Topic 1 Food Security and Safety Flashcards
What is food insecurity?
food insecurity. This means they cannot access the food they need in either the correct quantity or of a suitable quality that is conducive to a healthy life
Currently, we produce enough to feed the world’s population (around 7.2 billion in 2015), that is to supply every person on Earth with an adequate 2800 calories per day and 75 g protein. But despite this we still have a world population with approximately 870 million malnourished people (World Hunger Education Trust, 2015) and a stunning 2.8 billion overweight people (World Health Organization, 2015).
Bearing this in mind, why do we currently struggle to adequately feed our population? Click on the ‘Edit’ button below and use the response box that appears to type and save your answer.
There are serious problems with global food systems which mean that food supplies are not equitably distributed. Issues affecting global food security are extremely complex; they depend not just on global farming practices and the agricultural sciences that support them, but on political and social issues too.
What is the world population?
7.7 billion (2019)
As with all the topics in this module, it’s important that you keep in mind both the social and scientific aspects of the topic. So as you read this material, it’s worth bearing in mind what three questions:
To what extent do science and technology offer solutions?
To what extent can scientific methods and thinking contribute towards informed debate?
Are there aspects of the topic where an understanding of the scientific issues alone is insufficient to offer meaningful solutions?
It is possible that some of the reasons for reduced food security and poor nutrition given in the table may be addressed by the application of science and technology or at least by taking a science-informed approach.
Can you suggest ways in which science has already offered solutions to some of the world’s food security issues? Click on the ‘Edit’ button below and use the response box that appears to type and save your answer.
You may find it useful to compare your list with the following one suggested by the author.
An understanding of plant genetics has already contributed to the breeding of more productive plants, which are well suited to changing environmental conditions. Further developments in this area are well established.
An understanding of environmental sciences has contributed to a better understanding of the requirements of plant growth and how these can be optimally supplied.
Analytical science has improved food safety testing, ensuring our food is safe to eat.
Scientific studies in the field known as dietetics have established the general requirements for a healthy diet, the need for specific nutrients and how food can be fortified to contain these nutrients.
The chemical sciences have informed agricultural techniques that allow greater productivity, including use of fertilisers, pesticides and herbicides.
what should be considered in the four module themes as you study each individual topic?
Communication
Risk
Ethical issues
Decision-making.
What huge changes in agricultural practice has come about in the last 20 years?
This increase has largely come about as a result of the application of frequently criticised ‘modern farming’ techniques. On a simple level, this means higher-yielding crop plants, larger farms, more efficient (mechanised) equipment and use of fertilisers, pesticides and irrigation. Application of these techniques has already boosted food production significantly.
What is the ‘green revolution’?
In the 1950s there were real fears that global food provision was insufficient to meet the demands of the growing population and that widespread famine was imminent in India, in East Pakistan (which since 1971 is largely Bangladesh) and also in South-East Asia. The previous 20 years had already seen huge changes in agricultural practices in the wealthier countries that had allowed food production to increase very significantly.
This increase has largely come about as a result of the application of frequently criticised ‘modern farming’ techniques. On a simple level, this means higher-yielding crop plants, larger farms, more efficient (mechanised) equipment and use of fertilisers, pesticides and irrigation. Application of these techniques has already boosted food production significantly.
In the face of concerns about food security, these agricultural practices were exported to the world’s low-income countries, beginning the so-called ‘Green Revolution’.
How many crop plants make up 90% of the worlds food energy intake?`
15 crop plants provide 90% of the world’s food energy intake.
What 3 crop plants make up 60% of the worlds energy intake?
Rice, maize (corn) and wheat are the most significant of these crop plants, providing 60% of the world’s food energy intake and are the staple food for 4 billion people (Food and Agriculture Organization of the United Nations, 1995).
How many edible plants in the world is there estimated to be?
There are estimated to be 50 000 edible plants in the world
Suggest a reason why the value for maize production is misleading when considering its impact on food security.
Not all crops are grown for food. You may be aware that around 20% of the world’s maize production is for other uses including biofuel.
What are genetics?
Genetics is the study of the patterns of inheritance of characters from one generation to the next.
Explain what a F1 hybrid plant is?
The first of these developments, in the 1930s, was the widespread introduction of ‘F1 hybrid plants’. Plant scientists discovered that they could produce superior varieties of some staple crop plants by selecting plants of the same species with different advantageous characteristics and crossing them together. The aim is to produce offspring that show the advantageous characteristics of both parents. The underlying techniques of plant breeding rely on an understanding of the science of genetics.
What is a gene?
Genetics is the study of the patterns of inheritance of characters from one generation to the next. These heritable characters are known as genes
What is a genotype?
heritable characters are known as genes and it is possession of different genes within an individual organism’s genotype that maintains differences (known as biological variation) between members of the same species.
What is a phenotype?
Some of these heritable characters in plant genotypes confer advantageous characteristics on the plant; as a result, these individuals have favourable phenotypes given certain environmental conditions.
What is the difference between phenotype and genotype and what is the relationship between the two for any given individual?
The phenotype describes the sum of all the characters an individual organism possesses; these can be structural, biochemical, behavioural or physiological features. The full complement of genes possessed by an individual, is its genotype. The phenotype of the individual is the combined action of their genes (their genotype) and their environment.
Suggest some potentially desirable phenotypic characteristics for crop plants that plant breeders might be interested in breeding into their crops.
You may have included any or all of the following phenotypic characteristics in your answer and you may have thought of additional characteristics not included here:
drought/flood resistance heat or cold tolerance resistance to disease resistance to insects specific flavour seed shape or size rapid maturation time ease of processing (e.g. grain is easily separated from the crop plant).
What are the two main stages of producing F1 hybrids?
Repeated inbreeding by self-fertilisation of the two selected parental varieties of crop plant
followed by
Cross-breeding of the two parents together to ensure cross-fertilisation.
What does self-fertilisation mean?
As each plant produces both male and female gametes, it is possible for many species to produce seeds by fertilising themselves. To do this the plant’s own pollen (male gametes) is used to fertilise its own ovules (female gametes).
What is repeated inbreeding?
Repeated inbreeding (self-fertilisation) Plant breeders select two parental varieties of the crop plant of interest with different advantageous phenotypes. For example, they may choose a cold-tolerant variety and a high-yielding variety of the same species. They then allow these parental varieties to self-fertilise repeatedly for many generations until they are sure that the plants ‘breed true’ for the given characteristics.
What is the desired effect of generations of self-fertilisation?
The desired effect of the generations of self-fertilisation is to check that the plants consistently produce offspring that are just like themselves, i.e. true breeding. This means there are no ‘hidden’ recessive genes in the parental genotypes, which may ‘reappear’ in the progeny of the all-important cross-breeding step
How many generations of self fertilisation need to be done to make sure plants are breeding true?
It takes around ten generations of self-fertilisation to be sure that the plants are breeding true.
Genetically describe what will happen to both alleles after generations of self fertilisation? and what is this called?
Technically this means that the parental plants are likely to be homozygous for most of their characteristics; that is, both the alleles (alternate forms of the same gene) for any characteristic are the same.
In genetics what do the terms allele, dominant and recessive mean?
The alternate forms of genes are referred to as alleles. A dominant allele is one that is expressed or shows up in the phenotype even when a recessive allele for the same gene is present in the genotype. The allele which is not expressed is said to be recessive.
What does F1 mean?
first filial generation
What is cross breeding?
After self fertilising (10 generations) to get the desired genetype. The next step is to cross these two true-breeding varieties of plants together by removing pollen from one parent and adding it to the female flowers of the other selected parent. The pollen fertilises the ovules, which develop into seeds. Once the seeds are grown into mature plants, it is possible to tell whether this generation of plants have inherited the desired advantageous characteristics from both parents. This new generation of plants are referred to as F1 hybrids. F1 means they are a first filial generation.
What does hybrid mean?
Hybrid means they are the product of two different parental varieties
What is the result of hybrid plants after cross breeding?
These resulting hybrid plants are said to have hybrid vigour or heterosis; they tend to be more robust, uniform in size and maturation time, but also show, to an even greater extent, all the favourable characteristics of the parent plants. Many different varieties of F1 plants were bred with different combinations of useful traits and farmers selected appropriate hybrids to match the environmental conditions on their land.
Explain the sequence of events that occur when cross breeding wheat?
In order to crossbreed wheat, pollen is removed from one plant, the male parent, and used to fertilise the ovules of another plant designated the female parent. The first step is emasculation. That is, removing the female plant’s own pollen producing anthers to ensure it cannot self pollinate. This head of wheat is being emasculated several days before it’s ready to flower. The male anthers are carefully removed, three from each flower.The technician counts the anthers to check that none have been missed. He now has a prepared spike ready for hybridisation. The spike is protected with a bag until the female organs of the flowers, containing the ovules, have time to mature. A few days later, a flowering spike is selected from another wheat variety chosen to be the pollen producing or male parent of the cross.The male parent flowers are cut open. After several minutes, the pollen begins to emerge. The top of the protective bag is removed, and pollen from the selected plant is emptied into the bag and mixed with the original emasculated spike. To protect the pollinated plant, the technician closes the bag to prevent any wind blown pollen from cross contaminating. This guarantees accuracy, and the tag records the data. If the breeding experiment succeeds, the result will be hybrid wheat with desirable characteristics from both parent plants.
What is the problem with F1 plants?
hybrids do not breed true; that is, they do not consistently produce offspring that are just like themselves.
So F2 seed (second filial generation) produced by these parents will, once grown, not consistently show the advantageous characteristics of the F1. Within only a few generations the plants will revert to the individual F1 parental types without the desired hybrid vigour. Figure 1.4 illustrates this gradual reversion to less desirable phenotypes.
For commercial producers of seed, hybrid plants present a win–win situation; can you suggest why?
For commercial plant breeders, this crucial drawback of hybrid plants is also an advantage; they can sell seeds over and over again, repaying the investment they have made in the breeding technology and making a healthy profit. You will return to this interesting potential conflict of interest a little later on.
For wealthy farmers in high-income countries this tends not to be too much of an issue. Hybrid seed is very costly but rebuying seed every year is worthwhile to ensure high yields. For traditional small-scale farmers in the developing world this is a very significant yearly expense.
What is a cultivar?
‘Cultivars’ is the term given to the varieties of plants which arise from plant breeding and cultivation.
What causes the pathogen rust in plants and how does this affect the plant?
Rust was and remains an extremely important plant pathogen. Rust can spread very rapidly and destroy a wheat crop within a few weeks. It is caused by the fungus Puccinia graminis, which weakens the host plant by utilising the plant’s own nutrients to fuel its growth. The wheat eventually lodges (falls over). Combine harvesters cannot then gather the crop, leading to a huge loss of yield.
Bearing in mind that naturally occurring rust-resistant wheat varieties do exist, but they are generally very low-yielding and of poor nutritional quality, what plant breeding could be carried out to achieve a useful rust-resistant hybrid? Click on the ‘Edit’ button below and use the response box that appears to type and save your answer.
The rust-resistant variety should be cross-bred with a high-yielding, yet rust-susceptible variety.
What is a heterozygous genotype?
Two alleles for a trait are different from each other e.g Bb, Rr
What is a homozygous genotype?
Two alleles for a trait are the same as each other e.g. BB, RR, bb, rr
What is backcrossing?
Once the two parental plants have been cross-bred together to generate F1 hybrids as you saw in Section 1.2, these F1 plants are then bred with the original high-yielding parental variety. This step is then repeated many times. This is called backcrossing because it is crossing ‘back’ with one of the parental lines. The progeny of each cross is selected and only those that show disease resistance are backcrossed each time.
Plant breeders are not interested in the rust-susceptible plants produced from the backcross, but they are interested in the rust-resistant offspring. Unfortunately, inspecting the seeds does not allow the plant breeders to tell which have the resistant phenotype.
How would they tell the two phenotypes apart?
The only way is to grow all the seeds to maturity, infect them with rust and check!
After the series of backcrosses and selecting the resistant plants each time, it is possible to achieve the perfect hybrid – a rust-resistant plant but with all the parental characteristics of the original recurrent parent. However, there is a snag. The resistant plants after repeated backcrossing are heterozygous and will not therefore breed true for this disease resistance. It is of great advantage to have plants that are homozygous for this trait.
Can you think of a method in which you could achieve homozygous R R progeny?
Allow the progeny of the final backcross to self-fertilise.
Aside from F1 hybrid super seeds what else contributes towards crop cultivation?
Use of F1 hybrid seed gives farmers access to truly ‘super seeds’. But at the same time as F1 hybrids and Borlaug’s rust-resistant crop plants were becoming widely available, other changes in farming practice were making an impact in the high-income countries. By the late 1940s the use of artificial fertilisers and pesticides was increasing dramatically. In addition an increasingly mechanised approach to crop cultivation, coupled with superior irrigation technology, meant that farmers were selecting cultivars that could produce huge yields under these specific growing conditions.
The availability of what influences the rate of growth in crop plants?
The availability of fertilisers is one of the most important factors that influence the rate of growth of crop plants
What are the most significant 3 nutrients obtained from the soil for the growth of crop plants?
In most agricultural situations, the most significant nutrients obtained from the soil are nitrogen, phosphorus and potassium – the so-called NPK familiar to gardeners from fertiliser packets. Plants also require smaller but significant amounts of calcium, magnesium, sulfur and also some other minerals in trace quantities.
Traditionally what did farmers use to restore nutrients back in to the ground? what changed?
Traditional farming methods use animal and crop waste to restore depleted nutrients to soils but the availability of cheap artificial fertilisers to farmers resulted in widespread change to agricultural practices.
What else do plant breeders now look for in selective breeds of plant aside from a high yield?
Plant breeders were now selecting for cultivars that have a high yield and:
would grow well under irrigation and with high artificial fertiliser input
would grow to a uniform size so they could be mechanically harvested
could tolerate high levels of pesticide and herbicide.
What happened initially to high yielding wheat crops when they were extensively fertilised and how was this resolved?
However by the 1940s and 1950s, the available high-yielding crops were causing problems. Farmers found that if they extensively fertilised their high-yielding plants (and supplied them with sufficient water) they grew so well that the weight of grains in the seed heads made the plants lodge (i.e. fall over) and ruin the crop.
Borlaug, following on from his success with rust-resistance, bred these high-yielding plants with dwarf wheat varieties and succeeded in producing new varieties that were shorter in stature (semi-dwarf) but with stronger stalks (also called straws) that could sustain the larger seed heads. These new cultivars of wheat were semi-dwarf, disease-resistant and highly responsive to fertiliser. And given that stalk growth was suppressed, more of the products of photosynthesis were directed to the grains, improving yield even further.
What was the name of the dwarf Japanese variety of wheat used by Borlaug?
Norin 10 was the dwarf Japanese variety used by Borlaug.
Describe the advantages conferred by cross-breeding high-yielding tall wheat with the Japanese dwarf variety.
The stem of the dwarf wheat produced from this cross is strong enough to support the weight of the grain and mature without lodging.
Some people suggest that the increased yields discussed may not be sustainable in the long term. What do you think is meant by the term sustainable in this context?
Sustainable in this example means in the future it may not be possible to continue to supply the inputs of water and fertiliser needed for the cross-bred plants to achieve their high yields. Sustainability is a widely used environmental concept, which will be discussed further both in Section 3 and in future topics.
M. S. Swaminathan suggests that a scientist’s job should not end when they have developed a technology, but only end when the appropriate public policy is in place. Which two of the four module themes (communication, risk, ethical issues and decision-making) are most relevant here?
The use of technology as a tool in foreign policy seems to clearly be an ethical issue. The availability of a specific technology may influence decisions made by one country in the absence of other available solutions. The Indian government for example needed an urgent solution to impending famine in the absence of adequate foreign aid and so was anxious to adopt the new technologies of modern agriculture on offer. In Borlaug they found a scientist who was prepared to work directly with them to achieve these aims. Therefore, arguably, the two most relevant themes are ethical issues and decision-making.
What breed of rice was nicknamed miracle rice?
Borlaug’s ground-breaking work with wheat soon spread to other staple crops. In 1962 the International Rice Research Institute (IRRI) in the Philippines produced IR8, nicknamed miracle rice; the first modern high-yielding rice variety ever bred.
Like Borlaug’s wheat cultivars, IR8 is a high-yielding, dwarf variety (Figure 1.11) that produces very high yields if fertilised and irrigated appropriately.
