The objective of this study was to evaluate eighteen Dolichos lablab genotypes for resistance to Maruca vitrata and Helicoverpa armigera in the field using morphological markers. The study design was Randomized Complete Block (RCBD) with separation of mean done using Turkey’s range of test. Eldoret, KALRO Njoro and KALRO Kakamega were the study sites. Morphological parameters of pods were studied to determine whether they have any influence on resistance of Dolichos lablab to M. vitrata and H. armigera. The pod damage (%) of each genotype was calculated and given a resistance rating of 1-5 score damage. Genotype G2, Bahati and W7 were resistant to M. vitrata in a scale of 1(0-10%; low infestation), Bahati and W7 were moderately resistant to H. armigera in a scale of 2(11-30%; moderate infestation). Genotype LG1MoiP10 was susceptible to M. vitrata in a scale of 4 (51-70%; severe infestation) and genotype M5 was intermediate to H. armigera in a scale of 3 (31-50%; high infestation). There was positive significant correlation in H. armigera and M. vitrata pod damage with days to maturity, growth habit, and pod attachment. Pod length and pod fragrance were positively correlated to M. vitrata. Negative correlation was detected in pod thickness, pod pubescence and raceme position to pod damage by H. armigera and M. vitrata. The study identified G2, Bahati and W7 as promising resistant genotypes and can be used in Dolichos breeding program. However, there is need to further evaluate them in different environments and seasons for reliability.

1. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
IJPBCS
Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes
for Resistance to Legume Pod Borers (Maruca vitrata and
Helicoverpa armigera) Using Morphological Markers
*L.C. Boit1, M. Kinyua2, O. Kiplagat3, E. Chepkoech4
1,2,3,4
School of Agriculture and Biotechnology, University of Eldoret, P.O. Box 1125, Eldoret, Kenya
The objective of this study was to evaluate eighteen Dolichos lablab genotypes for resistance to
Maruca vitrata and Helicoverpa armigera in the field using morphological markers. The study
design was Randomized Complete Block (RCBD) with separation of mean done using Turkey’s
range of test. Eldoret, KALRO Njoro and KALRO Kakamega were the study sites. Morphological
parameters of pods were studied to determine whether they have any influence on resistance of
Dolichos lablab to M. vitrata and H. armigera. The pod damage (%) of each genotype was
calculated and given a resistance rating of 1-5 score damage. Genotype G2, Bahati and W7 were
resistant to M. vitrata in a scale of 1(0-10%; low infestation), Bahati and W7 were moderately
resistant to H. armigera in a scale of 2(11-30%; moderate infestation). Genotype LG1MoiP10 was
susceptible to M. vitrata in a scale of 4 (51-70%; severe infestation) and genotype M5 was
intermediate to H. armigera in a scale of 3 (31-50%; high infestation). There was positive
significant correlation in H. armigera and M. vitrata pod damage with days to maturity, growth
habit, and pod attachment. Pod length and pod fragrance were positively correlated to M. vitrata.
Negative correlation was detected in pod thickness, pod pubescence and raceme position to pod
damage by H. armigera and M. vitrata. The study identified G2, Bahati and W7 as promising
resistant genotypes and can be used in Dolichos breeding program. However, there is need to
further evaluate them in different environments and seasons for reliability.
Keywords: Dolichos lablab, Legume pod borers (M. vitrata and H. armigera), plant résistance, morphological markers.
INTRODUCTION
Dolichos (Lablab purpureus) is an important highly
proteineous human food and animal feeds. It is used as a
cover crop and green manure. It is also known for its
medicinal value. Despite these diverse uses of lablab,
there are common production constraints that include: low
yields, poor cooking and flavor qualities, susceptibility to
diseases and pest which lower the economic value of the
crop.
The biotic pressure from insects’ pests and diseases limits
lablab maximum production in terms of yield and quality.
Legume pod borer (Maruca vitrata) is the most serious
pest of lablab worldwide (Liao and Lin, 2000). Larvae of
this insect attack flower buds, flowers and young pods
inducing over 80% yield losses (Arodokoun et al., 2003).
Maruca vitrata is a serious pest of grain legumes in the
tropics and sub-tropics because of its extensive host
range, destructiveness, and distribution (Margam et al.,
2011). Furthermore, Periasamy et al. (2015) discovered
that M. vitrata is a genetically complex species hence, it is
one of the major constraints in increasing the production
and productivity of grain legumes. The larva feeds inside
the pods causing damage to the developing seeds. It is
characterized by formation of webs, that aid in movement
from one plant and/or pod. The legume pod borer
(Helicoverpa armigera) on the other hand inflict serious
damage to legumes including Dolichos lablab (Rekha and
Mallapur, 2007).
*Corresponding Author: L.C. Boit, School of Agriculture
and Biotechnology, University of Eldoret, P.O. Box 1125,
Eldoret, Kenya Email: lechebo2006@yahoo.com
International Journal of Plant Breeding and Crop Science
Vol. 5(1), pp. 344-351, March, 2018. © www.premierpublishers.org. ISSN: 2167-0449
Research Article

2. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Boit et al. 345
Ninety % of all damage by H. armigera is done by the third
instars onwards. H. armigera destroys buds, flowers, and
pods. If flowers and pods are not available, they feed upon
leaflets, leaving the veins. On pods, conspicuous holes are
made by the entry of larvae. Usually developing and partly
matured seeds are eaten completely and at times a portion
of the seed and testa remain (Srinivasan, 2014).
Helicoverpa armigera remains the most serious insect pest
that causes significant yield losses due to its mobility, and
it being highly polyphagous, short generation duration, and
high reproductive rate. The preference of H. armigera to
feed on the harvestable parts of the host plants, along with
its mobility, migratory potential, facultative diapauses, and
tendency to develop resistance to insecticides have led to
its status as an important crop pest (Sarwar, 2013).
Several plant characters have been postulated to offer
resistance to the pod borers (Hemati et al., 2012).
According to Cotter and Edwards (2006), plants use a
number of resistance mechanism that can affect insect
feeding, including physical factors such as trichome
density or chemical factors such as toxic allelochemicals.
The type of trichomes and their orientation, density
and length have been correlated with reduced insect
damage in several crops. Determinate types where pods
are bunched together at the top of the plant suffered
greater pod borer damage than the non-determinate type
in pigeon pea (Cajanus cajan) (Sunitha, 2006). It has also
been noted in cowpeas that cultivars with pods held within
the canopy suffer significantly greater damage due to M.
vitrata than the cultivars where the pods are held in the
normal position (Jakhar et al., 2017). Similarly,
(Mallikarjuna et al., 2009) showed that lablab pods held
above the canopy were less damaged as compared to
those held within the canopy. They further reported that
flower fragrance was positively correlated to the pod
damage by M. vitrata. Pod size and rate of' pod growth
appeared to be important factors in cowpea susceptibility
to the pod borers (Jaydeep, 2004). The big pods provide
large surface for larval infestation and sufficient nutrition
for larval growth. Negative correlations with larval
population of H. armigera was detected on pod
pubescence on pods and leaves of chickpea, pigeon pea
and cowpea (Brar, 2014; Sunitha 2008; Jakhar et al.,
2017).
Several plant characters have been postulated to offer
resistance to the pod borers (Karen et al., 2012). However,
data on the role of morphological traits that provide
resistance to M. vitrata and H. armigera in Dolichos lablab
are inconclusive. Plant breeders need sources of
resistance that can be incorporated into adapted breeding
lines to help control the pest, since Dolichos lablab
growers have to spend much on inputs like pesticides. On
the other hand, use of chemicals can create hazards to
human health and produce undesirable side effects on
non-target insects, animals and plants. Also, inappropriate
use of chemicals can lead to development of strains that
are resistant to the chemicals and worsen the effort to
eradicate the pest. Little effort has been done on Dolichos
lablab regarding the search for pest resistance as
compared to other legumes. The study aimed to evaluate
the different morphological traits of Dolichos lablab in
relation to the damage by H. armigera and M. vitrata to get
resistant genotypes that can be used in Dolichos breeding
program.
MATERIALS AND METHODOLOGY
Experimental material
Eighteen genotypes of Dolichos lablab obtained from
University of Eldoret Dolichos Research Programme were
screened under field conditions for resistance to legume
pod borers (M. vitrata and H. armigera). The 18 lines are;
M5, G1, W7, LG1, B1, LG1Kari (T5S3P3) G2, Bahati,
LG1Kari (T5S3P7), LGIMoi (T5S1P10), B1Lanet (T3S2P26),
LG1 Kari (T5S3P2), LG1 Moi (T5S1P4), LG2 Kari (T5S3P7),
LG1 Kari (T5S3P9), B1Moi (T3S1P2), Local and Katumani
(DL1002). The first six genotypes were on National
performance trial while the last two were the check
genotypes.
Sowing was done in May, June and July 2014, in
Kakamega, Eldoret and Nakuru respectively. Kakamega
lies within 0°28’N, 34°75’E with an elevation of 1548m
average temperature of 20.4°C and average annual rainfall
of 1971mm; Eldoret lies within 0°35’N, 35°17’E, with an
elevation of 2094m average temperature of 16.8° and
average annual rainfall of 1055mm; Njoro lies within
0°20’N,35°56’E with an elevation of 2151m average
temperature of 16.1°C and average annual rainfall of
937mm.
The experimental design for the trial was Randomized
Complete Block Design (RCBD) with three replications.
Each genotype was sown by hand with a spacing of 75 x
50 cm and 1.5mm depth in a 1050m2 field plot. Sowing was
done at two seeds per hole, each genotype occupying two
rows per plot. A spacing of 1m apart per replication and 1m
apart per plot was maintained. Thinning was done after
three weeks to one seedling per stand. Weeding was done
when necessary. No pest management method was
applied to the crop in order to have the study under perfect
natural infestation.
Quantitative and qualitative data for the 18 genotypes of
Dolichos lablab were studied. The quantitative data were:
time required for 50% flowering, time required for 50%
emergence, time required for pod maturity, pod length and
width, and pod wall thickness. On the other hand,
qualitative data were: pod exposed above or below the
foliage, pod pubescence, pod fragrance, growth habit
(determinate, semi- determinate or indeterminate) were
observed and correlated with incidence of M. vitrata and

3. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Int. J. Plant Breed. Crop Sci. 346
H. armigera. A descriptor for the genus Lablab developed
by Gowda, (2008) was used to categorize morphological
parameters of the genotypes. Determination of level of
resistance on the incidences of M. vitrata and H. armigera
was based on pod damage and larval density on three
tagged plants in each plot for both pests. These were
recorded at weekly interval starting from 50% flowering to
pod maturity for each genotype. Larva density of M. vitrata
and H. armigera were determined by counting the number
of larvae found feeding on the pods of Dolichos lablab.
This was done on a weekly interval from 50% podding to
75% pod maturity. The pod damage was determined by
shriveling, twisting constriction, small sized holes and
conspicuous holes for damage by M. vitrata and H.
armigera respectively. Damage on the pods due to M.
vitrata and H. armigera in each genotype was done by
counting the total number of healthy pods and damaged
pods from the three randomly tagged plants. Damage by
M. vitrata is characterized by small holes while that of H.
armigera is characterized by large holes. Percentage pod
damage was calculated using the following formula by
(Bindra and Jakhmola, 1997 and Nazrussalam, et al.,
2007).
From the percentage, a scoring table was drawn as done
by Parvarthy et.al., (2011).
Table 1: Scoring the infestation rate of pod borers (M.
vitrata and H. armigera) in field bean and
categorization of resistance.
Score Scale Rate of
Infestation
Categorization of
resistance
1 0-10% Low infestation Highly resistant
2 11-30%
Moderate
infestation
Moderately resistant
3 31-50% High infestation Intermediate
4 51-70%
Severe
infestation
Susceptible
5 >71%
Very severe
infestation
Highly susceptible
Data analysis
Analysis of variance for the data was done using statistical
analysis package R (R Core Team, 2013). Correlation
analysis of the selected morphological parameters was
done to see their association with the pod damage and
incidence of the pest. Mean separation was done using
Turkey range of test (HSD).
RESULTS
The number of M. vitrata larvae was higher compared to
that of H. armigera across all sites. M. vitrata larvae was
with a mean of 3.53, 3.45 and 1.32 in Njoro, Eldoret and
Kakamega respectively. On the other hand, H. armigera
was with a mean of 2.97, 2.90, and 1.28 in Njoro,
University of Eldoret and Kakamega respectively as shown
in figure 1.
Figure 1. Incidence of M. vitrata and H. armigera in the
three sites of Study
For damage due to M. vitrata, genotypes Bahati, W7 and
G2 were categorized as highly resistant. Genotypes B1,
LG1, LG1MoiP4, LG1P3, T3S2P26, G1 and the check
genotypes (Local and Katumani), were found to be
moderately resistant, B1MoiP2, LG1KariP7, T5S3P9,
LG1KariP2, LG2KariP7, M5, were classified as
intermediate, LG1MoiP10 was categorized as susceptible.
There was no genotype categorized as highly susceptible
in the study. On the other hand, Bahati genotype was
categorized as highly resistant to H. armigera, M5 as
intermediate while the 16 remaining genotypes were
moderately resistant. This is summarized in the Table 2.
Significant variations (P ≤ 0.001) among the genotypes in
all the morphological parameters were observed as shown
in Table 3 except for growth habit which was significant at
(P ≤ 0.01).
Similarly, significant differences (P ≤ 0.001) across the
three sites were observed in number of pods per plant,
days to maturity, and days to 50% flowering, pod length
and pod fragrance.
Significant variations (P ≤ 0.05) were also observed in pod
wall thickness and pod pubescence across the sites.
However, there was no significant variation in raceme
position, pod attachment at maturity and growth habit
across the sites. There was also significant variation (P ≤
0.001) observed in site by genotype interaction in all the

4. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Boit et al. 347
Table 2: Scoring the infestation rate of pod borers (M. vitrata and H. armigera) in Dolichos lablab and categorization of
resistance
Scale
No
Scale of
infestation
Rate of Infestation
Categorization
of resistance
Scoring pod damage
(M.vitrata)
Scoring pod damage
(H.armigera)
1 0-10% Less infestation Highly resistant Bahati, W7, G2 Bahati and W7
2 11-30% Moderate
infestation
Moderately
resistant
B1, LG1,
LG1MoiP4,
Katumani,
LG1P3,Local, G1,
T3S2P26
B1, LG1, LG1MoiP4, Katumani,
LG1P3, Local, G1, T3S2P26,
LG1KariP2, T5S3P9, B1MoiP2,
LG1KariP2, LG2KariP7,
LG1MoiP10, G2
3 31-50% High infestation Intermediate LG1KariP2,
T5s3P9,
LG2KariP7,
LG1Kari P7,
B1MoiP2, M5
M5
4 51-70% Severe infestation Susceptible LG1MoiP10
5 >71% Very severe infestation Highly susceptible
Table 3: Means for the morphological parameters, % pod damage and larval counts across all the three sites during the 2014
cropping season
Key: Means with different letter within a column are significantly different (p≤0.05) where p≤0.05=*; p≤0.01=** and p≤0.001=*** as
analyzed b Turkeys. noppp- number of pods per plant, pod thick- pod thickness, pfrag- pod fragrance, ppubes- pod pubescence, rpos-
raceme position, pattunrip pod attachment unripe, grohab- growth habit, hpoddam- H. armigera pod damage, mpoddam- M.vitrata pod
damage, noofhlav- no. of H.armiger larva, noofmlav- no. of M. vitrata larva, daystom- days to maturity, G- genotype, Hsd- Honestly
significant difference.

5. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Int. J. Plant Breed. Crop Sci. 348
morphological parameters in the study except for pod
thickness, raceme position, and pod attachment at
maturity and growth habit. For the days to reach maturity
the range was (132.8-151.6) with the two checks Local
(151.6) and Katumani (145.4) taking the longest time to
attain maturity which was at par with G1 (146.3),
LG1KariP2 (140.3). B1MoiP2 took the shortest period to
reach maturity. The range taken by the genotypes to reach
50% flowering was (63.89-78.11) days with Local check
genotype taking a long period to reach 50% flowering
whereas M5 took a shorter period. Pod length was big in
LG1MoiP10 and small in M5. Pod wall was thick in W7 and
thin in genotypes B1, LG1KariP2, G1, LG1MoiP10,
T5S3P9, LG2KariP7, LG1KariP7, B1MoiP2 and T3S2P26
which were similar with the Local check genotype. Pod
pubescence were higher (5) in Bahati, and G2 whereas
low (2) in LG1MoiP10, LG1kariP7 and M5. Pod fragrance
was high in genotype B1, LG1MoiP10, LG1P3, M5 and the
check genotypes (Local and Katumani) however, it was
low in W7 and T3S2P26. Raceme position was high (7) in
Bahati, G2, B1, G1, LG1KariP7, W7 and low (3) in
B1MoiP2 and T3S3P9 while rest of the genotypes were
Intermediate (5). Pod attachment (unripe) was erect (1) in
all the genotypes except for B1MoiP2, LG1MoiP4,
LG1KariP7, and LG1KariP2 which were intermediate (2).
Growth habit of the genotypes was either Indeterminate (3)
or semi-determinate (2). The check genotypes (Local and
Katumani) were Indeterminate together with G2, B1,
LG1KariP2, T5S3P9 and T3S2P26. The rest of the
genotypes were semi- determinate.
When correlation analysis was done (Table 4), H. armigera
pod damage (r=0.17*) was significant and positively
correlated to days to Maturity. Number of H. armigera larva
(r=0.19*) was significant and positively correlated to
growth habit. Likewise, number of H. armigera larvae
(r=0.81***) and pod attachment when unripe (r=0.17**)
were significant and positively correlated to percentage
pod damage due to H. armigera. On the other hand,
significant negative correlation was detected in pod
thickness (r= -0.17*), pod pubescence (-0.24**) and
raceme position (-0.28***) to pod damage by H. armigera.
Significant positive correlation was recorded in number of
M. vitrata larvae (r=0.90***), pod attachment when
unripe(r=0.36***) and pod length (r=0.16*), while
significant negative correlation was observed in pod
pubescence (r=-0.31***), pod thickness (r= -0.25***) and
raceme position (r= -0.36***) to M. vitrata pod damage.
Pod attachment when unripe (r= 0.09***) recorded a
positive significant correlation to number of H. armigera
larvae, while pod pubescence (r= -0.10**), pod thickness
(r= -0.19*) and raceme position (r= -0.38***) showed a
negative significant correlation to number of H. armigera
larva. Positive significant correlation of pod attachment (r=
0.29***), pod fragrance (r= 0.17***) and pod length (r=
0.17*) to number of M. vitrata were also recorded.
Negative significant correlation in pod pubescence (r=
0.33***), pod thickness (r= - 0.31***) and raceme position
(r= -0.42 ***) to number of M. vitrata larva were observed
as shown in Table 4.
Table 4: Correlation analysis of morphological parameters and incidence/ severity of legume pod borers
daystom Grohab %hpoddam %mpoddam noofhlav noofmlarva pattunrip pfrag plength ppubes Pthick
Daystom _
grohab 0.16* _
hpoddam 0.17* 0.07ns _
mpoddam 0.01ns 0.02ns 0.81ns _
noofhlav 0.30*** 0.19* 0.81*** 0.74ns _
noofmlarva 0.02ns 0.12ns 0.77ns 0.90*** 0.78ns _
pattunrip -0.31*** -0.31*** 0.17** 0.36*** 0.09*** 0.29*** _
Pfrag -0.18* -0.07ns 0.04ns 0.19* 0.07ns 0.17*** 0.14ns _
plength -0.06ns -0.22** 0.07ns 0.16* 0.06ns 0.17* 0.37*** -0.02ns _
ppubes 0.15ns 0.022ns -0.24** -0.31*** -0.10** -0.33*** -0.22** -0.13ns -0.01ns _
pthick 0.15ns -0.12ns -0.17* -0.25*** -0.19* -0.31*** -0.22** -0.21ns 0.02ns 0.31*** _
Rpos 0.10ns -0.13ns -0.28*** -0.36*** -0.38*** -0.42*** -0.23*** -0.09ns -0.03ns 0.27ns 0.34ns
Key: Daystom- days to maturity, grohab - growth habit %,hpoddam –pod damage by H. armigera, %mpoddam- pod damage by M.
vitrata, noofhlav- number of H. armigera larvae, noofmlav- number of M. vitrata larvae, pattunrip- pod attachment unripe, pfrag- pod
fragrance, plength- pod length , ppubes- pod pubescence, p thick- pod thickness.
DISCUSSION
The genotypes showed variations to the attack by H.
armigera and M. vitrata across the three sites of study.
There were significant variations observed in number of
pod borer larvae per plant and pod damage. These
variations observed in terms of incidence and severity
among the genotypes may be due to the genetic makeup
of the plant and environmental factors (Patel, 2010). In all
the three sites of study, M. vitrata had higher number of
larval incidence compared to H. armigera which led to high
percentage pod damage by the former. The highest and
low pod damage and larval count observed among the
genotypes at Njoro and Kakamega respectively could be
explained by difference in temperature and amount of
rainfall in the different agro- ecological zones. This was
corresponding to a study byKumar and Nath, (2010),
where they reported that rainfall, average temperatures
and relative humidity have a positive impact on the
population buildup of legume pod borers. Kakamega

6. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Boit et al. 349
experienced a lot of rainfall especially during podding as
compared to Eldoret and Njoro which may have been the
cause for low levels of pod borers, due to unfavorable
weather conditions for oviposition. The rains might have
washed away the eggs of the insect. This was in line with
a study by Cheboi, (2015) where an evaluation for
resistance to pod borers in pigeon pea (Cajanus cajan)
was done. The author recorded low larval count and pod
damage of H. armigera in an area that received a lot of
rainfall during the time of pod formation. The fact that Njoro
recorded high pod damage and incidence of larva could be
attributed to legume pod borers preferring warm and
humid environments. Similar trend was realized by Ogah
et al. (2012) in a study of incidence of legume pod borers
on African Yam bean in Nigeria. They scored low incidence
of M. vitrata during dry season and concluded that it could
be due to lack of rains. They argued that less rainfall led to
less dense canopy formation that forms a hiding place for
the larvae against predators hence less larvae. Low pod
damage (0-10%) in genotypes G2, W7 and Bahati
categorized them as highly resistant to M. vitrata due to
low pest infestation. On the other hand, LG1MoiP10 was
categorized as susceptible to M. vitrata due to high pest
infestation of pod damage (51.45%). Parvathy et al. (2011)
in their study screened 40 genotypes of Dolichos lablab
and found only one genotype that showed resistance to
M. vitrata which had pod damage of 9.58% while the
susceptible one had 89.42%. This differed slightly from this
study that recorded a range of 4.64 - 51.45% which could
be attributed to environmental differences. On the other
hand, Rudranaik et al.(2009) reported that among 68
lablab genotypes screened for pod borer reaction, 6
genotypes were highly resistant as they recorded pod
damage of between (0 -9.42percent) for the resistant
genotypes which was almost similar to the resistant
genotypes in these findings (0 -7.49%). These shows that
most of Dolichos lablab genotypes available have low
resistance to pod borers.
Genotypes Bahati and W7 showed resistance (10.19%
and 10.77% respectively) to H. armigera while the high
percentage observed in M5 (35.56%) categorized it as
intermediate to the pest. The range of the percentage pod
damage due to H. armigera (10.19-35.56%) made these
results to differ with earlier workers such as Sarwar (2013)
who got a range of 4.06- 22.37% in a study that was
carried out on exploration on the resource of resistance in
chickpea (Cicer arietinum) genotypes to H. armigera. In a
study by Dinesh et al., (2017) on varietal response of
chickpea against H. armigera, none of the genotypes were
completely resistant. They reported lowest pod damage of
19.73 %( less susceptible) and highest pod damage
(37.04%) in moderately resistant genotype. The
moderately resistant genotype was similar to the finding of
this study though the less susceptible was slightly different.
Sarwar et al., (2011) while studying host plant resistance
relationship in chickpea against H. armigera, got a range
(13.24 - 38.0%) that was in agreement with the findings in
this study even though the crops were different. This could
be due to similar mechanisms exhibited by the leguminous
plants in response to attack by insect pest.
In the correlations of the morphological factors to pest
damage, it was evident that the number of H. armigera and
M. vitrata larva showed significant positive correlation to
pod attachment. The three resistant genotypes (Bahati, G2
and W7) had their raceme position (7) emerging from the
leaf canopy and their pod attachment as erect (1)
according to Dolichos lablab descriptor by (Gowda et al.,
2008). M5 genotype had more pod injury by H. armigera
while LG1MoiP4 showed susceptibility to M. vitrata
probably due to the intermediate raceme position exhibited
by the two genotypes. This could be explained by the fact
that the larva avoids exposed places. They prefer hidden
places where the predators hardly see them. This was in
agreement with Yadav et al., (2006) who noted that
spreading types of chickpea were more susceptible to H.
armigera damage than erect types. Mallikarjuna et al.
(2009) showed that lablab pods held above the canopy
were less damaged as compared to those held within the
canopy. The author further reported that pods contacting
any plant parts sustained more damage at the point of
contact.
In this study, there was no determinate genotype recorded,
but semi determinate type (G1, W7, Bahati, LG1,
LG1MoiP10, and M5) and the indeterminate genotypes
(G2, B1, the checks Katumani and local). Genotypes that
were resistant however seemed not to be influenced by
growth habit since they were in the same group as the
susceptible ones (M5 and LG1MoiP10). The indeterminate
type (T3S2P26 and Local and Katumani checks were
damaged by the pod borers. This contrasts with Saxena et
al.(1996) who reported that determinate genotypes are
more damaged by the legume pod borers as compared to
indeterminate types. Sharma et al. 1999) also showed that
in pigeon pea, genotypes with determinate growth habit,
where pods are bunched together at the top of the plant
were more prone to damage than in the indeterminate
ones. This could be explained by the fact that the resistant
types though having same growth habit to the susceptible
ones could be having some morphological or biochemical
factors influencing the feeding of the larvae.
Pod length was positively significant to M. vitrata larva,
LG1MoiP10 that had more pod damage by M. vitrata
possessed high length. This could be due to large surface
area that provides sufficient nutrition for the larvae. Similar
results were reported by (Jaydeep, 2004 and Sunitha et
al., 2008) who found out a positive correlation between pod
injury by M. vitrata and pod length on cowpea and pigeon
pea respectively. (Sangeeta, 2015), also realized a
positive correlation between pigeon pea pods and M.
vitrata incidence and stated that lengthy pods were more
suitable for damage by the pest as they harbored more
larvae per pod. Similarly, (Kumar et al., 2015) reported a
positive significant correlation in pod length and pod width

7. Evaluating Kenyan Dolichos (Lablab purpureus L.) Genotypes for Resistance to Legume Pod Borers (Maruca vitrata and Helicoverpa armigera) Using Morphological Markers
Int. J. Plant Breed. Crop Sci. 350
to pod damage by pod fly in pigeon pea. A negative
correlation in pod length to H. armigera in chickpea was
observed by Hossain et al. (2008). However, pod length
was not significant to H. armigera pod damage in this
study.
A negative correlation was detected in pod pubescence,
pod thickness, raceme position to M. vitrata and H.
armigera larvae and hence to the pod damage by the two
pests. It was evident that genotypes; Bahati, G2 andW7
that were resistant had high pod thickness as compared
with the susceptible one LG1MoiP10 and M5. Similarly,
(Halder and Srinivasan, 2011) reported a negative
correlation in pod thickness, angle between pods and pod
pubescence to pod damage by M. vitrata in cowpea. They
found that highly susceptible genotype had least number
of trichomes compared to highly tolerant genotype. A
negative correlation in pod thickness to pod damage was
also detected where the highly susceptible genotype had
0.077mm while the most tolerant recorded 0.089mm.
These results were in agreement to the findings in this
study where pod wall was 0.077mm in susceptible
genotypes and 0.114-0.119mm in resistant ones, except
that pod wall was thicker in Dolichos lablab walls.
Furthermore, (Kumar et al., 2015) reported a negative
correlation in pod wall thickness to pod fly damage. This
could be attributed to the fact that the larvae had hard time
penetrating thicker pods as compared to the less thick
pods.
The negative correlation realized in pod pubescence
coincided with a study done on cowpea by Oghiakhe
(1991) where the author detected high pod pubescent in
genotype that was resistant and reported that pubescence
affected oviposition, mobility, food consumption and
utilization by M. vitrata. Similarly, Kumar et al., (2015)
detected a negative correlation in pod pubescence to pod
damage by pod fly while undertaking their study on
morphological traits associated with resistance to pod fly
in pigeon pea. A negative correlation with larval population
of H. armigera was also detected on pod pubescence on
pods and leaves of chickpea (Brar, 2014)
Pod fragrance was significantly positively correlated to
number of M. vitrata larva but did not have significant
relationship with number of H. armigera larva. This showed
that M. vitrata larvae were affected by pod fragrance as
low fragrance was low in the resistant genotypes (Bahati,
G2 and W7) and high in susceptible one (M5). These
findings corresponded with Mallikarjuna (2009), who
reported positive significant relationship of pod fragrance
to larval boring in Dolichos lablab while studying the
relationship of morphological characters with pod borers’
damage.
CONCLUSION
Pod infestation and larval population could be used as a
selection criterion of resistant genotypes of Dolichos lablab
to H. armigera and M. vitrata. The study noted three
genotypes (G2, Bahati and W7) to be highly resistant to M.
vitrata, Bahati and W7 were highly resistant to H. armigera.
LG1MoiP10 was susceptible to Maruca vitrata while M5
was intermediate to H. armigera. These could be used in
Dolichos lablab breeding programs to come up with
genotypes that are resistant to the legume pod borers.
ACKNOWLEDGEMENT
University of Eldoret, Kenya Agricultural Livestock and
Research Institute (KALRO); Njoro and Kakamega are
highly appreciated for giving the land to undertake the
study. Great appreciations go to Miriam Kinyua who
provided the study material, Oliver Kiplagat for designing
the study, Emmy Chepkoech for managing the literature
and Leah Boit who did the analysis of the study and wrote
the first draft of the report.
COMPETING INTEREST
Authors have declared that no competing interest exists.
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Accepted 5 February 2018
Citation: Boit LC, Kinyua M, Kiplagat O, Chepkoech E
(2018). Evaluating Kenyan Dolichos (Lablab purpureus L.)
Genotypes for Resistance to Legume Pod Borers (Maruca
vitrata and Helicoverpa armigera) Using Morphological
Markers. International Journal of Plant Breeding and Crop
Science 5(1): 344-351.
Copyright: © 2018 Boit et al. This is an open-access
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