RESISTANCE AND QUALITY PARAMETERS OF SOME COWPEA VARIETIES INFESTED WITH COWPEA WEEVILS (Callosobruchus maculatus Fabricus).

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RESISTANCE AND QUALITY PARAMETERS OF SOME COWPEA VARIETIES INFESTED WITH COWPEA WEEVILS (Callosobruchus maculatus Fabricus).

ABSTRACT

This study evaluated the level of resistance in seven breeding lines of cowpea seeds from the Institute of Agricultural Research, Samaru, Zaria, Nigeria and three landraces collected from Agbani market, Enugu, Nigeria and conducted at the Centre for Agricultural Research and Extension laboratory of the Federal University of Technology, Owerri in 2015/2016 Academic session. All data were subjected to Analysis of Variance (ANOVA) and mean separation was done using least significant difference at 5% level of probability. The seeds were infested with cowpea weevils (Callosobruchus maculatus) in five repetitions. Proximate analysis, sensory, organoleptic and germination tests were carried out in the laboratory to evaluate the effect of bruchid infestation on the breeding lines and landraces of cowpea seeds in storage. 50g of each seeds were stored in plastic container covered with calico material. The proximate analysis for the seeds was to determine if infestation influenced the percent of crude protein, fat, fibre, ash, moisture and carbohydrate contents of the seeds. There was reduction in protein and carbohydrate content of the seeds (SAMPEA-1 from 23.53% to 18.17% and 21.72% protein then carbohydrate from 58.80% to 46.53% and 42.22%). In the first and second trial the results showed similarity. For the germination test among the seeds, SAMPEA-8 showed higher percent (35.0 and 45.0 % for field germination while 61.7 and 70.0 % for laboratory germination) than other seeds. Seed damage percent recorded lowest in SAMPEA-8 (10 and 14 %) than the other cultivars. In order to reduce postharvest losses of cowpea, the result from this research shows that planting of resistant variety such as SAMPEA-8 may reduce infestation and damage to seeds by cowpea weevils (Callosobruchus maculatus), enhance the shelf life and also boost food security programme in Nigeria.

Keywords: Callosobruchus maculatus, breeding lines, cowpea weevil, landraces, cowpea, cultivar.

TABLE OF CONTENT

 

 

CERTIFICATION                                                                                                                   i

DEDICATION                                                                                                                        ii

ACKNOWLEDGEMENT                                                                                                       iii

TABLE OF CONTENT                                                                                                          iv

LIST OF TABLES                                                                                                                  viii

LIST OF PLATES                                                                                                                   x

LIST OF FIGURE                                                                                                                   xi

ABSTRACT                                                                                                                            xii

CHAPTER   ONE

1.0         Introduction                                                                                                               1

1.2         Justification                                                                                                                4

1.3        Objectives                                                                                                                   4

 

CHAPTER TWO

2.0        Literature review                                                                                                        5

2.1        Brief history on origin, distribution and production of cowpea.                                5

2.2        Botany, characteristics and ecological requirements.                                                6

2.3        Cultivars of cowpea.                                                                                                   8

2.4        Sowing and spacing for sole cowpea                                                                          8

2.5        Economic importance of cowpea.                                                                              9

2.6        Insect pests and diseases of cowpea.                                                                          10

2.6.1     Field pests                                                                                                                   10

2.6.2     Storage pests                                                                                                               11

2.6.3     Description of callosobruchusmaculatus                                                                  11

2.6.4     Control of pests                                                                                                           12

2.6.5     Diseases of cowpea and their control.                                                                        13

2.7        Harvesting and storage of cowpea.                                                                             13

2.7.1     Harvesting.                                                                                                                  13

2.7.2     Storage.                                                                                                                       14

 

CHAPTER THREE

 

3.0        Materials and methods.                                                                                               15

3.1        Laboratory culture of insects.                                                                                     15

3.2        Sources of seed varieties.                                                                                           16

3.3        Treatment/ experimental design.                                                                                16

3.4        Germination tests.                                                                                                       18

3.5        Organoleptic evaluation.                                                                                             19

3.6        Mortality and oviposition count                                                                                 20

3.7        Emergence.                                                                                                                 22

3.8        Damage assessment                                                                                                    23

3.9        Properties’ evaluation.                                                                                                23

3.9.1     Seed coat colour                                                                                                         23

3.9.2     Seed size                                                                                                                     23

3.9.3     Seed texture                                                                                                                23

3.9.4     Mouldiness                                                                                                                 23

3.9.5     Seed weight loss assessment.                                                                                     23

3.10      Proximate analysis                                                                                                     24

3.11      Statistical analysis                                                                                                      24

CHAPTER FOUR

4.0        Results.                                                                                                                       25

4.1        Field and laboratory viability tests for uninfested and infested cowpea seeds

at 7days after planting.                                                                                              25

4.2        Percentage mortality of infested cowpea breeding lines and landraces for first

trial at 24, 48 and 72 hours after infestation with callosobruchusmaculatus.           27

4.3       Percentage mortality of infested cowpea breeding lines and landraces for  second trial at 24, 48, 72, 96, 120 and 144 hours after infestation.                     29

4.4        The mean number of eggs laid on some breeding lines and land races of

cowpea seeds.                                                                                                             31

4.5        The mean number of emerged callosobruchus maculatus from cowpea seeds

for the first trial.                                                                                                         33

4.6        The mean number of emerged bruchid at 24, 48, 72, 96, 120 and 168 hours

and second filial generation for second trial.                                                             35

4.7        Damage assessment of the breeding lines and landraces of cowpea seeds.               37

4.8        Result of organoleptic ratings of cooked uninfested breeding lines and

landraces of cowpea.                                                                                                  39

4.9        Organoleptic ratings of cooked infested cowpea for first and second trial.               41

4.10      Results of morphological properties of the breeding lines and landraces of

cowpea seeds.                                                                                                             43

4.11      Seed weight loss assessment of the breeding lines and landraces of cowpea.           45

4.12      The result of proximate analysis for uninfested cowpea seeds.                                  47

4.13      Results of proximate analyses for infested cowpea seeds of first and

second trial.                                                                                                                 49

CHAPTER FIVE

5.0        Discussion                                                                                                                  52

CHAPTER SIX

6.0        Conclusion and recommendation                                                                               57

REFERENCES                                                                                                                      59

APPENDIX                                                                                                              75

CHAPTER ONE 1.0        INTRODUCTION

Cowpea (Vigna unguiculata L. Walp) is a warm weather crop that is well adapted to dryer regions of the tropics like Nigeria where other food legumes do not thrive well. It is one of the most economically and nutritionally important indigenous African grain legumes produced throughout the tropical and subtropical areas of the world (Abate et al., 2011). Nigeria is the largest producer and consumer, accounting for 45 % of world’s production (Lowenberg-DeBoer and Ibro, 2008; Ndong et al., 2012) while Africa accounts for about 75 % (Brisibe et al., 2011). Vegetable cowpea called ‘akidi’ among the Igbos is botanically known as Vigna unguiculata sub-specie sesquipedalis in the legume family leguminosae and subfamily papallionoidae (Udensi et al., 2007). It has two genotypes that exist in the farming system of South-East Nigeria, namely; those with climbing habit called Vigna unguiculata subspecies sesquipedalis commonly called “Akidi enu”; and other with prostrate habit referred to as Vigna unguiculata subspecies denkintians and known as “Akidi ani” (Redden, 1987; Ano and Ubochi, 2008).

Ghaly and Alkoaik (2010) reported that cowpea seed, pods and leaves are consumed in fresh form as green vegetables in some African countries, while the rest of the cowpea plant, after the pods has been harvested, serves as a nutritious fodder for livestock (Abebe et al., 2005) and also a source of cash income when sold to farmers who use them as livestock feed (Dugje et al., 2009).

Cowpea nutritive value makes it an extremely important protein source to vegetarians and people who cannot afford animal protein (Adeyemi et al., 2012). The seeds are rich sources of mineral. Cowpea seed contains 23.4 % protein, 1.8 % fat, 60.3 % carbohydrate and is also a good source of vitamins and phosphorus (Adeyemi et al., 2012).

 

The chemical composition and nutritional properties of cowpeas vary considerably according to cultivar. For effective utilization of newly developed cowpea cultivars for human nutrition, the removal or reduction of antinutritional factors and evaluation of their nutritional properties are necessary (Giami, 2005). It is known that some antinutritional factors interfere with digestion and also make cowpea seeds unpalatable when consumed. These factors are divided into protein and non- protein factors (Duranti and Gaius, 1997; Sharma and Thakur, 2014). The non proteins include alkaloids, tannins, phytic acid, sapponins and phenols while lectin, antifungal peptides, trypsin and chymotrypsin inhibitors are protein antinutritional factors (Duranti and Gaius, 1997).

 

The qualities of staple crops such as cowpea in West Africa have been greatly impaired by the attack of insect pests in storage. The major storage pest of cowpea is Callosobruchusmaculatus (Brisibe et al., 2011) with infestations on stored grains may reach 50 % within 3-4 months of storage (Dugje et al., 2009). Perforations by these bruchids reduce the degree of usefulness and make the seeds unfit either for planting or human consumption (IITA, 1989; Ali et al., 2004). Similar to other stored product insect pests, oviposition, development and survival of these pests are influenced to a large extent by temperature and humidity (Lale et al., 1996). Callosobruchus maculatus (Coleoptera: Bruchidae) are tropical and subtropical agricultural pests which are extremely easy to manipulate, maintain and has a very rapid life cycle (Beck and Blumer, 2007). The attack on these crops begins in the field and continues in storage, which is liable to degradation with rapid increase in population of the pest. (Agboola, 1982; Ivbijaro et al., 1985; Lale, 1992). Losses of crops during storage, processing and marketing may be as high as 50 % (Okunola et al, 2007).

 

However, in the production and storage of this important food crop, cowpea, has faced so many constraints, such as diseases and the unlimited use of fertilizers and irrigation inputs but insect pest are one major constraint (Brisibe et al., 2011). If cowpea seeds are to be stored for longer periods, it is advisable to treat the seeds with recommended insecticides such as dust, aluminium phosphide (Asare et al., 2011).

 

Synthetic insecticides are widely used, and misused, to control storage insects, as evident in several literature reports. Sudden deaths, blindness, and skin irritation are among the problems attributed to use of inappropriate storage chemicals in Nigeria (Magaji et al., 2005). Control of insect with chemical insecticides has serious disadvantages such as the development of resistant strains, toxic residue, worker’s safety and increasing costs (Ofuya et al., 2008). Therefore, a modest way of increasing food availability to cope with the Nigerian ever-increasing population at low cost is to protect what has been produced and to achieve this, plant materials that are inexpensive, safe to the environment, and to users and consumers alike, need to be exploited as suitable alternatives to the expensive, toxic and environmentally unsafe synthetic insecticides eg diclorvos, chlorpyrifos, trichlorphon etc.

Sensory analysis is one of the oldest means of quality control. It is an essential part of the mandatory assessment of food quality, while also examining the deeper study of the interdependence between physiological and psychological phenomena in the very process of perception of sensory qualities. Sensory analysis, allow manufacturers to identify, understand and respond to consumer preferences more effectively (Fanatico et al., 2007; Saha et al., 2009). Additionally, the identification of sensory characteristics and consumer preferences, help manufacturers to increase competition in the market for other producers (Ponte et al., 2004;

Young et al., 2004).

JUSTIFICATION.

The production of cowpea is restricted by a number of biotic and abiotic factors both in the field and in storage. Among the constraining biotic factors are insect pests. Storage of cowpea grain over long periods, especially at small scale farming levels, is limited due to attack by cowpea bruchids (Callosobruchus maculatus F.). This study is an attempt to determine and evaluate the effect of quality and nutritional parameters, through sample analyses, viability and organoleptic tests, on the resistance of these seeds to Callosobruchus maculatus infestation. The result should aid local farmers and researchers alike in choosing cowpea seeds for planting and breeding purposes.

OBJECTIVES

The objectives of this study are to;

  • investigate the physical and organoleptic characteristics of cowpea as to whether they aid or deter bruchid infestation.
  • determine if the screened cowpea land races or breeding lines are resistant to bruchids.
  • assess the effect of infestation on the physical and organoleptic characteristics of infested cowpea seeds.
  • determine the damage and weight loss on the infested cowpea.

RESISTANCE AND QUALITY PARAMETERS OF SOME COWPEA VARIETIES INFESTED WITH COWPEA WEEVILS (Callosobruchus maculatus Fabricus).

 

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