Conference PaperPDF Available

Improvements in grain and fodder yield of cowpea (Vigna unguiculata) varieties developed in the Sudan savannas of Nigeria over the past four decades

Authors:

Abstract and Figures

A field study was conducted to determine the rate of genetic improvement in grain and fodder yields of cowpea genotypes developed in the Nigerian Sudan savannas from 1970 to 2004. Results showed that grain yield ranged from 568 kg/ha for an old variety TVX3236 to 1851 kg/ha for a recently released variety IT04K-321-2. The average rate of increase has been 28 kg/ha/year, which corresponds to a genetic gain of 3.6%. Fodder yield ranged from 1363 kg/ha for a variety released in 1976 (TVX1836-0131) to 3346 kg/ha for IT98k-476-8 released in 1998 corresponding to a genetic gain of 1.96%. This indicated that selection for dual-purpose cowpea varieties with increased fodder as well as grain yields has been successful. Total dry matter, fodder yield, harvest index, and 100-seed weight were significantly correlated with grain yield. The strong relationship between grain and fodder yields showed the success made in selecting for dual-purpose cowpea varieties.
Content may be subject to copyright.
179
Proceedings of the Fifth World Cowpea Conference
Improvements in grain and fodder yield of cowpea
(Vigna unguiculata) varieties developed in the Sudan
savannas of Nigeria over the past four decades
A.Y. Kamara1*, S.U. Ewansiha1, H.A. Ajeigbe1, R. Okechukwu1, H. Tefera2,
O. Boukar1 and L.O. Omoigui3
1International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, Nigeria
2IITA-Malawi, Chitedze Agricultural Research Station, PO Box 30258, Lilongwe, Malawi
3College of Agronomy, Department of Plant Breeding and Seed Science, University of Agriculture,
Makurdi, Nigeria
*Corresponding author: a.kamara@cgiar.org
Abstract
A eld study was conducted to determine the rate of genetic improvement in grain and
fodder yields of cowpea genotypes developed in the Nigerian Sudan savannas from 1970
to 2004. Results showed that grain yield ranged from 568 kg/ha for an old variety TVX3236
to 1851 kg/ha for a recently released variety IT04K-321-2. The average rate of increase
has been 28 kg/ha/year, which corresponds to a genetic gain of 3.6%. Fodder yield
ranged from 1363 kg/ha for a variety released in 1976 (TVX1836-0131) to 3346 kg/ha for
IT98k-476-8 released in 1998 corresponding to a genetic gain of 1.96%. This indicated that
selection for dual-purpose cowpea varieties with increased fodder as well as grain yields
has been successful. Total dry matter, fodder yield, harvest index, and 100-seed weight
were signicantly correlated with grain yield. The strong relationship between grain and
fodder yields showed the success made in selecting for dual-purpose cowpea varieties.
Introduction
Cowpea is a leguminous crop of vital importance to the livelihood of millions of people
in West and Central Africa. It provides nutritious grain and a less expensive source of
protein for both rural poor and urban consumers (Inaizumi et al. 1999). In addition to food
for humans, it is a valuable source of livestock fodder (Singh et al. 2003) making it very
attractive to farmers. Because of its ability to tolerate drought, cowpea is well adapted
to the semi-arid tropics. As a leguminous crop, cowpea improves soil fertility through its
ability to x atmospheric nitrogen (Sanginga et al. 2000). Together, these characteristics
have made cowpea an important component of the cropping systems of the dry savannas
of sub-Saharan Africa (Carsky et al. 2001). According to FAO statistics, cowpea is grown
on an estimated worldwide area of 14 million ha. Some 8 million ha of cowpea are grown
in West and Central Africa, especially in Burkina Faso, Cameroon, Mali, Niger, Nigeria,
and Senegal. In Nigeria, the production trend of cowpea shows a signicant improvement
with an increase of some 440% in area planted and an increase of some 410% in yield
over the period 1961 to 1995 (Ortiz 1998). According to Singh (2000), Nigeria produces
about 2 million tons of cowpea on 5 million ha of land. The production trend would have
moved upwards with the availability of more improved varieties and crop management
practices. Despite the potential for further yield increases, cowpea production faces
numerous problems including insect pest attack, Striga gesneroides parasitism, diseases,
and drought.
180 Innovative research along the cowpea value chain
Over the years, a great deal of progress has been made by IITA in breeding a range of high
yielding cowpea varieties with combined resistance to major diseases, insect pests, and
parasitic weeds and drought tolerance. Previously, from 1970 to 1988, cowpea research at
the IITA concentrated primarily on developing and distributing grain-type cowpea varieties,
which have been tested and released in many countries (Singh et al. 1997). Because
of the importance of cowpea grain and fodder in West Africa, IITA began a systematic
breeding program in 1989 to develop dual-purpose cowpea varieties (Singh et al. 2003).
This program combined breeding for high yield potential for grain as well as fodder with
resistance to major biotic and abiotic stresses. The general strategy is to develop a range
of cowpea varieties differing in growth habit and maturity, seed type, and for sole crop and
intercrop in different agroecologies (Singh et al. 2003). Since 1970, several cowpea lines
have been developed and distributed to partnership institutions in Nigeria and over 60 other
countries all over the world for evaluation and release (Singh 2000). Despite tremendous
improvement in cowpea yield over the past 40 years, there is still a wide gap between what
is obtained from the research station and that grown under on-farm conditions. However,
farmers that grow the improved varieties under well-managed conditions usually obtain
higher grain yields in the dry savannas of Nigeria. Ajeigbe et al. (2010 a, b) reported an
over 300% increase in the value of produce when improved cowpea varieties are used in
improved systems compared to local varieties under traditional systems. Although current
yield increases for most crops have resulted from the impact of both genetic and improved
crop husbandry, further improvement in yield may have to rely on genetic gains through
improvement in crop productivity per hectare or increased genetic tolerance to pests and
diseases (Francis 1991). This is because of high costs or non-availability of agrochemicals
and reduction in soil quality (Cassman 1999).
Plant breeders have been able to measure breeding progress by growing varieties
developed and released over a long period of time in the same environment (Tefera et
al. 2009). Evaluation of genetic improvement and the associated changes in agronomic
and physiological traits determining grain yield in crops may help identify traits of potential
value for future breeding. This kind of study has been undertaken for several major crops.
For example, Tefera et al. (2009) reported that grain yield potential of early maturing
soybean increased from 1117 to 1710 kg/ha during two decades of breeding in the Nigerian
savannas. Fodder yield also showed an annual increase of 22.8 kg per ha per year. Specht
et al. (1999) reported that soybean yields in the United States increased by 31.4 kg per ha
per year from 1972 to 1997. In Canada, a study on 41 early maturing soybean varieties
representing seven decades of breeding showed a yield improvement of 0.5% per year
with an associated decrease in protein content and improvement in lodging tolerance
(Voldeng et al. 1997). Kamara et al. (2004) reported a genetic gain of 0.41% per year for
maize varieties released from 1970 to 1999 in the Nigerian savannas. The increase was
associated with an increase in total biomass and kernel weight and reduction in plant
height and days to owering. No direct comparisons of grain yield potential and other
agronomic traits have been made for cowpea varieties developed in the Nigerian Sudan
savannas over the past four decades. Therefore, this study was carried out to determine
the rate of genetic improvement in grain and fodder yields and associated agronomic and
physiological changes.
181
Proceedings of the Fifth World Cowpea Conference
Materials and Methods
The eld experiments were conducted under rain-fed conditions in 2007 and 2008 at IITA
experimental station at Minjibr (12o 10’42N, 8o 39’ 33E, Alt. 453m) in the Sudan savanna of
northwest Nigeria (Table 1). A bulk soil sample was taken at the beginning of the trial and
analyzed for particle part analysis, N, P, K, and pH. Daily rainfall and minimum and maximum
temperature were also recorded.
Thirty-one medium-late maturing cowpea varieties (Table 2) representing cowpea varieties
developed for the Nigerian Sudan savannas from 1970 to 2004 were evaluated in this study.
These were best performing varieties selected to represent each decade. In both years, the trial
was laid out in a randomized complete block design with four replications. For all treatments,
prior to planting, each eld was disc-harrowed and ridged. The planting distance was 0.75 m
between rows and 0.25 m between plants. Three seeds of the cowpea varieties were sown and
later thinned to two plants per stand at two weeks after planting. Immediately after planting,
paraquat (1:1-dimethyl- 4, 4’-bipyridinium dichloride) was applied at the rate of 276 g a.i. L-1 to
control weeds. This was followed by hoe weeding three weeks later. Fertilizer at 15 kg each of N,
P and K was applied in the form of NPK 15:15:15 a week after planting. A standard formulation,
cypermethrin + dimethoate (Best Action) at the rate of 30 g +250 g a.i. L-1 was used to control
insect pests at ower bud formation, owering, and podding stages to control insect pests and
this was delivered with a knapsack sprayer.
Data were collected on days from sowing to when 50% of the number of plants per net plot
reached owering and to when 95% of the pods reached maturity. Mean number of pods per
plant, and total dry matter (leaf, stem, grain, and threshed pod) per plant were all taken from a
10-plant sample within the two central rows for each plot when the crop reached physiological
maturity. Harvest index was calculated by dividing grain weight per plant by total dry matter per
plant. Mean hundred seed weight was recorded for each plot. Grain yields were determined from
all plants harvested from two net 4-m-long central rows when the rst ush of pods was mature
and dry, and was reported on a 100% dry matter basis in kg/ha. Similarly, fodder yield was
based on all plants that were harvested from the two net central rows for each plot, sun dried to
constant weight, and calculated as kg/ha.
Analysis of variance and regression analysis were performed using PROC GLM and PROC
REG in SAS, respectively (SAS Institute 2003). Year and replications were treated as random
effects; varieties were treated as xed effects. In order to determine the annual rate of genetic
improvement for the period the varieties were released, linear regression analysis was used.
The regression analysis was based on the mean values of each trait for each variety against
the year of release for respective varieties. The ratio of genetic gain to the corresponding mean
values of the oldest varieties was used to estimate the relative gain of breeding for the period
1974–2004 (Tefera et al. 2010). Simple correlation coefcients were estimated between grain
yield and other traits.
Results and Discussion
Climate characteristics of the experimental site
In 2007, rains started in May, reached its peak in August, and ended in September with slight
shower. A total of 864.4 mm of rain was obtained in 34 rainy days (Table1). While in 2008 the
rains started in June, reached its peak in July, and ended in September with total rainfall of 698.3
mm in 41 rainy days. During the growth period, temperature ranged from a minimum of 23.05°C
to maximum of 31.48 °C in 2007 and minimum of 22.45 °C to maximum of 41.31 °C in 2008.
182 Innovative research along the cowpea value chain
Table 1. Rainfall and temperature at Mijibir during the trial period.
2007 2008
Month Rainfall Temperature Rainfall Temperature
(mm) (no) oC
(max)
oC
(min) (mm) (no) oC
(max)
oC
(min)
Jan 0 0 25.53 15.06 0 0 26.44 16.02
Feb 0 0 34.21 23.36 0 0 28.74 17.71
March 0 0 34.58 22.03 0 0 36.08 21.89
Apr 0 0 40 25.57 0 0 37.63 26.43
May 67.5 3 32.8 26.56 0 0 38.69 28.19
Jun 162.6 8 30.62 23.73 102.5 7 36.38 26.45
Jul 249.2 10 31.48 23.44 313.9 10 29.97 23.18
Aug 376 12 28.74 23.05 209.1 12 28.71 22.45
Sept 9.1 1 30.97 23.17 68.3 12 29.8 23.82
Oct 0 0 31.03 24.29 0 0 41.31 22.99
Nov 0 0 33.03 23.72 0 0 32.03 23.03
Dec 0 0 33.17 21.35 0 0 30.68 21.77
Total 864.4 693.8
Table 2. Cowpea varieties used for the evaluation.
Varieties Growth habit Year tested
IT00K-1207
IT00K-1263
IT00K-227-4
IT03K-316-1
IT03K-351-9
IT04K-217-5
IT04K-223-1
IT04K-321-2
IT04K-332-1
IT81D-985
IT81D-994
IT82D-889
IT84S-2246-4
IT86D-1010
IT86D-719
IT86D-721
IT87D-941-1
IT88D-867-11
IT89KD-391
IT90K-277-2
IT97K-1101-5
IT97K-461-4
IT97K-494-3
IT97K-499-35
IT98K-131-2
IT98K-476-8
IT98K-506-1
IT98K-628
TVx 3236 (SUVITA 4)
TVx 456-01F
TVx 66-24 (VITA 8)
TVx 1836-013J (VITA 10)
VITA 4 (TVu 1977-0D)
VITA 5 (TVu 4557)
Semi-determinate
Determinate
Determinate
Determinate
Semi-determinate
Semi-determinate
Semi-determinate
Semi-determinate
Determinate
Spreading
Semi-determinate
Determinate
Semi-determinate
Determinate
determinate
Determinate
Determinate
Semi-determinate
Semi-determinate
Semi-determinate
Determinate
Determinate
Determinate
Determinate
Semi-determinate
Semi-determinate
Determinate
Determinate
Semi-determinate
Determinate
Determinate
Determinate
Semi-determinate
Semi-determinate
2000
2000
2000
2003
2003
2004
2004
2004
2004
1981
1981
1982
1984
1986
1986
1986
1987
1988
1989
1990
1997
1997
1997
1997
1998
1998
1998
1998
1976
1975
1975
1976
1974
1974
183
Proceedings of the Fifth World Cowpea Conference
Variance analysis
Year and varietal effects were signicant for all the traits measured. Year × variety
interactions were signicant for all the traits except for harvest index which showed no
signicant interaction between year and variety (Table 3). The signicant year × variety
interaction was due to the differences in rainfall between the two years. Rainfall during
the growing period of cowpea (Table 1) was higher in 2007 than in 2008 both in amount
and distribution. The rainfall differences may have caused cross ranking of the cowpea
varieties between the two years. The signicant year effect for virtually all traits indicated
the sensitivity of the varieties to environmental factors that prevailed in the different
years. Tefera et al. (2009) reported similar year × variety interactive effects for most traits
measured in soybean in the Guinea savanna of Nigeria. Some of the varieties evaluated
have been reported to be tolerant to drought (Singh 2000) suggesting that they will perform
better in a year of low rainfall.
Table 3. Mean squares of 8 traits of cowpea varieties representing four decades of breeding
in the Nigerian Sudan savannas.
Source of
variation df Days to
owering Days to
maturity
Pod
(No./
plant)
Hundred
seed
weight
Total dry
matter
(No./plant) Grain yield
(kg/ha)
Fodder
yield
(kg/ha)
Harvest
index
Year
Variety
Year x Variety
Error
1
30
29
142
833.15***
117.86***
11.82***
1.69
2394.61***
264.61***
61.58***
3.76
89.18**
45.55***
33.68***
13.40
497.35***
33.79***
4.33**
2.36
6289.40***
794.29***
540.15***
153.11
105299.01ns
608187.04***
65638.61**
36605.94
1033735.21**
1615147.00***
1519372.85***
1519372.85
0.007**
0.012***
0.005
0.001
CV% 2.82 2.65 27.05 9.49 20.98 15.04 20.49 9.63
**Mean squares signicant at < 5% probability level
***Mean squares signicant at < 1% probability level
nsMean squares not signicant at 5% probability level
Mean performance of grain and fodder yields
Average grain yield ranged from 567.6 kg/ha for the variety released in 1976 (TVX3236)
to 1850.8 kg/ha for variety released in 2004 (IT04K-321-2) (Table 4). Grain yield showed
an increase from old to new varieties during the four decades of cowpea breeding at IITA
and this increase was signicantly associated with year of release (Figure 1). Average
grain yields of varieties released in the 2000s are 106% higher than that of varieties
released in the 1970s. The average rate of increase in grain yield was 28.2 kg/ha/yr (Fig.
1) corresponding to 3.6% (Table 5) annual genetic gain in yield. This gain is higher than
the 0.41% reported for maize (Kamara et al. 2004) and the 2.2 and 1.99% reported for
early and late maturing soybeans, respectively (Tefera et al. 2009; 2010) for the savannas
of northern Nigeria. This gain is also higher than the 1% gain reported for soybean in USA
(Wilcox et al. 1979) and the 0.5% reported for soybean in Canada during seven decades
of breeding (Voldeng et al. 1997). The result suggests that signicant progress has been
made in breeding cowpea for higher grain yield in the Nigerian savannas.
Fodder yield ranged from 1363 kg/ha for TVX1836-013J released in 1976 to 3346 kg/ha
for IT98K-476-8 released in 1998. There were signicant differences in fodder yield among
varieties and eras of release. Generally modern varieties showed higher fodder yield in
comparison to older varieties. Differences in fodder yield between the 1990 and 2000 were
however, not signicant. There was gain of 30.9 kg/ha/ yr (Fig. 2) with a genetic gain of
1.96% (Table 5). Top yielding varieties produced higher fodder yields (Table 4) suggesting
that efforts in breeding dual-purpose cowpea varieties at IITA have been a success.
184 Innovative research along the cowpea value chain
Table 4. Physiomorphological and yield characteristics of 31 cowpea varieties developed
over the past 40 years.
Year of
rst
testing
Variety
Days to
owering
Days to
maturity
Pod (No./
plant)
Hundred
seed
weight
Total dry
matter (No./
plant)
Grain yield
(kg/ha)
Fodder
yield
(kg /ha) HI
1974 VITA4 44.75 69.50 17.87 12.10 77.00 733.00 1868.75 0.29
1974 VITA5 46.50 69.00 13.88 14.00 55.50 660.00 1275.00 0.34
1975 TVX456-01F 40.67 63.17 11.41 17.53 39.70 780.98 1449.72 0.34
1975 TVX66-24 48.80 70.80 10.78 13.60 38.86 747.88 1675.00 0.31
1976 TVX1836-013J 42.60 63.60 10.58 13.60 48.54 862.64 1363.33 0.39
1976 TVX3236 46.83 69.33 14.27 11.33 43.20 567.60 1724.17 0.24
Mean 45.03 67.57 13.13 13.69 50.47 725.35 1559.33 0.32
SE (7 D.F.) 1.22 1.35 1.14 0.87 5.88 41.50 94.44 0.02
1981 IT81D-985 58.40 86.80 10.42 17.52 63.40 1199.33 2247.33 0.35
1981 IT81D-994 54.38 86.00 6.64 16.83 59.31 1107.57 2078.85 0.35
1982 IT82D-889 42.25 63.75 14.85 13.60 65.28 1034.07 1714.58 0.37
1984 IT84S-2246-4 47.00 73.00 11.58 14.25 43.61 930.69 1532.50 0.38
1986 IT86D-1010 41.50 66.83 12.15 17.40 51.68 1137.02 1779.44 0.39
1986 IT86D-719 45.43 78.57 13.08 12.51 52.59 1093.03 2177.38 0.34
1986 IT86D-721 46.25 76.88 13.56 15.60 64.92 1200.96 1880.00 0.39
1988 IT88D-867-11 45.86 74.71 12.65 19.03 59.04 1111.3 7 1837.62 0.38
1989 IT89KD-391 51.75 76.13 11.57 18.90 50.94 1195.56 1973.13 0.38
Mean 48.09 75.85 11.83 16.18 56.75 1112.18 1913.43 0.37
SE (41 D.F.) 1.88 2.55 0.78 0.78 2.49 29.46 76.52 0.01
1990 IT90K-277-2 45.63 70.63 16.74 16.60 61.66 1651.62 2202.08 0.43
1997 IT97K-461-4 37.17 64.33 15.12 18.20 53.55 1412.02 2531.39 0.36
1997 IT97K-494-3 44.63 68.00 17.42 15.50 55.73 1587.22 2155.00 0.42
1997 IT97K-499-35 42.13 70.75 12.80 16.10 57.41 1548.96 2444.38 0.39
1998 IT98K-128-3 48.67 74.33 16.37 15.60 81.40 1408.93 3213.97 0.31
1998 IT98K-131-2 46.33 71.83 18.70 14.93 69.79 1442.22 1799.44 0.45
1998 IT98K-476-8 48.63 79.13 13.78 16.45 71.63 1560.11 3346.48 0.32
1998 IT98K-506-1 42.00 66.13 13.19 17.90 49.35 1356.13 2085.21 0.40
1998 IT98K-628 39.00 65.29 14.86 15.54 51.29 1408.65 2005.95 0.41
Mean 43.80 70.05 15.44 16.31 61.31 1486.21 2420.43 0.39
SE (41 D.F.) 1.35 1.58 0.67 0.37 3.60 34.02 178.27 0.02
2000 IT00K-1207 47.86 83.43 14.19 13.83 57.46 1370.21 2048.69 0.40
2000 IT00K-1263 44.60 72.20 13.80 17.68 55.17 1398.90 2146.00 0.40
2000 IT00K-227-4 45.57 73.43 12.40 18.29 62.05 1194.39 1604.29 0.42
2003 IT03K-316-1 46.13 77.00 14.53 18.15 70.83 1707.70 2832.92 0.38
2004 IT04K-217-5 52.17 81.33 8.90 21.60 63.67 1349.49 2015.83 0.41
2004 IT04K-321-2 49.38 81.25 15.80 18.25 83.90 1850.77 2800.21 0.39
2004 IT04K-332-1 43.14 70.57 15.49 15.14 61.00 1582.42 2619.52 0.38
Mean 46.98 77.03 13.59 17.56 64.87 1493.41 2295.35 0.40
SE (28 D.F.) 1.16 1.92 0.89 0.94 3.69 86.71 175.10 0.01
Overall mean 46.00 72.83 13.53 16.05 58.69 1231.98 2078.33 0.37
Overall SE (139 D.F.)
0.79 1.18 0.47 0.42 2.01 59.05 89.86 0.01
This is important because of the increasing demand for cowpea fodder for animal feed
in the dry savannas of West Africa. Tefera et al. (2009) also reported signicant gains in
breeding dual-purpose soybean varieties in the Guinea savannas of Nigeria. Due to the
earlier emphasis on high grain yield, the improved varieties bred in the 1970s to early
185
Proceedings of the Fifth World Cowpea Conference
y = 28.193x + 772.72
R
2
= 0.782
500.00
700.00
900.00
1100.00
1300.00
1500.00
1700.00
1900.00
2100.00
0 5 10 15 20 25 30 35
Number of years since 1974
Grain yield (kg ha
-1
)
Figure 1. Relationship between grain yield of cowpea varieties and year of breeding
(expressed as number of years since 1974).
Table 5. Relative genetic gain, coefcients of determination (R2), slope and regression
coefcients (b) of grain and fodder yield from linear regression of the mean value of each
character for each variety against the year of rst testing for that variety.
Trait Relative genetic gain
(% per year) R2 a b
Grain yield
Fodder yield
3.65
1.96
0.78
0.41
772.72
1575.4
28.193**
30.873**
*signicant at 5% probability level (P < 0.05), **signicant at 1% probability level, ns = not signicant.
y = 30.873x + 1575.4
R2 = 0.405
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
0 5 10 15 20 25 30 35
Number of years since 1974
Figure 2. Relationship between fodder yield of cowpea varieties and year of breeding
(expressed as number of years since 1974).
186 Innovative research along the cowpea value chain
1980s were erect and were early-medium maturing (Singh and Sharma 1996). With good
management and heavy pod load, these varieties shed most of their leaves. The grain yields
of these varieties are therefore high but fodder yields are low (Singh et al. 2003) probably
because they have a short growth period for biomass accumulation and a greater harvest
index. To increase grain and fodder yields simultaneously, breeding emphasis shifted to
developing intermediate maturing varieties (75–80 days) with semi-erect growth habit and
canopy height of 30 cm or more. Such varieties which have been bred have enough time
for biomass accumulation but short enough maturity to escape terminal drought. These
varieties have yield potential of at least 2 t/ha grain and 2 t/ha fodder (Singh et al. 2003).
Mean performance of agronomic traits and association with grain yield
Signicant differences were found among the cowpea cultivars for number of pods per
plant, 100 seed weight, total dry matter, and harvest index (Table 4). There was no clear
trend in days to owering for all the varieties because early and late owering varieties were
found among both old and recent varieties. Three varieties (IT81D-985, IT81D-994, and
IT89KD-391) released in the 1980s were found to be signicantly late owering. Among
the recent varieties released in the 2000s, IT04K-217-5, IT04K-321-2 were found to be late
owering. Tefera et al. (2010) also reported that there was no consistent trend in days to
owering among old and new soybean varieties in the Nigerian Guinea savannas. There
were signicant differences between old and new varieties for days to maturity. Recent
varieties had higher number of days to maturity than varieties released in the 1970s. For
example, three varieties (IT04K-217-5, IT00K-1207, and IT04K-321-2) released in the
2000s were particularly late in maturity. This may be due to emphasis on dual-purpose
cowpea varieties since late 1980s (Singh et al. 2003). Number of pods per plant did not
show consistent change with era. For example, VITA 4, which was released in 1974 had
number of pods not signicantly different from that of 1T98K-131-2 released in 1998 which
produced the highest number of pods per plant. One hundred seed weight was signicantly
lower in varieties released in the 1970s compared to the other eras. Seed weight of varieties
released in the 1980s, 1990s, and 2000s did not however, differ signicantly suggesting
that no further progress was made in increasing seed weight after the 1970s.
Total dry matter per plant ranged from 38.86 g for TVX66-24 released in 1975 to 83.90
g for IT04K-321-2 released in 2004 (Table 4) indicating a signicant improvement in total
dry matter in the last 40 years. Several studies have reported a signicant genetic gain
in dry matter for grain crops (Kamara et al. 2004; Tollenaar 1991; Naylor et al. 1998).
Moreover, De Bruin and Pedersen (2009) reported that new cultivars of soybean produced
higher yields due to improved total dry matter accumulation, which is in agreement with
the present study. Averaged across varieties, mean harvest index (HI) was signicantly
lower for varieties released in the 1970s than those of the other eras. HI ranged from 0.24
for an old variety (TVX-3236) to 0.45 for a new variety (IT98K-131-2) released in 1998.
There were however, no signicant changes in HI from 1980 to 2004 probably due to the
emphasis on dual-purpose cowpea where breeders select for both grain and fodder yields.
This suggests that increasing HI will be at the expense of fodder yield. The rate of increase
of HI was therefore maintained at a low level. Tefera et al. (2009) reported modest changes
in HI for soybean over a 16-year period of breeding in the Nigerian savannas because
187
Proceedings of the Fifth World Cowpea Conference
the breeders selected for both grain and fodder yields. According to Singh et al. (2003),
cowpea breeders have shifted their focus to selecting for dual-type varieties since the late
1980s because of the increasing importance of cowpea for fodder.
Grain yield showed a positive and signicant correlation with fodder yield, harvest index,
total dry matter per plant, and hundred seed weight (Table 6). The strong association of grain
and fodder yields indicated that improvement has been made for both traits. This strong
association is also expected because cowpea breeders at IITA have been continuously
selecting for dual-purpose cowpea since the late 1980s (Singh et al. 2003). The same
trend has been observed in early and late maturing dual-purpose soybean varieties in the
savannas of Nigeria (Tefera et al. 2009; 2010). The strong association of grain yield with total
dry matter and HI suggests that grain yield improvement was partly due to improvement in
dry matter and HI. Kamara et al. (2004) attributed genetic gain in grain yield of maize in the
savannas of Nigeria to improvement in dry matter accumulation. Similarly, Tollenaar (1989)
attributed genetic gain in Central Ontario maize hybrids to improvement in dry matter
production but HI did not change between eras. The positive correlation of grain yield with
HI may be due to the deliberate emphasis on breeding cowpea for both grain and fodder.
Similarly Tefera et al. (2009) reported a positive correlation of soybean grain yield with HI in
the Nigerian savannas also because of breeding emphasis on both grain and fodder yields.
Table 6. Mean values and correlation coefcients of traits with grain yield of cowpea
varieties representing four decades of breeding in the Nigerian Sudan savannas.
1974–2004
Trait Mean Correlation coefcient (r)
Days to owering
Days to maturity
Grain yield
Fodder yield
Harvest index
Total dry matter per plant
Hundred seed weight
Number of pods per plant
46.00
72.83
1231.98
2078.33
0.37
58.69
16.05
13.53
–0.011
0.273
–0.742**
0.587**
0.529**
0.498**
0.348
*Correlation coefcients signicant at 1% probability level.
Conclusion
A study of 31 medium to late maturing varieties of cowpea released in 1970–2004 showed
that grain yield ranged from 568 kg/ha for an old variety TVX3236 to 1851 kg/ha for a
recently released variety IT04K-321-2. The average rate of increase has been 28 kg/ha/
year, which matches to a genetic gain of 3.6%. Fodder yield ranged from 1275 kg/ha for
a variety released in 1974 (VITA5) to 3346 kg//ha for IT98K-476-8 released in 1998. The
genetic gain in fodder yield was 1.96% which indicated that selection for dual-purpose
cowpea varieties with increased fodder as well as grain yields has been successful. Total
dry matter, fodder yield, harvest index, and 100 seed weight were signicantly correlated
with grain yield. The strong relationship between grain and fodder yields showed the
success made in selecting for dual-purpose cowpea varieties.
188 Innovative research along the cowpea value chain
References
Ajeigbe, H.A., B.B. Singh, J.O. Adeosun, and I.E. Ezeaku. 2010a. Participatory on-farm evaluation
of improved legume–cereals cropping systems for crop–livestock farmers: Maize-double cowpea
in Northern Guinea Savanna Zone of Nigeria. African Journal of Agricultural Research 5(16):
2080–2088. Available online at http://www.academicjournals.org/AJAR.
Ajeigbe, H.A., B.B. Singh, I.E. Ezeaku, and J.O. Adeosun. 2010b. On-farm evaluation of improved
cowpea–cereals cropping systems for crop–livestock farmers: Cereals-cowpea systems in Sudan
Savanna zone of Nigeria. African Journal of Agricultural Research 5(17): 2297–2304. Available
online at http://www.academicjournals.org/AJAR.
Carsky, R.J., B.B. Singh, and B. Oyewole. 2001. Contribution of early season cowpea to late season
maize in the savanna zone of West Africa. Biological Agriculture and Horticulture 18: 303–316.
Cassman, K.G. 1999. Ecological intensication of cereal production systems: yield potential, soil
quality and precision agriculture. Proceedings National Academy of Sciences USA 96: 59525959.
De Bruin, J. L. and P. Pedersen. 2009. Growth, yield, and yield component changes among old and
new soybean cultivars. Agronomy Journal 101: 123–130.
Francis, C.A. 1991. Contribution of plant breeding to future cropping systems. Pages 83–93 in Plant
Breeding and Sustainable Agriculture: Considerations for Objectives and Methods, edited by D.A.
Sleper, T.C. Baker, and P.J. Bramel-Cox. Crop Science Society of America Special Publication
No. 18, CSSA and ASA, Wisconsin, USA.
Iniazumi, H., B.B. Singh, P.C. Sanginga, V.M Manyong, A.A Adeshina, and S.A. Tarawali. 1999.
Adoption and impact of dry-season dual-purpose cowpea in the semi-arid zone of Nigeria. Page
14 in IMPACT. International Institute of Tropical Agriculture, Ibadan, Nigeria.,
Kamara A.Y., A. Menkir, M.A.B Fakorede, S.O. Ajala, B. Badu-Apraku, and I. Kureh. 2004. Agronomic
performance of maize varieties representing three decades of breeding in the Guinea Savannas
of West and Central Africa. Journal of Agricultural Science 142: 567–575.
Naylor, R.E.L., D.T. Stokes, and S. Matthews. 1998. Biomass, shoot uniformity and yield of winter
barley. Journal of Agricultural Science, Cambridge 131: 13–21.
Ortiz, R. 1998. Cowpeas from Nigeria: A silent food revolution. Outlook on Agriculture 27(2): 125–128.
Sanginga, N., G. Thottappilly, and K. E. Dashiell. 2000. Effectiveness of rhizobia nodulating recent
promiscuous soybean selections in the moist savanna of Nigeria. Soil Biology and Biochemistry
32: 127–133.
SAS Institute. 2003. The SAS system for Windows. Release 9.1. SAS Inst. Cary NC
Singh, B.B. 2000. Breeding cowpea varieties for wide adaptation by minimizing cultvar × environment
interactions. Pages 173–181 in Cultivar × Environment Interactions Analysis of IITA Mandate
Crops in Sub-Saharan Africa, edited by I.J. Ekanayake and R. Ortiz. International Institute of
Tropical Agriculture, Ibadan, Nigeria.
Singh, B.B., H.A. Ajeigbe, S.A. Tarawali, S. Fernandez-Rivera, and A. Musa. 2003. Improving the
production and utilization of cowpea as food and fodder. Field Crops Research 84: 167–177.
Singh, B. B., O.L. Chamliss, and B. Sharma. 1997. Recent advances in cowpea breeding. Pages
30–49 in Advances in cowpea research, edited by B.B. Singh, D.R. Mohan Raj, K.E. Dashiell, and
L.E.N. Jackai. Copublication IITA and JIRCAS. IITA, Ibadan, Nigeria.
Singh, B.B. and H. Sharma. 1996. Restructuring cowpea for higher yield. Indian Journal of Genetics
56: 389–405.
Specht, J. E., D.J. Hume, and S.V. Kumudini. 1999. Soybean yield potential: A genetic and
physiological perspective. Crop Science 39: 1560–1570.
Tefera, H., A.Y. Kamara, B.Asafo-Adjei, and K.E. Dashiell. 2009. Improvements in grain and fodder
yields of early maturing promiscuous soybean varieties in the Guinea savannas of Nigeria. Crop
Science 49: 2037–2042.
Tefera, H., A.Y. Kamara, B. Asafo-Adjei, and K.E. Dashiell. 2010. Breeding progress for grain yield
and associated traits in medium and late maturing promiscuous soybean. Euphytica 175: 251–
260.
Tollenaar, M. 1989. Genetic improvement in grain yield of commercial maize hybrids grown in Ontario
from 1959 to 1988. Crop Science 29: 13651371.
Tollenaar, M. 1991. Physiological basis of genetic improvement of maize hybrids in Ontario from
1959 to 1988. Crop Science 31: 119–124.
Voldeng, H.D., E.R. Cober, D.J Hume, C. Gillard, and M.J. Morrison. 1997. Fifty-eight years of genetic
improvement of short season soybean cultivars in Canada. Crop Science 37: 428–431.
Wilcox, J.R., W.T. Schapaugh, Jr., R.L. Bernard, R.L. Cooper, W.R. Fehr and M.H. Niehaus. 1979.
Genetic improvement of soybean in the Midwest. Crop Science 19: 803–805.
... Cowpea, in Africa and parts of Asia and the American countries, is called 'the poor man's meat' as it is a significant and cheap source of protein, minerals, and vitamins [77] for rural poor people who have limited access to protein from animal sources such as meat and fish [48,49]. It is a nutritious food source, as it is rich in protein and minerals, digestible and nondigestible carbohydrates, and potassium and has a very low lipid and sodium content [77,78]. ...
... According to previous studies, the amount and availability of minerals in cowpea leaves and immature pods are much higher than in the grain ( Table 2). The availability of some minerals like P, K, and Mn in cowpea grain varies widely due to environmental conditions [78]. Macro and micronutrients are essential for the physiological functions of the human body [94]. ...
Article
Full-text available
Currently, the world population is increasing, and humanity is facing food and nutritional scarcity. Climate change and variability are a major threat to global food and nutritional security, reducing crop productivity in the tropical and subtropical regions of the globe. Cowpea has the potential to make a significant contribution to global food and nutritional security. In addition, it can be part of a sustainable food system, being a genetic resource for future crop improvement, contributing to resilience and improving agricultural sustainability under climate change conditions. In malnutrition prone regions of sub-Saharan Africa (SSA) countries, cowpea has become a strategic dryland legume crop for addressing food insecurity and malnutrition. Therefore, this review aims to assess the contribution of cowpea to SSA countries as a climate-resilient crop and the existing production challenges and perspectives. Cowpea leaves and immature pods are rich in diverse nutrients, with high levels of protein, vitamins, macro and micronutrients, minerals, fiber, and carbohydrates compared to its grain. In addition, cowpea is truly a multifunctional crop for maintaining good health and for reducing non-communicable human diseases. However, as a leafy vegetable , cowpea has not been researched and promoted sufficiently because it has not been promoted as a food security crop due to its low yield potential, susceptibility to biotic and abiotic stresses, quality assurance issues, policy regulation, and cultural beliefs (it is considered a livestock feed). The development of superior cowpea as a leafy vegetable can be approached in different ways, such as conventional breeding and gene stacking, speed breeding, mutation breeding, space breeding, demand-led breeding, a pan-omics approach, and local government policies. The successful breeding of cowpea genotypes that are high-yielding with a good nutritional value as well as having resistance to biotics and tolerant to abiotic stress could also be used to address food security and malnutrition-related challenges in sub-Saharan Africa.
... The paternal parent, IT98K-476-8, was developed by IITA (International Institute of Tropical Agriculture) in Africa in 1998. It was developed as a dual purpose variety with increased grain and fodder yields (Kamara et al. 2010). The two parents are genetically different for several traits. ...
Article
Full-text available
Cowpea is an important pulse crop in the world. As with other leguminous crops, cowpea shows severe leaf chlorosis, when grown in calcareous soil. This study aimed to identify quantitative trait loci (QTLs) controlling iron deficiency chlorosis (qIDC) using a recombinant inbred line (F7:8) biparental mapping population derived from IDC tolerant parent, IT98K-476-8, and IDC susceptible parent, Golden Eye Cream. Phenotyping the population for IDC was done in calcareous soil at Corpus Christi and Weslaco by visible ranking and at Uvalde in the southern Texas, USA with a chlorophyll meter at four developmental stages. Genotyping-by-sequencing (GBS) was used to generate genotypic data. The QTL analysis was carried out on R/qtl and IciMapping v4.0 software. A total of eight QTLs were identified, including one environment-consistent QTL, one development-consistent QTL, two environment-specific QTLs, and four development-specific QTLs. Of these QTLs, sqIDC10.1 (LOD = 5.50) detected on chromosome 10 has the largest effect on IDC explaining 18.0% of the observed IDC phenotypic variation. From the qIDC10.1 interval, three adjacent putative genes, Iron Regulated1/Ferroportin 1 (IREG1/FPN1), IREG2/FPN2, and 2-oxoglutarate/Fe(II)-dependent dioxygenase-like (2-ODD), were identified, which may play important roles in IDC of cowpea. The IDC QTLs and putative genes identified herein provide necessary tools and gene resources not only for enhanced IDC tolerance breeding, but also for cloning and characterizing the genes involved in IDC in cowpea and related species.
... It is one of the most important legumes plants, considering a cheapest plant protein sources in the world. The protein content of cowpea seeds range between 22-33%, while the carbohydrates range 56.5-57.4% (Abudulai et al, 2016;Al-Furtuse et al, 2019), it is a valuable source of livestock fodder making (Kamara et al, 2012). It plays an important role in improving the soil fertility by the biological nitrogen fixation in the presence of specialized rhizobia (Nulik, 2013). ...
Article
Full-text available
A field experiment was conducted to evaluate the response of two cowpea varieties (Max and Ramshorn) to microbial inoculation (with and without inoculation) and four micronutrients fertilizer (control, 4 kg Fe ha-1 as FeEDDHA, 1 kg B ha-1 as boric acid and blend of 4 kg Fe ha-1 + 1 kg B ha-1). The experiment was a 4×2×2 factorial combination designed as factorial within split in randomized complete block design (RCBD) with three replicates. Ramshorn variety produced the highest no. of nodules in plant and their weight, no. of pods plant-1 , weight of 500 seeds and seeds yield, which were 31.54 nodule plant-1 , 143.7 mg, 25.49 pods Plant-1 , 136.6 g and 3512.9 kg ha-1 , respectively. Microbial inoculation treatment produced the highest no. of nodules, their weight, seeds pod-1 and seeds yield, which were (33.92 nodule plant-1 , 162.2 mg, 8.02 seed pod-1 and 3462.2 kg ha-1 , respectively. The results showed that micronutrients (Iron + Boron) had a significant effect on number of nodules and weight (34.50 nodules and 159.2 mg), seeds pod-1 (8.25) and seeds yield (3598.5 kg ha-1). The highest values of seed yield were obtained by using (Ramshorn var. * microbial inoculation * (iron + boron)), which recorded 4562.1 kg ha-1 .
... Protein content of cowpea leaves range from 27 to 43% and protein concentration of the dry grain range from 21 to 33% (Ahenkora et al., 1998;Ddamulira et al., 2015;Abudulai et al., 2016). Cowpea is a valuable source of livestock fodder making the dual purpose cultivars very attractive to farmers (Singh et al., 2003;Kamara et al., 2012). It is drought tolerant and adapted to stressful environments where many crops fail to grow well (Bisikwa et al., 2014;Ddamulira et al., 2015). ...
Article
Full-text available
In Chittoor dt, Cowpea has been grown in an area of 200 ha. But farmers are growing local non-descriptive varieties which are highly susceptible to pests and diseases and also pod and seed size are smaller which is reducing market value and also increasing cost of cultivation. In order to overcome these problems a new variety of Cowpea TPTC 29 (Tirupati Cowpea 1), released in the year 2017 by RARS, Tirupati was introduced in the district by Krishi Vigyan Kendra Kalikiri by conducting On Farm Trials and Front Line Demonstrations in farmers fields. This variety matures in 80-90 days, not sensitive to light. It is used as vegetable and also for seed purpose because of its long pod and bold seed. It has yield potential of 1000-1100 kg/ha. KVK, Kalikiri assessed the performance of TPTC 29 over Meghana in Front Line Demonstrations from 2018-19 to 2020-21. Yield attributes and yield are higher in TPTC 29 compared to Meghana. Yield of TPTC 29 and Meghana were 9.0 q ha-1 and 7.7 q ha-1 respectively. Net returns and B:C ratio of TPTC 29 28763 Rs ha-1 and 1:2.15, respectively. Whereas, Meghana recorded net returns and B:C ratio of 20263 Rs ha-1 and 1:1.79, respectively.
... Cowpea predominance in the dry zones of Africa is attributable to its inherent drought tolerance and capability to grow in marginalized soils where other crops fail (Ehlers and Hall 1997;Ewansiha and Singh 2006;Agbicodo et al. 2009;Hall et al. 2010;Fatokun et al. 2012). In the dry savannas of West Africa, cowpea is regarded as a dual purpose crop providing both human food and animal fodder (Singh et al. 2003;Kamara et al. 2012). Additional attractiveness of cowpea is seen in its ability to fix nitrogen in the soil, making it a key component of the traditional intercropping systems (Kyei-Boahen et al. 2017). ...
Article
Full-text available
The objective of this study was to determine genetic potentials in eight sets of cowpea lines for grain yield (GY), hundred seed weight (HSDWT) and days to 50% flowering (DT50FL). A total of 614 F6 genotypes constituting the sets, grouped by maturity, were evaluated across two locations in Northern Nigeria, in an alpha lattice design, two replications each. Data were recorded on GY, HSDWT and DT50FL.Variance components, genotypic coefficient of variation (GCV), and genetic advance (GA) were used to decode the magnitude of genetic variance within and among sets. Genetic usefulness (Up) which depends on mean and variance to score the genetic merits in historically bi-parental populations was applied to groups of breeding lines with mixed parentage. Principal component analysis (PCA) was used to depict contribution of traits to observed variations. GY and DT50FL explained the variance within and between sets respectively. Genotypes were significantly different, although genotype-by-location and set-by-location interaction effects were also prominent. Genetic variance (δ2G) and GCV were high for GY in Prelim2 (δ2G = 45,897; GCV = 19.58%), HSDWT in Prelim11 (δ2G = 7.137; GCV = 17.07%) and DT50F in Prelim5 (δ2G = 4.54; GCV = 4.4%). Heritability varied among sets for GY (H = 0.21 to 0.57), HSDWT (H = 0.76 to 0.93) and DT50FL (H = 0.20 to 0.81). GA and percentage GA (GAPM) were high for GY in Prelim2 (GAPM = 24.59%; GA = 269.05Kg/ha), HSDWT in Prelim11 (GAPM = 28.54%; GA = 4.47 g), and DT50F in Prelim10 (GAPM = 6.49%; GA = 3.01 days). These sets also registered high values of genetic usefulness, suggesting potential application in non-full sib populations. These approaches can be used during preliminary performance tests to reinforce decisions in extracting promising lines and choose among defined groups of lines.
... Cowpea predominance in the dry zones of Africa is attributable to its inherent drought tolerance and capability to grow in marginalized soils where other crops fail (Ehlers and Hall 1997;Ewansiha and Singh 2006;Agbicodo et al. 2009;Hall et al. 2010;Fatokun et al. 2012). In the dry savannas of West Africa, cowpea is regarded as a dual purpose crop providing both human food and animal fodder (Singh et al. 2003;Kamara et al. 2012). Additional attractiveness of cowpea is seen in its ability to fix nitrogen in the soil, making it a key component of the traditional intercropping systems (Kyei-Boahen et al. 2017). ...
Article
Full-text available
The objective of this study was to determine genetic potentials in eight sets of cowpea lines for grain yield (GY), hundred seed weight (HSDWT) and days to 50% flowering (DT50FL). A total of 614 F6 genotypes constituting the sets, grouped by maturity, were evaluated across two locations in Northern Nigeria, in an alpha lattice design, two replications each. Data were recorded on GY, HSDWT and DT50FL.Variance components, genotypic coefficient of variation (GCV), and genetic advance (GA) were used to decode the magnitude of genetic variance within and among sets. Genetic usefulness (Up) which depends on mean and variance to score the genetic merits in historically bi-parental populations was applied to groups of breeding lines with mixed parentage. Principal component analysis (PCA) was used to depict contribution of traits to observed variations. GY and DT50FL explained the variance within and between sets respectively. Genotypes were significantly different, although genotype-by-location and set-by-location interaction effects were also prominent. Genetic variance (δ2G) and GCV were high for GY in Prelim2 (δ2G = 45,897; GCV = 19.58%), HSDWT in Prelim11 (δ2G = 7.137; GCV = 17.07%) and DT50F in Prelim5 (δ2G = 4.54; GCV = 4.4%). Heritability varied among sets for GY (H = 0.21 to 0.57), HSDWT (H = 0.76 to 0.93) and DT50FL (H = 0.20 to 0.81). GA and percentage GA (GAPM) were high for GY in Prelim2 (GAPM = 24.59%; GA = 269.05Kg/ha), HSDWT in Prelim11 (GAPM = 28.54%; GA = 4.47 g), and DT50F in Prelim10 (GAPM = 6.49%; GA = 3.01 days). These sets also registered high values of genetic usefulness, suggesting potential application in non-full sib populations. These approaches can be used during preliminary performance tests to reinforce decisions in extracting promising lines and choose among defined groups of lines. Supplementary information: The online version contains supplementary material available at (10.1007/s10681-020-02763-y).
... It is truly a multifunctional crop, providing food for man and livestock, serving as a valuable and dependable revenue-generating commodity for farmers and grain traders [18-19-20] . Cowpea is also an important component of the traditional cropping systems because it fixes atmospheric nitrogen and contributes to soil fertility improvement particularly in smallholder farming systems where little or no fertilizer is used [21][22] . It is drought tolerant and adapted to stressful environments where many crops fail to grow well . ...
... IT98K-476-8 was developed by IITA (International Institute of Tropical Agriculture) in Africa in 1998. It was developed as a dual-purpose variety, with an increased grain and fodder yield (Kamara et al. 2011), and is cultivated for grains and fodder in West Africa. The two parental varieties are polymorphic for several traits. ...
Article
Full-text available
Cowpea (Vigna unguiculate (L.) Walp.) is a worldwide important multifunctional legume crop for food grain, vegetable, fodder, and cover crop. Nevertheless, only limited research has been conducted on agronomic traits. Here, we report quantitative trait locus (QTL) analysis of the days to flowering (DTF) and plant height (PH) using a dense SNP linkage map recently developed from a recombinant inbred line (RIL) population derived from a cross between Golden Eye Cream and IT98K-476-8. The population was phenotyped for DTF and PH through field and greenhouse trials under two environments. The QTLs controlling these traits were mapped using multiple-environment combined and individual trial phenotypic data. The combined data analysis identified one major QTL (qDTF9.1) for DTF, and one major QTL (qPH9.1) and a minor QTL (qPH4.1) for PH. qDTF9.1 and qPH9.1 were adjacent to each other on Chromosome 9 and each explained 29.3% and 29.5% of the phenotypic variation (PVE), respectively. The individual trial data analysis identified a minor QTL (qDTF2.1) on Chromosome 2 for DTF and two minor QTLs (qPH4.1 and qPH4.2) on Chromosome 4 for PH, while the major QTLs, qDTF9.1 and qPH9.1, were consistently identified in all trials conducted. Epistasis analysis revealed that qDTF9.1 interacted with one locus on Chromosome 4, contributed 50% of the PVE, and qPH9.1 interacted with one locus on each of Chromosomes 4 and 6, contributing 30% and 23% of the PVE, respectively, suggesting that epistasis plays an important role in the trait performance. These results, therefore, provide a deeper understanding of the genetic architecture of plant DTF and PH, and molecular tools necessary for cloning the genes and for enhanced cowpea breeding.
Article
Full-text available
In West Africa, cowpea (Vigna unguiculata) is an important source of protein for many people. To meet the protein demands, the cowpea yields per unit area and its seed protein content must be increased. We evaluated the effects of the planting density and topdressing (fertilisation) timing on the cowpea yield and its protein content. High density (HD: 40 × 40 cm) and super high density (SHD: 40 × 20 cm) plantings were the most efficient approaches for enhancing cowpea yields. Across different regions in Burkina Faso, under such approaches, the yield significantly increased by as much as 214.5%, with an average value of 88.9%. Fertilisation was not required to achieve the significant increases in cowpea production following dense planting. Although the yield increased, the seed weight per plant decreased with the increase in planting density. Applying topdressing when the plants started flowering increased the seed protein content significantly by up to 24.4%. Simple and robust technologies, such as high-density planting and topdressing, can be rapidly disseminated for increased cowpea yields and protein content improvement for Burkina Faso and for other countries
Article
Full-text available
Cowpea is a staple food crop and a primary source of protein for millions of people in developing countries. Although the crop is primarily cultivated for its mature grains, immature green pods and young green leaves can be consumed as a vegetable. The International Institute of Tropical Agriculture (IITA) was established in 1967; the organisation's extensive research has developed many improved varieties of most staple food crops to benefit people across Africa. For example, more than 100 IITA-bred materials and numerous germplasm lines of cowpea from the Genetic Resource Center (GRC) of IITA which is a mandate crop have been distributed across sub-Saharan Africa. Currently, IITA GRC houses one of the largest global cowpea collections of over 17,000 accessions from 89 countries. Here, we review the diverse approaches undertaken in cowpea research to evaluate the wide genetic resources of IITA for the development of new varieties and their successful dissemination. Notably, Japanese scientists have made constructive contributions to the progress in cowpea research at IITA over the past 50 years. Finally, in terms of research for development, collaborative measures among various national and international stakeholders for the appropriate delivery and social implementation of research achievements in the future are discussed.
Article
Full-text available
Cowpeas (Vigna unguiculata (L.) Walp.) are an important native African legume crop, whose seeds are sold in local urban and rural markets. West Africa is the main centre of diversity for cowpeas. Nigeria is the world's largest producer and second in acreage. The production trend shows a significant improvement of cowpea cultivation in this country from 1961 to 1995. In this period, Nigerian cowpea production increased by 441% according to available statistics of the United Nations Food and Agriculture Organization (FAO). This paper discusses the evolution of cowpea production from the early 1960s until recent years in Nigeria, along with new technology for cultivation (for example, improved cultivars) of this crop developed by the International Institute of Tropical Agriculture (IITA) in Nigeria.
Article
Full-text available
Soybean (Glycine max (L.) Merr.) yield has increased at a rate of 25 to 30 kg ha-1 yr-1 due in part to improved genetic gain, and has been further advanced by the addition of resistance to soybean cyst nematode (Heterodera glycines Ichinohe; SCN) in new cultivars. Th e objective was to determine specifi c growth changes that explain the yield improvement from old to new cultivars and the further yield improvement gained from the addition of SCN resistance. Studies were conducted at three Iowa locations during 2005 and 2006. Two old and two new SCN-susceptible, and two new SCN-resistant cultivars were evaluated for total dry matter (TDM) accumulation and leaf area index (LAI) through the season along with yield and yield components at harvest. New cultivars produced yields superior to older cultivars due to increased crop growth rate (CGR) culminating in greater TDM 105 days aft er emergence (DAE). Yield was strongly associated with the number of seeds produced m-2 and this yield component accounted for almost all of the yield diff erences among cultivars. Seeds m-2 was positively related to CGR between 42 and 105 (growth stage R1-R5.5) DAE and to LAI 105 DAE. New SCN-resistant cultivars produced yields 17 to 19% greater than new susceptible cultivars across three locations. Increased TDM and CGR explained the yield response at the low-yield location, but not at the high-yield locations. Apparent harvest index (HI) was similar among all cultivars at each location. Selection for increased yield has indirectly selected for increased TDM and CGR with a similar amount partitioned to seed dry weight. Future yield gains will be made by (i) increasing the amount and the rate of dry matter (DM) and (ii) through the increased production and duration of leaf area.
Article
Full-text available
Soybean [Glycine max (L.) Merr.] yields in the USA have risen 22.6 kg ha-1 yr-1 from 1924 to 1997, but in the last quarter century (1972-1997) have risen 40% faster, 31.4 kg ha-1 yr-1. This upward trend in on-farm yield is fueled by rapid producer adoption of technologies emerging from agricultural research. Published estimates of the annual gain in yield attributable to genetic improvement averaged about 15 kg ha-1 yr-1 prior to the 1980s, but is now averaging about 30 kg ha-1 yr-1 in both the public and proprietary sectors. Periodic advances in agronomic technology, and a relentless rise in atmospheric CO2 (currently 1.5 μL L-1 yr-1), also contribute to the upward trend in on-farm yield. In Nebraska, irrigated yield averages 800 kg ha-1 more than rainfed yield, and is improving at a 40% faster annual rate (35.1 vs. 24.9 kg ha-1). About 36% of the annual variation in the irrigated-rainfed yield difference is attributable to annual variation in absolute rainfed yield. Inadequate water obviously limits absolute crop yield, but also seems to be an obstacle in terms of the rate of yield improvement. Several physiological traits changed during six decades of cultivar releases in Ontario that led to a genetic gain in yield of about 0.5% yr-1. Changes in some traits were obvious (improved lodging), but more subtle in others (greater N2-fixation, greater stress tolerance). In terms of photosynthate supplied to sinks across a wide range of environments, recent cultivars seem to be superior to obsolete ones. To sustain and enhance soybean yield improvement in the future, technological innovation must be continually injected into the agricultural enterprise.
Article
Cowpea (Vigna unguiculata (L.) Walp.) is an important food legume and an integral part of traditional cropping systems in the semi-arid regions of the tropics. The estimated worldwide area under cowpea is about 14 million ha of which West Africa alone accounts for about 9.3 million ha with annual production of about 2.9 Mt. Cowpea grains are consumed as food and the haulms are fed to livestock as a nutritious fodder. Farmers often grow a short-duration spreading variety for grain and a long-duration spreading variety for fodder, but the grain and fodder yields are poor due to low yield potential of the spreading varieties and also due to early cessation of rains. Therefore, IITA in collaboration with ILRI has initiated a systematic programme to develop medium-maturing, semi-erect, dual-purpose varieties with higher grain and fodder yields and with enhanced fodder quality. By crossing the late, traditional spreading varieties with improved early, semi-erect varieties, a semi-erect group of medium-maturing, dual-purpose varieties has been developed which yield over 1.5 t ha−1 grain and 2.5 t ha−1 haulms. Despite the high grain and fodder yields, the haulms of improved dual-purpose varieties have similar crude protein content (17–18%) and dry matter digestibility (64–71%) compared to the local varieties. Controlled sheep feeding experiments have shown an average live weight gain of about 80 g per animal per day with 200–400 g per day of cowpea haulms as a supplement to a basal diet of sorghum stover. This was 100% higher than the average live weight gain of animals fed sorghum fodder alone. These results indicate that improved dual-purpose varieties can play an important role in enhancing crop–livestock integration in West Africa.
Article
Soybean [Glycine max (L.) Merr.] production in short-season areas has increased greatly because of improvements in cultivars and production practices. Previous studies of genetic improvement in soybean have reported yield increases of 0.5 to 1% per year. To evaluate the genetic improvement of short-season germplasm, 41 cultivars ranging from maturity group 000 to 0, released from 1934 to 1992, were grown for 8 station-years in Ontario and Quebec. Yield, maturity, plant height, lodging score, 100-seed weight, seed protein and oil levels, and yield stability were regressed on year of release to determine if improvements have been made. Yield has been improved about 0.5% per year during the period under study; however, since 1976 yield has been improved about 0.7% per year. There is evidence that the rate of genetic improvement of seed yield is accelerating. Significant lodging reduction was also observed. Seed protein levels hove been reduced 4 g kg-1 yr-1 and seed oil levels have increased 4 g kg-1 yr-1. Although yield has been increased, yield stability has remained constant.
Article
The optimum plant density for total grain yield increased from old to more recent hybrids, but the increase in optimum plant density did not continue for hybrids from the 1970s era to hybrids of the 1980s era. Approximately one-third of the genetic gain in machine-harvestable grain yield can be attributed to reduced stem lodging. A comparison of the oldest and most recent hybrids indicates that approximately 15% of the genetic gain in total grain yield can be attributed to increased harvest index. Consequently, increase in total dry matter accumulation attributed 85% to the genetic gain in total grain yield
Article
The ability of soybean to nodulate with a wide range of indigenous bradyrhizobia has been used in a breeding programme since 1997 in Nigeria. As far as is known, these indigenous bradyrhizobia strains have not been tested for compatibility and effectiveness with recent selections from a breeding programme which has proceeded without input from soil microbiologists for the last 20 yr. Twenty bradyrhizobia strains isolated from soyabean and cowpea grown in Ibadan and Zaria soils in Nigeria were examined in a pot experiment for symbiotic effectiveness on two promiscuous soyabean breeding lines (TGX 1660-19F and TGX 1456-2E) and a cowpea cultivar (IT 849-92). Two bradyrhizobial isolates (R25B and IRj 2180A) had an average symbiotic effectiveness (SE) of 2.36-fold and 1.62-fold of the uninoculated control when inoculated on 1456-2E and 1660-19F, respectively. These strains, however, were less effective on cowpea having a SE of 1.20-fold. Cowpea bradyrhizobia inoculated on promiscuous soyabeans produced less than 77 nodules plant−1 compared to an average of 120 by the two best bradyrhizobia strains from soyabean. The best isolates (R25B, IRj 2180A and their mixture) and one cowpea bradyrhizobia (IRc 461) were further tested on these lines under field conditions at three sites in different agroecological zones in moist savanna (Fashola, Mokwa and Zaria) in Nigeria. Both soyabean lines nodulated with the local rhizobia, but the degree of effectiveness depended on the plant genotype and field sites. Soyabean line 1456-2E showed improved growth and yield in response to N fertilizer application indicating that in this line N2 fixation induced by the indigenous bradyrhizobial community supplied less than optimal amounts of N. The mixture of bradyrhizobial isolates R25B and IRj 2180A increased grain yield of 1456-2E by 30 and 25% at Zaria and Mokwa but failed to do so at Fashola. Grain yield of 1660-19F was not affected by bradyrhizobial inoculation and N fertilizer at any of the three sites. Thus, the need for bradyrhizobia inoculation will be determined by the degree of promiscuity of soybean lines and the effectiveness of the community of indigenous bradyrhizobia present in the site.
Article
In the moist savanna zone with a 180 to 190 day growing period, early season cowpea immediately followed by a late season cereal crop can maximize the benefit of the legume to the cereal. Traditional cereal crops for this system are millet and sorghum but new early maize varieties can also be used. A study was conducted to estimate the contribution of the early season cowpea to late season maize during three years on two fields in central Kaduna State in northern Nigeria. Without insecticide application, early season cowpea grain yield averaged almost 500 kg ha over all environments including a site where P deficiency was corrected in the second year. N content of cowpea residues after grain harvest averaged approximately 15 and 30 kg ha at the low-P and moderate-P sites, respectively. Mean maize grain yield without urea or previous cowpea (290 kg ha in five environments) was increased to 760 kg ha with urea application (30 and 60 kg ha treatments combined) and 690 kg ha after early season cowpea (three varieties combined). Maize grain yield after early season cowpea without N application to maize was maintained at levels higher (at p < 0.06) than 30 kg N ha as fertilizer. Thus, cowpea cultivation in the early season appears to be an effective indigenous solution for supplying a small amount of N for cereal production. The study showed the importance of adequate P availability for the rotation system to succeed.
Article
Genetic improvement in grain yield of North American maize (Zea mays L.) hybrids during the past three to five decades can be attributed to increased phytomass production. The objective of this study was to identify the physiological traits that have contributed to the improvement in dry matter production of maize hybrids in Ontario. Experiments were conducted during 1987 and 1988 at two locations in Ontario with nine maize hybrids representing three decades of yield improvement in Ontario. Hybrids were grown at 2, 4, 8, and 13 plants m #752 and phenological development was studied from planting to maturity