IJERD – International Journal of Environmental and Rural Development (2012) 3-1

Research article
erdAllelopathic Activity of Peruvian Corn Varieties
CECILIA INES ONO MORIKAWA*
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan
Email: cecilia.ono@gmail.com

RIE MIYAURA
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan

AKIMI FUJIMOTO
Graduate School of Agriculture, Tokyo University of Agriculture, Tokyo, Japan

MARIA DE LOURDES TAPIA Y FIGUEROA
Institute of Biotechnology, National Agrarian University La Molina, Lima, Peru

VICTOR NORIEGA NALVARTE
Maize Program, National Agrarian University La Molina, Lima, Peru

YOSHIHARU FUJIITokyo University of Agriculture and Technology, Tokyo, Japan
Received 20 December 2011

Accepted 7 February 2012(*: Corresponding Author)

Abstract Corn (Zea mays L.) is one of the three most important cereals in the world. Peru
is one of the centers of biodiversity of corn in the world and has 35 ecotypes. In this study
we compared the allelopathic activity of Peruvian native varieties of corn using the plantbox method to evaluate the activity by root exudate and sandwich method to evaluate theactivity by leaf leachate for sustainable weed managements. An experiment using nativevarieties of 6 Peruvian corn races (Cuzco, Amarillo ancashino, Morado, Piscorunto,Chullpy, Terciopelo) was conducted at National Agrarian University La Molina, Peru.
Cuzco race (known as Giant corn) was the strongest with more than 75% of lettuce radicle
inhibition. Besides, these samples were evaluated by sandwich method using 10 and 50
mg of dry leaves (24 hours at 60 °C). Another experiment to compare Peruvian andJapanese varieties was conducted at National Institute for Agro-Environmental Science,
Japan. A total of 85 varieties (3 Peruvian varieties and 82 Japanese varieties) and 3 typesof teosinte Euchlaena mexicana were evaluated by plant box method. From thisevaluation, Peruvian varieties of Morado (known as Purple corn) and Maiz cancha, bothvarieties of soft corn type, showed a strong inhibitory activity. Kuromochikibi and otherJapanese varieties of waxy corn type showed also strong inhibition of lettuce radicle
growth. As a conclusion, we found that Peruvian native purple corn and varieties of soft
corn and waxy corn types have potent allelopathic activity and promising crop for weed
control at sustainable agriculture.
Keywords Zea mays, allelopathy, plant box method, sandwich method

INTRODUCTION
Allelopathy is a phenomenon of interaction between the compounds emitted by plants, which cancause inhibition or promotion effects to the organisms around. These compounds are called
allelochemicals and nowadays are increasing interest in use of them to suppress weeds by naturalexudation. This activity was reported from some crops and the evaluation of allelopathic potential
in different varieties or related species could be important in areas like plant breeding or weedmanagement (Wu et al., 2001).
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IJERD – International Journal of Environmental and Rural Development (2012) 3-1Corn (Zea mays) is one of the most important crops in the world. The global corn production
for 2011/12 is estimated around 867.5 million tons (USDA, 2011). This crop is native from Central
America and was probably introduced to Peru in an early stage. The geographical diversity
generates a high variety reflected in 51 Peruvian races and other 35 ecotypes (Abu-Alrub et al.,
2004; Salhuana, 2004; Sevilla, 2005). Corn is generally produced in monoculture and some casesof low production related to allelopathic effect of this crop have been reported (Sarobol andAnderson, 1992). Another research of continuous cropping of corn for 3 years showed a decreaseof 13% of production compared with a field with crop rotation (Lund et al., 1993). Most research
related to corn allelopathy is done with a limited number of varieties. We compare the allelopathic
activity of Peruvian varieties, as well as a large number of Japanese varieties and an ancestor ofcorn, teosinte.
METHODOLOGY
Plant materials
First experiment: The seedlings of varieties of 6 Peruvian corn races (Cuzco, Amarillo ancashino,Morado, Piscorunto, Chullpy, Terciopelo) were cultivated in sand substrate for one month in agreenhouse of Vegetable Program of National Agrarian University La Molina (UNALM). The
seeds were provided from Maize Program of UNALM. The plant box and sandwich method
experiments were conducted in laboratories of the Institute of Biotechnology of UNALM.
Second experiment: A total of 85 varieties of corn (3 Peruvian and 82 Japanese varieties) and 3types of teosinte (Euchlaena mexicana) were evaluated by plant box method on laboratories ofNational Institute of Agro-Environmental Sciences (NIAES), Japan. The seedlings were cultivatedin a greenhouse with sand substrate for one month.
Plant box method
Seedlings of around one month old were used for bioassay in a Magenta GA-7 vessel (6×6×10 cm,Magenta Co. Ltd., USA)   called   ‘plant-box’,   for   evaluating   the   allelopathic   activity   through   root  exudates (Fujii, 1992). After removal of seedlings from the pot, the roots were carefully washedwith distilled water and inserted into a column of a nylon mesh (0.22 mm) that was subsequently
placed at a corner of the plant box. Then, autoclaved agar 0.75% (w/v) (Nacalai Tesque Co. Ltd.,Japan) was placed at 40° C into the plant box. After gelatinization of the agar, a total of 33 seeds oflettuce (Lactuca sativa L., Great Lakes No. 366, Takii Co.) were sowed at different distances fromthe corner with the donor plant. The box was covered with clear wrap to prevent evaporation, andthen each box was put in a black vinyl pot to cover the roots of each seedling. Finally, all the plantboxes were kept at 20 ºC with a 12/12 h photoperiod for 5 days in an incubator (BITEC-500L,Shimadzu Instruments Co. Ltd., Tokyo, Japan). After incubation, the radicle and hypocotyl lengthof lettuce seedlings were measured. A plant box without donor plant was used as a control. The
experiment was conducted with three replications.
Sandwich method
Sandwich method was developed by Dr. Fujii as a bioassay to determinate the allelopathic activityof the leaches from donor plant leaves (Fujii, 1994). A total of 10 or 50 mg of dried leaves wereplaced into 3 wells of the six-well (around 10 cm2 area per well) multi-dish plastic plate(35mm×18mm, Thermo Fisher Scientific Inc.). Agar powder (Nacalai Tesque Inc.) was used asgrowth medium (0.75% w/v). In each well, 5 ml of agar solution was added on 5 ml agar to maketwo gelatinized layers in between and 5 seeds of the test plant lettuce (L. sativa L., Great Lakes No.
366, Takii Co.) were seeded on the surface. The multi-dish was covered with plastic tape, labeled,wrapped in aluminum foil and incubated in dark at 25ºC for 3 days. The length of hypocotyl andⒸ ISERD

11IJERD – International Journal of Environmental and Rural Development (2012) 3-1

radicle of lettuce seedlings were measured on the third day; these data were used to calculate thepercent elongation to control.
RESULTS AND DISCUSSIONFirst experiment
The results of evaluation of varieties of 6 Peruvian corn races by Plant Box Method showed astrong inhibition in the lettuce radicle growth (11%) by variety of Cuzco race. The inhibition
activity of other varieties ranged between 22 and 35% (Table 1).
Table 1 Evaluation of allelopathic activity of varieties of 6 Peruvian corn races by plant box
method and sandwich method
Peruvian corn races

Percentage of radicle growth of lettuce(%)
Sandwich Method
Plant Box Method
10mg
50mg

Cuzco

10.9

50

21

A. Ancashino

21.9

40

17

Morado

26.6

45

21

Piscorunto

29.7

37

15

Chullpy

31.9

53

22

Terciopelo

35.0

42

13

Cuzco   (‘Giant   corn’)   corresponds to the second derivation from primitive races of Peruvian
corn. This race is cultivated on the Central Andes at an altitude of 2,300 to 3,300 m and was spreadwith the expansion of Inca Empire from Ecuador to the north of Argentina. In Peru it is mostly
consumed by being boiled or as flour (Ortiz et al., 2008; Salhuana et al., 2004).
The allelopathy activity of leaves of the varieties of 6 Peruvian races was evaluated using 10and 50 mg of dry leaves by sandwich method. By 10 mg most of them showed around 50% of
inhibition of lettuce radicle growth; using 50 mg that was more than 80% in all varieties.
Piscorunto showed higher activity in both concentrations; 37 and 15% growth of radicle
respectively (Table 1). Piscorunto corresponds to the race derived from primitive races. This race iscultivated on the Southern Andes at an altitude of around 3,000 m (Salhuana et al., 2004).
Second experiment
The Peruvian corn varieties evaluated were Purple corn (from three commercial companies: El
Shaday, Inca's Food, Peru Cheff), Cancha corn and Chullpe corn. The other group of 82 Japanesevarieties was composed mostly by varieties of sweet corn. Another 3 types of teosinte, E. mexicana,(PI441932125, Ames8083, Ames21869) were obtained from North Central Regional Plant
Introduction Station (NCRPIS).
To compare all varieties, we classified them using the description of types of corn related tothe amount of starch in the grain (Tozawa, 2005).
Dent corn (Z.mays var. indentata): The grains have a depression on the top, with shape oftooth. Hard starch granules are accumulated in both sides and soft starch granules are accumulated
from the top to the middle. Three-quarter of percentage of starch is soft.
Flint corn (Z. mays var. indurata): The grain has the form of hard flint, with a round shape.
The soft starch is concentrated in small amount in the center covered by hard starch.
Sweet corn (Z. mays var. saccharata): Grain endosperm is mostly sugar. The sugar transported
from leaves and stems is directly stored in the grain.
Pop corn (Z. mays var. everta): This group has a similar carbohydrate configuration of FlintⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2012) 3-1corn, but is different in that it contains hard starch in the endosperm and a small portion of softstarch inside.
Flour corn (Z. mays var. amylacea): It is a round type of Flint corn. The endosperm is mostly
constituted by soft starch and the grain is light.
Waxy Corn (Z. mays var. ceratina): This type is a mutant from China. Most of the starch
consists of amylopectin with low amylose.
Table 2 Evaluation of 85 corn varieties and 3 types of teosinte by plant box methodCorn variety

Type*

Radiclegrowth(% )Corn variety

Type*

Radiclegrowth(% )Corn variety

Type*

Radiclegrowth(% )Purple corn (El Shaday)**Sf

3.02 Honey Bantam Peter 445

Sw12.0 Hazetomorokoshi

P

16.9

Purple corn (Inca's Food)**
Kuromochikibi

Sf

3.58 Yumemi Dream

Sw

12.2 New Dent 100 LG3457

D

17.1

W

4.35 Peter CornSw

12.5 Taiyo no megumi

Sw

17.5Cancha corn **Peter 001

Sf

4.91 Gosaku

Sw

12.6 Gold Dent KD640 [RM114]

D

18.0

Sw

5.06 SpectraP

12.6 Canberra 90

Sw

18.4

Ohisama corn 7Sw

6.00 Kyokuwase Jelly Bantam

Sw

12.9 Teosinte PI4419321250

T

19.8

Big Summer

Sw

6.74 Mirai 390

Sw

13.0 Gold Dent KD670 [MR117]

D

20.1

AjiichibanSw

6.95 MochimurasakiW

13.1 Gold Dent KD520 [RM105]

D

20.5

Cocktail E51

Sw

7.32 Miwaku no corn Gold RushSw

13.4 Canberra 86

Sw

21.6

Amaindesu

Sw

7.43 White QueenSw

13.8 New Dent 90 days ANJOU259

D

21.7

OomonoSw

7.65 Popcorn

P14.4 Dodeka corn Yusaku

Sw

23.2

MarukajiriSw

8.16 Chullpe corn**

Sw

14.5 Picnic corn

Sw

23.6

Purple corn (Peru Cheff)**
Sunny ChocolateSf

8.17 Harmony Chocolate

Sw

14.9 Silage corn NS-118

D

23.7

Sw

8.42 SnowDent Onatsu SH9904

D

15.0 Gold Dent KD772 Super [MR130]

D

24.0

Diachi no megumi

Sw

8.79 Cocktail 600

Sw

15.0 New Dent 85 days LG3263

D24.9

Cocktail 83L

Sw

9.23 Gold RushSw

15.3 New Dent 85 days Richmond

D

25.3

Shiromochikibi

W

9.25 Woody cornSw

15.3 Pioneer 106 days 36B08

D

26.7

Kiimochikibi

W

9.85 Fleet

Sw

15.3 Bikkuri Sweet

Sw

27.2

SakichanSw

9.94 Sweets Megumi 86

Sw

15.5 Salad corn

Sw

27.3

Ohisama cornSw

10.0 Honey Bantam Peter 610

Sw

15.5 Honey Bantam Wase 200

Sw

27.5

Kiihachiretsuurukibi (Longfellow)

F

10.1 Snow Dent 118 DKC61-24

D

15.5 Baby corn

P27.7Cocktail 84EX

Sw

10.3 Miwaku no cornSw

15.6 Pioneer 115 days Cecilia

D

28.4

Honey Bantam Peter cornSw

10.5 Teosinte Ames8083

T

15.7 Yawaraka Gold

Sw

29.3

Yume no cornSw

10.9 Golden HoneySw

15.9 Harmony Festival

Sw

29.7

AmamichanSw

11.2 White Popcorn

Sw16.2 Super Suite Big

Sw

31.7

Lucy 90

Sw

11.4

Honey Bantam Peter 235

Sw

16.5 Gold Dent KD850 [MR135]

D

36.1

Sunny FestSw

11.5 Cynthia Neo Dent 90 SL9945

D

16.5 Pioneer 135 days 30D44

D

40.3

Honey Bantam 20

Sw

11.7 Pioneer 88 days Deer HTD

16.5 Pioneer 120 days 31P41

D

44.7

Yellow Popcorn

P11.8 Super Sweet bicolor

Sw

16.8 Teosinte Ames21869

T49.8

Honey Bantam

Sw

11.8 AmairoSw

16.9 Strawberry corn

P

51.1

*

D Dent Corn, F Flint Corn, P Pop Corn, Sf Soft Corn, Sw Sweet Corn, W Waxy Corn, T Teosinte**Peruvian varieties

From the total of varieties and species evaluated, the lettuce radicle growth ranged from 3 to50%. Peruvian purple corn (El Shaday) showed the strongest inhibition effect in lettuce radicle
growth (3%). Other Peruvian varieties of soft corn also showed a strong inhibition. Purple corn isconsidered as one of the most important Peruvian native varieties. The main characteristic of thisvariety is the deep purple color due to anthocyanin, present in the grains and some other parts ofthe ear and plant. It is cultivated from 1,200 to 4,000 m of altitude from the Coast to the Andeanregion. The purple corn is used to make a traditional Peruvian sweets and the pigment is used in thefood industry. In recent years this compound attracts attention as a health food. (Salhuana et al.,
2004; SIRA, 2005; Tenorio, 2007). The second variety with a strong inhibition was Kuromochikibi
from the group of waxy type (Kuromochikibi, Shiromochikibi, Kiimochikibi). These two varieties,Purple corn and Kuromochikibi have same characteristic of dark color but it was not possible toknow the relation with their inhibitory activity.
From the 82 Japanese varieties evaluated, 63% of them (52 varieties) were sweet corn type
and the percentage of growth of lettuce radicle ranged from 5 to 30%. As for dent corn type, mostof the varieties showed low inhibitory activity. However, to clarify whether the differences inallelopathic activity is due to genetic differences, it is necessary to explore the ancestral lineage.
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IJERD – International Journal of Environmental and Rural Development (2012) 3-1

Among the features in plant breeding is mentioned the reduction of the chemical components ofprotection (Pickersgill, 2007).
Teosinte (E. mexicana) is considered an ancestor of corn (Galinat, 1995). Three varieties wereevaluated and two of them (Ames8083 and PI4419321250) showed a percentage of lettuce radiclegrowth of 16 and 20% respectively. Just Ames21869 reported a low activity (50%) compared toother types of this group.
CONCLUSION
In the evaluation of varieties of 6 Peruvian corn races by plant box, the growth of lettuce radicle
fluctuated from 11 to 35% and the strongest variety was from Cuzco race. The evaluation by
sandwich method of the same samples did not show significant differences.
The second evaluation of 85 varieties by plant box showed lettuce radicle growth percentage
from 3 to 51%. The strongest varieties were from the group of soft and waxy corn with varieties ofPurple corn (3%) and Kuromochikibi (4%) respectively.
Peruvian varieties evaluated in these two experiments showed high allelopathic activity under
the plant box method. Based on these results we can affirm that allelochemicals are exuded by theroots and activity differs according to varieties. However, it is necessary to confirm the relationshipbetween varieties and allelochemicals released from this species.
ACKNOWLEDGEMENTS
We are grateful to the persons   of   the   Vegetable   Program   “El   Huerto”   and   Institute   of  Biotechnology in UNALM for providing facilities and assistance in this research.
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