ABSTRACT
Field trials were conducted in 2012 and 2013 cropping seasons on a naturally heavily striga infested
field at the research farm of Federal University of Technology, Gidan kwano campus Minna to
evaluate the effect of seed treatment, sowing date and trap crop in the management of Striga
hermonthica. The experiment consisted of two varieties of sorghum (resistant ICSV1002 and
susceptible Gwari local varieties), three different concentration of Parkia pulp powder (0, 66 and
100 g/l) and one trap crop (soyabean variety TGX 1448-2E). Two sowing date (JUNE 15 and JULY
21) Were used in both years 2012 and 2013; the experiment was laid out in a randomized complete
block design with three replications. The screen house experiment, evaluated the variability of ten
soyabean, cowpea and groundnut varieties each, with respect to their ability to induce suicidal
germination of Striga hermonthica seeds. The experiment was 3x10x2 factorial laid out in
completely randomized design with five replications. Factor A consisted of Striga seeds at three
levels of inoculation (0, 2.5 and 5g) mixed with 20g of sterilized soil respectively. Factor B was 10
varieties of either soyabeans, cowpea or groundnut as trap crops. Factor C consisted of resistance
(ICSV1002) and susceptible (local) sorghum varieties. In the laboratory assay, the ten soyabeans,
cowpea and groundnut varieties each were screened for ability to stimulate the Striga seed
germination in vitro, using cut root technique .The experimental design was completely randomized
design (CRD) with four replications. In the field trial sorghum seeds soaked with 66g/l Parkia pulp
concentration significantly (p < 0.05) reduced Striga attack and produced higher yield in 2012 and
2013 compared to those primed with 100 and 0g/l (control) .The sorghum seed planted in July
significantly (p>0.05) had fewer Striga shoots and produced higher grain yield compared with those
planted in June in 2012 and 2013. Intercropping sorghum with soyabeans significantly (p<0.05)
reduced Striga attack per plot in both study years compared to sole sorghum. Among the ten
soyabeans, cowpea and groundnut varieties screened , soyabeans variety TGX 1448 -2E , cowpea
variety ITO4K -217-5 and groundnut variety RMP-91 had fewer Striga shoot and produced higher
grain yields compared to other varieties in the laboratory assay. The test crop (soyabeans, cowpea
and groundnut) varieties screened showed significant differences in stimulant production in their
ability to induce suicidal seed germination in Striga hermonthica. Soyabeans variety TGX 1448-2E,
cowpea variety ITO4K-217-5 and groundnut variety RMP-91 gave the highest germination
percentage compared to other varieties.
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TABLE OF CONTENTS
Title Page
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of tables ix
List of figures ix
List of plates xii
Abstract xii
INTRODUCTION 1
1.1 Distribution, production and uses of sorghum 1
1.2 Striga problem in sorghum 2
1.3 The trap crops 2
1.4 Statement of the problem 3
1.5 Justification 5
1.6 Objective 6
2.0 LITERATURE REVIEW
2.1 Biology of Striga hermonthica 7
2.2 Ecology and distribution of Striga species 8
2.3 Uses of Striga hermonthica 9
2.4 Host range 10
vii
2.5 Effect of Striga hermonthica on sorghum 10
2.6 Effect of different ecotypes of Striga hermonthica on cereals 12
2.7 Effect of sowing date, seed treatment and intercropping of
incidence of Striga hermonthica in sorghum 13
2.8 Host plant resistance mechanism 14
2.9 Factors influencing severity of attack 15
2.10 Methods of control of Striga hermonthica 15
2.11 Description of Parkia biglobosa 32
MATERIALS AND METHODS 33
3.1 Evaluations of seed treatment, sowing Date and trap crop in the
management of Striga hermonthica 33
3.1.1 Experiment 1 33
3.1.2 Experiment 2 37
3.1.3 Experiment 3 45
RESULTS 49
Experiment I: Evaluation of seed treatment, sowing date and trap crop in the
management of Striga hermonthica 49
Experiment II: Trap crops screening 105
Experiment III: Laboratory experiment 169
DISCUSSION
Experiment 1: Evaluation of seed treatment, sowing date and trap crop in the
management of Striga hermonthica. 177
Experiment II: Screening trial to evaluate the variability of ten soyabean genotypes,
ten cowpea genotype and ten groundnut genotype with respect to their ability
to induce suicidal germination of S. hermonthica seeds. 183
viii
Experiment III: An in vitro screening or bioassay of genetic variability of ten soyabean
genotypes, ten cowpea genotypes and ten groundnut genotypes with respect to
their ability to induce suicidal germination of Striga hermonthica seed.
185
Conclusion and Recommendation 187
REFERENCES 190
APPENDICES 204
ix
CHAPTER ONE
INTRODUCTION
Distribution, Production and Uses of Sorghum
It is believed that sorghum originated in Africa, more precisely in Ethiopia, between 5000
and 7000 years ago.From there it was distributed along the trade and shipping route around the
African continent and through the middle East to India at least 3000 years ago (FAOSTAT, 2011).
FAO reported the United States of America as top sorghum producer with a harvest of 9.7 million
tonnes followed by India, Nigeria, Sudan, and Ethiopia (FAOSTAT, 2011). The sub-Saharan Africa
produces about 18million tonnes of sorghum annually making it the second most important cereal
crop after maize (Zea mays L.) which is produced in about 27million hectares (Haussmann et al.,
2000,).
Nigeria is the leading sorghum producer in Africa followed by Sudan, Ethiopia and Burkina Faso.
However, in terms of productivity, Egypt achieved the highest yields per unit area followed by
Algeria, South Africa, Uganda and Ethiopia. Total sorghum productions from all sorghum producing
countries were 55.6 million tonnes in 2010 (FAOSTAT, 2006). Globally, sorghum (Sorghum bicolor
(L) Moench) is the fifth most important staple food crop after wheat, rice, maize, and barley (FAO,
2012). Sorghum is consumed by more than 70% of the population in the sub-saharan Africa (IITA,
2004). The crop is produced for its grain, which is used for food and stalks for fodder and building
materials. In developing countries, sorghum is used primarily as animal feed and in the sugar, syrup
and molasses industry (Dahlbert et al., 2004). Recent work has shown that sorghum and millet
(Pennisetum glaucum (L.) R. Br) are rich in antioxidants and gluten-free, which make them an
attractive alternative for wheat allergy sufferers (Dahlbert et al., 2004).
2
1.2. Striga Problem in Sorghum
Striga hermonthica is the most troublesome among the six common Striga species reported in
Nigeria, which has the highest potential of a serious economic damage in cereal production
(Emechebe et al. 1991)
Striga hermonthica has been reported to reduce the yield of the crop by up to 100% in Nigeria
when infestation occurs at an early stage (Ogborn, 1977). Striga problem has led to migration of
peasant families to Striga free areas, shifting cultivation, farm abandonment or change of cropping
pattern (Parker and Riches, 1993). Due to dwindling land resources, soil fertility problems and weed
build up; the increase in crop output is becoming difficult day by day. In these circumstances, the
only way to have more production is by increase in output per unit of land area (Khan et al., 2000).
Dugje et al. (2006) reported in a survey, that 94% of farmers sorghum fields in North- East Nigeria
were infested with S. hermonthica and that Striga control in sorghum is more challenging than other
cereal crops because sorghum matures late compared to maize.
1.3 The trap crops
Soyabean
Soyabean is a legume; like all other peas and beans, lentils and peanuts, it belongs to the
large botanical family leguminosae. It is a versatile grain legume because it has a variety of uses.
The crop has ability to fix atmospheric nitrogen and therefore, improves soil fertility.
Soyabean is used in the manufacture of cooking oil, margarine, salad dressing, milk, flour,
paints, vanishes, linoleum, rubber fabric, soap, printing ink, spaghetti, baby food, milk of plant
origin and meat substitutes and high protein beverages in the industry(Abdo and King, 1967, Metcalf
and Alkins, 1980). Soyabean is known to be a source of calcium which contributes to bone
development and reduce the problem of major bone disease called osteoporosis. It is also a source of
iron, zinc, phosphorous, vitamin A, C and B6, thiamine, riboflavin and niacin. Its inclusion in diet
3
helps to decrease cholesterol by an average of 13% and consequently reduce heart disease risk by
54%. Isoflavones present in soyabean prevent menopause diseases while genisten and daidzein also
produced by this crop prevent cancer disease (Anon, 1999).
Cowpea
Cowpea is leguminous crop that is widely grown in Africa under marginal production
systems. Cowpea is able to perform well even in marginal soils due to its ability to fix substantial
nitrogen in the soil (Hall, et al., 2003). Cowpea is an important source of affordable protein, B
vitamins, and minerals. Inadequate intake of protein in the diet is one of the factors that contribute to
high prevalence of malnutrition in developing countries.
Cowpea is widely grown as an intercrop with cereals, through improved breeding lines and
agronomic practices. There is potential for increased production of cowpea despite the prevailing
production challeng
es of declining soil fertility, unreliable rainfall, pest and diseases (Singh, 2005).
Groundnut
Groundnuts (Arachis hypogaea), also known as peanuts or monkey nuts, are the edible seeds
of a legume plant that grow to maturity in the ground. It is cultivated in nearly 100 countries, with
over 90% of which are developing countries, (Hall et al., 2003).
The nuts are high in edible oil content (40-50%) and protein (25%), and also serve as a good
source of a variety of essential vitamins and minerals. They can be consumed directly or processed
into oil or cake/meal, confectionary products or snack food. The kernels can be used for human
consumption, vines as fodder for cattle, and nitrogen fixed from its roots as nutrients for the soil.
1.5 Statement of the problem
Striga control is more difficult and complicated than the control of other weeds. This is due
mainly to its biology, because of Striga seeds after ripening requirements, not all are pre-conditioned
4
for germination at the same time thus necessitating persistent control.Striga problem has led to
migration of peasant families to Striga free areas, shifting cultivation, farm abandonment or change
of cropping pattern (Parker and Riches, 1993).
As population pressure and demand for food production increase, land use intensified. With
greater use of monocropping and little or no fallow, populations of these parasites have gradually
increased and become threats to food production (Doggett, 1984).Various methods have been
recommended for the control of Striga in sorghum, including cultural practices such as hand
weeding, planting of trap crops, planting of Striga tolerant or resistant varieties and chemical or
herbicide treatments such as the use of high levels of chemical fertilizers especially nitrogen and
ethylene gas to induce suicidal germination and herbicides, which give some reasonable results but
are prohibitively expensive or are either incompatible with the cropping system for the resource
poor farmer in Striga-stricken areas of Nigeria (Kuchinda et al., 2003).
Despite these efforts, there has been limited success and no single known control method is
effective in control of Striga in sorghum. The variability within and between Striga species and the
diversity of African farming systems is also contributing to constraint in Striga
control.Strigahermonthica is difficult to control because of the build-up of a large reserve of it in the
soil which remains viable for many years (Kanampiu et al., 2003).
5
Figure 1: General life cycle of Striga species
1.6 Justification
The various control methods such as land preparation, hand-pulling, hoe-weeding, trap cropping
have been tried out singly over the years with no conclusive and consistent results for the peasant
farmer, partly because of huge amounts of seeds that accumulate over time in the seed bank
(Oswald, 2004). Furthermore, variability within and between Striga species and the diversity of
African farming systems,and other methods of control such as the use of high levels of chemical
fertilizers especially nitrogenous, ethylene gas to induce suicidal germination and herbicides, which
give some reasonable results, are prohibitively expensive for the resource poor farmer in Strigastricken
areas of Nigeria (Kuchinda et al., 2003). This has aroused interest in a more integrated
6
approach among researchers. Dashiell et al., (2000) also reported that Striga control is likely to be
achieved by combining a range of individual component technologies into a programme of
integrated Striga Control (ISC) to provide more flexible and sustainable control over a wide range of
biophysical and socio-economic environments.Schulz et al., (2003) also reported that single control
options for S. hermonthica will not be as effective as combining a range of individual technologies
into integrated packages.
An alternative control approach against Striga would be the use of natural products that
would inhibit or induce the germination of Striga seeds in order to deplete the Striga seed bank in
the soil. Screen house evaluation of Azadirachta indica (neem) and Parkia biglobosa (locust bean)
to control S.hermonthica revealed that products based on the two species were effective to reduce
Strigaemergence (Marley, et al., 2004; Kolo et al., 2005, Kolo and Mamudu 2008).
An integrated Striga management package of combining host seed treatment, different dates of
planting and trap crop was considered in this research. So there is need for further investigation with
respect to the natural product and the trap crops used in this research with S. hermonthica strain from
other locations in Nigeria.
1.4 Objectives
The objectives of this research therefore were to:
i. Determine the effectiveness of seed treatment, sowing date and intercropping system in
integrated management of Striga hermonthica in sorghum;
ii. Evaluate the priming effect of Parkia pulp in the control of S.hermonthica in a Guinea
savanna ecosystem; and
iii. Evaluate the variability of ten soyabean, cowpea and ground nut species each with respect to
the ability of their root exudates to stimulate the germination of Striga hermonthica seeds.
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