ABSTRACT
The control of yam rot in storage using the leaf extract of Azadirachta indica, Piper nigrum, Vernonia amygdalina and Ocimum basilicum. The experiment was conducted in the Laboratory Department of Plant Science and Biotechnology, College of Natural Sciences, Michael Okpara University of Agriculture, Umudike, Using a Completely Randomized Design. The Yam tubers used were visually classified as having 40% nematode infestations and obtained from the Yam barn of National Root Crops Research Institute (NRCRI), Umudike, Nigeria. Four samples of fresh Yam were also collected from the barn for pathogenicity test. The plant extracts were diluted with tap water at the ratio of 1: 5 (1ml of plant extracts + 5 ml of water) respectively. 150 cl of tap water was thoroughly mixed with 10 ml of each diluted extracts in buckets and the infested yam were soaked for 24 hours. The Yam tubers were removed from the buckets while data on sprouting, Rot and Insects were recorded according to the method of Salawu. The proximate of evaluation of the treated and the untreated tubers were recorded in terms of Protein, Fibre, Fat, Moisture, Ash, and Carbohydrate contents. The pathogenic results shows that Fungi like Rhizopus, Penicillum, Aspergilus, Fusarium and B. theobrone were the identified rot organism. Sprouting of Yam, treated with different extracts showed that only A. indica ranged from 0.75 ± 0.500 – 1.0 ± 0.00. However the effect of extracts of P. nigrum, V. amygdalina and control had significant effect P < 0.05 on the sprouting of Yam tubers. From the means, control treatment ranging from 0.50 ± 0.58 to 0.75 ± 0.58 had the lowest sprouting rate. There was also a significant effect P < 0.05 of Water on the Yam rot. The rot affected the carbohydrate, Protein and Fat content of the Yam tuber. Generally the extracts had a strong advantage to the germination, pathogenicity and Nutritional content of Yam tubers in Storage.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of contents vi
List of tables viii
Abstract ix
CHAPTER ONE
1.0
Introduction 1
1.1 Justification 2
1.2 Aims and objectives 3
CHAPTER TWO
2.0 Literature review 4
2.1 Yam (Discorea
species) 4
2.2 Botany of yam 5
2.3 Yam rot 6
2.3.1 Classification of yam rot 6
2.3.2 Dry rot 6
2.3.3 Soft rot 7
2.3.4 Wet rot 7
2.3.5 Control of yam rot 7
2.4 Botanical
control of post harvest biodeterioration in yam tubers 9
2.5 Ocimum
brasilicum (scent leaf) 10
2.6 Azadirachta
indica (neem plant) 11
2.7 Piper
nigrum (uziza leaf) 13
2.8 Vernonia
amygdalina (bitter leaf) 14
CHAPTER THREE
3.0 Material and methods 16
3.1 Study area 16
3.2 Plant materials 16
3.3 Source of yam tubers 16
3.4 Preparation of leaf extracts 16
3.5 Dilution of extract/treatment 17
3.6 Isolation of fungi 17
3.7 Characterization and identification of
isolates 18
3.8 Fungi isolates 18
3.9 Pathogenicity test 18
3.10 Experimental design 19
3.11 Proximate test of yam tubers 19
3.11.1 Moisture determination 19
3.11.2 Determination of crude protein 20
3.11.3
Estimation of crude lipid 20
3.11.4
Determination of crude fibre 20
3.11.5
Determination of ash content 21
3.11.6
Carbohydrate determination 21
CHAPTER FOUR
4.0 Results
22
4.1 Effect
of plant extracts on yam sprouting 22
4.2 Effect
of leaf extracts on insect infestation 23
4.3 Effect
of leaf extract on the rot of yam tubers in storage 24
4.4 Proximate
analysis of treated yam tubers 25
4.5 Fungi
isolated from rotten yam 26
CHAPTER FIVE
5.0 Discussion/conclusion
27
5.1 Discussion
27
5.2 Conclusion 29
References 30
LIST OF TABLES
Table Title
Page
4.1: Effect of plant extracts on yam sprouting 22
4.2: Effect of leaf extracts on insect infestation 23
4.3: Effect
of leaf extract on the rot of yam tubers in storage 24
4.4: Proximate analysis of treated yam tubers 25
4.5: Occurrence of fungi isolate in rotten yam 26
CHAPTER
ONE
2.0
INTRODUCTION
One of the most pressing
problems facing the countries of third world is food scarcity. It is reported
that nearly one billion people are challenged by severe hunger in their nations
of which 10% actually die from hunger-related complications (Kana et al., 2012). A substantial part of
this hunger problem stems from inadequate agricultural storage and produce
preservation from microbes induced spoilage (Salami and Popoola, 2007; Kana et al., 2012). According to Arya (2010),
of all losses caused by plant diseases, those that occur after harvest are most
costly. However, post-harvest deterioration caused by microbial invasion of
tuber crops are the cause of losses in its production which contributes hugely
to the unsuccessful long-term storage of the root-tubers (Amadioha 2007; Okigbo et al., 2009). These pathogenic organisms gain entry into tubers
through the area where the tuber are separated from the stems at harvest, or
the root tips which break during harvesting or cracks on the tubers surfaces
sustained during harvesting, transit or storage (Okigbo et al., 2009). Apart from these huge losses in the quantity of
produce, post harvest rot-losses have a lot of other consequences on produce
quality (Nwachukwu et al., 2008).
Some workers reported that rot organism produce extra-cellular enzyme such as
amylases, celluloses, zylanases, polygalactunases and pectin-methyl esterases
which degrade cell wall component of susceptible produce leading to emission of
foul odour and water (Salami and Popoola, 2007; (Amadioha, 2012; Oladoye et al., 2013). Hence rots reduce the
market value of the affected produce, hamper the addition of value to them and
prevent produce to complete their roles in the
food chain. Fungal
pathogens produce various mycotoxins on produce like oil seeds, maize and
cereals. They are dangerous in minute quantities and present extreme toxicity
due to their ability to withstand heat (Okigbo, 2004; Shukla et al., 2012). The mycotoxins of most
agricultural importance are aflatoxins, fumonisins, ochratoxinA zearalenone and
deoxynivanelol (Bankole et al., 2013).
According to this source, fungal toxin contamination of food products can cause
acute or chronic intoxications, leading to reduced shelf life; exacerbate
disease conditions in humans leading to 40% loss of economic productivity
(Bankole et al.; 2003). Mycotoxins
are carcinogenic, cytotoxic, hepatotoxity, nephrotoxic and teratoxic (Shukla et al., 2012). They affect agricultural economy
of developing countries, reducing their produce exportability (Shukla et al., 2012). Enormous postharvest
losses have been attributed to fungal deterioration (Okigbo, 2002; Shukla et al., 2012). In a bid to control these
organisms and the deterioration from post harvest products, several control
technique have been devised among which are the use of botanicals.
1.1 JUSTIFICATION
The effect of storage rot
in yam cannot be over emphasized. Postharvest losses attributed to fungal
diseases and some microorganisms associated with deterioration in yams includes
Aspergillus flavus, A. niger,
Botryodiploidia theobronmae, Fusarum oxysporum, F. solani, Penicullum
chrysogenum, P. oxaleum, Trichoderma viride and Rhizopus nodosus (Okigbo
and Ikediugwu, 2000; 2001; 2002; Okigbo, 2004).The rot deterioration in yam has
lead to hunger and food scarcity in Nigeria where yam is a stable food (Kana et al., 2012). The carcinogenicity,
tetratogenic and non-biodegradability of synthetic or chemical control of rot
in yam makes it unfavourable thereby craving more indulgence to the use of
biological control in rot (Enyiukwu et
al., 2013a). Base on this background, the need to evaluate the use of some
indigenous plant leaf powder extracts on yam rot was considered. The plants
used includes Azadirachta indica, Ocimum
basilicum, Piper nigrum and Vernonia amygdalina. The result of this
research will serve as a reference point to the yam farmers, scientist, and
nutritionist in choosing the best plant pesticides used against yam rot in
storage.
1.2 AIMS AND OBJECTIVES
The objectives of this
research are;
·
To establish the
pathogenicity of fungal organisms associated with yam tuber rots (white yam
varieties).
·
To evaluate the effects
of some plant leaf extract on inhibition of yam rot in storage (Vernonia amygdalina, Azadirachta indica,
Ocimum basilicum and Piper nigrum).
·
To ascertain the effect
of the plant leaf powder on yam composition.
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