Plant breeding is the art and science of changing the traits of plants in order to produce desired characteristics. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to more complex molecular techniques (see cultigen and cultivar).Plant breeding has been practiced for thousands of years, since near the beginning of human civilization. It is now practiced worldwide by individuals such as gardeners and farmers, or by professional plant breeders employed by organizations such as government institutions, universities, crop-specific industry associations or research centers.
International development agencies believe that breeding new crops is important for ensuring food security by developing new varieties that are higher-yielding, resistant to pests and diseases, drought-resistant or regionally adapted to different environments and growing conditions.
Plant breeding started with sedentary agriculture and particularly the domestication of the first agricultural plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially early farmers simply selected food plants with particular desirable characteristics, and employed these as progenitors for subsequent generations, resulting in an accumulation of valuable traits over time.
Gregor Mendel's experiments with plant hybridization led to his establishing laws of inheritance. Once this work became well known, it formed the basis of the new science of genetics, which stimulated research by many plant scientists dedicated to improving crop production through plant breeding.
Modern plant breeding is applied genetics, but its scientific basis is broader, covering molecular biology, cytology, systematics, physiology, pathology, entomology, chemistry, and statistics (biometrics). It has also developed its own technology.Classical plant breeding uses deliberate interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties. Plants are crossbred to introduce traits/genes from one variety or line into a new genetic background. For example, a mildew-resistant pea may be crossed with a high-yielding but susceptible pea, the goal of the cross being to introduce mildew resistance without losing the high-yield characteristics. Progeny from the cross would then be crossed with the high-yielding parent to ensure that the progeny were most like the high-yielding parent, (backcrossing). The progeny from that cross would then be tested for yield and mildew resistance and high-yielding resistant plants would be further developed. Plants may also be crossed with themselves to produce inbred varieties for breeding.
Classical breeding relies largely on homologous recombination between chromosomes to generate genetic diversity. The classical plant breeder may also make use of a number of in vitro techniques such as protoplast fusion, embryo rescue or mutagenesis (see below) to generate diversity and produce hybrid plants that would not exist in nature.
Traits that breeders have tried to incorporate into crop plants in the last 100 years include:
- Increased quality and yield of the crop
- Increased tolerance of environmental pressures (salinity, extreme temperature, drought)
- Resistance to viruses, fungi and bacteria
- Increased tolerance to insect pests
- Increased tolerance of herbicides
Successful commercial plant breeding concerns were founded from the late 19th century. Gartons Agricultural Plant Breeders in England was established in the 1890s by John Garton, who was one of the first to commercialize new varieties of agricultural crops created through cross-pollination. The firm's first introduction was Abundance Oat, one of the first agricultural grain varieties bred from a controlled cross, introduced to commerce in 1892.
In the early 20th century, plant breeders realized that Mendel's findings on the non-random nature of inheritance could be applied to seedling populations produced through deliberate pollinations to predict the frequencies of different types. Wheat hybrids were bred to increase the crop production of Italy during the so-called "Battle for Grain" (1925–1940). Heterosis was explained by George Harrison Shull. It describes the tendency of the progeny of a specific cross to outperform both parents. The detection of the usefulness of heterosis for plant breeding has led to the development of inbred lines that reveal a heterotic yield advantage when they are crossed. Maize was the first species where heterosis was widely used to produce hybrids.
Statistical methods were also developed to analyze gene action and distinguish heritable variation from variation caused by environment. In 1933 another important breeding technique, cytoplasmic male sterility (CMS), developed in maize, was described by Marcus Morton Rhoades. CMS is a maternally inherited trait that makes the plant produce sterile pollen. This enables the production of hybrids without the need for labor-intensive detasseling.
These early breeding techniques resulted in large yield increase in the United States in the early 20th century. Similar yield increases were not produced elsewhere until after World War II, the Green Revolution increased crop production in the developing world in the 1960s.
In vitro-culture of Vitis (grapevine), Geisenheim Grape Breeding InstituteFollowing World War II a number of techniques were developed that allowed plant breeders to hybridize distantly related species, and artificially induce genetic diversity.
When distantly related species are crossed, plant breeders make use of a number of plant tissue culture techniques to produce progeny from otherwise fruitless mating. Interspecific and intergeneric hybrids are produced from a cross of related species or genera that do not normally sexually reproduce with each other. These crosses are referred to as Wide crosses. For example, the cereal triticale is a wheat and rye hybrid. The cells in the plants derived from the first generation created from the cross contained an uneven number of chromosomes and as result was sterile. The cell division inhibitor colchicine was used to double the number of chromosomes in the cell and thus allow the production of a fertile line.
Failure to produce a hybrid may be due to pre- or post-fertilization incompatibility. If fertilization is possible between two species or genera, the hybrid embryo may abort before maturation. If this does occur the embryo resulting from an interspecific or intergeneric cross can sometimes be rescued and cultured to produce a whole plant. Such a method is referred to as Embryo Rescue. This technique has been used to produce new rice for Africa, an interspecific cross of Asian rice (Oryza sativa) and African rice (Oryza glaberrima).
Hybrids may also be produced by a technique called protoplast fusion. In this case protoplasts are fused, usually in an electric field. Viable recombinants can be regenerated in culture.
Chemical mutagens like EMS and DMS, radiation and transposons are used to generate mutants with desirable traits to be bred with other cultivars - a process known as Mutation Breeding. Classical plant breeders also generate genetic diversity within a species by exploiting a process called somaclonal variation, which occurs in plants produced from tissue culture, particularly plants derived from callus. Induced polyploidy, and the addition or removal of chromosomes using a technique called chromosome engineering may also be used.
When a desirable trait has been bred into a species, a number of crosses to the favored parent are made to make the new plant as similar to the favored parent as possible. Returning to the example of the mildew resistant pea being crossed with a high-yielding but susceptible pea, to make the mildew resistant progeny of the cross most like the high-yielding parent, the progeny will be crossed back to that parent for several generations (See backcrossing ). This process removes most of the genetic contribution of the mildew resistant parent. Classical breeding is therefore a cyclical process.
With classical breeding techniques, the breeder does not know exactly what genes have been introduced to the new cultivars. Some scientists therefore argue that plants produced by classical breeding methods should undergo the same safety testing regime as genetically modified plants. There have been instances where plants bred using classical techniques have been unsuitable for human consumption, for example the poison solanine was unintentionally increased to unacceptable levels in certain varieties of potato through plant breeding. New potato varieties are often screened for solanine levels before reaching the marketplace.
Modern plant breedingModern plant breeding may use techniques of molecular biology to select, or in the case of genetic modification, to insert, desirable traits into plants. Application of biotechnology or molecular biology is also known as molecular breeding (see: Molecular breeding).
Modern facilities in molecular biology have converted classical plant breeding to molecular plant breeding
Steps of plant breedingThe following are the major activities of plant breeding:
- Collection of variation
- Distribution of the new variety
Marker assisted selection
See main article on Marker assisted selection.Sometimes many different genes can influence a desirable trait in plant breeding. The use of tools such as molecular markers or DNA fingerprinting can map thousands of genes. This allows plant breeders to screen large populations of plants for those that possess the trait of interest. The screening is based on the presence or absence of a certain gene as determined by laboratory procedures, rather than on the visual identification of the expressed trait in the plant.
Reverse breeding and doubled haploids (DH)
See also main article on Doubled haploidy.A method for efficiently producing homozygous plants from a heterozygous starting plant, which has all desirable traits. This starting plant is induced to produce doubled haploid from haploid cells, and later on creating homozygous/doubled haploid plants from those cells. While in natural offspring genetic recombination occurs and traits can be unlinked from each other, in doubled haploid cells and in the resulting DH plants recombination is no longer an issue. There, a recombination between two corresponding chromosomes does not lead to un-linkage of alleles or traits, since it just leads to recombination with its identical copy. Thus, traits on one chromosome stay linked. Selecting those offspring having the desired set of chromosomes and crossing them will result in a final F1 hybrid plant, having exactly the same set of chromosomes, genes and traits as the starting hybrid plant. The homozygous parental lines can reconstitute the original heterozygous plant by crossing, if desired even in a large quantity. An individual heterozygous plant can be converted into a heterozygous variety (F1 hybrid) without the necessity of vegetative propagation but as the result of the cross of two homozygous/doubled haploid lines derived from the originally selected plant. patent
See main article on Transgenic plants.Genetic modification of plants is achieved by adding a specific gene or genes to a plant, or by knocking down a gene with RNAi, to produce a desirable phenotype. The plants resulting from adding a gene are often referred to as transgenic plants. If for genetic modification genes of the species or of a crossable plant are used under control of their native promoter, then they are called cisgenic plants. Sometimes genetic modification can produce a plant with the desired trait or traits faster than classical breeding because the majority of the plant's genome is not altered.
To genetically modify a plant, a genetic construct must be designed so that the gene to be added or removed will be expressed by the plant. To do this, a promoter to drive transcription and a termination sequence to stop transcription of the new gene, and the gene or genes of interest must be introduced to the plant. A marker for the selection of transformed plants is also included. In the laboratory, antibiotic resistance is a commonly used marker: Plants that have been successfully transformed will grow on media containing antibiotics; plants that have not been transformed will die. In some instances markers for selection are removed by back crossing with the parent plant prior to commercial release.
The construct can be inserted in the plant genome by genetic recombination using the bacteria Agrobacterium tumefaciens or A. rhizogenes, or by direct methods like the gene gun or microinjection. Using plant viruses to insert genetic constructs into plants is also a possibility, but the technique is limited by the host range of the virus. For example, Cauliflower mosaic virus (CaMV) only infects cauliflower and related species. Another limitation of viral vectors is that the virus is not usually passed on the progeny, so every plant has to be inoculated.
The majority of commercially released transgenic plants are currently limited to plants that have introduced resistance to insect pests and herbicides. Insect resistance is achieved through incorporation of a gene from Bacillus thuringiensis (Bt) that encodes a protein that is toxic to some insects. For example, the cotton bollworm, a common cotton pest, feeds on Bt cotton it will ingest the toxin and die. Herbicides usually work by binding to certain plant enzymes and inhibiting their action. The enzymes that the herbicide inhibits are known as the herbicides target site. Herbicide resistance can be engineered into crops by expressing a version of target site protein that is not inhibited by the herbicide. This is the method used to produce glyphosate resistant crop plants (See Glyphosate)
PLANT BREEDING DEVELOPMENT IN USA
The following quotation from State Agricultural Experiment Stations. A History of Research Policy and Procedure (Knoblauch et al., 1962) is pertinent to this discussion of University of Minnesota research related to breeding disease resistant varieties of farm crops. “In 1962 we will commemorate the signing by Abraham Lincoln on May 15, 1862 of ‘An act establishing the United States Department of Agriculture,’ and on July 2, 1862, of ‘An act donating public lands to the several States and Territories’ which may provide colleges for the benefit of American agriculture and the mechanic arts.” These two acts were essential to the development of agricultural teaching and research in the United States.
Agricultural research has greatly modified agricultural production. After World War II, the assistant chief of the Bureau of Agricultural Economics stated that the breeding of disease resistant varieties, the development of hybrid corn, and mechanization had greatly helped win the war.
The information in the following two paragraphs was supplied by Dr. E. Fred Koller, Professor of Agricultural Economics, University of Minnesota.
Changes in farm production and efficiency have been great. In 1910 the number of persons supported by one farm worker was about 7, in 1951, about 15, and in 1961, 27. The ratio of farm population to total population has also greatly changed. In 1920, the total population was about 106 million with about 30 percent farm population. In 1950, the total was over 151 million with 16.5 percent farm population, and in 1960 over 180 million and 11.4 percent farm population.
Comparisons of people engaged in all occupations and in agriculture also give a striking picture of changes that occurred. In 1870, of nearly 12 million workers, 53 percent were engaged in agriculture; in 1920, of over 42 million, 27 percent were engaged in agriculture; in 1940, of over 56 million, only 17 percent were engaged in agriculture; and in March 1960, of over 70 million, only 6.4 percent were engaged in agriculture. The actual round numbers of persons engaged in agriculture in 1870, 1920, 1940, and 1960 were 6,850,000, 11,449,000, 9,540,000, and 4,565,000, respectively.
These gains in efficiency were largely due to results of research. The development of the State Agricultural Experiment Station research programs was of equal importance to that of USDA. Because both were made possible through federal support, cooperation has been fostered between these two agencies.
The first State Agricultural Experiment Station originated in Connecticut and is still functioning in New Haven. It is one of the few state stations not connected directly with a land-grant institution. S.W. Johnson was responsible primarily for its creation. When he failed to obtain support for initiating an agricultural station in Connecticut, he presented a plan for such a station to a prominent New York State society. Until 1887 Johnson and others worked tirelessly to gain support for the State Agricultural Experiment idea. He and colleagues developed a center for teaching research methods in agricultural chemistry at Sheffield Scientific School in New Haven where advanced students were training.
During my first year, 1909, at the Connecticut Station, I worked directly with E.M. East and gained from him great inspiration for a life work in genetics and plant breeding. On completing work for the M.S. degree in 1911, I was given charge of the work at Connecticut. During 1905, studies with corn and tobacco at the Connecticut Agricultural Experiment Station were supported largely by the Adams fund. E.H. Jenkins, director of the station, and East both believed that a trained research worker should have a free hand to conduct investigations. From them I learned the importance of an enthusiastic vital interest in research and the equal importance of individual freedom to conduct studies without being hampered by directives.
W.O. Atwater was also an outstanding advocate of the State Agricultural Experiment Station. With Johnson’s aid the first State Agricultural Experiment Station was set up at Wesleyan University, Middletown, Connecticut, where Atwater was professor of chemistry. The Connecticut State Legislature granted $2,800. Orange Judd, a farm paper publisher, gave $1,000. Atwater was placed in charge.
Because of administrative difficulties, Atwater and coworkers drew up a new plan. In 1877 the Connecticut Agriculture Experiment Station was created to be governed by a board of control and financed by a continued appropriation of $5,000 from state treasury funds. This board appointed Johnson as director and leased temporary quarters at Sheffield in New Haven. In 1882 the legislature authorized purchase of a small private estate in New Haven. The Connecticut Agricultural Experiment Station is today located in the same headquarters.
Six other states launched Agricultural Experiment Stations prior to the Hatch Act in 1887. These included: Tennessee, 1882; Wisconsin, 1883; Kentucky, 1885; New York Geneva Station, late 1880’s; New York Cornell Station, 1879; and Massachusetts, 1883. University trustees in California in 1875 encouraged a station movement and gave broad authority (by 1880) to a station director.
Even though experiment stations were not set up, experimentation was started early at most land-grant colleges. Either by charter provision or separate enactment, college governing bodies were directed to initiate and maintain agricultural experimentation.
Because of lack of direct federal support for the Agricultural Experiment Station idea, each state carried out experimentation according to the desires and research viewpoints expressed at different land-grant institutions. Unfortunately, when state legislatures authorized State Agricultural Experiment Stations, they were set up independently of land-grant institutions. Therefore, there was lack of coordination between early research at land-grant institutions and at stations. These difficulties were largely surmounted when Congress passed the Hatch Act as amended in 1887.
“In the winter of 1885-86, the committee on presidents,” (land-grant institutions) “assiduously cultivated the Congressional chairman of the agricultural committees, William H. Hatch in the House and James Z. George in the Senate.” These two chairmen were strong supporters of the station bill. Although Hatch encountered no great difficulty of obtaining support for the measure, two divergent viewpoints were expressed in Senate debates. George considered experiment stations to be extensions of USDA since both were to be financed by the federal government. Senator Joseph H. Hawley, Connecticut, took an opposite view. He proposed a substitute measure in which no reference would be made to USDA. Hawley was interested primarily in a plan whereby a state legislature could use Hatch Act funds for an experiment station which was not connected with a land grant institution.
PLANT BREEDING DEVELOPMENT IN NIGERIA
Plant genetics is used in agriculture to develop new and modern improved varieties through plant breeding. The varieties could be for high yield, improved mineral and vitamin content, early maturing, etc.
How would you relate the political will of Nigerian leadership to the agricultural needs of the nation?
One can conveniently say that it is not there. However, let us wait and see, perhaps with all promises made, something may come out of it.
Recently, the Global Food Security Index of the Economist Intelligence unit ranked Nigeria 80th among 105 other countries on food insecurity. What do you see as the reason for this ugly development?
It is quite unfortunate but the reasons that Nigeria is lagging behind in the provision of food security for the citizenry include inadequate funding and infrastructure for research; lack of adequate link between research and development; funding of development, where available, is not realistic or has been politicized and as such, does not reach the target farmers.
Do you see the current Nigeria’s Agricultural policy as truly addressing the problem of food crisis in the country?
Theoretically it can, but it has always been the problem of implementation. You cannot transform Agriculture when the infrastructure is not there; you cannot supply inputs through cell phones in a country where there is no power and literacy level is low.
What do you see could be the role of Agricultural Biotechnology in improving food production in Nigeria and by extension, African continent?
Agricultural Biotechnology can lead to a quantum leap in food production if utilized effectively and efficiently. However, bio-safety regulations must be respected.
Biosciences for Farming in Africa, B4FA has come into the continent with a view to creating awareness on the need for governments and farmers here to wholly adopt biotechnology in order to increase food production to meet up with the over-growing population. As a plant breeder, how would you advise the FG on this?
Government can adopt biotechnology. There is no problem with that but we must, first of all, place all the bio-safety regulations in place.
Ways for improving food production are by genetically modifying plants as well as genetically engineering crops such that would be resistant to deterring factors like pests and other plant diseases. According to your research and findings, how much of these are Nigerian farmers using?
There is practically none as of now; perhaps in the near future.
If, according to your research findings, no Nigerian farmer on the average is using genetically modified plants and genetically engineered crops, how do we start as a country?
Well you see the way to start even in the countries that have started; the first thing is to put in place, the bio-safety regulations like I said earlier. What are bio-safety regulations? These are regulations to ensure that there are no unwarranted or unwanted transfers of genetic materials to sources that they are not designed for.
If this takes place, then it may lead to the creation or development of very terrible and hazardous threat to the environment. And that is why before you start; make sure that the bio-safety regulations are being observed. To my knowledge, the bio-safety law has been passed by the National Assembly but not sure if it has been assented to by Mr.
President. Even if it has been assented to, what have we put in place to ensure that these things are working? If we don’t ensure that they are working and we just kick-start the project, I assure you that we will be in more trouble than we expect.
You have consistently mentioned the observance of bio-safety regulations as a precondition for Nigeria’s adoption of Agricultural Biotechnology. Specifically, which of these regulation are you referring to
These are regulations as to how and where you practice; how the laboratories will function and even the farmers are going to control, polling transfer and so on. So, these things have to be worked upon by a national committee of experts. We have teeming professors out there that could help in this regard. What remains is for the government to present this document for the experts to do some work on its workability.
How would you assess government’s support for research and development, especially in the area of agricultural biotechnology and the application of such research results for national development?
The basic infrastructure for biotechnology is lacking in the country as well as training and retraining. More so, funding for biotechnology research is lacking. We also need to prioritize and focus on certain key crops that will immediately solve the problem of food insecurity and for economic empowerment in order to reduce poverty; provide jobs through value addition to our crops, which in turn will attract international market.
In order to cover the whole country effectively, the Institute has established and sustains substations in six locations in which the mandate crops of the Institute can be economically cultivated. These are: Owena (Ondo State) which caters for cocoa, robusta coffee and kola, in the south-west zone rain forest belt, Uhonmora (Edo-State) which caters for cocoa in marginal forest areas. Ochaja (Kogi State) for cashew and kola: Ibeku (Abia State) in the south-east zone and also in rain forest belt to cater for cocoa and cashew. Ajassor (Cross River State) for cocoa and Kola in the south-east zone rain forest belt; and Kusuku-Mambilla (Taraba State) for Arabica coffee and tea. There are six experimental stations located all over the country in Okondi (Cross River State) for robusta coffee, Mayo-Selbe (Taraba State) for cocoa and robusta coffee, Ibule (Ondo State) for cocoa, Kabba (Kogi State) for robusta coffee, Ugbenu (Anambra State) for cashew, and Onisere (Ondo State) for cocoa.
Outreach and Extension Services
The aforementioned substations and experimental sites serve to facilitate the Institute’s outreach and extension services to farmers and industrialists operating on its mandate crops all over the country, namely:
(a) Serving as effective information channels whereby research findings get to farmers and industrialists. And the production constraints of farmers and industrialists are fed back to researchers.
(b) Improving the socio-economic status of farmers/farm families through improved and diversified income.
(c) Increasing productivity of farmers through effective utilization of on-farm trial methods thereby enhancing adoption of technology.
(d) Bringing about awareness to farmers on varied methods of utilizing farm by products.
(e) Assisting farmers and industrialists to become self-reliant in making certain production decisions
Manpower and other Existing Resources
The Institute as at January 3, 2013 has a total staff strength of 938, made up of 72 research Scientists 24 Laboratory Technologists and 63 Agricultural Superintendents, 33 professionals in Administration, Finance and Supplies and Engineering Works, 746 other service personnel, semi skilled and unskilled personnel. There are other physical infrastructures and social services available at the Institute headquarters in Ibadan and all the above mentioned substations and experimental sites. These are however insufficient to fully meet the mandate of the Institute.
Contributions of CRIN to the National Economy
As all the mandate crops of CRIN are commodity crops, research efforts on these crops can and will cause increase in productivity and ultimate gross production of these crops, leading to a direct increase in the foreign exchange earning of Nigeria. Furthermore, all the crops are industrial crops (for large, medium and small scale industries) which can be exploited to meaningfully contribute to the desired industrial growth of Nigeria, create employment for both rural and urban populace and in no small way increase the standard of living of the people involved in the industries.
Cassava Programme was one of the first three crop commodity programmes established in May 1973 when National Root Crops Research Institute, Umudike was known as Federal Agricultural Research and Training Station, Umudike. The mission of cassava Programme has been to improve cassava as a crop and its cultivation for sustainable food production and income generation. The main thrust of the Programme is cassava varietal development mainly through breeding, which is complemented by other disciplines for the selection of the desirable varieties
The breeding objectives include:
- High fresh root yield, dry matter and starch contents
- Resistance to the major cassava pests-cassava mealy bugs(CM), cassava green mite (CGM), and disease-cassava mosaic disease (CMD), cassava bacterial blight (CBB) and cassava anthracnose disease (CAD)
- Compatibility with intercrops with legumes, cereals, vegetables and other crops in intercropping systems
- Acceptable culinary qualities
- Extended in-ground storage
- Reduced cyanogenic potential and
- Early maturity (8-10 months after planting)
- A multi-disciplinary approach compliments the breeding process in cassava varietal development:
- Agronomy with focus on production packages and systems of cassava
- Plant Protection for the screening of cassava varieties for resistance to, and cultural control measures against, pests and diseases.
- Biochemistry for proximate analysis of tubers and product quality.
- International Institute of tropical Agriculture (IITA), Ibadan, Nigeria: a major collaborating Institution in the development of improved cassava varieties, pre-emptive management of severe form of CMD, Cassava Enterprise Development, Harvest plus as it relates to beta carotene in cassava tubers and integrated Pest Management of whitefly-transmission viruses of cassava and sweet potato.
- Donald Danforth Plant Science Centre (DDPSC). St. Louis, Missouri, USA in the area of genetic engineering to elevate resistance in farmers’ preferred cassava varieties but which are highly susceptible to CMD, and screening of some of farmers’ preferred varieties for bio engineering to improve the Pro-vitamin A content of cassava tubers, to reduce cyanogenic potential and to delay deterioration of cassava tubers after harvest.
- Centro International de Agricultural Tropical (CIAT), Call, Colombia with focus on the use of simple low cost market technology to pyramid useful genes for delayed postharvest physiological deterioration of cassava in addition to maintaining resistance to the major pests and diseases.
- International Atomic Energy Agency, Vienna, Austria for the conduct of research on the use of radiation to produce desirable mutants of cassava varieties.
- Raw Material Research Development Council, Abuja, Nigeria on research for early maturing (8-10 months after planting) cassava varieties.
- Cornell University, Ithaca NY, USA on the Next Generation Cassava Breeding (NEXTGEN Cassava) project which aims to significantly increase the rate of genetic improvement in Cassava breeding and unlock the full potential of Cassava. The project implements and is empirically testing a new breeding method known as Genomic Selection that relies on statistical modeling to predict cassava performance before field testing, and dramatically accelerates the breeding cycle.
- Combined efforts of NRCRI and IITA had led to the release of 43 improved cassava varieties to farmers in Nigeria which includes three beta carotene (Pro-Vitamin A) varieties. The cultivation of improved cassava varieties by farmers in Nigeria has enhanced the position of Nigeria as the world-leading producer of cassava.
- Development of appropriate best-bet agronomy practices for cassava cultivation. These include appropriate plant spacing in sole and in intercropping, the use of appropriate stem cuttings as planting material, appropriate fertilizer regimes, and weed management.
- Integrated control of cassava mealybugs and green mites through the joint efforts of IITA and NRCRI.
- The Biological control of the Cassava green mite.
- Development of cultural control measures for pests and diseases of cassava such as termites, and CMD.
- Identification of transgenic cassava plants with elevated resistance to CMD under screen house condition as DDPS, USA. The plants are awaiting testing under field conditions in Nigeria.
- A molecular biology laboratory established has metamorphosed into Biotechnology Programme . Exotic germplasm with desirable trials have been introduced from the center of primary diversity.
Cocoyam Programme is one of the seven crop-based programmes at the National Root Crops Research Institute, Umudike. Cocoyam became a mandate crop for research during the mid seventies when the Institute was charged specifically for study and improve holistically important root and tuber crops in Nigeria. Cocoyam ranks third in importance after cassava and yam among the root and tuber crops cultivated and consumed in Nigeria. Currently, Nigeria is the world’s leading producer of cocoyam (taro), accounting for up to 3.7 million metric tones annually. Cultivars of two species, Colocasiaesculenta (taro) and Xanthosomasagittifolium (tannia) are generally grown for food. Nutritionally cocoyam is superior to cassava and yam and taro starch is also more readily digested.
- Development of improved genotypes that possess desirable agronomic and culinary qualities as well as resistance to diseases.
- Multiplication and dissemination of healthy planting materials of elite cultivars.
- Development of farmer-friendlyand yield-enhancing low-cost cultural management practices.
- Development of environmentally-friendly technologies for the control of pre-and post-harvest biotic and abiotic stress factors.
- Diversification of value-added products obtained from corms and cormels to increase shelf life of cocoyam products and meet consumers acceptability.
Although no new improved genotypes of cocoyam have been developed largely due to difficulties not unconnected with conventional breeding methods in the crop, 10 distinct cultivars, of which three are Xanthosoma species and seven Colocasia species, identified from germplasm collections at NRCRI, Umudike, are recommended for cultivation.Concerted efforts by scientists in Cocoyam Programme over the years have resulted in the development of production packages that are beneficial to cocoyam farmers. They include:Cocoyam minisett technique for enhanced multiplication of cocoyam planting materials.
- Drastic reduction in seed outlay from 2 t/ha in farmers’ field to 0.5 t/ha, without compromising yield.
- Reduced cost of planting material by 40%.
- Increased yield output from 6-7 t/ha in farmers’ field to 15-20 t/ha.
- Manipulation of cormel size in Xanthosoma species through plant spacing in the field.
Development of improved field production package for high yield involving:
- Early planting
- Application of appropriate levels of inorganic and organic soil amendment materials.
- Mulching in open fields.
- Suitable inter-crops and time of introduction.
Cultural control of Cocoyam Root Rot Blight Complex (a devastating disease that attacks Xanthosomasp) by:
- Early planting (April/May)
- Use of fertilizer rich in potassium (80N,30P and 100K)
- Well drained soil with no water logging
- Use of clean planting material.
Development of value-added products to extend shelf life and meet consumer acceptability from targeted cultivars.
- Cocoyam crisps/flakes
- Soup thickener powder
- Flour(for confectionary)
In spite of the advances made in cocoyam research, several factors remain as challenges to sustained cocoyam production in Nigeria.
- The ignorance of the nutritive value and diversities of food forms from cocoyam by a large percentage of the populace is a major limiting factor to general acceptability and extensive production of the crop. The notion that cocoyam is a poor man’s crop is still prevalent and needs to be dispelled through the extension of proper information about the crop.
- The recycling of planting material (corms/cormels) year by year results in the accumulation of pathogens in them and this translates to yield decline with time. The 11% drop in national production figures between 2000 and 2004 (FAO 2001,2004) may not be unconnected with this phenomenon. Generation of ‘clean’ planting material through meristem tip culture and multiplication of these will not only stem this process but increase yield as well.
- A breakthrough in conventional breeding or through biotechnology is necessary to develop cultivars with more desirable traits,particularly resistance to diseases, other than those found in the local cultivars. This will widen the current narrow genetic base in the country.
- Nigerian cocoyam needs to enter the international trade market and generate foreign exchange for Nigeria. This will in turn stimulate production.
- On-going studies:
- Induction of flowering in cocoyam cultivars by chemical treatment
- Assessment of cassava starch-gelled medium for in vitro multiplication of cocoyam
- Efficiency of small-holder cocoyam production and storage in Anambra State
- Effect of post-harvest treatment on the control for rot in stored cocoyam planting materials.
- Cost and return analysis of cocoyam production at NRCRI Umudike.
Active research in sweetpotato commenced in the late 70’s. Prior to this period, the crop was mostly seen as a volunteer or discard crop the children picked mostly around refuse dump sites. The consumption of sweetpotato then was surrounded by the erroneous idea that it caused amoebic dysentery.
With active research over the years, there has been a tremendous improvement on the cultivation of the crop which has largely contributed to the agricultural /food economy of the nation.
The programme has the national mandate of genetic improvement of sweetpotato, production of improved production packages that will sustain high yield, formulation of disease and pest control strategies, development of post –harvest technologies and extension of findings of end users through established channels.
HIGHLIGHTS OF RESEARCH ACHIVEMENTS:
- The production, marketing and utilization of sweetpotato have expanded in the last decade to almost all ecological zones of Nigeria. Presently, over 1million hectare of land are under sweetpotato cultivation in Nigeria.
- Yields have increased from farmers’ pre-research era of 2-3 tons /ha to 10 tons/ha due to the availability of improved varieties and management practices. Nigeria today is the 2nd largest producer of sweetpotato in Africa with 3.4 MT annually. Globally, Nigeria is now the world’s third largest producer .
- Development of “2-node cutting and grooving techniques for rapid generation of planting materials”.
- Development of dry season irrigated sweetpotato nursery technique for the conservation of planting materials during the dry season since most sweetpotato fields dry up in the dry season.
- Development of cultural packages for the control of sweetpotato weevils, Cylas spp. Which is a major insect pest of sweetpotato.
- Development of improved agronomic packages for higher yield per unit area.
- Development of techniques for the storage of planting materials and storage of sweetpotato root tubers in moist saw dust for about 3-4 months as against the shelf life of 2-4 weeks of harvested roots if not properly stored.
- Introduction of three (3) forage varieties for livestock farmers.
- Development of various recipes and blends for different utility purposes.
- Development of hybrid seeds through open pollination.
- Introduction and selection of elite varieties for various ecological and uses in Nigeria.
- Development and release of 2 orange-fleshed Sweetpotato varieties with high β carotene (a precursor for pro-vitamin A) that can improve the nutritional well being of Nigerians
Crop research: the extensive strategies
To increase food production certain strategies must be highlighted here namely: Extensive arable land use and where it is necessary with the application of irrigation. Caution must be the watchword here. According to the Global Land Assessment of degradation (Glasod) estimation, of the 3.2 billion hectares available which are under pasture, 21 percent are degraded, while of the nearly 1.5 billion hectares in the crop lands, 38 percent are degraded in various degrees. The degradation of cropland appears to be most extensive in Africa affecting 55 percent of the crop area, compared with 51 percent in the Latin America and 38 percent in Asia. This all limits the extent of which we can make use of available arable land. Declining yields or increasing input requirements will be the consequence. Another strategy of making intensive use of the available arable land is to irrigate it where necessary. The potential for increasing the overall irrigated area in the developing countries is at 110 million hectares. This could provide an additional 300-400 million tons of grain, enough to provide a basic diet for more than 1.5 billion people (FAO Food Security Assessment Document WFS/tech/7, Rome 1996, p.16.)
Crop research: the intensive strategies
The constraints earlier highlighted leave us with the option of intensive method of Agriculture, which is knowledge based. The role of the crop research cannot be overemphasized namely: agronomy; plant breeding: plant physiology and biochemistry; plant protection; biotechnology etc. According to Ben Miflin (Journal of Experimental Botany, Vol.51, No.342 MP special issue, pp1-8, January 2000) , the vast majority of the increase in the crop yields that took place in the last century has been powered by changes in the genetical potential of the crop and the way in which it has been managed.
In the field of plant breeding, introduction of highly productive crops to the country will be of great importance and a rational solution to the existing problem of food security, it might also proved to be one of the lasting option to satisfy the increasing population with food stuff. Therefore, this aspect of crop research will be examined in details in this article.
Another area of crop research that this article will dwell into is plant protection, since the key to attaining food sufficiency is ensuring that crops stay healthy and protected from damages by pests and diseases.
Apart from pest and diseases, crops are equally subjected to adverse environmental conditions, like drought, ultra-violet radiation etc. Hence the need to factor this into the crop research strategy.
Innovative crop research techniques, like crop biotechnology, are now available and need to be incorporated into the above-mentioned crop research strategies to enhance their productivity.
Therefore, it is possible to make analysis of crop research strategies from three different angles namely: crop introduction/breeding, crop protection and crop biotechnology
The most important feature in the development of agriculture throughout the world is introduction of high-yielding cultivars from other agroecological zones and domestication of wild but desirable plants.
The development of today's crops is due in considerable measure to the introduction in the last half of the eighteenth century of cultivars of various crops that were suited to special needs or growing condition. For example, the domestication of Wheat, Oats, Soyabeans, Sorghum and Barley, notably improved food production in the USA
Introduction can be used to promote breeding activities: breeding materials are often collected from introduction and those with desirable qualities are selected. Therefore is the duty of Nigerian agronomists to introduce more crops to the country that will supplement the food ration requirement to the level of world standard. High quality cultivar of plant species from industrialised nation is always been distributed to other countries for introduction with the aim of improving the quantity and quality of the existing local varieties, for both food and industrial purposes. For example, sunflower from Russia was successfully introduced to Bulgaria, Belgium, Romania and Yugoslavia.
The following improved food crops are necessary to be domesticated for enhancing food security in Nigeria:
- Wheat v.Budimir developed in Krasnodar, Russia, is productive with high resistence to drought comparatively with other spring wheats, and can perform very well under tropical condition when temperature falls to 23-26.
- Rice cultivars v.CR.906, 907, CO.4, 21, 29 and CO.30 all developed in India. They are resistant to rice blast and v. CR.906 and CR.907 have vegetation period of not more than 135 days.
- Vegetable crops such as Chinese cabbage v. Pac choe k-163, this crop contains in its leaves vitamin C of lemon quality and protein of albumin and globulin type.
- Fodder crops, eg- Amaranth v.D-965 k.7 grown in India is a good source of Vitamin C for cattle.
Pest and Disease:
In order to permanently maintain the productivity, ability to function, regenerative power and the buffering capacity of the open system within which plants are cultivated, plant protection measures must be ecologically effective. This emphasizes the need for more concerted research involving integrated efforts of soil scientists, biochemists, plant physiologists and entomologists.
Breeders in conjunction with plant protectionists should also include in their research, the development of crop resistant varieties to pests and diseases. Most chemical factors responsible for the resistance of plants to insects and diseases studied to date, have involved the genetically controlled, injury-dependant accumulation of metabolites with allomonal activity. Other factors with the demonstrated capability to induce changes in levels of resistance include temperature, solar radiation, water stress, soil fertility, pathogen infection, weed competition and previous or current insect attack. The aforementioned environmental factors need deeper research to obtain cheaper methods for combating pests and diseases.
Considering the relevance of food sufficiency, agricultural policy makers in Nigeria should adequately invest in funding researches in crop protection. Meanwhile, a framework should be provided to farmers to ensure the affectivity of plant protection methods at hand. For example, they should be enlightened on how to identify the actual pests and diseases, determine the level of infestation and the symptoms to describe the pathological conditions of crops, to be able to establish the economic injury level values for pests and diseases in order to derive a farm-level relevant methods in the context of effective plant protection. They should be advised to include the critical use of right pesticides and other protective measures in order to satisfy the criteria of effective plant protection.
Drought and Ultra-violet radiation:
Crop production in Nigeria is mostly rain-fed. In the Northern part of the country, it is common knowledge that there is insufficient rainfall, and where available, it is not evenly distributed. Consequently, crops experience a period of water deficiency during the cause of its growth and development, which adversely affect its productivity.
Irrigation easily comes to mind as the best method in alleviating the effect of droughts. However, the following factors might mitigate against the extensive use of irrigation system by peasant farmers: cost-effectiveness, the land tenure system, land relief and topography, availability of qualitative water etc. Hence, the need to research more into crops that could make effective use of available water.
Different drought-research methods are available, such as modelling of drought in laboratory condition to study the mechanism involved in drought resistance. This could lead to the development of express methods of screening drought-tolerant crops.
Ultraviolet-B radiation reaching the earth's surface may constitute another significant environmental stress for crop plants. This radiation might cause morphological alterations involving both the inhibition and stimulation of growth in various plant organs, nucleic acid (DNA) lesions which results in the loss of 'DNA'biological activity, inactivation of proteins, etc. Physiological processes including leaf development, photosynthetic capacity, reproductive effort have also been shown to be altered by increased UV-B radiation.
Tropical plants are thought to have an inherent resistance to ultraviolet radiation, however, tropical plants are exposed to a wide range of ambient UV-B radiation as a result of light gaps or changes in elevation. Because of the large number of plant species in the tropics, alterations in light quality with increased ultraviolet radiation could, potentially, have a greater impact on plant productivity and species diversity.
Future research priorities should focus on the need to accurately assess the effects of UV-B radiation on tropical plant productivity and to make scientific and policy decisions as climate change continues. Information on the impact of increased ultraviolet radiation on ecosystem level processes such as nutrient recycling, production and distribution of secondary compounds, specie distribution and plant competition are also required.
It's also important to consider other environmental factors, such as increase in CO2 and temperature, humidity, etc. that modify ultraviolet effects. Today some few literatures exist on cross-adaptations of plants to different stress factors in combination. For example it has been established that increased CO2, temperature and drought could reduce the extent of ultraviolet radiation in plants. However the mechanism for this response is still being worked out.
Lastly, improvement of methodology in regards to ultraviolet radiation assessment studies should take in to account the practical reality of our ecosystems. It should also be noted that important research needs can only be met by establishing 'in situ' experiments with modulated supplemental UV-B radiation under tropical conditions, preferably on long-term basis.
Crop biotechnology is the latest revolution in agriculture and it comprises the following major areas of modern plant biology: Molecular Genetics and Plant cell and tissue culture.
The conventional methods used in Nigeria for disease diagnosis involve visual observation of disease symptoms and determination of pathogen specialization through inoculation of differential cultivars. Immunoassays (involving the use of polyclonal or monoclonal antibodies as probes) and nucleic acid-based hybridization assays (which uses DNA or RNA as probes) are the molecular probes that greatly facilitate disease detection and management process.
In conventional crop breeding, promising lines are identified only by their phenotypes. Apart from being time consuming, conventional breeding is also capital and labor intensive. Innovative breeding techniques, like molecular marker-assisted breeding, are required to break through. Marker-assisted screening is a rapid indirect method of detecting promising lines based on a certain banding patterns of linked molecular markers. Apart from increasing the accuracy and rapidity of screening promising lines for agronomic traits, marker-assisted selection is also of immense importance in the attempt to incorporate desired genes of wild exotic species into food crops that lack them.
Genetic engineering of crops is another tool of molecular genetics which involves, among other things, the exploitation of some species of Agrobacteria to incorporate desired genes into food crops. Transgenic food crops with resistance to herbicides and insect pests are now in commercial use in most developed countries. Nigeria might benefit from genetic modification of crops by selecting and introducing transgenic crops that fits its demands. However, compulsory biosafety measure must first be in place.
Plant Cell and Tissue Culture
This is another technique of biotechnology that is often exploited for:
- The production of haploid plants through microspore culture
- Recovery of disease-free plant materials
- The rapid development and selection of desired traits by cellular breeding
- Hybrid rescue through Embryo culture
- Somatic hybridization through protoplast culture
- Micropropagation of elite genotypes and conservation of exotic germplasm
All these opportunities, which plant cell and tissue culture offers, are yet to be fully exploited in Nigeria. Unlike the techniques of molecular genetics, tissue culture technologies could easily be transferred to Nigeria and adapted by conventional breeders.
The immediate major task, therefore, is for the government to invest heavily towards the training of enough specialists in the field of crop biotechnology and creation of well-equipped modern biotechnology laboratories at the various national agricultural research institutes of Nigeria. Available statistics in the USA and Canada show that extremely high social rates of returns of biotechnological research justify public investment. Nigeria cannot be an exception.