THE EFFECT OF FUNGICIDE SEED TREATMENTS ON GERMINATION AND VIGOUR OF MAIZE (ZEA MAYS L.) SEEDS

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Moisture Content

The moisture content of a sample is the loss in weight when it is dried in accordance with the rules outlined by International Seed Testing Association (ISTA) (ISTA, 2008). It is expressed as a percentage of the weight of the original sample. The methods prescribed for the calculation of moisture content of grain are designed to reduce oxidation, decomposition or the loss of other volatile substances while ensuring the removal of as much moisture as possible (ISTA, 2008). Moisture content is intimately associated with all aspects of physiological seed quality (Vertucci, 1989). Proven relationships exist between moisture content and seed maturity, optimum harvest time, longevity in storage, economies in artificial drying, injuries due to heat, frost, fumigation, insects and pathogens, mechanical damage and seed weight (Grabe, 1989). Problems in moisture measurement of seeds are imposed by the chemical composition of the seed and the interactions of seed and water. Water is held in the seed with varying degrees of strength, ranging from free water to chemically bound water (Hunt and Pixen, 1980 as cited in Grabe, 1989). During drying the free water is removed with difficulty. The moisture content is the amount of water in the seed and is usually expressed as a percentage. A small change in seed moisture content has a large effect on the effect on the storage life of the seeds (Spears, 2002). Seed moisture content and the temperature during testing are critical factors in many vigour tests. These are factors that require less precision during germination testing. Moisture content is important for results of standard germination and vigour tests (Grabe, 1989; Copeland and McDonald, 2001).

Germination

Germination is the emergence and development of the seedling to a stage where the aspect of its essential structures indicates whether or not it is able to develop further into a satisfactory plant under favourable conditions in soil (Copeland and McDonald, 2001). The object of the germination test is to determine the maximum germination potential of a seed lot as well as the evaluation of a particular seed lot under an ideal set of conditions (ISTA, 2008). In this process the seed’s role is that of a reproductive unit (Copeland and McDonald, 2001). Different definitions of germination exist. A seed physiologist would define germination as “the emergence of the radicle through the seed coat” (AOSA, 1991 as cited in Copeland and McDonald, 2001), while a seed analyst’s definition would be “the emergence and development from the seed embryo of those essential structures, which for the kind of seed in question are indicative of the ability to produce a normal plant under favourable conditions” (ISTA, 2008).

Light

The influence of light intensities varies greatly for different species. Some seeds require moonlight (100 lux) while light intensities from indirect light (1080-2160 lux) from the average seed-testing laboratory are probably adequate for germination of most species (Copeland and McDonald, 2001). The influence of light is strongest immediately after harvest and diminishes with age of the seed and eventually disappears (Toole et al., 1957 as cited in Copeland and McDonald, 2001). In a study conducted by Thanos and Mitrakos (1979), it was found that the maize caryopses sown in water germinate equally in either darkness or under any light regime (Thanos and Mitrakos, 1979). Further results proved the existence and involvement of phytochrome in the germination of maize caryopses (Thanos and Mitrakos, 1979).

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Vigour tests

Safe storage conditions were defined as those that maintain seed quality without loss of vigour for three years (Abba and Lovato, 1999). In 1979, the Association of Official Seed Analyst’s Vigour committee defined seed vigour as “those seed properties which determine the potential for rapid, uniform emergence and development of normal seedlings under a wide range of field conditions” (Copeland and McDonald, 2001). Seed vigour is defined by the ISTA as “the sum total of those properties of the seed that determine the level of activity and performance of the seed during germination and seedling emergence” (ISTA, 2006). Seed vigour assesses the ability to germinate under a wide range of environmental conditions (Shah et al., 2002; http://www.ag.ohio-state.edu/~seedsci/svvto1.html).

TABLE OF CONTENTS :

CHAPTER ONE: GENERAL INTRODUCTION
- 1.1 Background and motivation of the study
- 1.2 Objectives of the study
- 1.3 Structure of the thesis
- 1.4 Literature cited
CHAPTER TWO: LITERATURE REVIEW
- 2.1 Introduction to maize (Zea mays L.)
- 2.1.1 Origin and biology of Zea mays L
- 2.1.1.1 Africa
- 2.1.1.2 South Africa
- 2.1.2 Uses of maize
- 2.2 Diseases of maize
- 2.3 Chemical seed treatment to control maize diseases
- 2.4 Storage of grain
- 2.5 Aspects of seed quality and vigour
- 2.5.1 Moisture content
- 2.5.2 Germination
  - 2.5.2.1 Environmental factors that affect germination
  - 2.5.2.1.1 Water
- 2.5.3 Vigour tests
- 2.5.3.1 Imbibition
- 2.6 Ultrastructure of seeds
- 2.7 Literature cited
CHAPTER THREE: THE EFFECT OF TRADITIONAL STORAGE METHODS ON GERMINATION AND VIGOUR OF MAIZE (ZEA MAYS L.) FROM NORTHERN KWAZULUNATAL AND SOUTHERN MOZAMBIQUE
CHAPTER FOUR: THE EFFECT OF FUNGICIDE SEED TREATMENTS ON GERMINATION AND VIGOUR OF MAIZE (ZEA MAYS L.) SEEDS
Abstract
- 4.1 Introduction
- 4.2 Materials and methods
- 4.2.1 Treatment of the seed
- 4.2.2 Moisture content
- 4.2.3 Standard germination test
- 4.2.4 Vigour tests
  - 4.2.4.1 Imbibition
  - 4.2.4.2 Conductivity
  - 4.2.4.3 Tetrazolium test
  - 4.2.4.4 Cold test
- 4.2.5 Greenhouse trial
- 4.2.6 Statistical analysis
- 4.3 Results
- 4.3.1 Moisture content
- 4.3.2 Standard germination test
CHAPTER FIVE: THE EFFECT OF ACCELERATED AGEING AND LONG-TERM STORAGE ON FUNGICIDE TREATED MAIZE (ZEA MAYS L.) SEED Abstract
CHAPTER SIX: GREENHOUSE SEEDLING EMERGENCE FROM FUNGICIDE TREATED MAIZE SEED AND CONTROL OF FUSARIUM GRAMINEARUM SCHWABE Abstract
CHAPTER SEVEN: ULTRASTRUCTURE OF FUNGICIDE TREATED MAIZE SEED
- Abstract
CHAPTER EIGHT: GENERAL CONCLUSION
- 8.1 Literature cited