Occurrence Of Seed-Borne Diseases And Jatinangor Endemic Diseases On Several Accessions Of Cowpea (Vigna Unguiculata (L.) Walp.) Of Eastern Indonesian Regions.
Occurrence of Seed-borne Diseases and Jatinangor Endemic Diseases on
Several Accessions of Cowpea (Vigna unguiculata (L.) Walp.) of Eastern
Indonesian Regions
E Yulia1), T Suganda2), A Karuniawan3), and BL Visser4)
1), 2) Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Padjadjaran
3) Department of Agronomy, Faculty of Agriculture, Universitas Padjadjaran
4) Centre for Genetic Resources the Netherlands (CGN), Wageningen University Research
INTRODUCTION
Cowpea (Vigna unguiculata (L.) Walp.) is an annual legume originated in Africa and most of the crop is grown
there during the shorter rainy season (August to October) (1). This legume is an ideal crop for semiarid regions
of tropics where other food legumes may not perform well. In Indonesia, cowpea is grown especially in dry
regions with low annually rainfall such as East Timor Province in eastern Indonesia, as food crops. Cowpea
provides nutritious grain that contains about 25-28% protein which is rich in the amino acids, lysine and
tryptophan compared to cereal grains, and may provide a major source of protein, minerals, and vitamins in the
diet of resource-poor communities because of limited access to animal protein sources (2). However, cowpea is
susceptible to a wide range of pests and pathogens that attack the crop at all stages of growth. Some 40 species
of fungi are cowpea pathogens. Losses due to disease can be as high as 90% (3). Widely exploration and
cultivation of cowpea in several regions in Indonesia can be benefited for food security, besides cowpea
contribution to the sustainability cropping systems and soil fertility improvements. Eastern region of Indonesia
is known to have various types of cowpea of local origin. These genetic resources can be explored, both for their
potential and other characteristics including their ability to perform in new areas away from their region of
origin. To facilitate the development of cowpea cultivation in several regions in Indonesia, plant diseases on
cowpea that grown in different regions were investigated to know either the potential of disease occurrence or
prevent disease dissemination.
MATERIALS AND METHODS
The experiment was conducted during dry season at the field site of Jatinangor district, West Java, on 753
meters above see level from July to October 2006 with a few rainy days and means daily minimum and
maximum temperatures were 17.65-21.540C and 33.89-34.870C, and means daily minimum and maximum
humidity were 31.56-31.70 and 79.37-84.76. Soil type of the site is inseptisols. Twenty genotypes of cowpea
were used in this present study. Eighteen accessions that originated in eastern region of Indonesia (Timor,
Flores, and Lombok islands) and two local cultivars that originated in Java were tested and compared. The
laboratory test was conducted using washing technique and incubation technique to assess the presence of
microorganisms (seed-borne pathogens incidence) on the cowpea seeds. The fungal colonies growing on the
culture plates were identified morphologically on the basis of their colour, type of spores, colony texture, and
other growth characteristics. Field trial was conducted in Randomized Block Design with treatment and non
treatment with metalaxyl fungicide on cowpea seeds, arranged in one row plot with 5 plants per row. Disease
incidence and disease severity was assessed on all plant samples. Disease severity was rated using a modified of
Horsfall & Barrat with 0, 20, 40, 60, 80, and 100% of plant area affected (PAA) (1), while the disease incidence
was the percentage of 5 plants showing the symptoms. Disease samples were taken to the laboratory for
confirmation of symptoms and causal pathogens.
RESULTS AND DISCUSSION
The results of the laboratory test showed that most isolated and identified fungi belonged to the genera of
Aspergillus and Penicillium. Several fungi such as Rhizopus, Aspergillus, Penicillium, and Trichoderma were
isolated through washing technique. Some of them were easily isolated and grew very fast, and were isolated
from most accessions tested. These fungi can be assumed as contaminant fungi. Meanwhile, several species
such as Fusarium, Colletotrichum, and Phoma were mostly encountered on incubation technique; these are
more likely to be pathogenic fungi. Those fungi were found on most accessions and cultivars tested. The
appearance or occurrence of seed-borne or soil-borne diseases was low during the first month after planting
(considered to be an appropriate to count the occurrence of seed-borne diseases). This low disease occurrence
was considered to be caused by low disease incidence and low seed growth capacity that seed could not grow
and did not emerge. This case might because of low seed quality or high seed infection by pathogens causing
failure of germination. It proved that seed treatment with fungicide before planting gave higher plant emergence
1) endah.yulia@unpad.ac.id, 2) tarkussuganda@unpad.ac.id, 3) akaruni1@unpad.ac.id, 4) bert.visser@wur.nl
percentage than without seed treatment before planting. Seed-borne diseases occurred and assessed during one
month after planting included spots on the cotyledon, leaf blight, root rot, seedling wilt, seedling rot, lower stem
rot, and presumed viral diseases. The occurrence of seed-borne disease was higher on the seed that planted
without seed treatment with fungicide compared with lower occurrence of the disease on the seeds treated with
fungicide before planting (Fig. 1). Isolated causal agents of seed-borne or soil-borne diseases included
Sclerotium rolfsii, Rhizoctonia sp. (several anastomosis groups – Fig. 2), Fusarium sp., and Colletotrichum sp.
Disease incidence (%)
6
5
4
ST
3
NST
2
1
0
CS
LB
RR/W
SR
StR
VD
Diseases
Fig. 1: Percentage of disease incidence of several seed-borne or soil-borne diseases occurred on 20 genotypes on
28 days after planting. CS = Cotyledon Spot, LB = Leaf Blight, RR/W = Root rot/Wilt, SR = Seedling Rot, StR
= Stem Rot, VD = Viral Disease, NST = Non Seed Treatment, ST = Seed Treatment.
A
B
C
D
Fig. 2: Isolated Rhizoctonia species (A) Rhizoctonia sp. caused stem rot (B) Rhizoctonia sp. caused leaf blight
(C) Rhizoctonia sp. caused seedling rot (D) Rhizoctonia sp. caused cotyledon spot.
There was a significant different growth progress between plants with fungicide seed treatment and plants
without fungicide seed treatment that influenced the disease occurrence. The occurrence of air-borne diseases
included powdery mildew, bacterial wilt, fungal wilt, cercospora leaf spot, and viral disease with high incidence
of powdery mildew was recorded on most accessions during the experiment ranged from 25-100%. Although in
a very low incidence, a significant incidence of viral disease occurred in the appearance of witches broom
disease cause by Cowpea witches broom virus on several accessions (Fig. 3). Meanwhile, rust (Uromyces
vignae) was less common that occurred in several accessions with low disease intensity on aged plants. During
the study, there was no evident of the occurrence of the diseases on produced pods. Disease occurrence and
disease level were common and varied considerably among the genotypes tested.
A
B
Fig. 3: A viral disease symptom (A) Stunted and enation symptom on plant caused by Cowpea witches broom
virus infection (B) Comparison of stunted infected plant and healthy plant of the same accession.
REFERENCES
[1] Edema, R, E Adipala, and DA Florini. “Influence of season and cropping system on occurrence of cowpea
diseases in Uganda”. Plant Disease, vol. 81, pp. 465-468. 1997.
[2] James, AT and RJ Lawn. “Inheritance of selected traits in accessions of Vigna vexillata (L.) A. Rich of
Australian and African origin”. Australian Journal of Botany, vol. 39, pp. 415-429. 1991.
[3] Allen, DJ, G Thottappilly, AM Emechebe, BB Singh. Diseases of Cowpea. Pp. 267-324 in The Pathology
of Food and Pasture Legume (Eds. DJ Allen and JN Lenne). CAB International, Wallingford, UK. 1998.
1) endah.yulia@unpad.ac.id, 2) tarkussuganda@unpad.ac.id, 3) akaruni1@unpad.ac.id, 4) bert.visser@wur.nl
Several Accessions of Cowpea (Vigna unguiculata (L.) Walp.) of Eastern
Indonesian Regions
E Yulia1), T Suganda2), A Karuniawan3), and BL Visser4)
1), 2) Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Padjadjaran
3) Department of Agronomy, Faculty of Agriculture, Universitas Padjadjaran
4) Centre for Genetic Resources the Netherlands (CGN), Wageningen University Research
INTRODUCTION
Cowpea (Vigna unguiculata (L.) Walp.) is an annual legume originated in Africa and most of the crop is grown
there during the shorter rainy season (August to October) (1). This legume is an ideal crop for semiarid regions
of tropics where other food legumes may not perform well. In Indonesia, cowpea is grown especially in dry
regions with low annually rainfall such as East Timor Province in eastern Indonesia, as food crops. Cowpea
provides nutritious grain that contains about 25-28% protein which is rich in the amino acids, lysine and
tryptophan compared to cereal grains, and may provide a major source of protein, minerals, and vitamins in the
diet of resource-poor communities because of limited access to animal protein sources (2). However, cowpea is
susceptible to a wide range of pests and pathogens that attack the crop at all stages of growth. Some 40 species
of fungi are cowpea pathogens. Losses due to disease can be as high as 90% (3). Widely exploration and
cultivation of cowpea in several regions in Indonesia can be benefited for food security, besides cowpea
contribution to the sustainability cropping systems and soil fertility improvements. Eastern region of Indonesia
is known to have various types of cowpea of local origin. These genetic resources can be explored, both for their
potential and other characteristics including their ability to perform in new areas away from their region of
origin. To facilitate the development of cowpea cultivation in several regions in Indonesia, plant diseases on
cowpea that grown in different regions were investigated to know either the potential of disease occurrence or
prevent disease dissemination.
MATERIALS AND METHODS
The experiment was conducted during dry season at the field site of Jatinangor district, West Java, on 753
meters above see level from July to October 2006 with a few rainy days and means daily minimum and
maximum temperatures were 17.65-21.540C and 33.89-34.870C, and means daily minimum and maximum
humidity were 31.56-31.70 and 79.37-84.76. Soil type of the site is inseptisols. Twenty genotypes of cowpea
were used in this present study. Eighteen accessions that originated in eastern region of Indonesia (Timor,
Flores, and Lombok islands) and two local cultivars that originated in Java were tested and compared. The
laboratory test was conducted using washing technique and incubation technique to assess the presence of
microorganisms (seed-borne pathogens incidence) on the cowpea seeds. The fungal colonies growing on the
culture plates were identified morphologically on the basis of their colour, type of spores, colony texture, and
other growth characteristics. Field trial was conducted in Randomized Block Design with treatment and non
treatment with metalaxyl fungicide on cowpea seeds, arranged in one row plot with 5 plants per row. Disease
incidence and disease severity was assessed on all plant samples. Disease severity was rated using a modified of
Horsfall & Barrat with 0, 20, 40, 60, 80, and 100% of plant area affected (PAA) (1), while the disease incidence
was the percentage of 5 plants showing the symptoms. Disease samples were taken to the laboratory for
confirmation of symptoms and causal pathogens.
RESULTS AND DISCUSSION
The results of the laboratory test showed that most isolated and identified fungi belonged to the genera of
Aspergillus and Penicillium. Several fungi such as Rhizopus, Aspergillus, Penicillium, and Trichoderma were
isolated through washing technique. Some of them were easily isolated and grew very fast, and were isolated
from most accessions tested. These fungi can be assumed as contaminant fungi. Meanwhile, several species
such as Fusarium, Colletotrichum, and Phoma were mostly encountered on incubation technique; these are
more likely to be pathogenic fungi. Those fungi were found on most accessions and cultivars tested. The
appearance or occurrence of seed-borne or soil-borne diseases was low during the first month after planting
(considered to be an appropriate to count the occurrence of seed-borne diseases). This low disease occurrence
was considered to be caused by low disease incidence and low seed growth capacity that seed could not grow
and did not emerge. This case might because of low seed quality or high seed infection by pathogens causing
failure of germination. It proved that seed treatment with fungicide before planting gave higher plant emergence
1) endah.yulia@unpad.ac.id, 2) tarkussuganda@unpad.ac.id, 3) akaruni1@unpad.ac.id, 4) bert.visser@wur.nl
percentage than without seed treatment before planting. Seed-borne diseases occurred and assessed during one
month after planting included spots on the cotyledon, leaf blight, root rot, seedling wilt, seedling rot, lower stem
rot, and presumed viral diseases. The occurrence of seed-borne disease was higher on the seed that planted
without seed treatment with fungicide compared with lower occurrence of the disease on the seeds treated with
fungicide before planting (Fig. 1). Isolated causal agents of seed-borne or soil-borne diseases included
Sclerotium rolfsii, Rhizoctonia sp. (several anastomosis groups – Fig. 2), Fusarium sp., and Colletotrichum sp.
Disease incidence (%)
6
5
4
ST
3
NST
2
1
0
CS
LB
RR/W
SR
StR
VD
Diseases
Fig. 1: Percentage of disease incidence of several seed-borne or soil-borne diseases occurred on 20 genotypes on
28 days after planting. CS = Cotyledon Spot, LB = Leaf Blight, RR/W = Root rot/Wilt, SR = Seedling Rot, StR
= Stem Rot, VD = Viral Disease, NST = Non Seed Treatment, ST = Seed Treatment.
A
B
C
D
Fig. 2: Isolated Rhizoctonia species (A) Rhizoctonia sp. caused stem rot (B) Rhizoctonia sp. caused leaf blight
(C) Rhizoctonia sp. caused seedling rot (D) Rhizoctonia sp. caused cotyledon spot.
There was a significant different growth progress between plants with fungicide seed treatment and plants
without fungicide seed treatment that influenced the disease occurrence. The occurrence of air-borne diseases
included powdery mildew, bacterial wilt, fungal wilt, cercospora leaf spot, and viral disease with high incidence
of powdery mildew was recorded on most accessions during the experiment ranged from 25-100%. Although in
a very low incidence, a significant incidence of viral disease occurred in the appearance of witches broom
disease cause by Cowpea witches broom virus on several accessions (Fig. 3). Meanwhile, rust (Uromyces
vignae) was less common that occurred in several accessions with low disease intensity on aged plants. During
the study, there was no evident of the occurrence of the diseases on produced pods. Disease occurrence and
disease level were common and varied considerably among the genotypes tested.
A
B
Fig. 3: A viral disease symptom (A) Stunted and enation symptom on plant caused by Cowpea witches broom
virus infection (B) Comparison of stunted infected plant and healthy plant of the same accession.
REFERENCES
[1] Edema, R, E Adipala, and DA Florini. “Influence of season and cropping system on occurrence of cowpea
diseases in Uganda”. Plant Disease, vol. 81, pp. 465-468. 1997.
[2] James, AT and RJ Lawn. “Inheritance of selected traits in accessions of Vigna vexillata (L.) A. Rich of
Australian and African origin”. Australian Journal of Botany, vol. 39, pp. 415-429. 1991.
[3] Allen, DJ, G Thottappilly, AM Emechebe, BB Singh. Diseases of Cowpea. Pp. 267-324 in The Pathology
of Food and Pasture Legume (Eds. DJ Allen and JN Lenne). CAB International, Wallingford, UK. 1998.
1) endah.yulia@unpad.ac.id, 2) tarkussuganda@unpad.ac.id, 3) akaruni1@unpad.ac.id, 4) bert.visser@wur.nl