ArticlePDF Available




Seeds of five cowpea varieties Vigna unguiculata (L) Waf were analysed for their chemical contents. The seeds were infested with adults of Callosobruchus maculatus (F) (Coleoptera: Bruchidae) at room temperatures ranging from 28.0-34°C and relative humidity range of 68 - 80% and studies for their susceptibility to insect pests in storage in a randomized block experiment. The cowpea varieties differed in their overall chemical compositions and their responses to C. maculatus attack. The bruchid performance and overall development were significantly higher on Ife Brown which had the highest pest population density (47.75 ±10.7) and suffered the greatest percent weight loss (5.45 ± 10.) per 30g of seeds compared to IT81D - 994 with population density of (10.50 ± 3.1) and loss of (2.44 ± 0.5). The correlation analysis between the population density of the beetle, weight loss and damage were positively significant (r = 0096,P < 0.05 and r =0.98, P < 0.05) respectively. Also, correlation between the growth and development of the bruchid and the nutritional content of the cowpea seeds showed that the moisture content and population density were positive and significantly high. Weight loss due to insect feeding also showed significant positive relationship with the moisture content of the seeds. The studies therefore show that nutritional quality of cowpea varieties had substantial influence on the biological performance of C. maculatus during storage, and the varieties ranked in the following order of resistance. susceptibility from IT81D-994 > IT90K - 76 > TVX3236> Ex Potiskum > lfe Brown.
ournal of Applied Sciences 12 (1) : 8368 - ~379
E. N. hijindu"; N.
konkwo, T. Um
S. U.
Dep ent of Parasitology and EntomoJ ~y, P. O. ox ,2-.
namdi Azikiwe Universit , A vka, ligeria.
Tel: 08038802779
Email: chikanny@yahooocom
(Accepted 30 September 2 08)
Seeds of five cowpea varieties Vigna unguiculata (L)
analysed for their chemical contents. The seeds were infested with
adults of Callosobruchus maculatus (F) (Coleoptera: Bruchidae)
at room temperatures ranging from 28.0-34°C and relative
humidity range of 68 - 80% and studies for their susceptibility to
insect pests in storage in a randomized block experiment. The
cowpea varieties differed in their ove all chemical compo itions
and their responses to
maculatus attack. The bruchid
performance and overall development were significantly higher on
Jfe Brown which had the highest pest population density (47.75
10.7) and suffered the greatest percent weight loss (5.45
30g of seeds compared to IT81D - 994 with population density of
3.1) and loss of (2.44
0.5). The correlation analysis
between the population density of the beetle, weight loss and
damage were positively significant (r =0096,P
0.05 and r
0.98, P
0.05) respectively. Also, correlation between the growt
and development of the bruchid and the nutritional content of t
cowpea seeds howed that the moisture content and populatior
density were positive and
icantly high. Weight loss due to
insect feeding also showed s ignificant pas 'tive relationship wits
E. N. Chijindu, et al 8369
the moisture content of the seeds. The studies therefore show that
nutritional quality of cowpea varieties had substantial influence on
the biological performance of
maculatus during storage, and
. the varieties ranked in the following order of resistance.'
susceptibility from IT81D-994
IT90K -
TVX3236> Ex
Potiskum >lfe Brown.
Cowpea, Vigna unguiculata
Walp is a leguminous crop grown.
in Africa, Asia and other parts of the tropical and sub tropical
regions of the world. The crop is the mot readily and popular
source of plant protein in Africa with moderate protein content of
about 25% (1). They are additionally a valuable source of calcium,
iron, thiamine and riboflavin (2). It is also used as green crop in
nitrogen fixation and for erosion control (3).
In the West African sub-region where more than 70% of
the total world's crop is grown, cowpea has become an integral
part of the farming system. Nigeria principally produces about
58% of world total output of the crop annually, 80% of which
comes from the northern parts of the country (4 and 5). The 'dry
seeds of cowpea form a major source of storage and transportable
protein concentrate for the teeming population (4). The ability of
the cowpea plants to tolerate drought and poor soils make them an
important crop in Savanna regions where these constraints restrict
other crops. These factors make cowpea a vital crop to millions of
resource-poor people. However
is very susceptible to insect
pests and diseases which reduce yield.
Insects pests have remained the most important constraint
to cowpea production. About 37% is lost to pests during storage
for a period of nine months (6). The seeds of cowpea are attacked.
by bruchids more especially Callosobruchus maculatus Fab
(Coleoptera: Bruchidae) from harvesting until storage (7). C.
the cowpea bruchid is the principal insect pest of dried
cowpea seeds in storage and causes an estimated annual' loss of
$30 million (8). The insect is a field-to-store insect pest, as it~
Susceptibility of Cowpea Varieties (Vigna Unguiculata} (L) 8370
attack starts in the field if the crops are left unharvested, to the
store when the seeds have been harvested.
Attempts to preserve the seeds by application of chemical
insecticides have often produced undesirable ecological and health
consequences. In 1996 for example, Nigeria witnessed rampant
cases of food poisoning from cowpea seeds stored with highly
toxic pesticides (7). Attention is currently being focused on certain
cowpea cultivars and other legume crops which are resistant to
bruchids, in protecting the corps. The International Institute of
Tropical Agriculture (lIT A), Ibadan, has developed now high-
vreldinz. disease-resistant and good quality cowpea seed varieties.
rhe use of resistant varieties appears to be the most reasonable
approach to solving production constraints associated with insect
pest problems. This approach is an environmentally benign
alternative to insecticides.
All cowpeas are not equally susceptible to weevi
(9). This was confirmed by several authors (10 and' 11). Several
experiments carried out on screening cowpea lines revealed some
levels of variation in their ability to support weevil development.
For example, the comparative susceptibility of certain cowpea
varieties to C. maculatus infestation was determined and it was
reported that the differences between the treatments with respect to
adult emergence varied f6rm 32.89% for El{-7 to 74.01% for
B013-J - (12) (range of 53-80%) compared with commercial
varieties. <susceptibility and resistance to infestation by bruchids is
usually determined by the number of exit holes, number of eggs
deposited per seed and the percentage number of adults that
emerged (13).
The reports showed that resistant lines suffered only
insignificant damage for
3- 6
months of storage. During the same
period, the susceptible line, Ife Brown suffered 100% damage and
was completely unfit for human consumption.
. Also, in 1975, lITA Scientists identified a single source of
bruchid resistant, Tvu 2027, after screening the world germplasm
collection of about 7,000 cowpea cultivars (14). C. maculatus
E. N. Chij indu.
exhibits higher mortality and takes longer time to develop in Tvu
2027 than in more susceptible seeds. This variety contained an
elevated level
of trypsin inhibitor. which causes antibiosis in the
larvae ( 1:;). Two
new varieties Kanan Nado White (KNW
Tvu 11952)
and Kanan Nado Speckled (KNS
19953) have
31s(1been identified and selected from the local variety collected
from K<1Il<1nNado in
State (14). These proved resistant to
the hruchid as Tvu 2027 and differed only slightly in the rate of
weevil oviposition. egg hatchability and larval. penetration. It is
therefore. necessary to screen available cowpea varieties for
hruchids and attempt to find out the basis of their
resistance or susceptibility. Thus the present studies were carried
out to determine the influence of
nutrients present in
different cowpea varieties on the development and performance of
C. maculatus in relation to damage and weight losses.
The studies were carried out at room temperatures (28.0 - 34.0°C)
humidity of
(68 -
in the Department of
and Entomology. Nnamdi Azikiwe University
State. The proximate ana1ysis of the seeds was carried
Project Development Institute (PRODA) Science
I .aboraiorv. Enugu. The
experimental design was randomized
each treatment was replicated four times.
Sources of cowpea seed!'
Five cowpea varieties used in the present studies included:
- ()q4. nGOK -- 76. T\'x3236 (improved varieties), Ex Potiskum
and lfe
beans. The improved varieties and Ife Brown were
obtained f1'0111the international Institute for Tropical Agriculture
lbadan. OV0 State. Nigeria, while Ex Potiskum was
purchased from Eke - A wka market. Anambra State. Nigeria. The
cowpea seeds were properly sieved to remove debris. dust particles
and damaged seeds. They were fumigated with phostoxin for four
days to clear any existing infestations and subsequently aired in
Susceptibility of Cowpea Varieties
tlnguiculata) (L)
perforated containers covered with muslin cloth for 7 days. The
seeds were thereafter used for both proximate analysis and
artificial infestation with the insects to determine damage and
losses due to C. maculatus.
Proximate analysis, seed quality
artificial infestation
Twenty gramme samples of the c wpea seeds were mille . and
used for chemical analysis of Car ohydrate, Moisture, P 'otein,
Ash, Fat and Crude fiber contents.
nirty gramme samples each
variety were also weighed into glass vials and infested with twenty
1 - 3 day old adult C. maculqtus (I 0 pairs). The insects wer sexed
using the method describ'ld aHd.they were allowed to mate and
oviposit for 7 days after which they were removed (16 and 17).
The treatment vials were left to stand undisturbed on the laboratory
bench for 30 days after which records were taken. Infestatior rates
were estimated based on the newly emerged adult numbers,
damaged seeds and weight losses: Similarly, the physical qualities
and seed weight/size of each variety were recorded using
electronic microbalance. The information generated was u
classifying the seeds.
Statistical analysis
Data collected were statistically analysed. Analysis of Variance
were carried out using computer program for Genstat Release
(Pc/Windows 95), while Correlation Analysis was carried out
using SPSS for MS Windows Release to determine the relationship
between the nutritional composition of the cowpea varieti·s and
the aspects of the insect biology.
The infestation levels of the cowpea varieties are shown (Table I).
Ife Brown recorded adult population density of 47.75 ± 10.7 and
weight loss of 5.45
1.0% compared to the improved variety,
IT81D - 994 with adult density of 10.50 ± 3.1 and weight loss of
0.5%. The chemical and physical factors of the cowpea
E. N. Chijindu, et (1/ . 8373
combined may explain why IT81 D - 994 supported the lowest C.
maculatus number. The relatively high carbohydrate content
(38.59%) in the. latter variety and the rough texture and medium
size of the seed may have played some significant role (fables II
and III).It was also obvious that the carbohydrate content in the Ife
Brown was much lower (21J59%), than the improved variety, the
texture was equally rough but soft enough to permit easy
penetration by the larvae.
his observation was similar to earlier
reports (18). Conversely, he protein content of [T81D-994
(33.10%) was comparatively lower than the content (41.29%) in
the Ife brown variety. These factors together with the. seed coat
colour differences (brown and white) in local versus the improved
varieties, respectively, as well as variations in seed sizes (large
seeded Ife brown versus medium sized IT81D - 994) may have
influenced the outcome. This however, suggests that in IT8ID -
994 conditions were less favourable for larval development and
survival to adult stage. Seed texture, seed coat colour and high
protein content among other factors were linked to bruchid
resistance in cowpeas (19). In the present studies, only rough
textured varieties were used, thus eliminating any bias for the
bruchid preference to smooth seeds (Table III) (11). Thus, seed
colour, protein content and other chemical factors as trypsin
inhibitors that cause antibiosis in the larvae have also been
reported (14). It was also known that resistance of seeds to C.
maculatus was due to the presence of variant vicilins (storage
globulins) (20). The vicilin polypeptide dependent on tryptophan
residues expressed mostly in. cotyledons of resistance seeds are
associated with chitin synthesis, which is why these proteins are
detrimental to insects (21).
The low number of adult emergence recorded on IT81 D-
994 agrees with the report (14). Reporting on the susceptibility of
cowpea varieties of C. maculatus infestation it was observed'fhat
significant differences between treatments with respect to adult
emergence varied from 32.89% for ER-7 to 74.01% for B067-0
Susceptibility of Cowoea Varieties (V;'/j.'
compared to commercial varieties ( 2). Also it was reporteu
susceptibility and resistance to infestation by the bruchid is usually
determined by the number of exit holes, number of eggs laid per
seed and percentage number of adults that emerged (13). The order
of resistance/susceptibility in these varieties was thus, IT81D-994
Ex Potiskum
Ife Brown.
The quantity of food consumed by the developing larvae of
the insect and thus the amount of weight loss caused by them
during development were likely to be proportional to the number
of the final population. In the present studies, the percentage
weight loss tended to increase with increasing number of emerged
adult insects in all varieties. Correlation analysis between F 1
population density and percentage weight loss indicated positive
and significant (r
0.96, P
0.05) association (Table''4). Hence,
heavy infestations of bruchids on legume seeds caused severe
damage and culminated in increased weight losses. The major
losses due to insects ranged from 2.44 ± 0.5% in IT81 D-994
variety to 5.45
1.0% in Ife Brown, while the percentage damaged
seeds ranged from 4.94 ± 1.8% to 11.71 ± 5.4% (Table 1). C.
. maculatus alone caused an estimated loss of 12 - 15% on cowpeas
(22). Our observations here just for a single generation of the
insect (about 37 days) indicate this high level of loss. It was likely,
therefore, to be much greater for overlapping populations lasting
longer. Certain chemical qualities operating within the seeds may
be acting on the developing larvae in the different varieties,
thereby either supporting or acting against their biology. Hence,
resistant crops were less likely to support enough larval
development to adulthood. Judging by the opinion, the nutritional
levels of crops do contribute to the adaptation of insects (23). The
correlation analysis conducted in the present studies between the
biology of the pest and the chemical composition of the cowpea
varieties showed that association between moisture content and
population den.~ity was positive and significantly high (r
0.75, P
0.05) (Table 4). This equally supports the assertion that moisture
content of stored cowpea seeds determines the damages caused by
E. N. Chijindu, et
the bruchid as its growth and development are adversely affected
by very dry conditions (24).
Weight losses due to insect feeding also showed positive
significant association with the moisture content (r
0.82, P
O.OS)and ash content (r
0.72, P
0.05). There was no significant
association between protein and carbohydrate contents of the
COWP':!l1 seeds. This suggests that the amount of protein and
carbo: ydrate in the cowpea particularly in the improved varieties
might independently influence their resistance to bruchids, and
subsequent loss and damage to cowpea seeds. Tvu2027 contains an
elevated level of trypsin inhibitor which causes antibiosis in the
bruchid larvae and this may apply in the studies reported here (15).
There was also positive and significant relationship between the
ash content of the cowpea varieties and the insect biology (Table
0.79. P
0.05) indicating that ash content could playa
significant role in seed resistance to bruchids.
The present studies therefore, established the fact that food
values of the cowpea varieties affect, to some extent, the biological
performance of the bruchid. Efforts should therefore be made to
explore the biochemical basis of cowpea resistance for effective
control of the bruchids. Very high resistance against the weevil
may not be possible, but partial resistance should be considered
useful and virtually freely available to farmers once incorporated
into agronomically elite varieties. From the foregoing therefore,
IT81!) - 994 was the most resistant followed by rt90K-76 while
the most susceptible was Ife brown followed by Ex Potiskum.
Table I. Infestation level
cowpea seeds of C.
per 30
wt of
Damage (%)Cowpea Population
varieties density
IT81 0-994 10.50 ± 3.1
IT90K-76 14.75 ± 2.2
TYX3236 22.50 ± 6.4
Ex Potiskum 31.75 ± 7.5
Ife Brown 47.75 ± 10.7
Weight loss (%)
2.44 ± 0.5
2.89 ± 0.5
3.33 ± 0.7
3.58 ± 0.6
5.45 ± 1.0
4.94± 1.8
7.28 ± 2.4
10.08 ± 2.4
11.71 ± 5.4
Means of four replicates
E. N. Chijindu,
et af 8377
Department of Statistics, Nnamdi Azikiwe University, Awka, for
assistance in statistical analysis.
1. Ivbijaro. M. F. Preservation of Cowpea, Vigna ungiculata
(L) Walp with the Neem seed, Azadirachta indica. A. Juss.
Prot. Ecol. 5: 177 - 182. 1983~.
2. Nielson, S., Ohler, T. and Mitchell, C. Cowpea leaves for
human consumption: Production, Utilization and nutrient
Composition. Advances in Cowpea Research, IITA,
Nigeria 326 - 332. 1997.
3. Patel, P. N. Commercial Production of Cowpea in
Mississippi. Extention Service of Mississippi State
University Publication. Mississippi State University, USA
PP. 15-35 1986.
4. Okonkwo, N. J. The Linkage between Male Sterility and
Green Stem in Cowpeas, Vigna ungiculata (L) Walp.
African Journal of Science, 3:454-462. 2002.
5. Caswell, G. H. Damage to Stored Cowpea in Northern Part
of Nigeria. Journal of Agricultural Research 1: 11 - 19.
6. Caswell, G. H. The Storage of Cowpea in the Northern
States of Nigeria. Proceedings of Agricultural Society of
Nigeria 5: 4 - 6. 1968.
7. Ogbuinya, P. O. Advances in Cowpea Research.
Biotechnology and Development Monitor, 33:10 - 12.
8. IITA. International Institute of Tropical Agriculture.
Research Highlights. Ibadan, Nigeria. PP. 102 - 111. 1983.
9. Booker, R. H. Observation on three bruchids associated
with cowpea in Northern Nigeria. Journal of Stored
Products Research, 3:1 -15.1967.
10. Nwanze, K. F. and Hober, E. Seed Coats of Cowpeas
Affects Ovipostion and Larval Development of C.
maculatus. Environ. Entomol. 5: 213 -218.1976.
Susceptibility of Cowpea Varieties (Vigna Unguiculata) (L) 8378
11. Nwanze, K. F. and Horber, E. and Pittus, C. W. Evidence
for Ovipositionla Preference of C. maculatus for 'Cowpea
Varieties. Environ. Entomol. 4(3): 409-412.1975.
12. Javaid, 1., Poswal, M.A.T., Mokqatie, O. S. and Mahthodi,
S.M. Comparative Susceptibility of various Cowpea
landraces to Infestation by Callosobruchus maculatus (F)
(Coleoptera: Bruchidae). African Ent., 1 (2): 225 - 257.
13. UTA. International Institute of Tropical Agriculture.
Research Highlights, Ibadan, Nigeria. PP. 102 - 111. 1983.
14. IITA. International Institute of Tropical Agriculture.
Research Highlights, Ibadan, Nigeria. PP. 52 - 68. 1982.
15. IITA. International Institute of Tropical Agriculture.
Research Highlights, Ibadan, Nigeria. PP. 7 - 22. 1980.
16. Dobie, P., Haines, C. P., Hodges, R. J. and Prevett, P. F.
Insects and Arachnids of Tropical Stored Products. Their
Biology and Identification (A Training Manual). TDRI,
U.K. P. 27. 1984.
l7. Ofuya, T. I. Biology, Ecology and Control of Insect Pests
of Stored Food Legumes in Nigeria. In: Pests of Stored
Cereals and Pulses in Nigeria: Biology, Ecology and
Control. Ofuya, T. 1. and Lale, N.E.S. (eds). Dave Collins
Publication, PH., Nigeria. PP 54 - 58.2001.
18. Adams,
M. A guide to the objective and reliable
estimation of food losses in small-scale farmer storage.
Tropical Stored Products Information, 32:5 - 12. 1990.
19. Singh, S. R. Host Plant Resistance for Insect Pest
Management. Insect Science and Application, 8:765 - 769.
E. N. Chijindu, et al 8379
20. Xavier-filho, J., Campos, F. A. P., Ary, M. B., Silva, C. P.,
Carvalho, M M. M. Macedo, M. L. R., Lemos, F. J. A. and
Grant, G. Poor correlation between the levels of proteinase
inhibitors found in seeds of different cultivars of cowpea
(Vigna unguiculata) and the resistance/susceptibility to
predation by Callosobruchus maculatus. J. Agric. Food
Chern., 37: 1139 - 1143. 1989.
21. Mirinda, M. R. A., Oliveir, A. E. A., Fernandes, K. V. S.
and Xavier-filho, J. Chemical Modification of Vicilins
from Vigna unguiculata seeds. XXVII Meeting of the
Brazilian Biochemistry and Molecular Biology Society,
Caxambu (MG), Brazil. Abstract Book. P. 34. 1998.
22. Caswell, G. H. (1973). The Impact of Infestation on
Commodities. Tropical Stored Product Information, 25:19.
23. Kumar, R. Insect Pest Control with Special Reference to
Africa Agriculture. Edward Arnold Publishers Ltd. Great
Britain. PP. 88 - 107. 1984.
24. Hill, D. Agricultural Insect Pests of the Tropics and Their
Control. Cambridge University Press, Cambridge. PP. 373
- 374. 1975.
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
The p/Ittem of inheritance of certain characters in the cowpea was studied in the field at the IITA, Ibadan, using two male, sterile sources, Tvx 391 and Tvx 2920. X2 analysis oft the data obtained showed that the monogenic recessive characters of green pigmentation of the stem at the base of primary-branches (pbr) and male sterility (msz) ·did not sort independently in crosses with Tvx 391. The shortage in the number of F2 individuals bearing this pair of characters was highly significant (P~O.OOI), indicating that the colour factor and pol/en fertility were linked ThE estimated linkage intensity was 0.265+ 0.03 and in a repulsion phase. No male sterile plants were recovered in the F2 generation of the cr9sses with Tvx 2920 and this was attributed to a possibl« breakdown of the male sterility from this source.
Cowpea, a high protein food legume produced in several African countries is adapted to a wide array of soils and moisture conditions. However, average yields cannot be contemplated unless cowpea is accompanied by either heavy doses of insecticides or specific management measures such as intercropping or mixed cropping. The International Institute of Tropical Agriculture (IITA) and collaborators are currently working on varietal improvement based on host plant resistance. However, cowpea is produced mostly by smallholder farmers who have not adopted these newly developed varieties.
Three species of Bruchidae, Callosobruchus maculatus (F.), C. rhodesianus (Pic) and Bruchidius atrolineatus (Pic) were found associated with cowpea (Vigna unguiculata) in Northern Nigeria. The infestation in the field was at a low level with an average of 2 per cent of the seeds being affected. B. atrolineatus was the most common of the three species and C. rhodesianus was comparatively scarce.Only C. maculatus continued infestation in store for any length of time. It is concluded that this was because B. atrolineatus and C. rhodesianus have a mean developmental period and a period of emergence which are longer than those for C. maculatus. In addition B. atrolineatus and C. rhodesianus have a much reduced level of egg production soon after the storage period begins. An account is given of the wild hosts of B. atrolineatus and it is concluded that Vigna triloba and possibly other legumes are primary hosts of this species whereas cowpea is not. Nearly ten per cent of the seeds of V. triloba were attacked in the field.Observations on the biology of C. maculatus in the laboratory showed that the period of pre-adult development is negatively correlated with temperature and is also affected to a lesser degree by humidity, low humidity lengthening the pre-adult developmental period. The majority of eggs were laid during the early part of the female's life and there was a decrease in the viability of eggs laid later.C. maculatus has been bred on several hosts, but the only host comparable to cowpea is Phaseolus aureus, other hosts lead to heavy mortality and extension of developmental period. There are differences in the susceptibility to attack of different cowpea varieties, the larger seeded varieties of those tested being, in general, better as hosts. This was shown not to be due to larval competition within the seeds. There was a definite preference for oviposition on seeds with a smooth testa when there is a choice of smooth and rough, but there seemed to be no colour preference.One insect can cause a 3–5 per cent weight loss in a cowpea seed. The decrease in weight loss per individual insect is lower when there are several larvae per seed. Germination is adversely affected when there are three or more insects per seed.
Callosobruchus maculatus (F.) prefers smooth- to rough-seeded varieties and cheeks to other areas of the seeds for oviposition on cowpeas. It does not oviposit on the seed hilum, which is spongy and fibrillary in texture. Differences in seed-coat texture are considered to be responsible for the preferences. Scanning electron microscopy revealed deep pits in seeds that are rough-coated but not in those that are smooth-coated.
Callosobruchus maculatus (F.), the cowpea weevil, previously known to prefer smooth over rough seeds, readily distinguishes between rough and smooth varieties of cowpeas, Vigna sinensis L. The Hopkins' host-selection principle does not apply to weevils ovipositing on cowpeas. The surface of the underlying cotyledons is the same texture in both rough and smooth seeds and the seed coat is not a reprint or replicate of this surface. More 1st instar larvae successfully penetrate the seed coat in smooth than in rough seeds. The arrangement of macrosclereids of the epidermal layer of seed coats and how eggs are attached to the seed surface account for differences in larval penetration of rough- and smooth-coated varieties.
Insect pests are major constraints in cowpea production. Breeding for insect resistance is a major objective of cowpea improvement programme at IITA. Resistance to leafhoppers and aphids has been incorporated in advanced breeding lines thus eliminating the need for other control measures. Similarly, a moderate level of resistance to thrips and cowpea storage weevil has also been incorporated thus reducing the damage due to these two pests. A moderate level of resistance to legume pod-borer and pod sucking bugs has also been identified and is being incorporated in advanced breeding lines. The long term strategy is to develop cowpea cultivars with multiple resistance to insect and diseases with superior agronomic characters and local adaptability.RésuméLes ravageurs constituent le principal facteur limitant dans le cadre de la production du niébé. C'est pourquoi le programme d'amélioration du niébé de l'Iita a placé la sélection pour la résistance aux insectes nuisibles au premier rang de ses priorités. Ainsi, il est parvenu à incorporer la résistance aux jassides et aux aphides à certaines lignées de sélection avancées, écartant de la sorte le recours à d'autres mesures de lutte. De même, on a pu réduire les dégâts imputables aux thrips et aux bruches des magasins en conférant au matériel de sélection un niveau modéré de résistance à ces deux insectes. Une source de résistance modérée aux foreuses des gousses et au complexe de punaises a également été identifiée, et l'on procède à l'heure actuelle à son incorporation dans des lignées de sélection avancées. La stratégie à long terme du programme consiste à mettre au point des cultivars du niébé dotés d'une résistance multiple aux ravageurs et aux maladies, dotés de caractères agronomiques supérieurs, et adaptés aux conditions locales.