Journal of the Science of Food and Agriculture J Sci Food Agric 87:668–675 (2007)

Iron and zinc concentration of nativeAndean potato cultivars from a humannutrition perspectiveGabriela Burgos,1 Walter Amoros,1 Maximo Morote,2 James Stangoulis3 andMerideth Bonierbale1,∗1International Potato Center (CIP), P.O. Box 1558, Lima 12, Peru2Instituto Nacional de Investigacion y Extension Agraria (INIEA), P. O. Box 2791, Lima 12, Peru3University of Adelaide, School of Agriculture, Food and Wine, Waite Campus, PMB 1, Glen Osmond, South Australia 5064, Australia

Abstract: The determination of iron (Fe) and zinc (Zn) concentrations in 49 native Andean potato varieties revealedsignificant genotypic variation. Comparison of mineral concentrations of 37 of these germplasm accessions grownin two highland locations further revealed significant variation due to environments and genotype × environmentinteraction. Concentrations in raw, peeled tubers ranged from 9 to 37 mg Fe kg−1 and 8 to 20 mg Zn kg−1 (dry weight)with accessions 703274 and 701165 showing the highest levels of Fe and Zn, respectively, in both locations. Fe andZn concentrations were significantly and positively correlated on a fresh weight basis in each site. Assessmentof Fe and Zn retention during processing revealed no losses due to cooking, and the only significant differencesfound in iron content of peeled versus unpeeled potatoes could be attributed to contamination with soil iron, asconfirmed by elevated levels of aluminium in the samples. The ranges of micronutrient concentrations reportedindicate ample genetic diversity that might be exploited in breeding programmes seeking to increase Fe and Znlevels in human diets. 2007 Society of Chemical Industry

Keywords: iron; zinc; native potatoes; genetic diversity; micronutrient; retention; nutrition

INTRODUCTIONPotatoes are the world’s fifth most important staplefor human consumption and provide food for morethan two billion small land-holders and consumers inAfrica, Asia and Latin America.1

Over three billion people are currently malnour-ished, with the highest rates in developing countrieswhere iron (Fe), zinc (Zn) and vitamin A are the mostcritical micronutrient deficiencies. Micronutrient mal-nutrition diminishes the health and productivity ofover half the world’s population, impacting primarilyon the well-being of women, infants and children.2

About 40% of the world’s population is deficient inFe.3 In young children, Fe deficiency impairs physi-cal growth, cognitive development and immunity andaffects school performance, while in pregnant women,it causes fetal growth retardation or low birth weight,and is responsible for a large proportion of maternaldeaths. In adults, Fe deficiency causes fatigue andreduced work capacity.4

Recently, several plant breeding initiatives have setout to increase the Fe and Zn concentration of staplecrops as a means to help improve human nutrition.It has been demonstrated, for example, that rice andbeans can be enriched for micronutrient content (i.e.

biofortified) using conventional plant breeding and/ortransgenic strategies,5 and results from a recent studyamong religious sisters in the Philippines showed thatconsumption of biofortified rice was efficacious inimproving iron stores of women with iron-poor diets.6

These findings provide evidence for the potential ofplant breeding to improve the nutrient status of Fe-and Zn-deficient individuals in developing countries.

Significant levels of Fe and Zn7–11 and moderateavailability of Fe12 have been reported for potato, butbroad genetic resources have not been surveyed toprovide knowledge of the potential for enhancing Feand Zn concentration through selection or varietyimprovement. Of particular interest are the manydiverse native potato varieties that are cultivated inthe high Andes where Fe deficiency rates are high.Native Andean potatoes are narrowly adapted tohighland environments (3800–4200 m above sea levelin the Andes), where they are a dietary mainstay ofrural populations, and especially appreciated for theirculinary properties including high dry matter content.According to a recent survey in Peru, women andchildren in the Department of Huancavelica (withone of the country’s highest rates of poverty andmalnutrition) consume on average 800 g and 200 g,respectively, of potatoes per day.13,14

∗ Correspondence to: Merideth Bonierbale, International Potato Center (CIP), P.O. Box 1558, Lima 12, PeruE-mail: m.bonierbale@cgiar.orgContract/grant sponsor: HarvestPlus Challenge ProgramContract/grant sponsor: Instituto Nacional de Investigacion y Techologıa Agraria (INIA), Spain(Received 28 February 2006; revised version received 13 June 2006; accepted 10 July 2006)Published online 2 February 2007; DOI: 10.1002/jsfa.2765

2007 Society of Chemical Industry. J Sci Food Agric 0022–5142/2007/$30.00

Iron and zinc concentration in Andean potato

Improving the Fe and Zn concentration of potatoeseaten in this region might significantly improve thenutrition of populations at risk of malnutrition.However, to maximize the nutritional benefits ofFe and Zn-dense potato, promoters and inhibitorsof Fe and Zn absorption,15 either contained in thisstaple crop or accompanying it in diets, shouldalso be considered. For example, ascorbic acid is apotent promoter of Fe absorption, while phytic acidand phenolic compounds are inhibitors. Knowledgeof genetic diversity, bioavailability and stabilityof micronutrients in potatoes grown in differentenvironments, and after processing and cooking, willhelp guide strategies that may contribute to reducingmicronutrient malnutrition. The objective of this studywas to assess variability for Fe and Zn concentrationsin unique germplasm toward setting the basis forpotential impact on nutrition through potato breeding.

MATERIALS AND METHODSPlant materialThirty-seven accessions representing five taxonomicgroups of cultivated potato conserved in the in trustgermplasm collection at CIP, and 12 prominent nativecultivars grown and consumed in Huancavelica, Peru,were used for this study. The 37 germplasm accessionswere grown in randomised complete block designswith three replications of 10 hills per plot in eachof two sites: Inyaya Alto (3700 m above sea level(asl), District of Chiara, Huamanga, Ayacucho), andAymara (3800 m asl; District of Pazos, Tayacaja;Huancavelica, Peru. Thirty to sixty unblemished60–90 g tubers of each germplasm accession werecollected in bulk from across the replicate plots (takingone tuber from each plant) at each site, while the12 predominant cultivars from Huancavelica werepurchased locally. One native cultivar, Runtus, wascommon to both the germplasm and the local cultivarsets. All genotypes were analysed as raw, peeled tubers.Parallel experiments were conducted to determinethe effects of peeling, using five accessions from theexperimental plots in Inyaya, and of cooking, usingthe 12 farmers’ cultivars from Huancavelica.

Sample preparationRaw tubersThree samples of 10 tubers each were taken from thepooled plot replicates of each genotype at each site, foranalysis in the raw state. Tuber samples were obtainedas described in previous literature.16 Tubers werepeeled, washed thoroughly with tap water (to removesoil residue), rinsed with deionised, distilled water andpatted dry with paper towels. Potatoes were then cutlongitudinally (stem to bud end) into four sections.Two opposite sections of each of the 10 tubers werecombined to prepare each sample for mineral analysis.Two or three slices were taken from each section toobtain a 50 g sample, which was placed in a glassPetri dish and oven-dried for 24 h at 80 ◦C. The dried

samples (approximately 12–16 g) were weighed andground in an IKA A11 stainless steel mill.

For comparison, three additional samples of 10unpeeled tubers were prepared from the pooledplot replicates of each of five accessions at Inyaya.Unpeeled tubers were washed and soaked in0.5 mol L−1 hydrochloric acid to remove any soilresidue from the skin and prepared for analysis asdetailed above for peeled potatoes.

Cooked tubersThree samples of 10 tubers of each of the 12 localvarieties from Huancavelica were cooked to assesschanges in mineral concentration during preparation.Unpeeled tubers were placed in stainless steel pots,covered with water, and cooked over uniform heatuntil a stainless steel probe could penetrate themeasily. Cooked tubers were then peeled and preparedas detailed above for raw tubers.

Mineral determinationAnalytical sub-samples of 0.6 g were taken fromeach of the three respective dried samples of eachgenotype from each site, and digested at 140 ◦C in70% (w/w) HNO3/HClO4. Samples were analysedfor Fe, Zn and aluminium (Al) by inductively coupledplasma–optical emission spectrophotometry (ICP-OES) using an ARL 3580B ICP (ARL, Switzerland).As Al is commonly found in higher levels in the soiland in very low levels in crops, it was analysed to givean indication of Fe contamination from soil or dustparticles.

Statistical analysisTo assess the variability of Fe and Zn concentra-tions among genotypes, simple analysis of variance(ANOVA) considering a randomised complete designwith three replications was performed for each site,and genotypic means were compared by Tukey’s test.The effect of environment (Inyaya and Aymara) andthe genotype × environment interaction (G × E) wereanalysed by combined ANOVA considering ‘geno-types’ as fixed and ‘sites’ as random effects.

The effects of peeling and of cooking were analysedby ANOVA, considering the genotypes as randomeffects, and the peeling (peeled vs. unpeeled) andcooking (cooked vs. uncooked) treatments as fixedeffects, and means were compared by Tukey’s test.

Correlations between the iron and zinc concentra-tions within sites were assessed by the Pearson test anda T-test was used to determine the difference of therespective correlation coefficients from zero. All statis-tical tests were performed using SAS/STAT (version8.2) software.17

RESULTS AND DISCUSSIONMineral concentration of raw tubersIronThe Fe concentration of each of the 37 native potatoaccessions grown in Inyaya and Aymara and of

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the 12 local cultivars from Huancavelica are shownin Tables 1 and 2, respectively. ANOVA indicatedsignificant (P < 0.001) genotypic variation in the Feconcentration of the different genotypes in each site.The Fe concentration observed in the germplasmaccessions grown in Inyaya and Aymara and in thecultivars from Huancavelica ranged from 16.1 to36.7 mg kg−1, from 13.6 to 29.4 mg kg−1 and from9.4 to 25.2 mg kg−1 on a dry weight (DW) basis. Theranges of the mineral concentrations on a fresh weightbasis (FW) which depend on their respective drymatter percentage (% DM) are shown in Table 3. The% DM for the different set of raw material is shown inTables 1 and 2. Direct comparisons cannot be madebetween the germplasm accessions and the locallypurchased cultivars because the crop and post-harvest

management conditions of the latter are unknown.However, the standard genotype (Runtus: 703 985)which had the highest Fe concentration of the 12 localcultivars also ranked among the highest in the set ofgermplasm accessions evaluated. Consistent, low Alcontent (<5 mg kg−1) of the samples prepared frompeeled tubers was taken to indicate freedom fromcontamination. The wide range in Fe concentrationobserved among genotypes suggests that suitableFe-dense parents are available for improving Felevels in diets or in new varieties. Diploid (2n =2x = 24) and tetraploid (2n = 4x = 48) cultivatedpotatoes can readily be crossed with commercialpotato (Tuberosum; 2n = 4x = 48) and represent avaluable gene pool for broadening its genetic base andenhancing specific traits.18,19

Table 1. Iron and zinc concentration (mg kg−1 DW) and dry matter content (% DM) of potato accessions grown in Inyaya and Aymara

Fe Zn %DM

CIPnumber Cultivar name

Taxonomicgroup(1) Inyaya(2) Aymara(2) P(3) Inyaya(2) Aymara(2) P(3) Inyaya Aymara

703 274 Unknown Phu (2×) 36.7a 29.4a ∗∗ 12.1abcdef 14.3ghijk ∗∗ 27.7 24.2702 453 Waca -uno Adg (4×) 28.5b 21.2bcd ∗∗ 13.4abc 14.0ghijkl 24.3 24.3703 265 Yurac Sole Adg 26.2bc 22.0b ∗∗ 12.4abcdef 18.5ab ∗∗ 32.0 28.1702 815 Morar Nayra Mari Stn (2×) 24.3bcdef 21.9b ∗∗ 14.5ab 16.8bcdef ∗∗ 26.1 28.8700 234 SA-2563 Adg 25.2bcd 20.2bcdef ∗∗ 12.1abcdef 13.8ghijklm ∗∗ 25.1 24.5703 985 Runtu Gon (2×) 24.5bcde 20.4bcde ∗∗ 13.1abcde 17.9abc ∗∗ 32.2 31.2701 997 Sullu Adg 24.7bcde 18.9bcdefgh ∗∗ 11.3bcdef 12.9jklmno ∗∗ 27.1 25.6703 287 Cceccorani Stn 20.8defghijk 21.6bc 11.3bcdef 14.8fghij ∗∗ 36.2 33.8701 165 Calhua Rosada Stn 21.6cdefghij 20.4bcde 14.7a 20.2a ∗∗ 32.0 29.1703 421 Poluya Stn 23.6bcdefg 17.8efghijk ∗∗ 13.2abcd 16.6bcdef ∗∗ 29.6 25.8706 191 Cuchi Chucchan Adg 23.3cdefgh 17.9efghijk ∗∗ 9.7fg 10.9pqr ∗ 30.9 29.1703 197 Yana Sucre Adg 20.5efghijk 20.4bcde 10.8cdef 12.4klmnop ∗∗ 31.9 29.6703 825 China Runtush Gon 19.9fghijk 19.6bcdefg 9.7fg 12.9jklmno ∗∗ 29.9 29.2704 481 Amarilla Gon 20.4efghijk 18.8bcdefgh 10.4cdefg 12.8jklmno ∗∗ 28.8 29.6705 009 Purranca Tbr (4×) 20.8defghijk 18.2defghij ∗∗ 13.0abcde 17.2bcde ∗∗ 23.2 20.1700 313 Cuchipa Ismaynin Stn 21.9cdefghij 17.1fghijk ∗∗ 11.7abcdef 13.2hijklmn ∗ 33.0 30.1703 741 Ambar G × S(2×) 21.2defghij 17.7efghijk ∗∗ 13.2abcd 16.7bcdef ∗∗ 29.3 26.2703 268 Bolona Adg 21.9cdefghi 16.9ghijk ∗∗ 10.2efg 10.3r 28.6 25.1702 395 Puma Maqui Adg 20.3efghijk 17.8efghijk ∗∗ 11.4abcdef 13.2hijklmn ∗∗ 31.9 27.6703 317 Chingos Stn 20.0fghijk 17.8efghijk ∗ 11.1cdef 15.3defg ∗∗ 27.9 26.2702 363 Socco Huaccoto Adg 19.3hijkl 18.5cdefghi 10.9cdef 12.0mnopq 23.2 22.8704 393 Maria Cruz Gon 19.3hijkl 18.2defghij 11.1cdef 13.1ijklmn ∗∗ 34.3 31.8701 273 Muro Shocco Stn 20.5efghijk 16.2hijk ∗∗ 10.3defg 10.4qr 26.3 26.4703 899 Chaucha Roja Adg 18.5ijkl 17.9defghij 8.3g 9.9r ∗∗ 28.2 29.7703 312 Morada Taruna Adg 18.4ijkl 17.8hijk 11.0cdef 15.6cdefg ∗∗ 28.7 26.2702 736 Puca Micnush Stn 19.1hijkl 17.1fghijk ∗ 11.7abcdef 14.0ghijkl ∗∗ 31.6 31.8701 515 Rucuma o Lucuma Adg 20.0fghijk 16.2hijk ∗∗ 10.5cdefg 11.2opqr 26.1 25.4701 675 Tarmena Adg 19.3ghijkl 16.8ghijk ∗∗ 11.7abcdef 14.7fghij ∗∗ 32.1 29.1703 768 Huayro Roja G × S 19.1hijkl 16.6ghijk ∗∗ 11.7abcdef 13.9ghijkl ∗∗ 31.8 30.8707 135 Duraznillo Cha (3×) 19.5ghijkl 16.1hijkl ∗∗ 12.1abcdef 15.1efghi ∗∗ 31.4 29.5704 143 Negra Ojosa Stn 18.4ijkl 16.2efghijk ∗ 8.3g 10.2r ∗∗ 26.8 24.8704 022 Kellu Suito Stn 18.0jkl 16.3hijk 13.2abcd 17.6abcd ∗∗ 28.5 28.8703 168 Puca Pishgush Gon 18.9ijkl 15.1kl ∗∗ 10.7cdef 11.5nopqr 31.6 30.2702 464 Natin Suito S × G(2×) 18.2ijkl 15.5jkl ∗∗ 10.0fg 12.1lmnop ∗∗ 29.1 29.7700 787 EE-2057 Cha 19.3ghijkl 13.6l ∗∗ 11.5abcdef 10.0r ∗ 26.6 28.9705 543 Yana Warmi Cha 17.3kl 15.6jkl 10.3defg 15.2defgh ∗∗ 33.5 30.3705 280 Murunguilla Adg 16.1l 15.9ijkl 10.7cdef 15.1efghi ∗∗ 33.5 30.1

(1) Phu = Phureja, Adg = Andigena; Tbr = Tuberosum; Gon/G = Goniocalyx; Stn/S = Stenotomum; Cha − Chaucha.(2) Mean values (n = 3). Different letters indicate significant differences between accessions for each site. HSD = 5.7 (α = 0.05).(3) Differences between sites for each accession: ∗ = significant at 5% level and ∗∗ = significant at 1% level.

670 J Sci Food Agric 87:668–675 (2007)DOI: 10.1002/jsfa

Iron and zinc concentration in Andean potato

Table 2. Iron and zinc concentration (mg kg−1 DW) and dry matter

percentage (% DM) of raw and cooked tubers of 12 predominant

native potato varieties consumed in Huancavelica

Raw Cooked

Variety Fe Zn%

DM Fe Zn%

DM

Ajo Suytu 18.4b 9.5d 30.4 16.4bc 9.1e 34.7Allga Palta 9.4d 11.7abdc 27.3 10.4d 13.2cb 29.5Ayrampo 19.8b 13.2abc 38.3 16.7bc 11.6cbd 33.8Gorimarquina 18.5b 10.9bcd 24.4 19.1ab 11.1cd 26.0Pasna 24.5a 11.5abdc 31.3 22.3a 13.1cb 31.0Peruanita 13.9c 10.9bcd 30.0 14.5c 11.5cbd 30.9Poccya 21.0ab 14.8a 27.0 22.4a 16.1a 29.9PucaHuayro 19.1b 10.5cd 29.4 20.4ab 11.8cbd 28.2RetipaSisan 18.7b 10.7bcd 28.7 18bc 10.7ed 32.5Runtus 25.2a 13.4abc 25.4 22.4a 13.2cb 29.1Sirina 18.5b 14.3ab 28.5 18.7ab 13.7b 30.4Sortiguillas 10.4cd 12.9abcd 20.8 9.8d 11.6cbd 29.9

Mean values (n = 3). Different letters indicate significant differencesbetween accessions for each treatment.HSD = 5.1 (α = 0.05).

Table 3. Range of iron and zinc concentration (mg kg−1) on fresh

weight basis

Site Fe (FW) Zn (FW)

Inyaya 4.5–10.5 2.2–4.7Aymara 3.7–7.1 2.5–5.6Huancavelica 2.2–8.0 2.7–5.0

The native accession 703 274 (group Phureja)showed the highest Fe concentration in both locations.Its value is significantly above those previouslyreported for varieties analysed without peel.8

At the rates observed in this study, women andchildren could increase their Fe intake significantly byconsuming a variety with high Fe content comparedwith one of low Fe content (Table 4). Past studieshave suggested that due to considerable amounts ofascorbic acid in potato, Fe availability is moderatelyhigh.12 However, further information is still neededon the content of enhancers (ascorbic acid andcarotenoids) and inhibitors (polyphenols and phytates)of Fe absorption, and in vitro or feeding studies shouldbe conducted to estimate the bioavailability of Fe frompotatoes as a staple food and as a dietary componentare warranted to assess the potential impact on humannutritional status.

In Huancavelica, children and women have amean intake of 200 and 800 g day−1, respectively.14

Considering the recommended nutrient intake (RNI)corresponding to 10% bioavailability of Fe from thediet, we estimate that the native cultivar 703 274(mean iron concentration across the two localitiestested: 8.6 mg kg−1, on a fresh weight basis) couldprovide 29 and 24% of the RNI of Fe for childrenbetween 1 and 3 years old (6 mg day−1)20 and womenof fertile age (29 mg day−1).20

Table 4. Iron intakea provided by the potato cultivars with the lowest

and highest iron concentration

Iron intake from potato(mg day−1)a

Cultivar Children Woman

With the lowest ironconcentration (2.1 mg kg−1)

0.48 1.92

With the highest ironconcentrationb (8.6 mg kg−1)

1.72 6.88

a Assuming an intake of 200 g per day for children (1–3 years old) and800 g for an adult woman (19–50 years old).b Considering the mean concentrations across the two evaluation sites.

ZincThe Zn concentration of the 37 potato accessionsgrown in Inyaya and Aymara and the 12 nativecultivars from Huancavelica are shown in Tables 1and 2. Significant (P < 0.001) differences in Znconcentration of the tubers were observed among thevarieties in each site. Zn concentration of germplasmaccessions grown in Inyaya and Aymara and from thecultivars purchased in Huancavelica ranged from 8.3to 14.7 mg kg−1, from 9.9 to 20.2 mg kg−1 and from9.5 to 14.8 mg kg−1 on a DW basis. The ranges ofthe zinc concentrations on a FW basis are shown inTable 3.

The accession 701 165 (group Stenotomum) andthe cultivar Ayrampo, grown in Inyaya and Huan-cavelica, respectively, showed the highest Zn concen-trations. Although significant variability was foundin this study, higher Zn concentrations have beenreported before for both peeled8 and unpeeled10 pota-toes. Considering a mean intake of 200 g of potatoesfor children and 800 g for women, and an RNI cor-responding to moderate bioavailability of Zn in thediet, the cultivar with the highest Zn concentration(mean zinc concentration across the two localities:5.3 mg kg−1, on a fresh weight basis) could provideabout 29% and 87% of the RNI of Zn for childrenbetween 1 and 3 years old (4.1 mg day−1)20 and womenof fertile age (4.9 mg day−1).20

Effect of environment and genotype ×environment interaction for mineral contentsCombined analysis of variance of the Fe and Znconcentrations of the 37 germplasm accessions grownin two locations (Inyaya and Aymara) revealedsignificant effects due to environment and genotype ×environment (G × E) interactions as well as genotypic(P < 0.0001, CV < 6% for both minerals) (Table 5).While Fe concentrations were similarly distributedin the two environments (Fig. 1A), the distribution ofvalues for Zn was broader in the Aymara site (Fig. 1B).

Regarding Fe, with the exception of 12 acces-sions that were stable across environments, most ofthe accessions showed significantly lower Fe con-centrations in tubers from Aymara than from Inyaya(Table 1). In the case of zinc, with the exception of

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A

0

5

10

15

20

25

0

Iron (mg kg−1 DW)

Fre

qu

ency

Inyaya

Aymara

B

0

5

10

15

20

25

0 5 10 15 20 25

Zinc (mg kg−1 DW)

Fre

qu

ency

Inyaya

Aymara

10 20 30 40

Figure 1. Frequency of distribution of iron and zinc concentrations (mg kg−1 FW) in native potato at two sites. (A) Iron; (B) zinc.

Table 5. Combined ANOVA for Fe and Zn concentration (mg kg−1

DW) of potato accessions in Inyaya and Aymara

Fea Zna

Source of variation d.f MS MS

Genotype (G) 36 0.022 ∗∗ 0.025 ∗∗Environment (E) 1 0.228 ∗∗ 0.385 ∗∗G × E 36 0.003 ∗∗ 0.004 ∗∗Error 148 0.001 0.001Corrected total 221

CV 5.49 5.85Mean 19.74 12.69r2 0.93 0.93

a log10 transformed.∗∗ Significant at 1% level.

6 accessions which were stable across environments,higher concentrations were found in Aymara than inInyaya (Table 1).

Despite the significance of G × E interaction therewere no dramatic changes in ranks (Fig. 2A and

B) and cross-over interactions were only notedamong genotypes with similar ranges of micronutrientconcentrations (high, medium or low concentrations).The cultivar 703 274 consistently showed the highestFe concentration across environments: 36.7 mg kg−1

DW in Inyaya and 29.4 mg kg−1, DW in Aymaraand the cultivar 701 165 showed the highest Znconcentration: 14.7 mg kg−1 DW in Inyaya and20.2 mg kg−1, DW in Aymara.

Soils from both of the highland sites are acidic (pH5.2 and 3.8 for Inyaya and Aymara, respectively), highcation exchange capacity (26 and 20 meq 100 g−1),high organic matter content (6.4 and 5.1%) andsufficient Fe content for a good Fe supply. However,soil sampling and monitoring of other factors werenot sufficient to attempt resolving the contributionof environmental factors to the differences in Fe andZn concentration of the cultivars across the sites.Further studies are required to dissect the geneticand environmental components of variance for Feand Zn concentrations into underlying factors, andto estimate the heritability of the Fe- and Zn-dense

A

5

10

15

20

25

30

35

40

Inyaya Aymara Inyaya Aymara

Iro

n (

mg

kg

−1 D

W)

703274702453703265702815700234703985704022703168702464700787705543705280

B

0

3

6

9

12

15

18

21

24

Zin

c (m

g k

g−1

DW

)

701165702815703985703265704022705009700787706191701273703268704143703899

Figure 2. Genotype × environment interaction for micronutrient concentration of the upper and lower six germplasm accessions evaluated in twolocations. (A) Iron; (B) zinc.

672 J Sci Food Agric 87:668–675 (2007)DOI: 10.1002/jsfa

Iron and zinc concentration in Andean potato

traits to examine the ease with which stable increasedFe levels can be achieved. In rice, environmentaleffects are present but are smaller than the geneticeffects. Narrow-sense heritability of the Fe-dense traitin rice was moderately low (43%) with large differencesbetween narrow-sense and broad-sense heritability(88%) confirming the importance of non-additive geneaction.21

Correlation between iron and zinc concentrationThe correlations between Fe and Zn concentrationsin Inyaya and Aymara were only weakly positive(P < 0.05) when calculated on a dry weight basis.However, when calculated on fresh weight bases, thesecorrelations were significantly and positively correlated(r = 0.52, and r = 0.54 (P < 0.05)) (Fig. 3A and B)and significantly different from zero in both sites.These positive correlations suggest that simultaneousselection for enhanced levels of both minerals shouldbe possible in this gene pool, if dry matter content istaken into account.

Three cultivars with high dry matter content:703 287, 703 265 and 703 985 showed particularly

high concentrations of both minerals, on a fresh weightbasis. This combination of desirable characteristicspoints to the direct and the potential breeding value ofselected native cultivars.

Effect of peeling and cookingPeeled potatoes represent predominant consumptionpatterns by Andean consumers, and minimise chancesof contamination of samples with soil. Comparativeanalysis of Fe and Zn concentration of peeledand unpeeled potatoes showed significant (P < 0.01,CV 8% and 9%, respectively) genotype × peelingeffects for Fe, but not for Zn. Comparisons onthe Fe concentrations of the peeled and unpeeledtubers of five genotypes are shown in Fig. 4.Fe contents detected in two of the genotypeswere respectively 36 and 51% greater in samplesprepared with their skins than in samples withoutthem, while a third cultivar showed a smallerdifference in the same direction. However, elevatedAl concentrations (>7–16 mg kg−1), which most likelyindicate contamination from soil were observed in thesame samples. Previous reports of dramatically high Fe

2

3

4

5

6

4 3 4 5 6 7 88 10 12

Fe

Zn

r = 0.52(n = 37)

A

2

3

4

5

6

7

8

Fe

Zn

r = 0.54(n = 37)

B

6

Figure 3. Correlation between Fe and Zn concentrations (mg kg−1 FW) of native potatoes grown in two highland sites. (A) Inyaya; (B) Aymara.

0

5

10

15

20

25

30

35

380389.1 706191 704393 703312 702363

Iro

n (

mg

kg

−1, D

W)

UnpeeledUnpeeled

Figure 4. Mean Fe and Zn concentration (mg kg−1 DW) of native potato accessions with and without peeling.

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concentrations in unpeeled potatoes (115 mg kg−1 ona DW basis)7 along with high Al levels (75 mg kg−1 onDW basis) suggest possible contamination of sampleswith soil particles. Fe from soil is poorly soluble ingastric juices and hence its bioavailability is expectedto be poor.22,23

Since potatoes are eaten in various cooked forms,and not in the raw state, we established the degreeof loss in micronutrient content likely to occur inthe cooking process. Results are shown in Table 2.Comparative analysis of Fe and Zn concentrationof raw and cooked potatoes indicated no significantdifferences due to ‘cooking’ or ‘genotype × cooking’interaction. Thus, information from micronutrientdeterminations on raw potatoes may be used directlyin comparisons among varieties and calculations ofpotential impact on the diet.

CONCLUSIONSThis research demonstrated significant genetic diver-sity for Fe and Zn concentrations in potatoes, whichmay allow for directed selection of parents in a breed-ing programme.

Although genotype × environment interactions weresignificant for both mineral concentrations, the samegenotypes ranked highest for Fe and Zn: 703 274(Phureja) and 701 165 (Stenotomum), respectively, inboth sites, and no drastic changes in ranking (e.g. lowto high) were observed across environments.

Fe and Zn concentrations were significantly andpositively correlated when values on a fresh weightbasis were used. This may permit simultaneousselection for increased concentrations of both min-erals.

The comparison of peeled and unpeeled tubersdemonstrates the risk of obtaining misleading values(i.e. confounding mineral content available and notavailable to the diet) for the Fe concentrationof potatoes, if precautions are not taken duringpreparation to avoid contamination of samples withsoil or dust particles.

The lack of significant differences in the Fe and Znconcentrations of raw and cooked potatoes found hereindicates that either type of material is suitable use ingermplasm evaluation.

The genetic material sampled in this study haspotential to impact on Fe and Zn status of populationsat risk of micronutrient malnutrition through direct useas potato cultivars and/or through crop improvement.

ACKNOWLEDGEMENTSThis research was supported by the HarvestPlusChallenge Program (Harvest Plus Agreement 5019)and the Government of Spain through the InstitutoNacional de Investigacion y Tecnologıa Agraria(INIA). Trace-element analysis was conducted bythe Waite Analytical Service. We thank Elisa Salasfor assistance with statistical analysis and helpful

comments on the manuscript and Stef de Haan for theidentification of farmers’ cultivars in Huancavelica.

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