Difference between revisions of "2. History of Plant Breeding"
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by Nino Brown, Institution of Plant Breeding, Genetics and Genomics, University of Georgia
The domestication of the plant was man’s crowning achievement. It allowed us to develop into the complex global society that we are today. We are arguably more dependent on those same crop species domesticated by early man up to 10,000 years ago than we ever have been. Whether early man joyfully embraced the new technology of agriculture is debatable, but once it caught on it spread quickly across continents. The hunter-gatherer systems of old were notoriously land inefficient. It took large acreages to support these early humans, and so agriculture arose from necessity and allowed more people to survive on fewer acres.
The process of man’s conversion to agricultural systems was spurred along by the warming of the earth and the scarcity of large land mammals previously hunted for food and clothing. The plants used to fill the void were less selected than they were chanced upon. Traits that made domestication possible were controlled by few genes. These traits were fixed quickly and we are left with those same original domesticated crops from antiquity. The crops have certainly evolved, but not as much as they did during those first centuries.
With domestication came some negative aspects such as reduced genetic diversity. The genetic bottle neck effect seen in modern crops is a product of man’s selection for desirable agronomic traits. Unfortunately modern crops are often susceptible to disease, insects, and abiotic stresses. To find resistance genes it is often necessary to go back to their wild ancestors and close relatives. This is can be problematic due to the setback in yields attained when crossing to wild relatives, but it necessary for advancement of the crop. An understanding of crop domestication can help the plant breeder in her pursuit of the next best plant.
Early humans lived as hunter gatherers, victims of the wax and wane of the ecosystem in which they inhabited. For those that lived in grassland systems, a nomadic existence, following the plants and animals they fed upon was necessary. Tropical forest dwellers or those that lived in ecosystems where food was available year-round could build more permanent homes. They all depended on that which sprang forth from the ground naturally for their sustenance however, which meant that their fates were not necessarily their own to choose. Food availability depended on what the ecosystem could provide, and searching for that food required a great deal of early man’s time and energies. Survival was a full-time job. This inherent lack of control over their fates changed roughly 5,000 to 10,000 years ago with the domestication of the plant species that would become the first agricultural crops (Smith and Pluciennik, 1995). The change did not occur abruptly (Anderson, 1956), and certainly did not resemble what we today would call agriculture for quite some time.
The domestication of the plant was arguably the single most important technological advance in our history, and allowed us to develop into the highly complex civilization we have become. As technologically advanced as we might be, we are still as dependent on plants as we have ever been. It could be argued, that with the current population and rate of growth, we are more dependent on these crops than ever. There were 6.1 billion humans on earth in 2000, and current population estimates for 2050 range from 7.4 billion to 10.6 billion (UN, 2004). Not only is that a lot of mouths to feed, but homes for 7 to 10 billion people covers large amounts of land. Much of that same land will be needed for food and fiber production.
It is interesting that the crops we grow globally today, to feed an ever growing society, in most cases were the same species our ancestors originally domesticated thousands of years ago. The beginnings of agriculture and plant domestication occurred at different times and places, with different plant species, for different societies around the globe (Flannery, 1973). It appears that some societies did this independently of each other, and for other societies the technology was introduced. An in-depth review of the archaeological evidence is beyond the scope of this chapter however, a discussion of plant domestication is impossible without an archaeological perspective.
Man’s Domestication of The Plant
The most likely model of man’s transition to food production from hunting and gathering is one that includes several explanatory variables and probably occurred gradually in several stages (Ford, 1985; Harris, 1989; Redding, 1988). The exact mode of action is contentiously debated; however, Redding (1988) provides a useful generalized method. The proposed model involves the hunter-gatherer population for a given environment reaching the carrying capacity of the land and using methods to side-step the carrying capacity, either by avoidance or by directly increasing the capacity. The inhabitants of the over-populated environment would have dealt with the lack of resources by 1) emigration, 2) reducing reproductive rate, 3) diversification, or 4) storage (Redding, 1988).
It is necessary to explain these methods clarified by Redding (1988), as they are tantamount to the evolution of agriculture. Emigration to a new environment with more available plants and animals to hunt is probably the easiest and most common method ancestral man used to escape the limited carrying capacity of a given environ. Reducing the reproductive rate would have held the population level at the environment’s carrying capacity for a longer period. Diversification involved finding new sources of nutrition like a novel food plant or devising new technology to process an available resource not yet utilized for food, such as a mortar and pestle. To decrease the uncertainty of the food supply, humans would have had to broaden their food choices and devise new methods to exploit novel sources (Flannery et al., 1969; Stiner et al., 2000).
Storage could be considered a form of diversification, as it in many cases involves development of technology. It is most likely the source from which agriculture evolved. Food storage could include capturing more animals than a group could consume immediately, and tying them up for later consumption. It could also include the storage and carrying of edible seeds to eat later. The storage and transport of seeds could have easily led to planting the seeds for later harvest the next time the hunting-gathering group camped in the same area (Redding, 1988).
Any number of likely scenarios exists for the small leap from simply carrying around a few extra seeds for a later snack, to the conscious effort of saving some seeds to plant in a favorite tribal camping ground. The small leap might have been spurred along by the rapidly changing climactic conditions of the late Pleistocene and early Holocene (Richerson et al., 2001). As the earth warmed and glaciers receded the large land mammals became less numerous. As the preferred nutrition of our hunter-gatherer forebears declined in numbers, human populations simultaneously increased. This increase in human population and decrease of such a vital resource caused the early humans to search for new resources and develop new behaviors (Binford and Binford, 1968; Flannery et al., 1969).
The Spread of Agriculture
It is commonly held that agriculture arose at as many as nine different locations scattered around the globe, independently of each other. These agricultural origins essentially mirror Vavilov’s originally proposed “centers of origin.” These centers of origin are the places where Vavilov suggested the currently cultivated crop species were originally domesticated from the wild type (Vavilov, 1926). It is from these centers that domesticated plants and agriculture first spread. The spread of this new technology would have been a slow process. It is unlikely that wholly nomadic peoples converted to sedentary agricultural systems over-night. It is more likely that the transition was a slow one, involving both methods together for quite some time before finally settling down into a wholly agrarian existence (Smith, 2001a; Smith, 2001b).
These new methods and new plants would have spread faster going east or west across the globe from their origin. This east/west spread was easier due largely to plant adaptability to climate (Diamond, 1997). As was found to be the case in Africa, the spread north or south was more difficult due to climate adaptation (Marshall and Hildebrand, 2002). Cohen et al. (1984) suggest that the beginnings of agriculture would have resulted in decreased fitness for adherents to the new method. This could very well be the case for groups who were forced to switch from an entirely hunter-gatherer existence to an entirely agricultural existence due to lack of prey animals or some catastrophe. The agricultural outputs would have struggled to catch up with necessity. In an experiment to test the difficulty of harvesting wild grains by hand, one researcher went to a naturally occurring stand of wild wheat in Turkey. He demonstrated that a person could easily harvest a year’s supply of grain in just a couple of weeks using nothing but their hands, and considerably more grain with a hand-held sickle made of flint (Harlan, 1967). So, given a shortfall in the productivity of a certain environ, it would have been quite easy to harvest sufficient food from the plant-scape of one’s environment. The limiting factor would be knowledge of which plants to taste or eat. Once the knowledge hurdle was crossed, the idea would have spread quickly within and without camps.
The domestication of the plant and the subsequent development of agriculture allowed people to set down permanent roots and develop the rich cultures that led to our existence. With agriculture came the production of excess food and sedentary villages that were hitherto unobtainable. The excess of food, and the decrease in time required to spend foraging, lead to a division of labor, the development of such things as art and science, and gave birth to modern civilization (Diamond, 2002). Population growth, thought to be a contributing factor to the development of agriculture, was also a consequence of agriculture’s increased sedentism (Lee, 1980). Fortunately, more people could be sustained by a smaller land area with agriculture than before.
Consequences of Domestication
Few plant species, of the thousands of possibilities, were ever domesticated for food, fiber, or other human use. In the immensely popular book, “Guns, Germs and Steel: The Fates of Human Societies”, Diamond (1997) cites a simple explanation for the domestication of this small percentage of available species. His basic hypothesis is that these species were used for their ease of breeding for those traits that made them useful plants. That is, the traits which made some plants desirable to the early plant breeders/domesticators were controlled by few genes (Diamond, 1997). This idea is supported by a great deal of molecular work discussed later in this paper. This is interesting, and answers some very important questions. An example of this simple inheritance of important agricultural traits is the shattering system in wheat and barley. The mechanism by which wheat and barley scatter their seeds at maturity is controlled by a single gene. When man selected for the non-shattering type wheat, the trait was fixed quickly and easily, making the crop preferable to others that might have been candidates (Zohary and Hopf, 1988). It is obvious that our early ancestors would have preferred these cereals to all others simply because the grain stayed on the plant longer, and so the harvest window was longer than others.
It seems that crop species were not necessarily selected, but serendipitously discovered because they did not need much tinkering to become valuable food sources and agricultural models. The leap from useless weed to valuable food source was short and relatively easy. Almonds provide another example of simple inheritance of beneficial traits. The wild progenitors of almonds contained bitter chemicals to fend off predators, however, the mutation that makes the distasteful compounds absent is a single gene system and as such was easy to select. Oak tree acorns, on the other hand, have similar distasteful compounds within them, but the trait is a polygenic trait, making selection difficult, especially for the unwitting plant breeders of antiquity, which might explain why oak trees have never been domesticated (Diamond, 1997).
Among the cultivated species, a certain set of traits exist that are common to nearly all of them. It was originally postulated by Charles Darwin that differences seen in cultivated plants from their wild relatives was due to selection pressures by early man (Darwin, 1859; Darwin, 1868). These are the traits that make the plants productive and beneficial to human society. This group of traits is commonly referred to as “domestication syndrome,” first proposed by Hammer (1984) and later expounded upon by Harlan (1992). The domestication syndrome traits imbued the crop plants with uniformity, predictability, and high productivity (Table 1). There are several traits involved or contributing that include short stature (rice, wheat), large fruit with tasty flesh (tomatoes, apples), non-shattering (rice, wheat, sorghum), reduced seed dormancy (common beans), and reduced feeding deterrents (virtually all). These traits are summarized by Frary and Doganlar (2003), and in the summary there is included a discussion on how few genes control each of these critical traits.
There is no better example of how these traits can come together to produce something truly nutritive, than corn and its progenitor teosinte. Teosinte is a weedy looking grass with a small seed head made up of only two rows of several small, hard seeds. It looks as though it came out of a gardener’s nightmare. But somehow this wild and bushy bunch grass became the robust, single stalked behemoth we now know as field corn, whose constituents are used as ingredients in a plethora of food products consumed heartily by Americans daily.
The domestication traits would have been immensely important to the early agriculturalist, and rapidly fixed within their germplasm. It has also been shown by several researchers that many of these domestication traits are clustered near each other on the chromosome, and so are often closely linked (Cai and Morishima, 2002; Khavkin and Coe, 1997; Koinange et al., 1996; Poncet et al., 2000; Xiong et al., 1999). This clustering of domestication traits along the genome, and the small number of genes controlling these traits, suggest that the jump from wild, weedy progenitor might have occurred quite quickly, perhaps in as little as 100 years (Frary and Doganlar, 2003). This is of course hard to prove without archaeological evidence.
The Bottleneck Concept
It is evident that genetic diversity of our crops is much lower than that of their wild relatives. Early farmers would have noticed these few mutants or deviants that exhibited a beneficial trait, kept them and planted them over and over again. This reduction of genetic diversity gave rise to what is known as the genetic bottleneck due to domestication. The bottleneck effect of domestication on the genetic diversity of crops was most likely due to small founder populations of the plants and strong selection pressures imposed upon these populations (Iqbal et al., 2001; Tanksley and McCouch, 1997).
Plant domestication was arguably the single most important advancement in the history of mankind. Once developed, agriculture spread across the globe like wild-fire. Our early ancestors unwittingly selected for traits that were easily fixed within the crop species, and as a product of their selection pressures, we now have reduced genetic diversity within our crops. Genetic bottlenecks have reduced the base of breeding materials available to the modern-day plant breeder. Fortunately, however, we know of this short-coming, and have tools to combat it. We know the centers of origin for most crops and have the wild relatives to use as sources of diversity. There is much that can still be achieved through plant breeding of the crops and genetic resources we have. As easy as it may be to complain and dwell on the lack of genetic diversity within our crops due to domestication. A discussion of plant domestication would be insufficient if it was not mentioned that our ancestors did an amazing job as amateur plant breeders. For people who never had the opportunity to attend a plant breeding class, much less learn how to tie a shoe, they did quite a service for us. It is truly amazing that the crops domesticated thousands of years ago are still with us today feeding 6 billion individuals.
Plant Breeding before Mendel
by Paige Speed Catotti, Department of Horticulture, University of Georgia
Following the ancient domestication of crop species, plant breeding occurred only informally for thousands of years. During that time, farmers might have chosen to save seed from the healthiest or highest-yielding plants from one generation to the next, but they lacked the scientific knowledge of inheritance to permit deliberate breeding for traits or understand the causes and effects of the widely-used method of mass selection. Jensen (1994) described these practices as crop husbandry, distinct from scientific attempts at improving plants.
However, it is important to remember that without written records of their methods, much of what we know of the development of landraces and prehistoric agricultural practices comes from our gleanings of the archeological evidence. Although we do not know exactly when agriculture was invented, Mangelsdorf (1952) considers that it must have been relatively recent, based on archeological dating of the oldest cultivated plant remains. For example, much investigation has been done into the domestication of maize – inarguably a vital crop; the oldest example of which was found in the Tehuancan Valley of central Mexico, dating back 7,000 years (Jensen, 1994). Nonetheless, even though it was known that maize is related to teosinte, there were still widely divergent opinions for many years regarding how or where or from what maize was domesticated. Even a mere six decades ago, although Randolph (1952) was tentatively willing to commit to Mexico/Central America as the domestication origin of maize, he felt that the possibility of Asiatic domestication (via emigration through the Bering Straits) should not be discarded. Many other domesticated plants have experienced similarly drastic changes during a comparatively brief time period as the result of only a few hundred or thousand years of effort by humanity (Mangelsdorf, 1952). Furthermore, Mangelsdorf reminds us that, contrary to Darwin’s beliefs, mutations are what powers evolution in domestication – domestication itself does not produce new inheritable variation.
An early example of plant breeding – as opposed to crop husbandry – began in the early part of the 17th century, when pilgrims from Europe to the New World discovered that their traditional crop varieties were eminently unsuited to their new home. Kloppenburg (2004) describes how the initial settlers obtained and grew Native American varieties for sustenance while slowly adjusting their own varieties to the new environment, with subsequent immigrant groups contributing their own species and varieties to the stock. During these early days of American agriculture, farmers would select the best plants from each year’s crop to provide the seed for the next generation and sometimes acquire seed from other farmers and immigrants, engaging in both simple mass selection and introduction of new germplasm (Kloppenburg, 2004). Although they were not deliberately selecting for specific traits or using scientific methods, their obligate labors for survival still resulted in the adaptation of varieties via basic plant breeding.
The more advanced developments in plant breeding would have been impossible without the initial scientific forays of the 17th century. Two of the leading plant anatomists, Marcello Malpighi and Nehemiah Grew, each made substantial contributions to early understandings of plant anatomy and reproduction (Ingensiep, 2004). Using the novel innovation of microscopy, Malpighi described plant structures and the generation of seeds in his 1675 publication, and then went on in 1679 to elaborate on the germination and growth of young plants. Although flower sexuality was still an unknown concept at that time, he used his considerable background in medicine and animal anatomy to give names to some of the reproductive parts of the plant (Ingensiep, 2004). Similarly, in his seminal plant anatomy lectures, Grew (1682) also made comparisons between animal and plant structure and development, and although he recognized that plants have two sexes, he misidentified the megagametophyte as male instead of female.
Furthermore, although many gardeners in the late 17th century believed that seed production involved pollen, for most of them it was merely a philosophical conjecture. In 1694 Rudolph Camerarius was able to prove this, demonstrating the necessity of pollen through a series of systematic experiments in which he emasculated flowers from a variety of species and hand-pollinated some of them (Thompson, 2010). When only the pollinated flowers produced seed, he was able to conclude that the anthers, which produce the pollen, must be male, and the ovaries, style, and stigmas that had received the pollen must be female. Even though Camerarius’ discoveries were largely ignored for several decades – possibly due to his colleagues’ blind adherence to the belief that plants are asexual, as Thompson surmises – his research served as a stepping stone for Joseph Koelreuter’s own investigations into pollination seventy years later and for many others yet to come, including Carolus Linnaeus’ focus on sexual characteristics as a means of classifying plants (Thompson, 2010).
Following the anatomical investigations of the 17th century, the 18th century saw an increased focus on a relatively new innovation in agriculture – the hybridization of one kind of plant with another. One of the earlier successes with this technique was performed in 1717 by Thomas Fairchild, who made a cross between a carnation and a sweet william that resulted in a (sterile) flower known appropriately as ‘Fairchild’s Mule’ (Thompson, 2010).
Continuing Camerarius’ previous research in pollination, Joseph Koelreuter performed a systematic series of scientific experiments in hybridization to determine whether characteristics in plants are always inherited only from the mother or the father. Working with a wide variety of flower species and tobacco, Koelreuter demonstrated that hybrid offspring display characters from both parents, generally in an intermediate form, and that these hybrids only produced seed when their parents were of closely related species (Thompson, 2010). Additionally, by performing crosses from hybrid tobacco and dianthus plants back to their parents, he was able to show that over many generations the progeny resumed the phenotype of the recurrent parent (Bailey, 1906). This process is the foundation of the backcrossing method, which is still extensively used today.
In contrast to Koelreuter, Thomas Andrew Knight performed substantial amounts of plant breeding during the latter part of the 18th century as a gentleman farmer without the benefit of a formal scientific education. As described by Thompson (2010), Knight’s curiosity regarding a wide variety of topics related to plant growth and production led him to perform hybridization of various fruits and vegetables in order to generate improved cultivars. After creating two improved hybrid strawberry varieties, in 1787 he began experimenting with crossing inbred lines of sweet pea plants, foreshadowing Mendel’s revolutionary studies with the same species by the better part of a century (Thompson, 2010). Although he could not explain the performance of what we now know as dominant and recessive alleles, Knight (1809) was able to produce practical breeding results and demonstrate some of the building blocks of what would become the science of genetics, even without having a scientific background himself.
Just a year before Knight began his work with peas, however, Franz Achard initiated a breeding program for sugar beets that operated from 1786 until about 1830. By performing mass selection on fodder beets for increased sucrose content, Achard and the von Koppy family were able to create a new cultivar with vastly higher levels of sucrose. This deliberate improvement of a specific quality factor of a fodder crop served to elevate it into a food crop that resulted in the creation of a major industry, the extraction of sucrose from sugar beets (Dudley, 1994).
The 19th century continued the trend of organized efforts in plant breeding being performed by various groups and organizations, rather than by various curious and scientifically-minded individuals as had historically been the case (Jensen, 1994). In the 1906 edition of his classic text on plant breeding, Liberty Hyde Bailey describes some of the recent plant breeding practices of that time, including the efforts of Luther Burbank, those whom Bailey considers to be “practical” plant breeders for commercial purposes, the agricultural experiment stations of the United States and Canada, and the United States Department of Agriculture.
During his years as a plant breeder, Burbank was responsible for the creation of approximately 800 varieties of a wide range of plants, including a (now extinct) spineless cactus intended for livestock fodder, the Santa Rosa plum, the Freestone peach, and the Burbank and Russet Burbank potatoes (Thompson, 2010). Bailey (1906), himself no mean horticulturalist, described Burbank as a genius and preeminent plant breeder of their time and praised him both for his thorough dedication to plant breeding and for his kind nature.
In addition to Burbank and the commercial plant breeders, much work was also being done at the experiment stations and agricultural colleges, not only in research and variety improvement, but also in the distribution of high-quality seed and its ideal conditions (Bailey, 1906). The sheer scope of these works and the manpower behind them allowed them to yield results in untold numbers of projects. Similarly, Bailey (1906) credits the USDA at the time as being “the largest organized governmental plant-breeding enterprise in the world”, having been created in 1862 and continuing the American government’s tradition of collecting and disseminating germplasm to growers (Kloppenburg, 2004).
One of the foremost seed companies for much of this period was the French Vilmorin Company, founded in the 18th century by the de Vilmorin family. Beginning in 1840 and for the ensuing four decades, the company focused on an original method of selection based on plant lineages, rather than individuals, that would later be known as “genealogical selection” (Gayon and Zallen, 1998). The Vilmorin Company also enjoyed considerable economic success with wheat and other crops through its methodical combination of hybridization and selection, begun in the 1870s (Gayon and Zallen, 1998). Altogether, members of the de Vilmorin family had significant influence in the realm of plant breeding over the span of more than a century, not only through variety creation and improvement, but also more abstract philosophical contributions to the field (Bailey, 1906).
Plant Breeding in the 20th Century
Watson & Crick
The Green Revolution
by Kiranjit Kaur, Institution of Plant Breeding, Genetics and Genomics, University of Georgia
List of Abbreviations
CGIAR: Consultative Group on International Agricultural Research
CIMMYT: International Corn and Wheat Improvement Centre
FAO: Food and Agricultural Organization
GM Crops: Genetically Modified Crops
IRRI: International Rice Research Institute
USAID: U.S. Agency for International Development
HYV: High Yielding Variety
The Green Revolution marks the period between 1960 and 1980 when a remarkable increase in the production of wheat and rice was achieved. This was made possible by the efforts of the Rockefeller and Ford foundations and the diligent leadership of Dr. Norman E. Borlaug. The establishment of CIMMYT and IRRI contributed tremendously towards development of modern varieties of wheat and rice and were the main reasons behind the success of the Green Revolution. The high yield potential of these varieties is attributed to their short stature and high responsiveness to fertilizers. Soon after their development, these were adopted on a large scale in the developing countries, and manyfold increase in production in these areas was achieved. In recent times there is again a need to boost the production levels considering the food scarcity and hunger situation in the world. In this scenario, genetically modified crops and the use of biotechnology in agriculture can be potentially useful in future.
To provide food for an ever-increasing population is one of the main challenges that science has always faced. A major breakthrough occurred in this direction when a remarkable increase in the production of wheat and rice was achieved in South Asia through the utilization of new wheat and rice varieties developed at the International Corn and Wheat Improvement Centre (CIMMYT) in Mexico and the International Rice Research Institute (IRRI) in Philippines respectively. This breakthrough is known as the Green Revolution, the term coined by William Gaud of the U.S. Agency for International Development (USAID) in 1968 and marks the period between mid-sixties and mid-eighties when a remarkable increase in production of wheat and rice was observed in developing countries (Murphy, 2007; Swaminathan, 2006). The most significant impact of the Green Revolution was observed in India, Pakistan and the Philippines during 1960-1970 and China after 1980 (Borlaug, 2000). The success of the Green Revolution in these developing countries is ascribed mainly to the adoption of High Yielding Varieties (HYVs) of wheat and rice along with increased use of fertilizers, pesticides and irrigation (Davies, 2003).
Famines and Food Scarcity
Humanity has been facing problems like famines and food scarcity since times immemorial. Worth mentioning is the Irish potato famine of 1840s that led to the death of about one million people (Nusteling, 2009). India has witnessed devastating famines, most notably the Gujarat famine of 1899 and the Bengal Famine of 1943 which led to the death of about three million people (Burton, 2010; Basu, 1986). P.V. Sukhatme (1961) of the FAO reported that between 300 and 500 million people were undernourished in the world and between one-third to one-half of the world’s population suffered from hunger and malnutrition. Thomas Malthus, in 1798, argued in his famous prediction that the population has the tendency to grow geometrically whereas the food production follows an arithmetic increase. This would lead to depletion of food resources as the population grew and consequently humanity would face famine. However, Malthus could not visualize at that time that technological advancements could make a tremendous difference in the food production and that it could keep pace with the population curve. Also, advances in the field of health sciences can help restrain population growth by adopting measures such as family planning and contraception (Sachs, 2008). The ever impending food scarcity problem necessitates steps be taken in the direction of improving agricultural production so that the future of mankind can be safeguarded. The Green Revolution was one such step which commenced with the arrival of the Rockefeller Foundation.
The Rockefeller Foundation and the Legacy of Norman E. Borlaug
The grounds for the Green Revolution were set when US vice president Henry Wallace approached the Rockefeller Foundation to launch a program for crop breeding in Mexico. Himself a successful crop breeder, Wallace had helped to produce the first sterile hybrid corn in the 1920s and was the founder of Pioneer Hi-Bred seed company (Murphy, 2007). In 1943 the Rockefeller Foundation launched its Mexican Agricultural Program. The primary objective of this program was to develop HYVs having higher response to agrochemicals. The initial results of the program were very encouraging and the Rockefeller Foundation decided to establish an independent institute known as CIMMYT in Mexico, which acquired its present name in 1963, though its foundation had already been laid in 1943 ( CIMMYT, 2010). Before that, between 1920 and 1940, the Rockefeller Foundation started supporting hybridizing efforts in corn to produce improved crop for industrial agriculture. As a result there was a boost in hybrid corn seed sales around the 1930s and corn yield increased significantly after introduction of double cross hybrids. Later replacement of double cross hybrids with single cross hybrids further increased yields in the 1960s (Hindmarsh, 2003 ; Khush, 1999). Tollenaar and Lee (2006) reported that the mean yield improvement of corn in the US between 1939 and 2004 was 100 kg/ha/year or 2% per year. He further mentioned that the genetic contribution to corn yield improvement in the past seven decades in the US was about 75%. The Rockefeller Foundation further spread its hybrid corn production program to Brazil in 1946, Argentina in 1947 and Kenya in 1956. On the other hand, simultaneous efforts were being made to introduce the Green Revolution programs in developing countries including India, Philippines and Indonesia in 1960s (Hindmarsh, 2003). Meanwhile a major development took place when the Rockefeller and Ford foundations joined hands with the Philippines government to establish the International Rice Research Institute (IRRI) near Manila in 1960. At IRRI, the focus was totally on research and breeding of rice which is the staple food of over one billion poor people across the world (Murphy, 2007).
The credit for success of the Green Revolution goes to Dr. Norman E. Borlaug who is honored as the “Father of the Green Revolution”. Dr. Borlaug spent almost his entire life working to alleviate food scarcity from the world. Borlaug is very well known in developing nations, but he was away from lime light in western circles and for this reason he is also called “the forgotten benefactor of humanity”. The world came to know about him in 1970 when he was awarded with a Nobel Peace Prize for his exemplary work. Born in 1914 in Cresco, Iowa, he earned a PhD in Plant Pathology from the University of Minnesota in 1941. Later, he joined the Rockefeller Foundation and worked as a scientist under the Cooperative Mexican Agricultural Program as the head of the Wheat unit from 1944 to1960. After the establishment of CIMMYT, he became the leader of the Wheat Program in 1963, the position he held until his retirement in 1979. The new varieties developed at CIMMYT, along with improved management practices, revolutionized the wheat production in Mexico in the 1950s. He spread this successful model of wheat production technology to other developing nations like India and Pakistan in the mid-60s and as a result, between 1964 and 2001, the wheat production in India increased from 12 to 75 million tonnes while in Pakistan an increase from 4.5 to 22 million tonnes was achieved.. Thus, the work of Dr Borlaug revolutionized agriculture in the developing countries and saved millions of people from starvation (CIMMYT, 2010; Easterbrook, 1997).
The Green Revolution: Wheat and Rice
The main part of the success story of the Green revolution was the new semi dwarf varieties of wheat and rice. Borlaug (1971) himself stated that the main reasons of success of these varieties, were their wide adaptation, short stature, high responsiveness to inputs and disease resistance. The genesis of semi dwarf wheat varieties started when Japanese scientists developed the semi dwarf wheat variety Norin 10 using Daruma as the donor of the semi dwarfing trait. The recessive genes responsible for dwarfing were named rht1 and rht2. To begin with, Daruma, which was a Japanese semi-dwarf variety, was crossed to Fultz, which was a high yielding U.S. winter wheat, giving rise to Fultz-Daruma. Fultz-Daruma was later crossed with Turkey Red which was also a high yielding U.S. winter wheat. This gave rise to Norin 10 which was a semi dwarf and high yielding variety. Norin 10 semi dwarf wheat was later brought to the US and led to the breeding of the cultivar Gaines by Dr. Orville Vogel in the 1950s by crossing locally adapted lines with Norin 10. Dr. Borlaug later used the Gaines wheat to develop modern semi dwarf varieties by crossing it with local strains (Swaminathan, 2006; Dalrymple, 1978). Swaminathan (2006) further describes the shuttle breeding methodology used by Dr. Borlaug wherein alternate generations were grown at two diverse locations. As these locations differed in terms of soil, temperature, rainfall and photoperiod, the methodology resulted in production of strains possessing wide disease resistance and insensitivity to photoperiod. This, in turn, increased the adaptability of the strains in different environments. The CIMMYT wheat program also made efforts to breed resistance to rust in wheat by utilizing the variety Hope, which had durable stem rust resistance and Frontana, which had durable resistance to leaf rust. This resistance is found to be conferred by minor genes which have an additive interaction relationship (Rajaram, 2005). The genesis of dwarf rice varieties occurred when the recessive gene, sd1, for short height was incorporated from a Chinese variety Dee-geo-woo-gen meaning short-legged (Khush, 2001). The IRRI team developed a semi dwarf variety IR8 in 1962 by using Peta as female parent which was tall and vigorous, and Dee-geo-woo-gen as the male parent which had stiff straw and conferred the genes for semi dwarf nature. The resulting IR8 had stiff straw, was resistant to lodging and its insensitivity to photoperiod made it a very well adaptable variety. This variety became so popular that it began to be called the “miracle rice” (Hargrove et al., 1988). The success of these rice and wheat varieties is mainly attributed to their short stature. The wheat and rice varieties grown prior to the Green Revolution had tall stature, leafy nature and weak stems. These tended to grow excessively tall, lodge and yielded less when applied with high doses of nitrogenous fertilizers. Also, these earlier varieties had a harvest index of 0.3, which means the ratio of grain to straw was 30:70. They had the capacity to produce a total biomass of 10-12 t/ha, hence their maximum yield potential was 4t/ha. While on the other hand, the improved Green Revolution semi dwarf varieties of wheat and rice had a harvest index of 0.5. Their total biomass potential was 20 t/ha, hence their maximum yield potential was 10 t/ha (Khush, 1999; Sakamoto and Matsuoka, 2004). Khush (1995) considers the improvement in the harvest index as the most important architectural change in rice and wheat varieties that was responsible for increasing their yield potential. The other factors that led to the success of the Green Revolution, apart from the improved varieties, were the utilization of high levels of inputs such as inorganic fertilizers, improvement in irrigation facilities, and the formulation and implementation of supportive government policies. The worldwide irrigated land area increased from 94 million ha in 1950 to 240 million ha in 1990, while worldwide fertilizer used rose from 14 million tons in 1950 to 140 million tons in 1990 (Khush, 1999 ; Brown, 1996).
Impacts of the Green Revolution
The world production of cereals has increased about 2.53 times during 1961-2006 (FAO, 2007). During the same period, the cereal production in developing countries has increased 2.7 times, compared to 2.3 times in developed countries. The irrigated land area was 139 million ha in 1961, which increased to 210 million ha in 1980 and to 271 million ha in 2000. Worldwide fertilizer usage increased from 31 million tonnes in 1961 to 117 million tonnes in 1980 and to 137 million tonnes in 2000 (FAO, 2007). The world production of rice, wheat and corn during 1961-2000 also showed increasing trends (Fig. 1). Area planted under HYVs of wheat in 1978-79 was 72.4 percent of the total area under wheat in Asia, while 30.4 percent of the total area under rice was planted with HYVs (Table 1) (Dalrymple, 1978). In recent times, the second and third generation modern varieties (HYVs) have evolved and replaced the original modern varieties in many areas (Evenson and Gollin, 2003). In India, the total cereal production has increased from 70 million tonnes in 1961 to 186 million tonnes during 1961-1999, while in China, an increase from 91 million tonnes to 390 million tonnes during the same period has been observed. The number of tractors in developing countries rose from 0.2 million in 1961 to 4.6 million in 1998 (FAO, 2000).
Though the Green Revolution was successful in increasing the food production tremendously, it has faced criticism for starting an era of chemical farming. Some argue that the high input agriculture methodology triggered problems such as soil degradation, soil salinity, chemical pollution and differential socioeconomic impacts leading to instability (Davies, 2003; Evenson and Gollin, 2003). Another argument against the Green Revolution is that it has itself led to poverty. Critics argue that only the big farmers could access the costly technology introduced in the developing countries while the smaller farmers suffered and their economic condition further deteriorated and this widened the economic gap (Strauss, 2000). The supporters of the Green Revolution argue against these criticisms by stating that the Green Revolution actually reduced the poverty and helped the poor more than the rich because it was also associated with reduction in food prices as the production increased (Lipton, 2007). In spite of all the criticisms, Green Revolution is still a huge step undertaken by mankind in the direction of getting rid of hunger and food scarcity.
Emergence of CGIAR
As the Green Revolution started by CIMMYT and IRRI became successful, the need to expand their areas of operation was felt. The operations were to include more countries and more crops which required more staff and experts to test varieties in different agro-climatic areas. As a result, the Rockefeller and Ford foundation, with support from the World Bank and the UN Food and Agriculture Organization, established the CGIAR (Consultative Group on International Agricultural Research) in 1971, an organization which coordinates agricultural research in developing countries worldwide with support from the World Bank and various Governments. At present, CGIAR has about 15 international agricultural research centers (Murphy, 2007; CGIAR, 2010).
Fatigue in the Green Revolution and Hunger in the World
It has been observed that the state of agriculture is different in recent times than it was during the Green Revolution periods. Many experts are of the view that a slowdown in the Green Revolution has occurred and the various factors involved are, increase in demand accompanied with a loss of pace in the supply and the rising costs of food grains. Secondly, the support for agricultural research is decreasing and the shift of research from public to private sector is being witnessed. Hence, compared to the type of public research carried out by charitable organizations, which kindled the Green Revolution and helped the poor is losing its grounds and multinational companies are taking over (Runge and Runge, 2010). According to the FAO (2010), the share of agriculture in GDP decreased from 30 percent to 11 percent in south East Asia between 1965 and 2004. Also, a decrease in production in major producing countries has been observed with China’s wheat production decreased from 123 million tonnes in 1997/98 to 100 million tonnes in 2000/01 and further decrease to 91 million tonnes in 2004 (FAOSTAT, 2007). FAO (2010) estimated the number of malnourished people in the world to be 1.02 million in 2009 and a major portion of these to be residing in Asia Pacific (Fig. 2).
Future: Can Transgenic Crops Replace Modern Varieties?
An important question that science faces is how to safeguard the future of humankind and save millions of people from hunger and poverty. Many advocate the use of biotechnology to develop genetically modified (GM) crops or transgenic plants to further boost agricultural production. The major traits of genetically modified crops that are currently under cultivation are pest resistance with Bt Cotton as an example, and herbicide tolerance, for example Roundup Ready crops. The main GM crops under cultivation are soybean, corn, canola and cotton while China also produces virus resistant peppers, tomatoes and flower-color-altered Petunias on small scale (Pingali and Raney, 2005). James (2004) reported that during 1996 and 2004, the global area under GM crops has increased 47 times. The herbicide tolerant soybean occupied the maximum area among the various GM crops (Table 2). The USA grew the maximum area under GM crops (59 percent of the global area) followed by Argentina, Canada, Brazil, China and Paraguay. Though the food production can be boosted with development and adoption of genetically modified crops, various concerns about health and environmental issues of transgenic crops have been raised. Secondly, the people have developed a negative attitude towards anything which has been genetically altered. The need is to raise the awareness of the common people about the positive and negative effects of GM crops to enable them to make reasonable decisions using scientific and logical approaches.
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