HORTSCIENCE 51(1):8–14. 2016. and cultivated throughout the United States for many generations (Gepts, 1988; Hendrick, 1931; Silbernagel and Hannan, 1988). Seed Yield Stability of Heirloom Dry Bean savers, farmers, and specialty seed compa- nies, however, more often refer to landrace (Phaseolus vulgaris L.) Cultivars in populations as ‘‘heirloom,’ ‘‘heritage,’’ ‘‘folk,’’ or ‘‘farmer-bred,’’ all of which em- Midwest Organic Production phasize a horticultural or anthropological component (Camacho et al., 2006). Heirloom Hannah R. Swegarden1 populations are known for their deep cul- Department of Horticultural Science, University of Minnesota Twin Cities, tural connections, traditional uses, and eco- Alderman Hall, 1970 Folwell Avenue, St. Paul, MN 55108 logical adaptation to the region in which they were first cultivated (Burgess, 1994; Craig C. Sheaffer Nazarea, 2005). As a result of exchange, Department of Agronomy and Plant Genetics, University of Minnesota Twin migration, and human selection, heirloom cultivars today are typically characterized Cities, Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108 as populations of variable plants occasion- Thomas E. Michaels ally lacking in desired agronomic traits (Lioi et al., 2005; Rodino~ et al., 2009). Department of Horticultural Science, University of Minnesota Twin Cities, Previous studies conducted in northern Alderman Hall, 1970 Folwell Avenue, St. Paul, MN 55108 Colorado (Walters et al., 2011), Michigan Additional index words. common bean, landrace, niche markets (Heilig and Kelly, 2012), and northwest Washington (Wagner et al., 2006) indicated Abstract. Heirloom dry bean (Phaseolus vulgaris L.) cultivars are distinct in their seed the yields of heirloom dry beans were sub- characteristics, although little information regarding their performance at the field scale in stantially lower than commercial market the Midwest is currently available. Demand for organic heirloom dry beans from direct-to- class cultivars. Issues related to harvest consumer markets in Minnesota motivated our examination of the crop’s suitability for maturity and labor costs of trellising climb- local production. Heirloom cultivars were evaluated on the basis of yield and yield stability ing plant habits were cited as primary yield at four small-scale organic vegetable productions in southeast Minnesota. Yield data from constraints within heirloom cultivars (Wal- 2013 and 2014 were subject to static and dynamic stability biplot analyses. The mean yield ters et al., 2011); improved disease resis- of heirloom cultivars was ’44% lower than commercial market class checks included in tance and architectural traits among modern the trial; heirloom yields ranged from 825 to 2127 kg·haL1, with a mean of 1362 kg·haL1. cultivars provided competitive yield advan- Stability analyses and economic incentives suggest that the production of heirloom tages (Heilig and Kelly, 2012). To date, cultivars, especially ‘Jacob’s Cattle Gold’, ‘Lina Sisco’s Bird Egg’, ‘Peregion’, and however, yields of heirloom cultivars, spe- ‘Tiger’s Eye’, could provide growers with the opportunity to diversify their production, cifically upright and bush-type cultivars, differentiate themselves in local markets, and maintain economic return. have not been evaluated at the field scale in Minnesota. In addition, the diversity of organic production environments and the In response to consumer demand, land Miles, 2012; Maeder et al., 2002; USDA, potential for variability within heirloom dedicated to certified organic dry bean 2015). Western and southern regions of cultivars necessitate an analysis of stability (P. vulgaris L.) production nearly quadrupled Minnesota have seen recent growth of di- across growing environments. The objec- in Minnesota between 2008 (241 ha) and versified organic vegetable producers cater- tive of this study was to evaluate yield and 2011 (1011 ha) (Greene et al., 2009; Greene, ing to urban outlets and direct-to-consumer yield stability of several heirloom dry bean 2013; USDA, 2011a). A similar trend was markets, including restaurants, community cultivars across small-scale organic vegeta- observed on a national scale; organic dry supported agriculture, and farmer’s markets ble production environments in southeast bean production increased from 1.08% to (Adam, 2006; Schnell, 2007; USDA, 2012). Minnesota. This research will provide guid- 2.38% of total dry bean acreage between For the past 2 years, the Regional Sustain- ance to small-scale vegetable growers in the 2008 and 2011 (USDA, 2011b). Organic dry able Development Partnerships (RSDP, un- region regarding favorable heirloom culti- bean price premiums and ecological system published data, 2014) at the University of var choices when supplying novel dry beans services serve as primary incentives to adopt Minnesota has conducted surveys regarding to local markets. organic production practices (Kremen and supply chains and local production of dry beans in Minnesota. Materials and Methods Surveys from RSDP (unpublished data, 2014) suggest that there is new demand among Plant material and seed pretreatments. Received for publication 25 Aug. 2015. Accepted consumers and restaurants for locally pro- Untreated seed of 17 heirloom dry bean for publication 2 Dec. 2015. duced, organic dry beans. In particular, there (P. vulgaris L.) cultivars were sourced This work was supported by the USDA National is expressed demand for heirloom cultivars from commercial vendors (Osborne Family Institute of Food and Agriculture Organic Agri- with identifiable traits, such as cooking quality, culture Research and Extension Initiative (Proj- Farms, 2014; Purcell Mountain Farms, 2014; ect No. MIN-13-G24) and represents a portion of flavor, and interesting seedcoats. Participating Seed Savers Exchange, 2014; Vermont Bean the primary author’s graduate thesis submitted to restaurant managers cited an average willing- Company, 2014) (Table 1; Fig. 1). Heirloom the faculty at the University of Minnesota. ness to pay (WTP) of $10.52 per kilogram for cultivars were assumed to be heterogeneous We thank the following partners for their field heirloom, organic dry beans (RSDP, unpub- populations of homozygous plants with low support: Cornercopia Student Organic Farm, Gar- lished data, 2014). According to growers who levels of outcrossing. These cultivars were dens of Eagan, Foxtail Farm, and Fresh Earth Farms primarily sell their heirloom dry beans through selected because of their novel seed appear- and thanks to Joshua Larson, Claire Flavin, Sanna farmer’s markets, consumers exhibit a WTP ance, bush-type plant architecture, and po- Beek, Trentin Tracanna, and Laura Hayes for their between$13.20and$17.60perkilogram tential as a cultivar for local niche markets. technical support. Reference to commercial products or trade names is (John Breslin, personal communication, 30 Seed size descriptors, including 100 seed made with the understanding that no discrimination Jan. 2015; Paula Foreman, personal com- weight (g) average seed length (mm), width is intended and no endorsement by the University of munication, 10 Oct. 2013). (mm), and thickness (mm) were collected Minnesota is implied. Heirloom cultivars are landrace plant from original seed stock in 2012 and yield 1Corresponding author. E-mail: [email protected]. populations that were informally exchanged trial stock from 2013 trials (Table 1). In
8 HORTSCIENCE VOL. 51(1) JANUARY 2016 addition, seedcoat characteristics such as coat color, corona color, and seedcoat pat-
(mm) tern were recorded (Leaky, 1988). Three Thickness commercial market class cultivars, Eclipse, Lariat, and OAC Rex (Michaels et al., 2006; Osorno et al., 2009, 2010) were (mm)
Width included as commercial checks in the trial; commercial control cultivars were assumed to be pure lines with low levels of out- crossing. In addition, commercial checks (mm) Length were selected to represent the most widely grown market classes grown in the Midwest and commercial types that show potential in organic production. Germination of all
color seed stock was tested using the ‘‘between Corona paper’’ method specific to common bean (Rao et al., 2006). Just before planting, seed was inoculated with a commercial source (Novozymes, Franklinton, NC) of nitrogen-
w fixing Rhizobium bacteria (Rhizobium leguminosarum biovar phaseoli) in a peat- pattern
Seedcoat based suspension. Experimental design. Experiments to de- termine the yield and yield stability of heir- loom dry bean cultivars were conducted during 2013 and 2014. Plots were established at four locations: Fresh Earth Farm in Afton, MN; Foxtail Farm in Osceola, WI; Gardens of Eagan in Northfield, MN; and The Corner- copia Student Organic Farm in St. Paul, MN color
Seedcoat (Table 2). The Northfield, MN, and St. Paul,
) cultivars included in the 2013–14 yield trials. Seed descriptors (seed size, shape, weight, coat color, MN, locations were United States Department of Agriculture certified organic, whereas the Afton, MN, and Osceola, WI, locations had been managed according to the UDSA guide- lines for more than 10 years before the onset of
(g) the experiment (Paul Burkhouse, personal x
Phaseolus vulgaris communication, 2013; Chris James, personal wt 100-Seed communication, 2013; USDA, 2014). The University of Minnesota’s Research Analyti- cal Laboratory (http://ral.cfans.umn.edu/ references/; St. Paul, MN) performed soil fertility tests (Table 3) in the fall of 2013 Seed shape and 2014 using standard extraction methods for pH, organic matter (OM), P, K, Ca, and Mg. Previous crops and soil nutrient com-
y position differed among locations (Table 3). size
Seed No fertilizer, insecticides, or herbicides were applied during these experiments. All
z locations were maintained as nonirrigated, rain-fed sites. Plant habit Each experiment was a randomized complete block design with three replica- tions. A block consisted of 20 dry bean cultivars as treatments. Heirloom cultivar Lina Sisco’s Bird Egg was omitted from the origin 2014 trials as a result of improper planting. Seed stock An experimental plot consisted of a single treatment planted in a 2-row plot that was 4.6 m (15 feet) long with 0.61 m (24 inches) row spacing. Seed count was adjusted for germination percentage plus 5% seedling mortality to obtain a target seeding rate of
name 215,186 plants/ha (87,120 plants/ac) or Cultivar four plants per 0.304 m (1 foot). The soil had been prepared by chisel plowing and thenfinishedbyfieldcultivatingorrototil- ling before seeding. Experiments were seeded between Julian days 152 and 161
coat patter, corona color, length, width, and thickness) were evaluated from 2012 original seed stock (n = 15) and 2013 yield trial stock (n = 15). (1 June to 10 June) in both seasons. Weed- Seedcoat pattern as defined by Leaky (1988). S = small (<25 g/100Weight seeds); (g) M of = 100 medium seeds (25–40 (i.e., g/100 100-seed seeds); weight). L = large (>40 g/100 seeds). Plant habit: V = vine; UV = upright vine; USV = upright short vine; B = bush. Table 1. Descriptions (cultivar name, seed origin, and plant habit) of commercial and heirloom dry bean ( z y x w Cultivar code BBCALDGECL Bumble Bee CalypsoHSICA Dapple Grey EclipseJCJCG Hutterite SoupKP Ireland Creek Annie SeedKYE Savers Jacob’s CattleLAR Jacob’s Cattle Gold Seed Purcell Savers Mt. SeedLC Savers Koronis Purple KenearlyLS Yellow Seed Eye Savers Lariat B NDSUPER VT Bean Co.PP Seed Savers Low’s Osborne B Champion Family B BREX Lina L Sisco’s Seed PeregionSOL Bird Savers B Egg BSYE B M Painted M OAC M Pony SeedTE Rex USV VT Cuboid B Savers Bean Co. SoldierYY M Round L Steuben Kidney; B Oval L Yellow cuboid NDSU S Eye L Round Tiger’s Eye B B Kidney Yin Kidney VT Yang Purcell Bean Seed 35.4 Oval L Mt. Co. Savers Round 55.7 U. Guelph M L Kidney Yellow 38.3 USV Osborne White; Family V 36.3 dark red B 28.1 Truncate V Seed oval Round Savers 41.0 M 52.0 Black; white USV B VT Bean White;free S mixed 18.4 Co. 41.7 grey Yellow S M Oval Gold; 38.9 Red-purple; white S USV white 48.0 plots M Oval Black White; gold Round Kidney Maximus B virgarcus L Oval Red 40.6 Purple; white Cuboidwere Major Uniform punctatus Dark red Stellatus majus Kidney L Cream-beige; Major red-purple punctatus maintained 32.9 Dark grey 24.7 14.4 Major 39.1 Round 18.5 punctatus Uniform Rhomboidius Black Red-purple Cream-beige; light 38.9 Maximus brown 19.3 virgarcus Grey 12.5 Brown; Uniform; White; white 8.8 punctatus Cream-beige; gold black; Dark 50.1 15.9 brown greyusing Uniform Brown Rhomboidius White; White red Ochre Pale beige 11.3 Striatus; 7.5 uniform Uniform Gold; 7.5 14.7 41.8 red-purple a Light 6.6 13.9 grey wheel 12.1 12.1 8.3 Beige Beige 16.4 Black; 6.0 7.3 white 10.7 Black 7.0 Virgata 6.2 minor 7.8 8.0 Stellatus majus Grey 6.8 7.1 Striatus 6.8 12.3 12.1 Maximus 6.1 virgarcus 5.6 Black 6.7 Uniform 6.4 Light 9.1 grey White 7.9 6.3 5.7 5.7 12.0 Stellatus majus 12.2 6.1 12.7 Gold 13.8 4.7 7.6 4.8 7.6 Black White 4.7 5.7 7.0 5.9 16.5 6.5 11.5 4.8 8.9 6.5 7.7 8.1 5.9 5.7 6.9 5.2
HORTSCIENCE VOL. 51(1) JANUARY 2016 9 Fig. 1. Photos of twenty dry bean (Phaseolus vulgaris) cultivars included in the 2013–14 yield trials. Heirloom cultivars were selected on the basis of identifiable seedcoats and bush-type plant architecture. Commercial control cultivars are denoted by cultivar codes ECL, LAR, and REX; all others represent heirloom cultivars.
Table 2. Description (location, geographic coordinates, elevation, rainfall, and growing degree days) of m a b ðÞab e yijk = + i + ðÞk j + ij + ijk trial sites of the 2013–14 dry bean (Phaseolus vulgaris) yield trials. National Weather Service (NOAA Online Weather Data, 2015) estimates represent accumulated rainfall (mm) and growing degree days where yijk is the measured yield observation (‘GDD’ calculated with base ‘50’) during the Julian period 152–174 (1 June to 1 Oct.). of the ith cultivar in the jth environment (i =1, 2013 2014 2, .,g;j =1,2,., e; k = 1, 2, .,rj), m is the a th Location Coordinates Elevation (m) Rainfall (mm) GDD Rainfall (mm) GDD overall mean, i is the effect of the i z b th Afton, MN 44 85#N, 92 82#W 269 298 2347 470 2266 cultivar, (k)j is the effect of the k replication z y th Northfield, MN 44 53#N, 93 18#W 289 274 2033 596 — nested within j environment, (ab)ij is the Osceola, WIz 45 23#N, 92 73#W 315 354 1467 559 1967 effect of the ith cultivar with the jth environ- # # St. Paul, MN 44 98 N, 93 19 W 305 337 2288 438 2308 ment, and eijk is the random error term. Fixed z Afton, Northfield, and Osceola estimates acquired from Hastings, Cannon Falls, and Amery stations, effects included m and ai whereas b(k)j,(ab)ij, respectively. and eijk were fit as random effects; random yData missing from August to October. effects, b(k)j,(ab)ij, eijk were declared in- dependent, normally distributed, and scaled 2 2 2 hoe (Valley Oak, Chico, CA) in the early yields represent weights at ambient relative toward zero with a variance of sb , sab , se , season and biweekly hand cultivation mid- humidity expressed in kg·ha–1. respectively. The significance of each ran- to-late season. Statistical analysis. Environments were dom effect variance component was deter- Data collection. Plots were hand har- defined as specific location–year combina- mined from the log-likelihood ratio test vested when all pods were beyond physio- tions. To account for heterogeneity in vari- statistic, comparing models fit via maximum logical maturity in late September or early ances between heirloom cultivars and likelihood with and without the variance October (Nowatzki, 2013). The inner 2.44 m commercial checks, yield data were subject component in question, with a Chi square (8 feet) of each 2-row plot was hand har- to a square root transformation, on the basis distribution and one df (Table 4). Effects vested. Plant populations within the har- of a Box–Cox test (Box and Cox, 1964). All were declared significant at a = 0.05. Profile vested area were determined during the data analyses were performed using R soft- confidence intervals (95%) were calculated 2014 growing season. Harvested pods were ware (version 3.1.2) (R Core Team, 2014); for each fixed effect. placed in a low-temperature (35 C) dryer models were executed using the ‘‘lme4’’ Yield stability analyses. Heirloom culti- overnight and then threshed with a small belt package (Bates et al., 2014) and evaluated var stability was evaluated according to the thresher (Agriculex, Guelph, Ontario, Can- using the ‘‘lmerTest’’ package (Kuznetsova Type I (static) and Type II (dynamic) con- ada). To maintain a marketable yield for et al., 2015). To account for the unbalanced cepts of stability classified by Lin et al. direct-to-consumer markets, harvested seed nature of the yield data set, the following (1986) and described further by Becker was cleaned of debris, splits, and diseased linear mixed effects model was fit using and L eon (1988). Stability under the Type seed before weighing. Reported per-plot restricted maximum likelihood: I concept was evaluated by calculating
10 HORTSCIENCE VOL. 51(1) JANUARY 2016 Table 3. Soil types, cropping history, and soil nutrient information for trial site locations included in the 2013–14 heirloom dry bean (Phaseolus vulgaris) yield trials. Soil sampling was performed in the fall of 2013 and 2014 across all locations and replications. Soil tests were performed by University of Minnesota’s Research Analytical Laboratory. Site history Fall soil testing results
Site Soil type Yr Previous crop(s) pH OM (%) BrayP (ppm) NH4OAc-K (ppm) Ca (ppm) Mg (ppm) Afton, MN Baytown silt loam 2013 Cover mixture of dikon radishes, 5.6 4.4 9 82 — — annual rye, and crimson clover 2014 Cover mixture of dikon radishes, 5.5 4.2 11 105 1406 252 annual rye, and crimson clover Osceola, WI Santiago silt loam 2013 Onions 6.9 2.4 25 60 — — 2014 Tomatoes 7.3 2.2 50 77 1260 266 Northfield, MN Wadena loam 2013 Cover mixture of white 6.7 3.0 53 136 — — clover and annual rye 2014 Lettuce followed by soybean/sorghum 6.5 3.9 25 88 2158 312 St. Paul, MN Waukegan silt loam 2013 Onions, broccoli, peppers, lettuce, 6.7 3.6 143 296 — — cabbage, tomatoes 2014 Tomatoes, garlic, watermelons, 7.4 3.8 174 444 2183 383 winter squash eggplant OM = organic matter.
Table 4. Random effect variance components and environments. A regression method of sta- average yield of 2447 kg·ha–1.Yieldsof their respective contribution to yield model used bility using an environmental index, pre- heirloom cultivars differed (P # 0.05) from to evaluate the 2013–14 heirloom dry bean sented here as b(k)j, was first proposed by one another, with yields ranging from (Phaseolus vulgaris) yield trials conducted at Eberhart and Russell (1966). This envi- 924 kg·ha–1 (‘Dapple Grey’) to 2127 kg·ha–1 four locations in southern Minnesota. Models ronmental index, however, was not di- (‘Peregion’) and an average yield of were fit via maximum likelihood with and –1 without the variance component in question rectly compared with the yield in the 1362 kg·ha across all heirloom entries. and compared using a Chi square (x2) present modified method. Rather, the cul- The yield performance of heirloom cultivar distribution (df = 1). tivar · environment (ab)ij effects were Peregion was 36% greater than the mean Effectz Variance SD Contribution x2y first regressed on the environmental index yield of all other heirloom cultivars and b –1 2 ( (k)j) as a means of evaluating stability 530 kg·ha greater than the next highest sb(k) 3.248 1.802 9.2% 30.217*** 2 sb 7.759 2.785 22.0% 87.016*** without directly using yield. Much like the yielding heirloom cultivar, Lina Sisco’s Bird 2 sba 7.58 2.75 21.5% 27.124*** Type I stability biplot, the plot was divided Egg. Both commercial checks and heirloom 2 se 16.649 4.08 47.2% — into four quadrants by a vertical line drawn cultivars did not attain target plant popula- z 2 2 2 2 where sb(k) , sb , sba ,andse represent the at bi = 0.0 and a horizontal line drawn at tions; commercial checks (x =199,853 plants/ variance associated with replication nested within the mean observed yield (1525 kg·ha–1). ha) and heirloom (x =177,443 plants/ha) environments, environment, cultivar · environment Type II (dynamic) stability in this biplot cultivars were 7% and 18%, respectively, interaction, and random error, respectively. Note was best illustrated by cultivars with high below target plant population levels. Lower that cultivar effects are fixed. yield (i.e., those with a yield greater than plant populations were attributed to early- y # NS, *, **, ***Nonsignificant or significant at P 0.05, the trial mean of 1525 kg·ha–1)andre- season weed competition, although unifor- 0.01, or 0.001, respectively. gression coefficient (bi)nearzero. mity of weed densities throughout field plots suggests that differential plant pop- a cultivar’s CV , whereby the square root of Results ulations did not affect yield comparisons the cultivar’s variance among environ- among cultivars. ments was divided by the grand mean yield The final yield model reported random The average CV for yield was similar for (Francis and Kannenberg, 1978). To visu- effect variances of replication nested both commercial (23.5%) and heirloom ally assess Type I stability, a cultivar’s CV within environment, environment, and cultivars (23.5%) (Table 5). ‘Jacob’s Cattle wasplottedonthex-axis against its esti- cultivar · environment interaction that Gold’ had the lowest CV (15.4%) and third mated mean yield (kg·ha–1)onthey-axis significantly (P #0.001) contributed to highest yield of the heirloom cultivars (Fig. 2). The biplot was divided into four the model’s variance (Table 4). Effect of (1543 kg·ha–1). In contrast, ‘Dapple Grey’ quadrants based on the mean CV (23.5%) environment and cultivar · environment exhibited the highest CV (36.6%) and lowest and mean observed yield (1525 kg·ha–1) both accounted for 22% of the exhibited yield(924kg·ha–1) of all heirloom culti- across cultivars. Stable cultivars within variance, where just over 47% of the vars. Five cultivars, Lariat, OAC Rex, these trials, according to the Type I defini- model’s variance was attributed to random Peregion, Jacob’s Cattle Gold, and Lina tion of stability, exhibited high yield, a low error. No clear correlation between envi- Sisco’s Bird Egg displayed Type I (static) cv, and appeared in the upper left quadrant ronmental data and yield results was ob- stability, though only Jacob’s Cattle Gold of the biplot. served, although some of the strongest and Peregion had a CV less than 20% within Visual assessment of Type II (dynamic) environmental effects were observed at the that group (Fig. 2). An additional seven heir- stability (Becker and L eon, 1988; Lin et al., Afton and Northfield locations in 2013. loom cultivars had CVs less than the average CV 1986) was achieved by plotting an environ- Although both locations exhibited very high (23.5%) across cultivars, though all seven were –1 mental regression coefficient (bi)(x-axis) levels of OM, lower rainfall precipitation in below the mean yield (1525 kg·ha )ofall against the estimated yield (y-axis) of each 2013 (Table 2), may have affected pod set cultivars in the trial. heirloom cultivar (Fig. 3). The environmental and development. Low pH and P levels Calculated environmental regression co- regression coefficient was calculated from (Table 3) at the Afton location may have efficients ranged from bi = –0.568 (‘Lariat’) the regression of the predicted random ef- also contributed to lower yields, though, to bi = 0.512 (‘Yin Yang’) (Table 5). Visual fects of cultivar · environment (ab)ij against given adequate yields in 2014 at the Afton assessment of the Type II (dynamic) stability the predicted random effect of environment location, these may not be consistent caus- biplot identified three heirloom cultivars with b(k)j. A negative regression coefficient in- ative factors in yield reduction. an environmental regression coefficient near dicated superior performance in poor (nega- Average yield of commercial control culti- zero: ‘Jacob’s Cattle Gold’, ‘Tiger’s Eye’, tive b(k)j) environments, a positive coefficient vars was 44% greater than average yield of and ‘Jacob’s Cattle’ (Fig. 3). Of those three, indicated superior performance in favorable heirloom cultivars (Table 5). Commercial con- only ‘Jacob’s Cattle Gold’ was above the ––1 (positive b(k)j) environments, and a coeffi- trol cultivar yields ranged from 2355 kg·ha mean yield of all cultivars in the trial (Fig. 3). cient of zero indicated stability across all (‘OAC Rex’) to 2617 kg·ha–1 (‘Lariat’), with an Three cultivars (Eclipse, Peregion, and Lina
HORTSCIENCE VOL. 51(1) JANUARY 2016 11 environments superior to its mean yield performance in favorable environments (Fig. 3).
Discussion
The assessment of heirloom cultivar yield performance in Minnesota was accented by yield stability evaluation. Ex- amination of the 95% profile confidence intervals indicated a significant difference between the highest and lowest yielding heirloom cultivars, Peregion and Dapple Grey, but there were 11 cultivars with intermediary (1200–1500 kg·ha–1)yield performance that were not readily distinct in their performance (Table 5). Without additional stability analyses, cultivars Kor- onis Purple, Steuben Yellow Eye, and Ying Yang would have been selected as superior on the basis of yield alone. These cultivars, however, did not appear readily stable according to either the Type I or Type II stability assessments. Under the Type I (static) stability concept, Fig. 2. Type I (static) yield stability of dry bean (Phaseolus vulgaris) cultivars in the 2013–14 dry bean a cultivar is considered stable if its among- yield trials conducted at four locations in Minnesota. Static stability is best represented by cultivars in environment variance is relatively small and the upper left-hand quadrant (i.e., those with high yield and a low CV). Commercial control cultivars are its performance is unaffected by changing denoted by cultivar codes ECL, LAR, and REX; all others represent heirloom cultivars. Stability environmental conditions (Becker and L eon, parameters for heirloom cultivar LS represent estimates from only the 2013 growing season. 1988; Lin et al., 1986). In that sense, this stability parameter is the best estimate of a cultivar’s biological stability, independent of other cultivar treatments in the trial. Lin et al. (1986) indicated that a satisfactory Type I stability parameter (i.e., CV) is often associated with poor yield performance, which makes the results of the heirloom yield trials somewhat counterintuitive. Half of the heirloom cultivars in this trial exhibited low variation and (relatively) high yield (Fig. 2). This trend may be unique to heirloom dry bean cultivars, whereby greater plant-to- plant variation may exist within the cultivar and, as a result, lower variation across envi- ronments. Further breeding work is required to estimate variation within these popula- tions, but, given that the mean CV of all heirloom cultivars was the same as the commercial control cultivars, it can be as- sumed that heirloom cultivars exhibit ade- quate static stability. The Type II (dynamic) stability biplot (Fig. 3) is a unique way to use the predicted environmental effects in a linear mixed effects model as a means of simultaneously selecting a cultivar for high yield and sta- Fig. 3. Type II (dynamic) yield stability of dry bean (Phaseolus vulgaris) cultivars in the 2013–14 dry bean bility across environments. This biplot de- yield trials conducted at four locations in Minnesota. Dynamic stability is best represented by cultivars picts dynamic stability that incorporates the · –1 with high yield (i.e., >1525 kg ha ) and an environmental regression coefficient (bi) near zero. predicted effect of cultivar · environment Commercial control cultivars are denoted by cultivar codes ECL, LAR, and REX; all others represent heirloom cultivars. Stability parameters for heirloom cultivar LS represent estimates from only the regressed on an environmental index, which, 2013 growing season. in this case, was the predicted effect of each environment (Eberhart and Russell, 1966; Lin et al., 1986). The Type II (dynamic) Sisco’s Bird Egg) were placed in the upper coefficient (bi = 0.099) of all commercial stability biplot is convenient for identifying right-hand quadrant of the plot, indicating cultivars. Though heirloom cultivars Steu- cultivars whose yields respond predictably superior yield in favorable environments ben Yellow Eye and Koronis Purple yielded to increased agronomic inputs and/or man- (Fig. 3). Two commercial cultivars, Lariat below the trial mean, their negative envi- agement practices (Ferreira et al., 2006). and OAC Rex appeared in the upper left-hand ronmental regression coefficients suggest In addition, this biplot allows for visuali- quadrant, suggesting a competitive yield ad- a yield advantage in unfavorable environ- zation of cultivars that may retain some vantage in unfavorable environments; ‘Eclipse’ ments. In no instance, however, was a culti- selective yield advantage to abiotic stressors exhibited the smallest environmental regression var’s mean yield performance in unfavorable or are better adapted to poor environmental
12 HORTSCIENCE VOL. 51(1) JANUARY 2016 Table 5. Ranked yield results (cultivar name, yield, 95% confidence interval, CV across locations, and markets within the Twin Cities and Greater environmental regression coefficient) from the 2013–14 dry bean (Phaseolus vulgaris) yield trials Minnesota regions. conducted at four locations in southern Minnesota. Trait averages for commercial control cultivars have been tabulated separately from heirloom cultivars. Literature Cited 95% Profile CI Stability analyses Adam, K.L. 2006. Community supported agricul- –1 Cultivarname Yield (kg·ha ) Lower Upper CV (%) bi ture. ATTRA—National Sustainable Agricul- Control cultivars Lariat 2617 2307 2946 20.1 –0.568 ture Information Service. 5 Mar. 2015.
HORTSCIENCE VOL. 51(1) JANUARY 2016 13 Kuznetsova, A., P.B. Brockhoff, and R.H. Bojesen Osorno, J.M., K.F. Grafton, J.B. Rasmussen, U.S. Department of Agriculture (USDA). 2011a. Christensen. 2015. lmerTest: Tests in linear G.A. Rojas-Cifuentes, R. Gelin, and A.J. Table 07 – U.S. certified organic beans, by mixed effects models. R package version 2.0-20. Vander-Wal. 2009. Release of ‘Eclipse’ black State, 2011. Economic Research Service 4 Feb. 2015.
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