm manager decided not to replant. Due to their small size, plants from minitubers are typically smaller and less vigorous than plants from field-grown seed potatoes, and if shaded by early weed pressure, may not be able to produce well.

At Paradox Farm, minitubers were planted into heavily mulched beds. Yields for Carola, French Fingerling, and Red La Soda were rated well by the farmer, and tubers were saved for replanting, but Yukon Gold did not yield well and was not saved. At White Earth LRC, minitubers were planted into beds and managed with hand cultivation. All four varieties gave low yields (Table 1).

Table 1: White Earth Land Recovery Project field and harvest observations for plots planted with minitubers

In 2016, saved tubers for Red La Soda and French Fingerling were replanted at White Earth LRP, with 30 plants for each variety. Certified seed potatoes for varieties Red La Soda and Carola were grown as comparisons. In addition to saved seed potatoes from minituber plantings, the farmer at White Earth LRP replanted saved seed for four other varieties, Purple Pelisse, Picasso, Barbara, and Dark Red Norland, that had been part of a 2015 potato variety trial. Although the seed potatoes planted in this 2015 trial were not certified seed potatoes, they were produced from disease-free minituber stock in 2014, and the crop was closely inspected for evidence of disease.

Yields for replanted tubers for Red La Soda were comparable from saved and certified seed sources. No comparison to certified seed was made for French Fingerling, but the marketable yield was comparable to other varieties grown at White Earth (Table 2). However, high levels of common scab, a tuber defect caused by the soil bacterium Streptomyces scabies, were noted for unmarketable French Fingerling tubers.

Table 2: Yields from saved and certified seed potatoes at White Earth Land Recovery Project

At Paradox Farm, saved potatoes for varieties Carola, French Fingerling, and Red La Soda were replanted in 2016 and 2017. Yields were reported to be comparable to other varieties grown by the farmer.

b. Hoophouse and greenhouse production of seed potatoes from minitubers

In both 2017 and 2018, hoophouse grown plants at Snug Haven Farm were harvested between mid-June and mid-July. For all varieties except the breeding lines PxC, vines were still green at harvest. PxC vines had senesced naturally at harvest. One tuber was sampled from each plant for Potato Virus Y tests, and a zero incidence of PVY was seen for each variety in each year. Yields of new potatoes were low relative to main harvest field production, but the farmer was satisfied with yields due to the premium price obtainable for early potatoes at Madison WI farmers’ markets ($5/lb). It was clear that much higher yields could be obtained for all varieties with another month of growth.  

Table 3: Potato yields for Snug Haven organic hoophouse production

*Cherries Jubilee was harvested later than other varieties in 2017 due to its later maturity. Yield was reported by the famer to be comparable to Early Bangor and Hunter.

At Hillview Urban Agriculture Center, yields of Corne de Mouton, Early Bangor and Cherries Jubilee suggest a positive effect of vermicompost on potato productivity (Table 4). Sampled tubers from harvests showed zero incidence of Potato Virus Y. However, since all the tubers stored by the center sprouted by the end of March, they were unable to trial replanting their saved tubers, and decided not to repeat the trial.

Table 4: Potato yields for Hillview organic greenhouse production

At the Bad River Indian Reservation, we built on previous connections with Joy Shelble, 4-H Youth Development Coordinator, to provide seed potatoes for planting in the youth-managed hoophouse, as a small pilot trial in 2017. Despite the late July planting, the early December harvest, used for a dinner at a community event, was substantial enough that the group participated in hoophouse variety trials in 2018 (supported by a separate grant). Bad River is an extremely economically disadvantaged community, and production of high quality seed potatoes within the community has the potential to increase local food production, impacting human nutrition and quality of life.

c. On-farm production of seed potatoes from foundation seed potatoes

Foundation seed potatoes were planted in small plots within participants’ usual potato fields and managed according to their usual practices. Farmers provided samples of harvested tubers for Potato Virus Y (PVY) testing. Potato Virus Y incidence from farms that planted foundation seed potatoes is summarized in Tables 5 (2016 trials) and 7 (2017-2018 trials) below.

Of the 11 farms participating in 2016, 7 had no PVY incidence in tested tubers. Three (Engel, Igl and Noltnerwyss) had high PVY incidence in all or most seedlots that would preclude replanting, and the remaining farm (Dietz) had intermediate PVY incidence in one seedlot. It is notable that the three farms with high PVY incidence in 2016 grow substantially larger acreages than the other participants.

Table 5: Potato Virus Y (PVY) incidence in 2016 potato harvest from foundation seed potato stock, by farm and variety. All seed potatoes planted were foundation class (<0.5% PVY).

Two of the farms that had committed to replanting saved tubers had high levels of PVY in multiple seedlots, which made replanting inadvisable (Noltnerwyss, Igl). A third farm replanted comparisons of saved and certified seed ptoatoes but lost all plots due to extensive flooding. The Mortimore farm (Orange Cat Community Farm, in central WI) replanted 5 lb of saved Carola seed potatoes for which no PVY was detected, in comparison to 5 lb of certified seed potatoes purchased from Vermont Valley Community Farm. They additionally replanted saved Goldrush and Dark Red Norland seed potatoes (grown in 2016 from certified, not foundation stock) in comparison to certified seed potatoes of each variety. Farmer observations were that emergence, crop vigor, and yield were comparable between saved and certified seed potato sources for Carola and Dark Red Norland, but that saved Goldrush seed potatoes had “much lower vigor than normal” and “slow emergence”. Marketable yields were lower for plots planted with certified seed compared to saved seed (Table 6), but it should be noted that due to wet spring weather, planting of certified seed potatoes was delayed by two weeks after planting of saved seed potatoes, and this would account for the lower yields.  

PVY incidence in samples from plots planted with certified seed potatoes (5% virus threshold) were at or almost at 100% for all three varieties, indicating substantial virus spread within the crop after planting. PVY incidence in plots from saved Goldrush seed potatoes (unknown starting incidence) were also at 100%, but PVY incidence in plots from saved Dark Red Norland (unknown starting incidence) and Carola (0% PVY starting incidence) seed potatoes were much lower at 12.8% and 0% respectively.  

Table 6: Yields and PVY incidence for potato plots planted with either saved seed potatoes or certified seed potatoes at Orange Cat Community Farm.

In 2017, 2 farms participated in seed potato trials, and both had low PVY incidence in seedlots (Table 7). At Igl Farms, 9 of 10 varieties were below the virus incidence standard for certified seed potatoes, with 7 varieties having no PVY detected in sampled tubers. At Carter Farms, all 8 varieties grown from Wisconsin foundation seed were certified as seed potatoes, with 5 having no detectable PVY. However, in 2018 (Table 7), while all seedlots from 7 of the participants were free of PVY, only one seedlot from the Igl farm was PVY-free, with all 8 other seedlots having high PVY incidence ranging from 13-72%.

Table 7: Potato Virus Y (PVY) incidence in 2017 and 2018 potato harvests from foundation seed potato stock, by farm and variety. All seed potatoes planted were foundation class (<0.5% PVY). WIP= work in progress.

In 2017, Carter Farms provided PVY incidence data for 9 other seedlots planted with foundation seed from Colorado (2 seedlots, failed certification), Montana (3 seedlots, passed certification), Minnesota (1 seedlot, passed certification) and their own saved foundation grade seed potatoes (3 seedlots, passed certification).

Table 8: Varieties tested in 2017 at Carter Farms only

Yields from foundation seed stock were recorded at Igl Farms in 2017 and 2018 (Table 9). Some varieties were rejected by farmers due to tuber defects (Carola, Mercury and Red La Soda 10) or failed due to seedpiece decay (W8890-1R). In 2017, marketable yields from acceptable varieties ranged from 1.6-2.6 lb per row foot. In 2018, yields were considerably lower, possibly due to drought conditions, ranging from 0.4-1.0 lb per row foot.  

Table 9: Yields from plots planted with foundation seed at Igl Farm, Antigo WI

Objective 2: Provide training, coordination and resources for a farmer-participatory potato breeding network.

a. Selection of outstanding potato lines from true seed populations

Parental lines for true potato seed populations were selected due to good performance in previous organic variety trials, and several lines were included based on their resistance to Potato Virus Y. Parental lines are listed in Table 10.

Table 10: Potato varieties used as parents for true potato seed populations

Three participating farmers selected lines from true potato seeds to replant. Results from the initial selection year are shown in Table 11. Yields from plants started from seed ranged from 0.09 to 1.89 lb/plant across the three sites. Participants selected tubers to save and replant in the following year (Table 12).

Table 11: Yields from potato lines started from botanical seed at three sites. Potato lines were trialed at White Earth Land Recovery Project by Zachary Paige in 2015 and 2016; at Middleton Outreach Ministry Community Garden by Pat Dunn in 2017 and 2018; and by Wausau WI trial participant Paul Whitaker in 2017 and 2018. *True potato seed collected by Zachary Paige in 2015.

Each participant selected tubers to save and replant based on yield, appearance and flavor. Yields and comments for replanted tubers are shown in Table 12. At White Earth Land Recovery Project, Zachary Paige saved tubers from multiple plants for each of 5 populations to replant in 2016. Yields ranged from 1.3 to 2 lb per plant. Eating quality of these lines was comparable to named varieties that he grew at the same location, and he continued to save and replant tubers for the Yukon Gold-Chieftain cross for another two years. Other participants saved tubers from individual plants representing clonal lines. Pat Dunn saved two lines to trial, from Spartan Splash x Red Endeavor and Huckleberry x Red Endeavor crosses respectively. Both have good eating quality and moderate yields, and will be trialed in 2019 at the West Madison Agricultural Research Station. Paul Whitaker trialed 9 lines in 2018; 7 from a Huckleberry x Picasso cross and 2 from a Spartan Splash x Picasso cross. Yields ranged from 1.5 to 3.8 lb per plant, and Paul selected 6 lines to trial again at his location as well as at the West Madison Agricultural Research Station in 2019.

Table 12: Yields and comments for farmer-selected potato breeding lines

Lines shown in Figure 1, in addition to 5 other farmer-selected lines mentioned above, will be trialed at the West Madison Agricultural Research Station in 2019 as part of a Specialty Crop Block Grant-funded project. 

In 2015, breeding lines were selected from mixed progeny populations for the crosses described above, plus selfing of Adirondack Blue (AxA series), crosses of Eva (a Potato Virus Y resistant variety) with breeding line 118, and crosses of Keuka Gold with Yukon Gold (KKGxYKG). Breeding lines were planted in plots of 5-10 plants (depending on availability of seed potatoes) in the West Madison Agricultural Research Station organic field in 2016. Two parental varieties were also planted – Fenton Blue (FEN) and Sweet Yellow Dumpling (SYD) – as well as a widely adapted check variety, Red La Soda (RLS); these varieties were planted in replicated plots whereas single plots were planted for the breeding lines. As shown in Figure 2, several lines had marketable yields substantially above the parental lines. Due to a late blight outbreak in September, tubers from these lines were not saved for 2017 field trials, but healthy tubers were selected for introduction into tissue culture.

In 2016, minitubers for 14 breeding populations were planted in the organic seed potato production field at West Madison ARS. Seven of these populations derived from crosses between Potato Virus Y-resistant lines (PVY^R; resistance derived from Eva, Tacna, or White Lady) and popular varieties including Carola, Adirondack Blue, Red La Soda, and Spartan Splash. The other seven populations were open-pollinated populations from female parents Aylesbury Gold (PVY^R), Barbara (PVY^R), Picasso (PVY^R), Early Bangor, Makah, Purple Pelisse, and Red Thumb. Total yield data was collected for each population and averaged 0.85 lb/plant, ranging from 0.3 to 1.9 lb/plant. Although late blight incidence in nearby plots ruled out saving tubers for field trials, select tubers were collected for introduction into tissue culture and future trials. In 2017, minitubers for a set of breeding populations was multiplied in the organic seed potato production field at West Madison ARS, and tubers for individual plants were selected for replanting. Breeding populations were derived from the following varieties, as shown in Figure 3 legends and Table 10, either as crosses or from open pollinations (OP): Aylesbury Gold (AYG), Adirondack Blue (ADB), Adirondack Red (ADR), Barbara (BRB), Early Bangor (EAB), Huckleberry (HRL), Picasso (PIC), Purple Pelisse (PEL), Red Endeavor (REN), Spartan Splash (SPS), Tacna (a PVY resistant breeding line, TAC),  and Y1 (a PVY resistant breeding line). Lines abbreviated "TASR" are from crosses between an F1 plant from a Tacna x Adirondack Blue cross and an F1 plant from a Spartan Splash x Red La Soda cross. These lines were trialed under organic management in 2018 at West Madison ARS. Most lines were planted as single plots due to limited tuber quantities, in comparison to replicated check varieties. Total and marketable yields for four market classes are shown in Figure 3 A-D. 

b. Mixed progeny populations as seed tubers

In 2016, seven participating growers trialed progeny populations from crosses for productivity and marketability, as a test of the feasibility of using true potato seed (TPS) as the basis for a production system. Growers were asked to answer the following questions: would they want to grow these populations again; what were the strongest and weakest points; and to rate the marketability and eating quality (1-5 scale with 5=best). Grower feedback is shown in Table 13. 

Table 13: Grower evaluations of mixed progeny populations from potato crosses Adirondack Blue and Fenton Blue (AxF series), Sweet Yellow Dumpling and Adirondack Blue (SxA series), White Lady and Adirondack Blue (WxA series) and Yellow Rose and Adirondack Blue (YxA series).

For 14 trials of mixed populations, 11 were acceptable to growers to grow again, with one "maybe". Of the 9 populations, 4 rated higher than average for marketability, and 6 rated higher than average for eating quality. Populations derived from crosses Adirondack Blue x Fenton Blue (red tubers) and White Lady x Adirondack Blue (red, purple and yellow tubers) were the most promising.