Effects of the Pesticide <i>Furadan</i> on Traits Associated with Reproduction in Wild Potato Species

doi:10.4236/ajps.2012.311194

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American Journal of Plant Sciences, 2012, 3, 1608-1612

http://dx.doi.org/10.4236/ajps.2012.311194 Published Online November 2012 (http://www.SciRP.org/journal/ajps)

Effects of the Pesticide Furadan on Traits Associated with

Reproduction in Wild Potato Species

Alfonso del Rio1, John Bamberg1, Ruth Centeno-Diaz2, Alberto Salas2, William Roca2, David Tay2

1USDA/Agriculture Research Service, US Potato Genebank, Wisconsin, USA; 2International Potato Center (CIP), Lima, Peru.

Email: [email protected]

Received August 5th, 2012; revised September 18th, 2012; accepted October 20th, 2012

ABSTRACT

Natural populations of wild potato species are the backups for the diversity held in genebanks for research and breeding.

Some potato species are known to grow in close proximity to cultivated fields, thus are potentially impacted by human

activity, including exposure to pesticides. The present study tested the effects of a common pesticide on reproductive

traits of potatoes known to grow in or near pesticide-treated fields in central Peru. Furadan® 4F, an insecticide—

nematicide (common name = carbofuran) was applied at two different rates to populations representing 15 wild potato

species in a greenhouse environment in Peru. Flowering duration of these populations was usually significantly reduced

in comparison to a water control, and in a few cases, percent viable pollen also was. These findings suggest that ag-

richemicals may be having unintentional effects on wild potato populations in ways that could compromise their genetic

diversity.

Keywords: Potato Species; Pesticide Contamination; Genetic Drift; Reproductive Capacity

1. Introduction

Wild potato populations are being impacted by human

activity, most extremely when they go extinct, per se, as

a result of having their habitats converted to some other

uses (Coca-Morante and Castillo-Plata, 2007) [1]. But

more subtle influences may be occurring, perhaps only

eliminating specific traits or otherwise narrowing the

genetic base of populations.

According to a recent taxonomic estimate by Spooner

(2009) [2], potato wild relatives are represented by about

100 species which are distributed in many different types

of eco-geographic niches from the southwestern USA to

southern Chile (Hijmans and Spooner, 2001) [3]. Some

are known to grow within or very close to fields in which

potato or other crops are cultivated. Pesticides are used in

virtually all potato fields in the Andean region. These

fields receive up to seven pesticide applications per sea-

son with each application averaging 2 - 3 different prod-

ucts (Yanggen et al., 2003) [4]. Carbofuran and metami-

dofos are the major insecticides used and constitute 47%

and 43%, respectively, of all the active ingredients ap-

plied (Forbes et al., 2009) [5].

Flowering and pollen production are essential in plant

sexual reproduction, so changes could impact genetic

diversity and population fitness (Ennos 1994 [6]; Ham-

rick et al., 1979 [7]; Loveless and Hamrick, 1984 [8]).

There is evidence that agrichemicals can alter plant bio-

chemistry and metabolic mechanisms as well as disrupt

mitotic and meiotic cycles in plants. Application of pes-

ticides was related to the modulation of the biosynthetic

pathways leading to polyphenol formation in peas, oats,

potatoes, raspberries, etc. (Daniel et al., 1999) [9] and,

Lydon and Duke (1989) [10] reported significant changes

in the content of secondary compounds. Asita and Mate-

besi (2010) [11] found that pesticides caused cytotoxic

and genotoxic effects in root meristems of Allium cepa,

Vicia faba and Zea mays. These effects varied from point

mutations to chromosome aberrations. Other studies in-

dicated that fungicides affected germination, mitotic and

meiotic activity, and pollen fertility in barley and toma-

toes (Behera et al. 1982 [12]; Fairbanks et al. 2002 [13];

Tort et al. 2005 [14]), pollen viability in tomatoes (Cali

and Candan 2009) [15] and flower production in differ-

ent species (Spiers et al. 2006) [16]. The literature, how-

ever, does not report impacts of agrichemicals in species

related to potatoes.

Ahmad et al. (1979) [17] reported that site-specific

environmental variables determine persistence of pesti-

cides and their biological impact. For example, while

carbofuran degrades rapidly at high soil pH, Finlayson et

al. (1979) [18] estimated it has a half-life of about 16

years in soils of pH 5.5. The pH of the Andes soils, from

which the species tested in our study originated, are

Effects of the Pesticide Furadan on Traits Associated with Reproduction in Wild Potato Species 1609

known to be very acidic—sometimes lower than pH 4.0

(Arica et al. 2006) [19]. It follows that yearly applica-

tions could result in buildup of carbofuran in the soil. For

this reason, the effects of exposure of wild species to

levels higher than the recommended rate were also of

practical interest.

The present study was initiated to assess flowering and

pollen viability effects in wild potato populations after

controlled application of carbofuran, a pesticide to which

they would likely be unintentionally exposed in the farm

field setting.

2. Methods and Materials

2.1. Plant Material

Twenty-one populations from 15 different potato species

from diverse regions in the Andes were selected because

of their known natural proximity to farm fields. Plants

used in this study originated as botanical seed from CIP’s

potato germplasm collection. Table 1 provides identities

and other details of the plant material used.

2.2. Pesticide Selection and Application

A survey of farmer’s communities at Quilca, Colpar and

Nunhuayo in the Mantaro Valley confirmed that

Furadan® as the most consistently-used pesticide in the

region (100% of farmers). The responses were gathered

from interviews made to 14 potato farmers who were

leaders and responsible of agricultural decisions in their

respective communities. Furadan® is the commercial

name for Carbofuran (2,3-dihydro-2,2-dimethyl-7-ben-

zofuranyl methylcarbamate), a carbamate with insecti-

cidal and nematicidal properties resulting from inhibition

Table 1. Identities and origins of wild potato populations used in this study.

Solanum...a Population codeb Chromosome number Original location (site, province, elevation)c

acl OCH 11322 48 Huarochiri, Lima, 3154 m

acl OCHS 11889 48 Acora, Puno, 3840 m

alb OCH 11842 72 Kawish, Ancash, 4200 m

alb OCHS 16023 72 Shojlla, Cajamarca, 3550 m

amb OCHS 11865 24 Choccec, Pasco, 2800 m

buk HJT 5444 24 Lircay, Huancavelica, 3800 m

buk OCH 13713 24 Ckumuccacca, Cusco, 3650 m

chq OCH 13963 24 Cajon, Cajamarca, 2850 m

hcr OCH 11692 24 Llusupuquio, Ancash, 2800 m

lgl OCH 11617 24 Intihuatana, Cusco, 2800 m

lmb SS 7205 24 Phara, Puno, 3640 m

med OCH 12044 24 Surco, Lima, 2240 m

med SSTS 7302 24 Hongos, Lima, 2880 m

mga OCH 11941a 24 Mollepunco, Potosid, 3880 m

mtp OCHS 11307 24 Canta, Lima, 2800 m

rap HHCH 5141 24 Sacsayhuaman, Cusco, 3550 m

rap OCH 13626 24 Paucarpata, Cusco, 3800 m

spl SS 7213 24 Tarapata, Cusco, 2900 m

trp OCHB 15687a 24 Luruchayocc, Cusco, 3400 m

trp SS 7216 24 Tarapata, Cusco, 3200 m

uru SS 7225 24 Vilcabamba, Cusco, 2600 m

aPotato species abbreviations: Solanum acaule (acl), S. albicans (alb), S. ambosinum (amb), S. bukasovii (buk), S. chiquidenum (chq),

S. hypacarthrum (hcr), S. lignicaule (lgl), S. limbaniense (lmb), S. medians (med), S. megistracolobum (mga), S. multiinterruptum

(mtp), S. raphanifolium (rap), S. sparsifilum (spl), S. tarapatanum (trp) and, S. urubambae (uru); bPopulation code represents the

original collector’s identifier as listed in CIP’s germplasm database; cAll but one of the provinces listed in the table are located in

Peru; m = meters above sea level; dProvince of Bolivia.

Effects of the Pesticide Furadan on Traits Associated with Reproduction in Wild Potato Species

1610

of cholinesterase, which catalyzes the neurotransmitter

acetylcholine. Furadan® is systemic, with high water

solubility and rapid uptake from roots and leaves (PAN

2008) [20].

The experiment was conducted in the greenhouses at

CIP’s Santa Ana Station in Huancayo, Peru (12.067˚S ×

75.217˚W; 3380 m) in the summer (January-March).

Each of the 21 populations was replicated 3 times in a

Completely Random Design with experimental units

composed of 5 seedlings each. Seeds were sown and

transplanted into 20 cm plastic pots filled with a mix of

soil and peat moss, and fertilized and hand watered as

standard for optimal growth. Furadan® in liquid form

(480 g/L active ingredient) was obtained from Farmagro

S.A., Lima. Two treatment concentrations (per liter) were

applied: trt3.5 = 3.5 ml, trt4.5 = 4.5 ml, and compared to

control plants. Leaves of all plants were sprayed to drip a

total of 5 times at 10-day intervals over the growing sea-

son. The control plants (similarly sprayed but with pure

water) were grown in a separate greenhouse to prevent

accidental exposure to the pesticide.

2.3. Trait Evaluation

Flowering was considered to have begun when at least

one plant in the experimental unit had five inflorescences

in bud stage, and to have ended when all flowers had

dried up. Plants were inspected daily to see if these con-

ditions were met. Pollen was collected from each popula-

tion at estimated peak flowering, from at least one flower

from each plant in the experimental unit. Pollen grains

were collected by mechanical vibration using a doorbell

buzzer and were examined microscopically in a 2% solu-

tion of acetocarmine glycerol. The average percent stained

pollen was recorded for three random fields of view at

40×. Acetocarmine is not a vital stain per se, but staining

indicates that normal pollen development has occurred,

so unstained grains were considered inviable.

Analysis of variance was conducted using JMP statis-

tical software (JMP9 2011) [21] to calculate treatment’s

LSD in each trait assessed. In the test of pollen viability,

percentdata were arcsine transformed before analysis.

3. Results and Discussion

3.1. Flowering Duration

Populations varied in control flowering duration from 30

to 79 days (see Table 2). The standard application of

Furadan (trt3.5) commonly depressed flowering duration

at average of 25% relative to controls (from 48 to 36

days), which was significant (p < 0.05) for 17 of the 21

populations examined. Populations with more robust

control flowering tended to be reduced more in response

to Furadan exposure. Note for example, that the four

populations which did not show significant reduction in

response to Furadan application all had among the lowest

control flowering. The mechanism responsible for the

observed differences in pesticide sensitivity is not known,

but it is common for a pesticide to be toxic to one plant

species and not to another (Dalvi et al. 1972 [22]; Pereira

et al. 2010 [23]). Increasing the dosage to trt4.5 did not

often result a significant additional reduction of flower-

ing duration—being the case in only for three of the

populations.

3.2. Stainable Pollen Percent

Pollen viability estimates were very high in control, av-

eraging 91% and ranging from 75% to 100% (see Table

2). Standard Furadan application (trt3.5) reduced percent

stainable pollen by an average of only about 7%, and

only significantly in 3 of the 21 populations. The greatest

effect was found in populations of buk and lgl, where

pollen viability was reduced by 25% and 24%, respec-

tively. In three other populations, the higher dose (trt4.5)

resulted in significant reduction compared to control.

While Furadan treatment never resulted in a substantial

increase in flowering duration, in one case (med-OCH

12044), it appeared to increase percent stainable pollen.

This coincided with particularly low percent stainable

pollen in the corresponding control plants. This observa-

tion implies need for follow-up experiments to confirm

the pollen viability-enhancing effect of Furadan and

identify the sub-optimal control environment conditions

that the presence of Furadan apparently improves in

some germplasm.

This experiment was not designed to differentiate spe-

cies according to Furadan effects, nor associate flowering

and pollen effects in a given population. However, re-

sults in Table 2 do not suggest any obvious pattern of

species susceptibility, and the correlation between Furadan

impact on flowering and pollen viability is a non-sig-

nificant −26%, suggesting no obvious link between the

two.

3.3. Potential Impact on Potato Genetic Diversity

Solanum species and other native plants in the Andes

often compete for the same few insect pollinators that are

available at high elevations. Altered flowering could di-

vert bees to other plants and impact potato reproduction

potential by suppressing (or limiting) pollination (Hus-

band and Schemske 1996) [24]. The prospects of popula-

tion genetic impact seem particularly relevant consider-

ing that majority of the potato species examined here are

diploid obligate out crossers (Table 1)—a breeding sys-

tem that is vulnerable to genetic drift when effective

population size is restricted (Bamberg and del Rio 2004

25]; Loveless and Hamrick 1984) [8]. [

Effects of the Pesticide Furadan on Traits Associated with Reproduction in Wild Potato Species 1611

Table 2. Effects of Furadan treatments on flowering and pollen of wild potato spe cies.

Flowering Duration (Days)2 Stainable Pollen Percent3

Species1 Population Control trt3.5 trt4.5 Control trt3.5 trt4.5

acl OCH 11322 53 37* 36 99 95 93

acl OCHS 11889 52 24* 21 100 99 87

alb OCH 11842 79 53* 48 99 95 93

alb OCHS 16023 69 57* 51 97 93 92

amb OCHS 11865 39 27* 22 75 83 67*

buk HJT 5444 36 36 31 95 71* 89

buk OCH 13713 51 44* 41 94 88 90

chq OCH 13963 49 38* 36 90 83 81

hcr OCH 11692 50 34* 24* 84 76 77

lgl OCH 11617 49 39* 33 96 73* 70

lmb SS 7205 62 42* 41 91 84 79

med OCH 12044 42 37 28* 78 91+ 90

med SSTS 7302 43 36* 31 93 89 89

mga OCH 11941a 38 23* 23 82 73 73

mtp OCHS 11307 40 26* 27 91 80 88

rap HJTCH 5141 30 31 23* 93 81* 90

rap OCH 13626 50 37* 34 96 96 97

spl SS 7213 39 24* 22 93 94 94

trp OCHB 15687a 35 29 30 92 84 78*c

trp SS 7216 57 36* 40 78 75 68*c

uru SS 7225 52 39* 37 96 87 84*c

Averages 48

36* 32 91 85* 84

1See Table 1 for full species names; 2LSD0.05 flowering duration = 8.53; 3LSD0.05 stainable pollen percentage pollen = 10.63; Control = water, trt3.5 = 3.5 ml/L,

trt4.5 = 4.5 ml/L; + = significantly greater than control; trt1* = significantly less than control, trt2* = significantly less than trt1 and control; trt2*c = significantly

less than control but not sign less than trt1.

The significance of human influence on in situ germ-

plasm depends on the sensitivity of the germplasm in

question, the level of exposure, and the value/rarity of the

germplasm with respect to agriculture and the ecosys-

tem. This preliminary survey demonstrated that the pes-

ticide Furadan, to which in situ germplasm may be ex-

pected to have high exposure, can indeed have a negative

influence on reproductive indicators in greenhouse-

grown plants. More focused follow-up studies are in

progress to better characterize the patterns and mecha-

nisms by which these reproductive traits are depressed,

and quantify the consequences on genetic diversity that

could logically follow in the wild.

4. Acknowledgements

The authors wish to express thanks to the staff of CIP-

Santa Anta Agricultural Station in Huancayo, Peru for

their cooperation and technical assistance.

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