Low Glycemic Potatoes, a value-added crop for Montana

2014 Annual Report for SW12-108

Project Type: Research and Education
Funds awarded in 2012: $154,000.00
Projected End Date: 12/31/2015
Region: Western
State: Montana
Principal Investigator:
Dr. David Sands
Montana State Univ

Low Glycemic Potatoes, a value-added crop for Montana

Summary

The overall goal of our lab is to develop value-added crops with highly desirable nutritional attributes that are suitable for production in the state of Montana. This nutritional focus includes high-protein, gluten-free, and low glycemic index. The purpose of the Western SARE funded project is to identify, introduce, and commercialize potatoes with low glycemic index. We have screened a large collection of U.S. potato lines/varieties and selected five varieties with the most promising starch profiles. Confirmation that the selected varieties are agronomically adapted to Montana is ongoing.

The first objective in this proposal was to develop quick and inexpensive laboratory analyses to estimate the starch profile of potatoes or seed. The starch profile is a significant determinant of the glycemic index (GI). The glycemic index of a food is determined by feeding the food to test subjects and measuring the effect on blood glucose. A high GI indicates that consumption of a food results in a very rapid increase in blood sugar. A low GI indicates that the food is digested slower with a lower, steadier increase in blood sugar. Spikes in blood sugar are especially undesirable in individuals with diabetes or struggling with weight reduction. The GI test involves human subjects (10-25/food) and is subsequently very expensive (estimate $10,000-25,000/per variety). The cost of this human assay precludes its use as a tool to screen crop populations and select low GI varieties. We proposed that controlled laboratory analysis of potato would provide more reliable, reproducible results and would be a powerful tool for variety selection. Our initial assumption was that a single test could rank all of the varieties relative to their glycemic index. We compared three different assays of potato starch composition (granule structure, spectrometry and enzymology) and ranked the varieties. The potatoes were ranked differently depending upon the chosen assay. However, by combining the results of all three of the tests in a sequential manner, we were able to reliably rank cultivars and have narrowed our focus to the five cultivars of potatoes.

Development of this system and ranking of germplasm has taken longer than we projected, but we are very confident that this system gives a true analysis of starch profile and can be applied to a number of crop species. Unfortunately, the human GI ranking is the only meter recognized by the food industry and consumers to predict the effect of a food on blood sugar. Thus, we must demonstrate that our lab assay of starch profile reliably predicts GI and are seeking supplemental funding for the GI studies.

The five varieties that we have selected performed better in laboratory tests than varieties touted for their “low glycemic” scores. For example, variety Nicola has a relatively low GI index of 58 (Russet potatoes have a GI index ranging from ~80 to 110). Nicola falls in the top quarter or our ranking but not in the top five.

Objectives/Performance Targets

The overall goal of this project is to develop low glycemic potato as a value-added Montana crop. The specific objectives are to:

I. Identify low-glycemic index potato cultivars that are adapted for production in Montana.

a. Screen available germplasm for starch composition (determine amylose: amylopectin ratios).

b. Isolate and produce disease-free micro-tubers (MSU Seed Potato Laboratory). The state of Montana has provided funding for the first year of this project. This objective will be completed by researchers at MSU under the direction of Dr. David Sands.

II. Evaluate selected cultivars in field studies in collaboration with Montana seed potato producers and select the most-promising cultivars for seed production scale-up. Continue to evaluate and select varieties throughout commercial scale-up. Dr. Barry Jacobsen (MSU extension) will work directly with seed and commercial potato producers to evaluate the selected germplasm. These field studies will be replicated on private potato fields and on MSU Ag Research station fields. The studies on private fields will be maintained by our cooperative producers, and the plots on Ag Research Stations will be maintained by MSU personnel.

III. Generate a feasibility analysis, including economics of low GI seed and commercial potato production and estimated market demand. Dr. Alice Pilgeram will work directly with the Montana Seed Potato Growers, the American Diabetes Society, natural food distributors and food developers to evaluate and develop research demand. The State of Montana will assist in marketing newly developed agricultural crops and products (www.madeinmontanausa.com).

IV. Evaluate selected lines in greenhouse studies for disease susceptibility (year 1) and impact of agronomics on starch profile (year 2 and 3). This portion of the study will be done jointly by researchers in the MSU Plant Science department and the MSU seed potato lab.

V. Evaluate selected cultivars in field studies in collaboration with Montana potato producers to determine the most-promising cultivars for low-GI potato production in Eastern MT. Work with producers to scale-up production to commercial levels.

VI. Evaluate cultivars in local and university taste studies (MSU, Extension and Producers).

Accomplishments/Milestones

Objective I. The data presented in the 2013 annual report was the preliminary results from our experiments optimizing spectrophotometric and microscopy techniques. These results enabled us to quantify the differences between varieties, starch composition, and their physical-­?chemistry properties.

 Starch Granules: The starch granules are formed by d-­?glucose molecules linked together through glucosidic links forming complex polymer structures. Potato starch is composed of two forms of carbohydrate, amylose (linear chain of glucose) and amylopectin (branched chain of glucose). The balance and organization between these two types of carbohydrate will determinate the morphology of the granule.

 Swelling power: Starch granules are practically insoluble in cold water, but when they are heated, the structure opens up allowing the absorption of moisture. Amylopectin is primarily responsible for water absorption capacity because its structure is more complex and once it is opened there are many sites where water molecules can adhere. It is also known that amylose has a higher crystallinity degree than amylopectin (i.e amylose is harder to dissolve in water than amylopectin).

 We ranked potato varieties for:

  1. Degree of irregularity in the granular surface (GS) of the starch
  2. Swelling power (SP). The ability of the heated granule to absorb and retain water, and
  3. Spectrophotometric quantification of percentage of amylose present in the starch.

All data was statistically analyzed and we concluded that even though none of the correlations are perfectly linear, the concentration of amylose in a variety is directly proportional to the degree of fracture observed on the granular surface and inversely to the capacity to absorbed water (Table 1).

 

Variety

% Amylose

GS

SP

Green Mountain

61

3

13

Muru

59

5

10

Bzura

50

5

13

Huckleberry

45

5

9

Multa

45

5

12

Oct Blue x Col Rose

44

3

9

Monona

28

2

22

Picasso

24

1

21

Purple Valley

24

2

18

Table 1: List of 6 potato varieties candidates for Low GI vs. 3 varieties with high GI

Objective II. Field evaluation of the selected potato lines will be continued through the 2015 growing season. To date we have evaluated numerous lines in the greenhouse, a few lines with commercial growers, and several lines in home gardens. As previously mentioned, we have purchased 50 pounds of green mountain seed for production in 2015. We also have on-going production of Muru in California. This potato will be harvested in the next month and for production in Montana in June. The 2015 production will be in collaboration with commercial organic seed potato producers in Manhattan Montana and at the Towne’s harvest community garden at Montana State University. The 2015 harvested potatoes will be used for glycemic index testing and distributed to consumers through local farmers markets.

 Objective III. The feasibility analysis is in progress and will be completed in 2015.

 Objective IV. The primary disease concerns are PVY and Late Blight, all of our varieties are equally susceptible to PVY. We can only do this study in the MSU greenhouse as Montana is purposely free of PVY. Late Blight can be a problem in Montana. Disease incidence is sporadic and completely dependent on weather conditions. In 2013-­14 we did not see Late Blight in potatoes in Montana. However, Green Mountain is reported to be resistant to Late Blight and is a valuable source of resistant germplasm for future crosses. We will complete the initial evaluations of susceptibility in 2015.

 Objective V. Six low GI cultivar plus a control will be planted in June 2015 at the Eastern Ag Research Center (EARC) in Sidney Montana. Preliminary data on production and adaptability will be completed at the end of the 2015 growing season. The potatoes will be show-­cased at the EARC annual AG day. If the cultivars do well, we will work with the EARC personnel to expand production in the region.

Objective VI. Montana State University recently established a food science laboratory that is currently performing taste studies on herbal teas. The potatoes taste studies will be incorporated into this existing survey using the existing panels. We project that we will have adequate amount of potatoes at the end of 2015 growing season. With the exception of varieties Nicola and Valley, we do not have an excess of the low GI potatoes. Unfortunately, Nicola and Valley did not make the cut for low GI varieties.

All top five varieties are being increased and 50 pounds of the Green Mountain cultivar has been ordered from a commercial seed producer. These will be held for glycemic testing in humans when supporting funds can be found. The Montana Seed Potato Association (Director Dr. Nina Zidack, Montana State University), has received four of the five germplasm for virus free verification and cultivation in tissue culture and the Peruvian cultivar will be tested this spring. The objective is to test the best, most promising agronomic line for glycemic index and simultaneously develop enough virus free germplasm for growers interested in this niche market crop.

Three seed potato growers (one is organic) have been identified and are very interested in expanding their market into low glycemic potato production at the retail level and as seed producers. Initially, this would be local distribution, followed by national, as production is linked to market growth.

There is no question that we have a lot to do in order to complete these objectives. We are confident that the selected low GI potatoes meet our agronomic requirements. Our emphasis in 2015 will be production scale-­up with commercial growers and marketing. We do feel that we will complete the objectives by the end of 2015. Our biggest hurdle in this project is that we did not include funding to complete an actual glycemic test in the Western SARE proposal. This was a mistake.

We know that the selected potatoes have a starch profile that is characteristic of low glycemic foods, but market acceptance and consumer recognition will require an actual glycemic index #. We are currently seeking funding for this test from other sources including the USDA, state of Montana, and the Montana seed growers association.

Impacts and Contributions/Outcomes

We are actively pursuing funding for the human GI test in order to validate the laboratory analyses. If we can validate the potato starch analysis as a economic means to predict GI, we will expand the study to include other Montana Crops, including low glycemic peas (Norm Weeden, MSU), low glycemic oats, and low glycemic wheat (Mike Giroux, MSU). Market analysis of any newly introduced crop in the past has emphasized many additional positive crop features. For this reason, in this project, we embarked on the selection of a low glycemic potato that is also high in lysine, both value-added traits. High lysine was assayed by GC-mass spectroscopy. To our knowledge this high lysine line will be the first of its kind. We used a similar selection as we used some years ago to obtain three lines of high lysine wheat. None of our new crops were used with GMO technology, and therefore, we do not have to market under the perceived stigma of a GMO label.

It will remain to be seen how the human testing of glycemic index unfolds. The whole project is centered on public recognition of the problems of obesity and diabetes as they are linked to diet. If the testing proves positive and points to the possibility that low glycemic index potatoes are part of a better diet, first for diabetics and pre-diabetics, will then there be a market response and how will that be implemented? The absolute credibility of the testing laboratory is important.

Collaborators:

Dr. Barry Jacobsen

uplbj@montana.edu
Professor
Montana State University
119 Plant Bioscience Building
Bozeman, MT 59717-3150
Office Phone: 4069945161
John Venheizen

Grower
Spring Creek Farms
3990 Churchill Road
Manhattan, MT 59741
Office Phone: 4062844233
Steve Cottom

Grower/owner
Cottom Seed, Inc
P.O. Box 445
Dillon, MT 59725
Office Phone: 4066606266
Dan Lake

lakeseed@ronan.net
Grower
Lake’s Glacier View Farm
35822 Spring Creek Road
Ronana, MT 59684
Office Phone: 4062533638
J.E. Day

Grower
J.E. Day Seed Potatoes
P.O. Box 61
Twin Bridges, MT 59754
Office Phone: 4066845669
Roger Starkel

Producer
Starkel Farms, Inc
42530 North Foothills Drive
Ronan, MT 59864
Office Phone: 4066758231
Dr. Alice Pilgeram

pilgeram@montana.edu
Research Professor
Montana State University
119 Plant Bioscience Building
Bozeman, MT 59715-3150
Office Phone: 4069945155
Art Mangels

Grower
Mangels Seed Potatoes, Inc
2660 Albers Road
Dillon, MT 59725
Office Phone: 4066834356
Dr. Nina Zidack

nzidack@montana.edu
Director Montana Seed Potato Lab
Montana State University
Plant Growth Center 223
Bozeman, MT 59717
Office Phone: 4069946110
Dennis Day

thedays@3rivers.net
Grower
J.E. Dayy Seed Potatoes
PO Box 61
Twin Bridges, MT 59754
Office Phone: 4066845669
Sid Schutter

sidschutter@gmail.com
Producer
Schutter Seed Farm, Inc
3627 Wooden Shoe Road
Manhattan, MT 59741
Office Phone: 4062846478