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Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
173
Available Online at EScience Press
Plant Protection
ISSN: 2617-1287 (Online), 2617-1279 (Print)
http://esciencepress.net/journals/PP
UNRAVELING SEED DORMANCY AND HOST SPECIFICITY OF ALECTRA VOGELII IN
MALAWI
Christopher Kalima Phiri, Vernon H. Kabambe, James Bokosi
Department of Crop and Soil Sciences, Lilongwe University of Agriculture and Natural Resources, Post office Box 219,
Lilongwe, Malawi.
A R T I C L E I N F O
A B S T R A C T
Article history
Received: 3rd July, 2023
Revised: 2nd August, 2023
Accepted: 3rd August, 2023
Parasitic angiosperm Alectra vogelii Benth is a growing problem in Malawi,
particularly with the current emphasis on legume crops. Therefore, a pot
experiment was conducted in Lilongwe, Malawi to evaluate the effects of site, A.
vogelii dormancy-breaking period on Mkanakaufiti and IT82E-16 cowpea varieties.
Varieties of cowpea were grown in A. vogelii-infested pots sourced from three
agroecological zones and subjected to varied dormancy-breaking periods. The
experiment was arranged in a Randomized Complete Block Design and replicated
four times. The study revealed that dormancy breaking had impacts depending on
the A. vogelii source. However, the Alectra source affected the A. vogelii shoot
counts and cowpea grain weight. Neno-Manyenye collections had a higher
incidence without induced dormancy breaking periods while Lilongwe-Kamowa,
and Salima-Matumba collections had a high incidence after the dormancy-breaking
period. Late infestation (at 119 to 149 days after planting) on resistant
Mkanakaufiti cowpea variety by A. vogelii collections used indicated apparent
strain variability of collections used. The results confirmed the delayed resistance
mechanism of Mkanakaufiti against A. vogelii. Nevertheless, the variety reactions on
the parasitic weed depends on suitability, compatibility, and specificity, although
some resistant genotypes tend to lose the resistance mechanism with time. A.
vogelii seeds organic carbon % varied (4.87±1.73 to 9.13±0.95) from the three
agroecological zones which signified the collections’ variability due to warmer
temperatures, relative humidity, and crop husbandry practices under long-term
conditions. Therefore, screening efforts for resistance or evaluation of agronomic
options to suppress the weed should be intensified.
Keywords
Agro-ecological zones
Agronomic options
Cowpea genotypes
Dormancy
Organic carbon
Corresponding Author: Christopher Kalima Phiri
Email: christopherphiriphiri90@gmail.com
© 2023 EScience Press. All rights reserved.
INTRODUCTION
Vigna unguiculata (L.) Walp (cowpea) is a common crop
grown by smallholder farmers in Malawi (Kabambe et
al., 2014; MoAFS, 2020). The crop is useful as a
rotational cover crop (Somenahally et al., 2018; Bybee‐
Finley et al., 2022) as it fixes nitrogen (Munjonji et al.,
2018; Namatsheve et al., 2020) in their nodules once
adequate phosphorus is available in the soil which later
leaches into the soil, thereby, meeting a cash crop’s
nitrogen needs. The crop provides important nutrients
for both humans and animals through seeds or leaves
which accumulate higher protein, vitamin, and mineral
contents (Eziz et al., 2017). Significantly, cowpea is a
drought-tolerant crop (Gomes et al., 2020) which makes
it valuable in rain-fed agriculture or non-irrigated fallow
fields.
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
174
Cowpeas are commonly attacked by Alectra vogelii
(Benth) which is predominant in Africa, where yield
reduction can reach 80 to 100 % on susceptible
genotypes (CABI, 2017; Phiri et al., 2023). The parasitic
weed associates with low soil fertility (Lambers and
Oliveira, 2019) unreliable rainfall, and high
temperatures (Zitta et al., 2014; Zagorchev et al., 2021).
A successful attachment of host-parasite occurs only
when the three conditions illustrated in Figure 1
interact.
Figure 1: Cowpea -Alectra vogelii (Host-parasite) interaction.
A. vogelii is becoming a serious threat in several
countries in East, Central, and Southern Africa
(Fernández-Aparicio et al., 2020). The parasitic weeds
are rather difficult to control because they produce a
high number of seeds, and adaptation or dormancy
mechanisms, permit the seeds to stay alive in the soil for
several years (Zwanenburg et al., 2016; Qasem, 2019).
Seeds of A. vogelii are dormant and require a period of
after-ripening followed by conditioning in a warm, moist
environment before responding to germination
stimulants (CABI, 2017). After-ripening period on A.
vogelii, seeds differs due to temperature variability as in
hotter areas it is short as compared to cool environments
(Holzner and Numata, 2013). Some of the postulated
changes during the period are various structural and
metabolic changes in the seed coat associated with
increased softening of the seed coat making it more
permeable to water, increased signaling enzymes, and
protein changes (Meimoun et al., 2014). On the other
hand, the embryo may occur an increase in respiratory
substrate levels (CABI, 2017). After this phase, the seeds
can germinate within 5 days with the availability of a
suitable stimulant such as alectro or strigolatone to the
dry seed at 28-30oC (Brun et al., 2018).
Before the parasitic seed can respond to them, it also
requires a period of conditioning subsequently to after-
ripening (Ueno et al., 2014; CABI, 2017). The stage
allows the leaching of germination inhibitors which
probably increases the permeability of the seed coat
and changes in level of activity (Karanja et al., 2013;
Qasem, 2019). However, the duration of conditioning
depends on factors such as temperature, origin, and age
of the seeds, and the conditioning period of A. vogelii
collection ranges from several days up to weeks with a
specific temperature of 23oC (Meimoun et al., 2014).
However, lengthy periods of imbibition of Alectra seed
in water, in the absence of stimulants do not induce the
wet dormancy characteristic which commonly occurs
in Striga seeds (CABI, 2017; Phiri et al., 2023). Several
studies have been undertaken to find the effects of
Host
•Host plant produce
exdates which move
within the soil moisture
Environment
•Signaling chemmical allows
a parasitic seed to germinate
Parastic weed
•Germinated seeds attach
their hostrorium to the host
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
175
Alectra and Striga sourced from different regions and
countries on their reaction to cowpea, common bean,
soybean, groundnut, flax, chickpea, pigeon peas, and
other legume crops (Mwaipopo, 2014; Phiri et al., 2019;
Kabambe and Bokosi, 2020). However, no studies have
been done on Alectra vogelii sourced from a wide range
of agroecological zones and dormancy-breaking
periods within Malawi. The study aimed at evaluating
the effects of collection site and dormancy breaking
period on A. vogelii reaction on the variety effect and it
was hypothesized that variation on the Alectra
collection, dormancy breaking period by variety effect
could occur.
MATERIALS AND METHODS
Experimental site and Alectra collection sites
Alectra-host interaction study was conducted in a well-
ventilated plastic greenhouse during the warm dry
season for 160 days at Crop and Soil Sciences Students’
Research Farm. The site is located at 14o35' S, 33o50' E,
with an elevation of 1200 meters above sea level, in
Lilongwe, Malawi (Phiri et al., 2019). Mature Alectra
plants with ripened capsules of Alectra were uprooted
and packed in A2 envelope papers (Kabambe and
Drennan, 2005). The Alectra seeds were collected from
Dedza-Nyombe, Ntchisi-Chimanjamanja, Lilongwe-Kamowa,
Salima-Matumba, and Neno-Manyenye districts and Table
1 presents A. vogelii collection sites, a global positioning
system, elevation, and host crops on which the collections
were made. Depending on the readiness of the host crop,
the collection was in phases because in Neno crop
matures earlier than all the four districts, thereby
creating a gap difference in the collection period.
Immediately after Alectra collections from each site, the
collections were sun-dried for 0, 10, 20, and 30 days to
break dormancy. The wide range of dormancy breaking
periods and Alectra source was to achieve an after-
ripening period and to see if required or not. Alectra
sources were hypothesized with different environmental
conditions, soil status, crop management practices, and
weather parameters. This could probably define the
variability of Alectra collection on their effects on the
two cowpea varieties. Thereafter, A. vogelii seeds were
manually threshed by hand and the seeds were sieved by
passing them through a sieve of 125-micron openings.
Later on, the inoculum was stored at room temperature,
approximately at 26oC in plastic bottles (Kabambe and
Drennan, 2005; Phiri et al., 2018).
Experimental set-up
There were one hundred and sixty (160) plastic pots with
a uniform diameter and depth of 22 and 20 centimeters,
respectively. The pots were filled with sandy loamy soil
sourced from the Bunda forest. The forest soil was chosen
to prevent Alectra contaminations. Approximately 1500
(0.015 g) A. vogelii seeds were inoculated per pot after
mixing with fine sandy and coarse sandy soil (Kabambe
and Drennan, 2005; Phiri et al., 2018; Singh, 2020).
However, the high amount of Alectra seeds does not
guarantee germination because some could be dead,
immature and at times irrigation might wash the seed
downwards limiting their germination. Then, four seeds
of the two selected cowpea varieties were planted per pot
and thinned to three, one week after planting (WAP),
representing an experimental unit. The plants were
staked at 9 WAP. Irrigation was done on daily basis for
each variety and it was done until the two varieties
reached their physiological maturity. There was no
application of any kind of fertilizer or manure to the pots.
All weeds, except A. vogelii were manually uprooted
throughout the growing period. At 160 days after sowing
(DAS), cowpea samples were uprooted gently using a
hand trowel and their roots were washed thoroughly.
Then shoot weights were taken followed by oven drying
for 24 hours at 70oC and reweighed.
There were three experimental factors as follows:- variety
(V): Mkanakaufiti and IT82E-16, A. vogelii source (AS):
Dedza-Nyombe, Ntchisi-Chimanjamanja, Lilongwe-Kamowa,
Salima-Matumba and Neno-Manyenye, and dormancy-
breaking period (DB): 0, 10, 20, 30 days of sun drying of
Alectra collections. A 2×4×5 factorial treatment
combination was arranged in a Randomized Complete
Block Design (RCBD) and replicated four times.
Data collection
Days to first Alectra emergence per pot, periodic Alectra
shoot counts at 7, 8, 9, 10, 11, and 12 WAP per pot,
number of dead Alectra shoots per pot, Alectra fresh and
dry biomass at harvest (g) per pot data were collected.
A. vigour ratings were done at harvest using Striga rating
scale adopted from Tignere (2010) and Phiri (2018), as
narrated below with some modifications:-
0 = No emerged Alectra plant
1 = Average height of Alectra plants <5 cm.
2 = Average height 5-10 cm.
3 = Average height 10-15 cm.
4 = Average height 15-21 cm.
5 = Average height >21 cm.
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
176
Cowpea data recorded per pot were crop fresh and dry
biomass at harvest (g), number of pods, pod weight (g),
and grain weight (g).
Organic carbon percentage determination in Alectra
seed
Walkley-Black Wet Oxidation Method described by Faina
et al. (2012) and Khoshnaw and Esmail (2020) was used
at the Soil Science Laboratory in the Department of Crop
and Soil Sciences to determine the organic carbon
content in Alectra seeds from all five sites as a composite
sample in each site. However, no ANOVA was done on
organic carbon (%) as only one site collections were
available and triplet sampling was done per site. The
organic carbon percentage in Alectra seed was
calculated using the formulae below:
weight sample seed Alectra
100 x x1.30.5 x Sample)-(Blank
%carbon Organic
Nitrogen percentage determination and density
(g/cm³) in Alectra seed
George, (2023) macro Kjeldahl method was employed to
determine nitrogen in Alectra vogelii seeds from selected
sites. Alectra seed weight was measured in 27cm³ vial
and its density was determined. However, ANOVA was
not conducted due to single-site collections; triplet
sampling was performed for nitrogen, Alectra weight,
and density.
Statistical analysis
GenStat® 18 Edition (VSN International, Hemel
Hempstead, UK) was used to perform analyses of variance
(ANOVA). Differences between means of significant
variables were separated using a least significant
difference (LSD) at 5% and 10% level of significance for
crop and Alectra data, respectively due to high variability
on the data. However, all data sets which violated ANOVA
normality assumption were analysed after the square root
transformation of the data [(x +0.5)0.5] (Rana and Kumar,
2014; Phiri et al., 2019).
RESULTS
ANOVA Summary for days to first Alectra emergence
(DFAE) and Alectra shoot counts
Variety × dormancy-breaking period and Alectra source
× dormancy-breaking period interaction effects
significantly affected days to first Alectra emergence. On
the other hand, variety × Alectra source, Alectra source
× dormancy-breaking period, and variety × Alectra
source × dormancy-breaking period interactions
significantly (p>0.1) affected Alectra shoot counts at 9,
10, and 11 WAP (Table 2). However, on days to the first
Alectra emergence, Alectra shoot counts, dead Alectra
shoot counts, and Alectra vigour score were significantly
affected by varietal effects. On the other hand, Alectra
shoots counts at 9 and 10 WAP was significantly affected
by Alectra source (Table 2).
Interaction effects for days to first Alectra
emergence
The results revealed that dormancy-breaking period ×
cowpea variety interaction was significant on days to the
first Alectra emergence (Table 3) where Mkanakaufiti
showed consistently late infestation. On the other hand,
Alectra source × dormancy-breaking period interaction
affected days to the first Alectra emergence where the
Neno-Manyenye collection had an earlier emergence
without dormancy period on the genotype used while
after the dormancy-breaking period, Ntchisi-
Chimanjamanja followed by Salima-Matumba and
Lilongwe-Kamowa collection was seen in earlier
emergence. However, the increasing dormancy-breaking
period delayed the emergence of A. vogelii.
Interaction effects on Alectra shoot count at 9 WAP
Variety × Alectra source × dormancy-breaking period
interaction significantly (p>0.1) affected Alectra shoot
counts at 9 WAP (Table 4). On the other hand, cowpea
variety × Alectra source × dormancy-breaking
interaction revealed that Neno-Manyenye collections
were more severely without dormancy breaking period
on two varieties while Salima-Matumba (30-day sun
drying) and Lilongwe-Kamowa (10 days sun drying)
showed to be more dominant after a dormancy-breaking
period on the collections across all dormancy-breaking
period on Alectra shoot counts. Only Mkanakaufiti was
revealed to be less infested by the collections used, as
after dormancy-breaking Ntchisi-Chimanjamanja
collections were seen as dominant. Eighty percent and
above of the A. vogelii population was supported by
IT82E-16 than Mkanakaufiti, either without or after the
dormancy breaking period.
Interaction effects on Alectra shoot count at 10 WAP
Cowpea variety × Alectra source × dormancy-breaking
period interaction significantly (p>0.1) affected Alectra
shoot counts at 10 WAP (Table 5). Furthermore, Neno-
Manyenye collections were observed with a high
incidence without dormancy breaking on both varieties
while after the dormancy-breaking period Salima-
Matumba, followed by Lilongwe-Kamowa collections
were observed with a high incidence on IT82E-16.
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
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Table 1: Alectra vogelii collection sites, a global positioning system (GPS), elevation, and Alectra host crops.
Site
GPS
Masl
AE+ zone
Alectra host crop
Neno- Manyenye
S 15o21.479'; E 034o53.788'
498
Low
groundnuts
Salima- Matumba
S 13o39.078'; E034o17.488'
576
Low
groundnuts
Lilongwe- Kamowa
S 14o11.584'; E 033o46.64'
1179
Mid
groundnuts
Dedza- Nyombe
S 14o16.710'; E 043o05.207'
1257
High
groundnuts
Ntchisi- Chimanjamanja
S 13o17.411'; E 033o53.237'
1277
High
groundnuts
AE+ = Agro-Ecological, Masl = meter above sea level.
Table 2: Summary of F probabilities from the analysis of variance for days to first Alectra emergence (DFAE), Alectra shoot counts (AC) per pot at
different weeks after planting (WAP), dead Alectra counts, and Alectra vigour score.
Source of variation
DF
F probability values
DFAE
AC 7 WAP*
AC 8
WAP*
AC 9 WAP*
AC 10
WAP*
AC 11
WAP*
AC 12
WAP*
Number of
dead Alectra
shoots*
Alectra
vigour
score
Block
3
V
1
<.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
AS
4
0.972
0.573
0.414
0.066
0.040
0.138
0.5730
0.209
0.581
DB
3
0.294
0.701
0.790
0.433
0.699
0.735
0.7010
0.971
0.112
V x AS
4
0.764
0.158
0.164
0.062
0.094
0.170
0.1580
0.162
0.289
V x DB
3
0.030
0.529
0.962
0.210
0.352
0.616
0.5290
0.923
0.616
AS x DB
12
0.018
0.623
0.283
0.009
0.002
0.060
0.6230
0.929
0.376
V x AS x DB
12
0.166
0.532
0.257
0.010
0.006
0.072
0.5320
0.932
0.150
Grand mean
93.7
0.78
1.23
2.37
2.78
3.19
3.15
1.49
2.19
CV %
117
33.4
55.8
55.5
46.5
46.5
54.8
55.8
86.8
50
*Analysis was performed after square root transformation of the data [(x +0.5)0.5]; Variety (V), Alectra source (AS), dormancy-breaking period (DB),
Cowpea variety × Alectra source (V × AS); cowpea variety × dormancy-breaking period interaction, (V × DB) Alectra source × dormancy-breaking period
interaction (AS × DB), and Alectra source × dormancy-breaking period × cowpea variety (V × AS × DB) interactions.
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
178
Table 3: Effects of variety × dormancy-breaking period and Alectra source × dormancy-breaking period interactions on days to first Alectra emergence.
Variety x dormancy breaking period interaction
Variety (V)
Dormancy-breaking period (DB) (days)
0
10
20
30
IT82E-16
53.9
53.0
64.4
53.2
Mkanakaufiti
131.8
124.2
119.2
149.9
LSD 10 %
19.58
F prob. (V x DB)
0.030
Alectra source × dormancy-breaking period interaction
Alectra source (AS)
Dormancy-breaking period (DB) (days)
0
10
20
30
Dedza-Nyombe
86.5
106.2
86.6
95.2
Ntchisi-Chimanjamanja
105.4
71.0
84.9
106.2
Lilongwe-Kamowa
82.5
72.7
120.0
93.4
Salima-Matumba
110.0
98.1
71.6
106.0
Neno-Manyenye
79.9
94.6
84.9
106.6
LSD 10 %
30.96
F. prob. (AS x DB)
0.018
Table 4: Effects of cowpea variety × Alectra source × dormancy-breaking period interactions on Alectra shoot counts at 9 WAP.
Variety × Alectra source x dormancy-breaking period interaction
Variety (V)
Alectra source (AS)
Dormancy-breaking period (days)
0
10
20
30
IT82E-16
Dedza-Nyombe
3.16
2.93
3.65
3.01
Ntchisi-Chimanjamanja
4.11
4.31
2.12
3.43
Lilongwe-Kamowa
2.59
5.54
3.16
5.12
Salima-Matumba
2.40
3.77
4.27
6.19
Neno-Manyenye
5.13
4.07
5.48
3.91
Grand mean
3.48
4.12
3.74
4.33
Mkanakaufiti
Dedza-Nyombe
0.71
0.71
0.71
0.84
Ntchisi-Chimanjamanja
0.71
1.34
1.25
0.71
Lilongwe-Kamowa
0.97
0.71
0.71
0.84
Salima-Matumba
0.71
0.71
0.84
0.71
Neno-Manyenye
1.34
0.71
0.71
0.71
Grand mean
0.89
0.83
0.84
0.76
LSD 10 %
1.55
F. prob (V x AS x DB)
0.010
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Table 5: Effects of cowpea variety × Alectra source x dormancy-breaking period interaction on Alectra shoot counts at 10 WAP.
Variety × Alectra source x dormancy-breaking period interaction
Variety (V)
Alectra source (AS)
Dormancy-breaking period (DB) (days)
0
10
20
30
IT82E-16
Dedza-Nyombe
4
3.43
4.63
3.41
Ntchisi-Chimanjamanja
4.76
5.18
2.94
4.02
Lilongwe-Kamowa
2.98
4.46
5.03
7.21
Salima-Matumba
2.94
6.47
3.97
6.16
Neno-Manyenye
6.46
4.49
7.11
4.5
Grand mean
4.23
4.81
4.74
5.06
Mkanakaufiti
Dedza-Nyombe
0.71
0.71
0.71
0.84
Ntchisi-Chimanjamanja
0.71
1.39
0.84
0.71
Lilongwe-Kamowa
1.19
0.84
0.71
0.84
Salima-Matumba
0.71
0.71
0.84
0.71
Neno-Manyenye
1.43
0.84
0.71
0.71
Grand mean
0.95
0.90
0.76
0.76
LSD 10 %
1.81
F. prob (V x AS x DB)
0.006
However, Mkanakaufiti cowpea variety was
observed with a high incidence of Alectra
shoots after the dormancy-breaking period.
After dormancy-breaking, Alectra shoot counts
increased for 10 and 30 sun-dried collections
and 81% of Alectra counts infested IT82E-16
than Mkanakaufiti. However, a drop in Alectra
counts was observed from 0 up to 30 days of
dormancy breaking on Mkanakaufiti.
Interaction effects on Alectra shoot count at
11 WAP
Variety × Alectra source × dormancy-breaking
period interaction significantly (p<0.01)
affected Alectra shoot counts at 11 WAP (Table
6). Neno collections were observed with the
highest incidence without dormancy-breaking
period on IT82E-16 while Neno-Manyenye,
Salima-Matumba, and Lilongwe-Kamowa
collections were more dominant after
dormancy-breaking period on the Alectra shoot
counts at 11 WAP. On the other hand, Lilongwe-
Kamowa followed by Neno-Manyenye
collections were more dominant on the
Mkanakaufiti variety without a dormancy-
breaking period but after dormancy breaking
Ntchisi-Chimanjamanja collections consistently
maintained high Alectra counts. Approximately,
80% of Alectra counts were observed on IT82E-
16 as compared to Mkanakaufiti across all
dormancy breaking period.
Effects of cowpea variety and Alectra source
on days to first Alectra emergence and
Alectra shoot counts per pot
Days to the first Alectra emergence were
significantly affected by the cowpea variety but
not the dormancy-breaking period and Alectra
source (Table 7). Similarly, Alectra shoot count
at all sampling times was significantly affected
by varieties. However, few Alectra shoots
appeared in the late phenological stage of
Mkanakaufiti. Furthermore, Alectra shoot counts
at 9 and 10 WAP were significantly affected by
Alectra source while the dormancy breaking
period did not significantly affect Alectra shoot
counts at all sampling times. In addition, higher
Alectra shoot counts at 11 and 12 WAP were
observed on the dormancy-breaking period
effect. Neno collections were observed with a
very high incidence followed by Salima-
Matumba and Lilongwe-Kamowa collections on
Alectra shoot count from 7 to 12 WAP.
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
180
Table 6. Effects of variety × Alectra source × dormancy-breaking period interaction on Alectra shoot counts at 11 WAP.
Cowpea variety × Alectra source × dormancy-breaking period interaction
Variety (V)
Alectra source (AS)
Dormancy-breaking period (DB) (days)
0
10
20
30
IT82E-16
Dedza-Nyombe
5.01
5.06
5.17
4.36
Ntchisi-Chimanjamanja
5.32
6.01
2.67
4.79
Lilongwe-Kamowa
4.62
7.03
4.4
6.49
Salima-Matumba
4.19
5.46
5.82
7.75
Neno-Manyenye
7.66
5.49
7.8
4.8
Grand mean
5.36
5.81
5.17
5.64
Mkanakaufiti
Dedza-Nyombe
0.84
0.71
0.84
0.84
Ntchisi-Chimanjamanja
0.71
1.56
1.00
0.71
Lilongwe-Kamowa
2.59
0.97
0.71
0.84
Salima-Matumba
0.71
0.71
0.84
0.71
Neno-Manyenye
1.48
0.84
0.84
0.71
Grand mean
1.27
0.96
0.85
0.76
LSD 10 %
2.23
F.prob (V x AS x DB)
0.072
Table 7. Effects of cowpea variety and Alectra source on Alectra shoot counts (AC) per pot at different weeks after
planting (WAP).
Factor
AC at
7
WAP*
AC at
8
WAP*
AC at
9
WAP *
AC at
10
WAP*
AC at
11
WAP*
AC at
12
WAP*
Variety
IT82E-16
0.85b
1.75b
3.92b
4.71b
5.50b
5.39b
Mkanakaufiti
0.71a
0.76a
0.83a
0.84a
0.96a
0.98a
LSD 10 %
0.06
0.22
0.35
0.40
0.50
0.56
F. prob
<.001
<.001
<.001
<.001
<.001
<.001
Alectra source
Dedza-Nyombe
0.74
1.14
1.96a
2.30a
2.85
2.99
Ntchisi-Chimanjamanja
0.81
1.22
2.24ab
2.57a
2.85
2.98
Lilongwe-Kamowa
0.77
1.26
2.45ab
2.89ab
3.45
3.00
Salima-Matumba
0.78
1.18
2.45ab
2.83ab
3.27
3.58
Neno-Manyenye
0.80
1.45
2.76b
3.28b
3.70
3.33
Grand mean
0.78
1.25
2.37
2.77
3.23
3.18
LSD 10 %
0.101
0.34
0.55
0.64
0.79
0.88
F. prob
0.63
0.414
0.066
0.04
0.14
0.21
CV %
26.20
55.50
46.50
46.50
49.30
55.80
*Analysis was performed after square root transformation of the data [(x +0.5)0.5]
Dead Alectra counts at 14 WAP and Alectra vigour
score
Dead Alectra counts at 14 WAP were significantly
affected by the variety effect (Table 8) where IT82E-16
was observed with high death counts compared to
Mkanakaufiti.
However, both Alectra source and dormancy-breaking
period did not affect dead Alectra counts. Alternatively,
Alectra vigour score was significantly affected by the
variety effect, where IT82E-16 registered a high vigour
score compared to Mkanakaufiti. However, Alectra
vigour score was not significantly affected by Alectra
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181
source and dormancy-breaking period effects (Table 8).
ANOVA summary of Alectra biomass, cowpea biomass,
cowpea yield, and yield Components
Variety × Alectra source interaction resulted in a
significant (p<0.05) effect on the number of pods, pod
weight (g/pot), and grain weight (g/pot). In contrast,
Alectra source × dormancy-breaking period and
variety×Alectra source × dormancy-breaking period
interactions did not affect the number of pods (Table 9).
Conversely, Alectra fresh and dry biomass, fresh and dry
cowpea biomass, number of pods, and grain weight were
affected by the variety effect. On the other hand, the
number of pods, and grain weight (g) was significantly
(p<0.01) affected by Alectra source. At all sampling
times, cowpea biomass, yield, and yield components
were not affected by the dormancy-breaking period.
Table 8. Effects of cowpea variety on dead Alectra counts at 14 WAP and Alectra vigour score.
Variety
Number of dead Alectra shoots at 14 WAP
Alectra vigour score
IT82E-16
2.25b
3.89b
Mkanakaufiti
0.73a
0.49a
Grand mean
1.49
2.19
LSD 5%
0.4
0.34
F prob
<.001
<.001
CV %
86.8
50
Table 9: Summary of F probabilities from the analysis of variance for Alectra biomass, cowpea biomass, cowpea yield,
and yield components per pot.
Source
of
variation
D.F
F probability values
Alectra
fresh
mass
Alectra
dry mass
Cowpea
fresh mass
Cowpea
dry mass
Number of
pods
Pod
weight *
Grain
weight *
Block
3
V
1
<.001
<.001
<.001
<.001
<.001
<.001
<.001
AS
4
0.668
0.438
0.379
0.432
0.009
0.208
0.057
DB
3
0.900
0.951
0.649
0.324
0.737
0.396
0.827
V × AS
4
0.646
0.552
0.226
0.835
0.003
0.019
0.023
V × DB
3
0.792
0.659
0.467
0.129
0.504
0.551
0.871
AS × DB
12
0.421
0.402
0.974
0.952
0.080
0.404
0.309
V × AS × DB
12
0.483
0.452
0.815
0.938
0.020
0.161
0.348
CV %
117
51.8
52.5
39.3
39.7
49.4
30.4
30.9
*Analysis was performed after square root transformation of data [(x +0.5)0.5]; Variety (V), Alectra source (AS),
dormancy-breaking period (DB), variety × Alectra source (V × AS); variety × dormancy-breaking period, (V × DB)
Alectra source x dormancy-breaking period (AS × DB), and Alectra source × dormancy-breaking period x variety (V ×
AS × DB) interaction
Effects of cowpea variety on Alectra and cowpea
biomass (g) parameters
Both Alectra and cowpea biomass production were
affected by variety effects, where, IT82E-16 was observed
with a higher Alectra biomass than Mkanakaufiti (Table
10). However, cowpea biomass production was higher on
Mkanakaufiti than on IT82E-16.
Interaction effects on the number of pods per pot
V × AS × DB (p<0.05) interaction significantly affected
the number of pods per pot on both genotypes used in
the study (Table 11).
However, Ntchisi-Chimanjamanja Alectra collections
before the dormancy-breaking period affected the
number of pods per pot on IT82E-16, as they were
lower after the dormancy-breaking period. The same
observation was made on Salima-Matumba Alectra
collections (sun-dried for 20 days) followed by
Lilongwe-Kamowa (sun-dried for 20 days) where pod
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182
number per pot on IT82E-16 was affected. However,
Neno-Manyenye Alectra collections affected the
number of pods on Mkanakaufiti across all dormancy-
breaking periods plus before dormancy-breaking
periods. In general, Mkanakaufiti was observed with
higher pods as compared to IT82E-16.
Table 10. Effects of cowpea variety on Alectra and cowpea biomass (g/pot) parameters.
Variety
Fresh Alectra
biomass *
(g)
Dry Alectra
biomass * (g)
Fresh cowpea
biomass*
(g)
Dry cowpea
biomass * (g)
IT82E-16
2.35b
1.86b
3.15a
2.57a
Mkanakaufiti
1.62a
1.26a
6.70b
5.20b
Grand mean
1.98
1.560
4.930
3.89
LSD 5 %
0.32
0.26
0.61
0.48
F. prob
<.001
<.001
<.001
<.001
CV %
51.80
52.500
39.300
39.70
*Analysis was performed after square root transformation of data [(x +0.5)0.5].
Table 11: Effects of cowpea variety × Alectra source × dormancy-breaking period interaction on the number of pods
per pot.
Variety × Alectra source × dormancy-breaking period interaction
Variety (V)
Alectra source (AS)
Dormancy-breaking period (DB) (days)
0
10
20
30
IT82E-16
Dedza-Nyombe
3.50
5.25
4.00
3.75
Ntchisi-Chimanjamanja
2.25
4.50
6.25
4.25
Lilongwe-Kamowa
4.75
1.75
5.00
3.75
Salima-Matumba
4.75
3.25
0.25
2.25
Neno-Manyenye
3.00
4.25
4.25
4.00
Grand mean
3.65
3.80
3.95
3.60
Mkanakaufiti
Dedza-Nyombe
9.75
14.75
10.5
7.5
Ntchisi-Chimanjamanja
18
10.25
10.25
12.75
Lilongwe-Kamowa
13.5
13.75
13.75
21.25
Salima-Matumba
14
12.25
15
11
Neno-Manyenye
7
6.25
6.75
14
Grand mean
12.45
11.45
11.25
13.30
LSD 5 %
5.49
F prob (V × AS × DB)
0.020
Interaction effects on pod weight (g/pot)
Variety × Alectra source interaction affected pod weight
(g/pot) where lower pod weight was observed on
IT82E-16 genotype across the Alectra sources as
compared to Mkanakaufiti (Table 12). On the other
hand, a higher cowpea pod weight per pot interaction
was observed on seeds sourced from Lilongwe-
Kamaowa, infested on Mkanakaufiti genotype. Salima-
Matumba and Neno-Manyenye Alectra collections
consistently affected pod weight on IT82E-16 and
Mkanakaufiti, respectively.
Interaction effects on grain weight (g/pot)
Variety × Alectra source interaction significantly affected
grain weight (g/per pot) with a higher interaction of
grain yield on Mkanakaufiti infested with collections
sourced from Lilongwe-Kamowa (Table 13). Grain
weight (g) on IT82E-16 × Salima-Matumba Alectra
collections interaction was the lowest as an indicator of
severity. There was no difference amongst A. vogelii
sources on IT82E-16 while a significant suppression
lowest weight for Mkanakaufiti was observed on Neno-
Manyenye collections.
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183
Effects of variety and Alectra source on yield and
yield components
The number of pods and grain weight (g/pot) were
significantly affected by variety and Alectra source
effects, where high yield output was realized on
Mkanakaufiti (Table 14). Yield and yield components
were drastically affected by the high incidence of Alectra
collections from Neno-Manyenye and Salima-Matumba
districts, however, the traits were significantly higher on
the genotypes when infested with Lilongwe-Kamowa,
Ntchisi-Chimanjamanja, and Dedza-Nyombe Alectra
collections. Nevertheless, yield and yield components of
cowpea varieties were not affected by the Dormancy-
breaking period on the Alectra collections used.
Table 12. Cowpea Variety × Alectra source interaction effects on pod weight (g/pot).
Variety (V)
Alectra source (AS)
Dedza-
Nyombe
Ntchisi-
Chimanjamanja
Lilongwe-
Kamowa
Salima-
Matumba
Neno- Manyenye
IT82E-16
2.34
2.43
2.35
1.78
2.20
Mkanakaufiti
3.87
4.17
3.56
4.32
4.74
LSD 5 %
0.68
F prob (V × AS)
0.019
Table 13. Effects of cowpea variety × Alectra source interaction on grain weight (g/pot).
Variety (V)
Alectra source (AS)
Dedza-
Nyombe
Ntchisi-
Chimanjamanja
Lilongwe-
Kamowa
Salima-
Matumba
Neno- Manyenye
IT82E-16
2.03
2.05
2
1.53
1.93
Mkanakaufiti
3.38
3.49
2.86
3.46
4.06
LSD 5 %
0.58
F prob (V × AS)
0.023
Table 14. Effects of cowpea variety and Alectra source on yield and yield components.
Factor
Number of pods per pot
Grain weight
per pot* (g)
Variety
IT82E-16
3.75a
1.91a
Mkanakaufiti
12.11b
3.45b
LSD 5 %
2.23
0.26
F. prob
<.001
<.001
Alectra source
Dedza-Nyombe
7.38ab
2.71ab
Ntchisi-Chimanjamanja
8.56bc
2.77ab
Lilongwe-Kamowa
9.69c
3.00b
Salima-Matumba
7.84abc
2.50a
Neno- Manyenye
6.19a
2.43a
Grand mean
7.93
2.68
LSD 5%
1.940
0.41
F. prob
0.009
0.05
CV %
49.40
30.90
*Analysis was performed after square root transformation of data [(x +0.5)0.5]
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184
Effect of dormancy-breaking period and site on
organic carbon (%) in Alectra collections
Organic carbon (%) was higher on Alectra collections
without dormancy breaking while those sun-dried for 30
days had the lowest organic carbon % (Table 15).
However, Neno-Manyenye collections were observed
with the lowest organic carbon content as compared to
all the sources. On the other hand, Alectra weight in 27
cm3 vials and Alectra density was lower on Neno-
Manyenye collections. N (%) was higher on collections
sun-dried for 30 days while non-sun-dried collections
were observed with lower quantity. Only Salima-
Matumba collections were observed with lower nitrogen
percentages.
Table 15. Alectra vogelii organic carbon (%), nitrogen (%), seed weight (g), and seed density (g/cm3).
Dormancy-breaking
period (Days)
Organic carbon
(%)
Nitrogen (%)
Weight in 27
cm3 vial (g)
density (g/cm3)
0
8.07 ± 3
0.05±0.01
2.56 ± 0.66
0.10 ± 0.02
10
7.54 ± 2.40
0.06±0.03
2.12 ± 0.33
0.08 ± 0.01
20
7.54 ± 1.92
0.06± 0.02
2.36 ± 0.83
0.09 ± 0.03
30
7.26 ± 2.08
0.07± 0.01
2.20 ± 0.87
0.08 ± 0.03
Alectra source
Dedza-Nyombe
8.63 ± 0.97
0.07±0.02
2.07 ± 0.17
0.08 ± 0.01
Ntchisi-Chimanjamanja
6.83 ± 2.09
0.05±0.01
3.20 ± 0.66
0.12 ± 0.02
Lilongwe-Kamowa
9.13 ± 0.95
0.078±0.01
2.26 ± 0.93
0.08 ± 0.03
Salima-Matumba
8.56 ± 2.28
0.04±0.01
2.21 ± 0.25
0.08 ± 0.01
Neno- Manyenye
4.87 ± 1.73
0.07±0.02
1.83 ± 0.14
0.07 ± 0.01
Overall mean
7.09±0.02
0.06±0.02
2.31±0.67
0.09±0.02
Presented are means with their standard deviation and no ANOVA
DISCUSSION
Interaction effects
Results revealed that cowpea variety × dormancy-
breaking period and Alectra source × dormancy-
breaking period interactions affected days to the first
Alectra emergence. This was due to the susceptibility of
cowpea varieties used, the temperature difference in the
sites of Alectra seed collection, Alectra seed
biochemistry, root exudate levels released by cowpea
varieties, and other unknown factors not mentioned.
Furthermore, earlier emergence was observed on
Alectra seeds dried for 10 days which revealed the
effectiveness of dormancy breaking in the study but
contradicted other studies where seeds are dried for 30
days (CABI, 2017; Phiri et al., 2019). However the study
increased the dormancy-breaking period, delayed
Alectra emergence on both Mkanakaufiti and IT82E-16.
This could be due to the cool season when the trial was
conducted although Alectra seeds germinate anytime
when host plants are available. Alternatively, cowpea
variety × dormancy-breaking period interaction
significantly affected DFAE, where an increased
dormancy period delayed the emergence of A. vogelii.
The seed dormancy breaks easily as it occurs at a dry
room temperature (Joel et al., 2017). Significant
interactions were observed on collections with
dormancy breaking as compared to without. Results
revealed that cowpea variety × dormancy-breaking
period and Alectra source × dormancy-breaking period
interactions affected days to the first Alectra emergence
(DFAE). This was due to the susceptibility, however,
delayed emergence of A. vogelii on the Mkanakaufiti
variety reflected a resistance mechanism which
probably resulted in lower yield reduction and early
infestation may guarantee high yield reduction (Kutama
et al., 2014; Dieni et al., 2018) though, some tolerant
genotypes may overcome the pressure thereby, leading
to reasonable yield.
CV × AS × DB, AS × DB, and CV × AS interactions
significantly affected the number of Alectra shoots at 9
and 10 WAP, which revealed diverse reactions of the
cowpea varieties on the collection used. Though AS × DB
interaction was significant, Neno-Manyenye collections
across all dormancy-breaking periods were more
dominant while on CV × AS × DB interaction, only Neno-
Manyenye collections across all dormancy-breaking
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185
periods were observed with a high incidence followed by
Salima-Matumba collections. Furthermore, Neno-
Manyenye Alectra collections were observed with a
higher incidence without dormancy while Salima-
Matumba and Lilongwe-Kamaowa collections were more
dominant after dormancy breaking, therefore, revealing
consistency effects on the yield and yield components.
The high severity could be due to the warmest weather
conditions in Alectra collection sites (CABI, 2017;
Musango et al., 2022). However, A. vogelii shoot counts on
Mkanakaufiti as compared to IT82E-16 were lower across
all dormancy-breaking periods which reflected the
resistant mechanism. A closer significant (p<0.01) trend
was observed on Alectra source × dormancy and cowpea
variety × Alectra source × dormancy-breaking
interactions on Alectra shoot counts at 11 WAP. More
than 80% of A. vogelii counts were supported by IT82E-16
than Mkanakaufiti either without or after the dormancy-
breaking period. However, without dormancy-breaking
the Alectra counts were higher while after dormancy-
breaking the counts were dropping.
CV × AS × DB interaction affected the number of pods
per pot which agrees with interactions in Tables 7 and 8.
The results revealed the effects of Alectra shoots as they
significantly affected pod numbers on Neno collections
followed by Salima-Matumba collections across all
dormancy-breaking periods. Furthermore, 77% of the
pods were harvested from Mkanakaufiti infested with
Alectra seeds without dormancy-breaking. However,
after dormancy breaking, a low pod number (74%) was
observed on Mkanakaufiti infested with 20 days sun-
dried Alectra collection. The results revealed a low
reduction in the number of pods in Mkanakaufiti
infested with Alectra seeds sourced from Lilongwe-
Kamowa which was an indicator of diminishing
resistance mechanisms in the genotype (Kabambe et al.,
2014). A. vogelii is more dominant in the mid-altitude
where most of the cowpea genotypes are adaptable. This
could be an indicator that the variety will not be
resistant for a longer period (Vernon Kabambe, personal
communication, 2018) and this agrees with the findings
of Mwaipopo (2014), Makaza et al. (2021) and
Makanjuola et al. (2023). On the other hand, cowpea
variety × Alectra source interaction gave a significant
effect on both pod weight (g) and grain weight (g) per
pot which agrees with the effects on the number of pods.
Roles of cowpea variety on A. vogelii effects
Days to first Alectra emergence was affected by the
varietal effect which revealed host specificity and
suitability. Earlier Alectra invasions on IT82E-16 but not
on Mkanakaufiti reflected a resistance mechanism. Even
though, Mkanakaufiti is resistant to A. vogelii (Kabambe
et al., 2014), in the study infestations occurred in the late
phenological stage which could be due to juvenile
resistance. Significantly, late infestation coincided with
no Alectra seed production which probably could reduce
soil seed bank, thereby, controlling the parasitic weed in
the field. Furthermore, the emergence of A. vogelii on
Mkanakaufiti indicated that resistance to the variety
might be diminishing or the biochemistry of the parasitic
weed is changing which is in agreement with climate and
environmental changes (Mviha et al., 2011; Kabambe et
al., 2014). This is worthy of exploring as the variety is
considered resistant to A. vogelii in Malawi.
Alectra shoot counts at all times of sampling was
significantly affected by the cowpea variety due to host
specificity, as IT82E-16 was susceptible to A. vogelii in
comparison to the Mkanakaufiti variety. However, IT82E-
16 was severely infested with A. vogelii while
Mkanakaufiti supported few which agreed with the
findings of Mbwaga et al. (2010). This suggested that the
cowpea varieties had different levels of susceptibility.
Njekete et al. (2017), Jia et al. (2019) and Mounde et al.
(2020) reported that strigolactone or alectrol determined
the level of infestations on suitable host plants which
could be the case here. However, in the late phenological
stages, the variation disappeared due to high death counts
on Alectra shoots which occurred before flowering
thereby leading to a reduction in A. vogelii soil seed bank.
Death of Alectra shoots mirrored resistance mechanisms
as photo-assimilates could be limited on highly infested
genotypes (Rubiales and Fernández-Aparicio, 2012;
Karanja et al., 2013; Phiri et al., 2018).
The number of dead Alectra shoots was affected by the
cowpea variety which could be due to inhibitions of
Alectra shoots on the host genotypes (Reuben, 2018).
This agreed with the mechanism of resistance as some
genotypes allow growth and development of the
parasitic weed and then inhibition (James Bokosi,
personal communication, 2018; Fernández-Aparicio et
al., 2020). Mechanism of resistance by the host plants on
the parasitic weed had been observed through delayed
Alectra infestations on Mkanakaufiti, Alectra shoots
death could be due to the genetics of the host crops
(Dieni et al., 2018; Makaza, 2019). Though, IT82E-16
supported high Alectra shoots, mortality of Alectra
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186
shoots was high which probably reflected starvation for
growth resources, nitrogen content in the soil, high
temperatures, relative humidity, and apoptosis reaction.
The apoptosis mechanism is common in resistant
cowpea varieties which probably inhibit the
development of Alectra shoots (Hu et al., 2020). Alectra
vigour score was affected by the variety effect which was
in agreement with a higher number of Alectra shoots
observed on IT82E-16 than Mkanakaufiti. Therefore, it
was not a surprise as IT82E-16 was highly susceptible to
A. vogelii which probably explains the high Alectra
vigour scores observed in the study.
Higher biomass of A. vogelii on IT82E-16 revealed
susceptibility levels of the host plant. The results agreed
with the findings of Makaza et al. (2021), where Alectra
infestations were associated with new sinks for growth
thereby, decreasing the shoot biomass. The number of pods
and grain weight per pot were significantly affected by the
cowpea variety, with a high yield output realized on
Mkanakaufiti. Cardoso et al. (2011), Kabambe et al. (2014),
and Gwatidzo et al. (2020) reported that higher yields were
observed on resistant varieties which agreed with the
current findings. This indicated that the Alectra reaction
had an impact on the amount of yield on IT82E-16 as it was
highly susceptible to the parasitic weed and it was not a
surprise to observe as susceptible cowpea varieties suffer
yield reduction up to 100 % in a field situation (Boukar et
al., 2016; CABI, 2017; Chikoye et al., 2020).
Roles of A. vogelii source on A. vogelii severity
Alectra shoot counts at 9 and 10 WAP were significantly
affected by Alectra source which revealed the severity
levels of collections used in the study. During this stage,
Alectra shoot counts were at the peak, and in the later
stages, the death of A. vogelii disrupted the numbers
while in the earlier stages, it was too low to be
significant. The changes in Alectra counts could be
related to high temperatures, high humidity, and
starvation for growth resources as in some pots, they
overpopulated. Furthermore, Neno-Manyenye Alectra
collections were consistently observed with a high
incidence at all the sampling times which agreed with
the warmest weather conditions of the district. On the
other hand, Lilongwe-Kamowa and Salima-Matumba
collections were also observed with a high incidence of
Alectra on the cowpea varieties after dormancy
breaking. This reflected that in low to mid-altitude areas,
Alectra collections were more aggressive as they
associated with high assimilates demand from the host
plant thereby increasing shoot counts. The difference in
Alectra collections reaction could be due to soil fertility
status, crop husbandry practices, and collection genetics
which mirror site source.
The results revealed that grain weight (g) was
significantly affected by Alectra source which probably
agreed with an earlier observation of Alectra shoot
counts. Yield and yield components of cowpeas were
consistently reduced by the Neno-Manyenye collection
followed by the Salima-Matumba collections which were
observed with a high severity than other collections.
This indicated that the severity of A. vogelii used varies
with the site in their reaction toward yield and yield
components. The behavior revealed by the collections
could be due to environmental, altitude, and genetic
factors. In contrast, biomass production was not affected
by Alectra source which agrees with DFAE and Alectra
shoot counts. Alonge et al. (2001) and Qasem (2006)
reported that moderate infestation of A. vogelii on a non-
suitable host plant probably leads to less export of
assimilate to the parasite which ensures adequate
biomass accumulation and grain development. Site
differences in organic carbon were an indication that
levels of carbohydrates in seeds varied which
differentiated the collections’ physiology. The low
organic carbon percentage of Neno-Manyenye A. vogelii
seeds could be due to higher temperatures in the
collection site where the temperature ranges from 22 to
32oC (Anonymous, 2018) and after the ripening effect.
This implied that respiration in the seeds had been
continuous for a longer period in association with higher
temperatures at the site. On the other hand, there could
be the production of reactive oxygen species which have
a detrimental effect on the seed lots (Hayat and Bailly,
2008; Griffo et al., 2023). The changes in the seed colour,
size, and breakage could be attributed to seed ageing or
desiccation (Umarani et al., 2015; Plitta-Michalak et al.,
2022). A high quantity of N (%) in Alectra seeds mirrors
the maturity and vigour of the seeds (Taiz et al., 2015).
However, longtime sun drying allowed the leaching of
inhibitors in the seeds thereby allowing the conversion
of nitrogen form into other forms (Banful et al., 2011;
Taiz et al., 2015). Furthermore, the results indicated that
as dormancy breaking was increasing N quantity
increased too. This only was an indicator of dormancy
release and probably some conversions occurred in the
seed. The study has revealed that a dormancy breaking
period is a need in enhancing seed chemical reaction and
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187
might lead to deterioration if conditions are
unfavourable.
Role of the dormancy-breaking period on A. vogelii
severity
The result on Alectra shoot counts and days to the first
Alectra emergence at all sampling times were not
affected by the dormancy-breaking period though there
was an increase in Alectra shoot counts. This
contradicted the assumption that sun-dried collections
could be more problematic than non-sun-dried ones
which influence dormancy breaking as discussed earlier.
Besides, this could be due to the genetics of the
collections used, environmental conditions, and seed
biochemistry (CABI, 2017). Alectra seeds being minute
seeds fit Martin's description of dwarf rather than micro
seeds because they have differentiated embryos (Phiri,
2018). As a result, little embryo growth is possible
without rupturing the seed coat making morphological
dormancy impossible in Alectra and Striga seeds.
Therefore, dormancy breaking in the seed is easily
achieved in a dry room temperature and warm
stratification. However, it was assumed that collections
sun-dried for 30 days could probably germinate earlier
and more severely on both susceptible and resistant
genotypes. This entails that Alectra seed dormancy
breaking could occur easily on Alectra seeds once
mature, dry and favourable conditions are available.
Duke and Egley (2018) reported that Alectra seed coats
lacked a palisade layer of the macroscelerids making
them easily permeable to water. This revealed that the
seed biochemistry of Alectra easily changes with a short
duration of drying and conditioning, as sometimes in
Orobanchaceae pre-conditioning is not a prerequisite for
germination (CABI, 2017).
The dormancy-breaking period did not affect yield and
yield components which were contrary to the
expectation as collection sun-dried for 30 days was
assumed problematic on the cowpea genotypes used.
This was in agreement with the findings on days to the
first Alectra emergence and the number Alectra shoot
counts in the study. On the other hand, biomass
production was not affected by the dormancy breaking
period which agrees with NDFAE and Alectra shoot
counts. Seeds are a source of organic carbon and mineral
(N and P) nutrients for the growth of seedlings (Lamont
and Groom, 2013). The drastic drop of organic carbon
(%) in Alectra seeds sun-dried for 30 days could be due
to chemical reactions in the seeds and the conversion of
seed products into other forms (Banful et al., 2011; Taiz
et al., 2015). Dormancy breaking goes in with hand drop
in OC contents; while without dormancy breaking, the
contents remained higher. This implied that low
amounts of minerals and organic carbon associated with
low germination % as chemical reaction are low in the
seed (Lamont and Groom, 2013; Těšitel, 2016). This
could be attributed to the maturity of the seeds as drying
is associated with the leaching of chemicals (Leubner-
metzger, 2003; Daws et al., 2008; Singh, 2020). Some of
the chemical reaction which occurs during maturity,
after-ripening, and deterioration include lipid
peroxidation, membrane disruption, DNA damage, and
impairment of RNA and protein synthesis (Duke and
Egley, 2018; Chhabra and Singh, 2019), which was not a
surprise in the drop of OC.
The trends of OC (%) were similar to Alectra mass in 27
cm3 vials (g) which agreed with the density of the Alectra
collections (g/cm3). The difference in masses could be
due to the drop in OC (%) on Neno collections which is
worth exploring. During seed maturation, OC (%) was
transferred from the vegetation to the capsules of
Alectra seeds which probably differentiate the ability of
the collections (Salon et al., 2001; Phiri et al., 2018). Both
the dormancy-breaking period and Alectra source
showed variations in N contents in the seeds which was
in agreement with the reaction of Alectra collections on
the crop. After dormancy-breaking, N% increased while
without the dormancy-breaking period, the content was
lowest which agreed with the discussion on shoot counts
effects.
CONCLUSION
This study has revealed that some implications of
dormancy-breaking existed depending on the Alectra
source. However, Alectra source appeared to influence
Alectra shoot counts, grain weight, and shelling % for
both cowpea varieties Mkanakaufiti and IT82E-16. On
the other hand, the results have revealed that the Neno-
Manyenye collections had a higher incidence without
dormancy-breaking while Lilongwe-Kamowa and
Salima-Matumba collections had a higher incidence after
dormancy-breaking period due to variability in weather
patterns at sites of the source. Even though Mkanakaufiti
is resistant to the parasitic weed, the study has shown
late infestation on the crop from the Alectra collection
used which revealed apparent strain variability on the A.
vogelii collection used, however, the study has confirmed
Plant Protection, 07 (02) 2023. 173-191 DOI: 10.33804/pp.007.02.4663
188
the resistance mechanism of Mkanakaufiti on A. vogelii.
Nevertheless, the variety of reactions on the parasitic
weed depends on the suitability of the host and
compatibility of the parasitic weed with the host, though
some resistant genotypes tend to lose the mechanism
with time. On the other hand, the organic carbon content
in Alectra seeds varied from the three agroecological
zones which signified the collections variability due to
warmer temperatures, relative humidity, and crop
husbandry practices. Therefore, screening for resistance
in crops to suppress the weed should be conducted.
A further study on the changes of Alectra vogelli seed on
physiology and biochemistry sourced from different
sites is vital. It is advisable to promote the use of
resistant cowpea varieties like Mkanakaufiti to reduce
the risk of severe infestations and enhance crop
resilience against parasitic weeds. Furthemore, a
comprehensive and integrated approach that combines
host resistance, and climate-adapted management
practices is recommended to effectively control and
manage Alectra infestations in cowpea crops. Lastly,
breeding and introduction of new cowpea genotypes
with shorter duration, and large-seeded seeds to meet
consumer preferences are also required.
ACKNOWLEDGEMENT
The first author would like to acknowledge Lilongwe
University of Agriculture and Natural Resources and the
McKnight Cowpea Project for financial support to this
work. A word of thanks to the late Prof. Mumba for his
supervisory support during the study. Many thanks to
LUANAR Crop and Soil Sciences staff for their excellent
administrative and undying support.
AUTHORS’ CONTRIBUTIONS
Under VHK and JB's supervision, CKP conceived the idea,
conducted experiments, analyzed data, and authored the
manuscript.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
Data Availability Statement
Data are available upon request from the 1st author
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