CS 460: Conservation of Medicinal Plants 2021 PDF

CS 460: CONSERVATION OF MEDICINAL PLANTS COURSE LECTURERS DR. B. ANNOR & DR. I.K. AMPONSAH Faculty of Agriculture Building Dept. of Crop & Soil Sciences Room FF 22 KNUST, Kumasi Email: [email protected] 1 Mobile: 0548026716  Reco...

CS 460: CONSERVATION OF MEDICINAL PLANTS COURSE LECTURERS DR. B. ANNOR & DR. I.K. AMPONSAH Faculty of Agriculture Building Dept. of Crop & Soil Sciences Room FF 22 KNUST, Kumasi Email: [email protected] 1 Mobile: 0548026716  Recommended Textbooks ❖Principles of Plant Genetics and Breeding (2020), 3rd Edition, by George Acquaah, Wiley- Blackwell ❖Plant Breeding: Principles And Methods (2009), 1st Edition, by B.d. Singh 2 TO CONSERVE OR NOT TO CONSERVE? Genetic Erosion and Vulnerability 3  GENETIC VULNERABILITY ❖The condition that results when a crop is uniformly susceptible to a pest, or any environmental hazard as a result of narrow or uniform genetic base of available cultivars of the crop, thereby creating a potential for disaster. 4 HISTORICAL EXAMPLES OF GENETIC VULNERABILITY ❖The Great Famine or the Irish Potato Famine in Ireland due to potato late blight (caused by Phytophthora infestans) was a period of mass starvation, disease and emigration between 1845 and 1852. ❖During the Famine, Ireland's population fell by between 20 and 25%. ❖Approximately 1 million people died and a million more emigrated from Ireland. 5  HISTORICAL EXAMPLES OF GENETIC VULNERABILITY… ❖ Wheat-less days in the USA due to stem rust epidemics (caused by Puccinia graminis) In 1917. ❖ In the mid 1940s, there was complete elimination of all oats derived from the variety Victoria in the US due to the Victoria blight disease (caused by Helminthosporium victoriae). ❖ In 1943, there was famine in Bengal, India due to brown spot disease of rice (caused by Cochliobolus miyabeanus) and a typhoon. ❖ In 1970-71 there was an epidemic of southern corn leaf blight (caused by Helminthosporium maydis) on all US corn hybrids carrying the T-type cytoplasmic male sterility. 6 WHY THE MAJOR CATASTROPHIES Lack or loss of resilience of crops to: –Avoid pest –Overcome pest attack, or –Restrict pest infestation or infection –Compensate for pest damage –Tolerate pest attack 7  WHY LACK OR LOSS OF RESILIENCE? 1. Resilient local cultivars or landraces being replaced by higher yielding crop varieties due to: 2. DOMESTICATION 8  WHY ATTENTION ON HIGH YIELDING CROP VARIETIES? Ever increasing global food demand Reducing arable land – Hence breeding efforts shifted towards maximizing crop yield per unit land area 9 CONSEQUENCES OF BREEDING FOR MAXIMUM YIELD Selecting out genes for resistance RESULTING IN – Lack of genetic variability in cultivated crops 10 LOSS OF GENETIC DIVERSITY TOTAL POTENTIAL GENETIC RESOURCES ARE ABOUT 7000 SPECIES But only 30 SPECIES PROVIDE approximately 95 % OF MAN’S FOOD AND ENERGY Yet still only 6 SPECIES PROVIDE ABOUT 60 % OF MAN’S FOOD AND ENERGY 11  DOMESTICATION Definition Co-evolutionary process in which the selection of desirable traits or phenotypes results in genotypic restrictions or changes to make them useful and adapted to human intervention and landscape. 12  DOMESTICATION... Domesticated plants differ from wild ancestors – Due to changes resulting from natural or artificial selection of desirable qualities Natural evolutionary processes always being influenced or truncated by humans – to produce domesticated species suited to their needs 13  CONSEQUENCES OF DOMESTICATION 1. Loss of genetic diversity 2. Crop species experiencing GENETIC EROSION leading towards GENETIC UNIFORMITY Fig. 1 Loss of genetic diversity during crop domestication 14  CAUSES OF GENETIC EROSION 1. Introduction of new, highly uniform varieties Little genetic diversity 2.Spread of modern, commercial agriculture Resulting in loss of traditional farmers' varieties. 15  CAUSES OF GENETIC EROSION 3. Promotion of monoculture in many parts of Africa leading to: Loss of crops integrated into traditional farming systems Loss of resilience and sustainability of traditional farming systems 16 JUSTIFICATION FOR CONSERVATION 1. Increasing awareness about vanishing plant species 2. Increasing awareness about narrowing base of germplasm 3. Increasing demand for plant- based medicines 4. Increasing demand for botanicals due to increasing awareness about dangers of synthetic pesticides 17  WAY FORWARD CONSERVATION NECESSARY To prevent LOSS of: – GENES THAT CONFER RESILIENCE –Many valuable traditional crops and varieties –Many plants of medicinal value 18  GERMPLASM CONSERVATION 19 HISTORY OF PLANT CONSERVATION 20  HISTORY OF CONSERVATION ❖1910: Interest in origin of crop and use of wild relatives in breeding programmes raised ❖1924: Russian botanist, Nikolai Vavilov founded All-Union of Applied Botany and New Crops 21  HISTORY OF CONSERVATION... 1940: 200,000 accessions of various crops – wheat, potatoes, cotton collected and conserved by Vavilov 1960s: FAO initiated collection and conservation of crop genetic resources 22  HISTORY OF CONSERVATION... ❖1970: The term Genetic Resources coined and defined ❖1971: CGIAR (Consultative Group on International Agricultural Research) formed ❖1974: IBPGR (International Board for Plant Genetic Resources) and IPGRI (International Plant Genetic Resources Institute) founded 23  HISTORY OF CONSERVATION… ❖1984: International Convention on Genetic Resources signed. –Exploitation, evaluation and conservation for scientific and research purposes permitted – In situ conservation allowed and to be encouraged 24  HISTORY OF CONSERVATION... 1989: FAO proposes actions on animal genetic resources 1992/93: Convention on Biological Diversity held 1995: Inclusion of animal genetic resources in FAO International Convention 25  HISTORY OF CONSERVATION... ❖2001: International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) signed ❖2004: International Treaty on Plant Genetic Resources for Food and Agriculture entered into force. ❖2007: FAO tabled proposal on Microbial Genetic Resources 26  HISTORY OF CONSERVATION... ❖2013: FAO Global Plan of Action for Conservation, Sustainable Use and Development of Forest Genetic Resources adopted ❖Genetic resources for food and agriculture (GRFA) include plant, animal, aquatic, microbial, forest and other genetic resources of relevance to agriculture, farming and food systems 27  BASIC DEFINITIONS IN PLANT CONSERVATION 28  GENETIC RESOURCE ❖Any material of plant, animal, microbial or other origin containing functional units of heredity, that is of actual or potential value 29  BIOLOGICAL RESOURCE ❖All organisms or parts thereof, populations, or any other biotic component of ecosystems with actual or potential use or value for humanity 30  BIOLOGICAL DIVERSITY ❖Variability among organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part, including the diversity within and between species and ecosystems 31  LAND RACE A domesticated and adapted plant variety that has developed over many years through simple selection processes by farmers, and has a wide spectrum of quality traits. Land race may be low yielding but highly stable in its cultural environment and has local names and distinguishing features 32  LAND RACE A dynamic pop. of a cultivated plant that has historical origin, distinct identity and lacks formal crop improvement, and often genetically diverse, locally adapted and associated with traditional farming systems. Camacho Villa (2006). 33  LINE ❖A breeder’s material produced from a cross between two parents ❖Usually designated with parental or accession names of crosses they were produced from 34  VARIETY ❖Material with unique phenotypic characters controlled by specific genes acquired thru artificial hybridization (including genetic engineering) or mutation ❖OR ❖A breeder’s material (improved line) that has been named and officially released to farmers for cultivation 35  CULTIVAR ❖A land race, a line or a variety that has been grown by farmers for a long time and becomes adapted to its cultural environment and may only be known by its varietal or local name ❖Domesticated and cultivated material 36  ACCESSION ❖Sample of a population held in a gene bank or breeding program for conservation and use ❖Labelled with an Accession No. which may include: – site of collection (GPS coordinates) – name of Farmer – date of collection 37  GERMPLASM ❖Material that constitutes or represents physical basis of inheritance OR ❖Material that carries or contains the sum of hereditary material of a species 38  GERMPLASM... ❖Capable of regenerating a new whole plant of same species ❖Seed, leaf, stem cutting or any plant part or whole plant that can be propagated 39  GERMPLASM CONSERVATION 40  GERMPLASM CONSERVATION Definition: ❖Preservation, management, and use of genetic resources so that they may yield the greatest sustainable benefit to the present generation, while maintaining their potential to meet the needs and aspirations of future generations [(International Union for Conservation of Nature and Natural Resources) (IUCN, 1980)] 41  GERMPLASM CONSERVATION Alternative Definition: ❖The formulation of policies and programs which will allow the long- term preservation of genetic resources either in situ or ex situ in such a manner that the potential for continuing evolution or improvement would be sustained (Chang, 1985). 42 IMPORTANCE OF CONSERVATION ❖To ameliorate genetic restriction and erosion that accompany domestication and cultivar development ❖AND ❖To prevent extinction of species and populations 43 THE PROCESS OF EXTINCTION 44  WHAT IS EXTINCTION? Failure of a species or a pop. to maintain itself through reproduction (Frankel and Soule, 1981). Occurs when either: – last individual dies, or – remaining individuals incapable of producing viable or fertile offspring It is a process rather than an event. 45  FACTORS CONTRIBUTING TO EXTINCTION Ecological factors = either biotic or abiotic Notable biotic factors include: –Competition –Predation –Parasitism, and –Disease 46  FACTORS CONTRIBUTING TO EXTINCTION Major abiotic factors include: –Habitat alteration –Isolation??? Habitat alteration occurs thru: –slow geological change –climate changes –catastrophes –human activities 47  HABITAT ALTERATION AND DESTRUCTION Each species has unique habitat requirements for growth and dev. Hence every species as safe as its habitat. Altering critical habitat variables results in or initiates process of species extinction 48  CAUSES OF HABITAT ALTERATION 1. Slow geological change Include shifts in earth’s crustal plates (Sea floor plates) Causes changes in major current patterns and either increase or decrease area of certain habitats 49  HABITAT ALTERATION 2. Climate change Climate change may shift the range of species latitudinally and altitudinally Of concern when change becomes inimical to survival50  HABITAT ALTERATION... 3. Catastrophic events Earth quakes Volcanic eruptions Tsunamis Tornados Floods Avalanches and landslides 51  HABITAT ALTERATION... 4. Human disturbance Artificial dams Bush Fires Small-scale (Surface) mining Galamsey Deforestation (Logging) Shifting Cultivation All these cause loss of species 52  METHODS OF GERMPLASM CONSERVATION TWO MAIN METHODS IN SITU EX SITU 53  IN SITU CONSERVATION Conservation of germplasm in their natural environment by establishing biosphere reserves (or national parks/gene sanctuaries) Useful for preservation of land plants in a near natural habitat along with several wild relatives 54  IN SITU CONSERVATION... High priority germplasm preservation programme. Created and Protected Conservation Sites: –Forest and Game Reserves –Sacred Groves –Royal Mausoleums –Evil Forests 55  MAJOR LIMITATIONS TO IN-SITU CONSERVATION Risk of losing germplasm due to environmental hazards Cost of maintenance very high. 56  EX SITU METHODS Three main methods of ex situ conservation: 1. Field gene banks 2. Seed banks 3. In vitro conservation  EX SITU METHODS With the advent of biotechnology, a genebank may also include: – a collection of cloned DNA – fragments from a single genome – whole of the genome. EX SITU : FIELD GENEBANKS Field genebanks used for: – conservation of clonal crops – Recalcitrant seeds (do not survive drying and freezing) – crops that rarely produce seed Crops in this category include temperate and tropical fruit trees, crops such as cocoa, rubber, oil palm, coffee, banana and coconut as well as most root and tuber crops. EX SITU : FIELD GENEBANKS The rule of thumb is to use the same propagation techniques as the farmer. An example of the scale of management of field genebanks is that oil palm genetic resources in Malaysia are planted at a density of 140 palms per hectare, and the collection from Nigeria alone occupies 200 ha.  Oil palm field genebank Cocoa field genebank Cassava field genebank  EX SITU : FIELD GENEBANKS Management may be same as used during routine farming, and cultivation methods can be adapted to local circumstances. Conserved material can be readily characterized and evaluated and then accessed for research and use. Some natural selection may take place within and between accessions, but management is designed to prevent it.  EX SITU : FIELD GENEBANKS Major constraints faced by field genebanks include: – High maintenance costs – Natural hazards of farming, including pests and diseases and drought – Temporary but severe natural disasters such as floods, cyclones etc.  EX SITU : SEED BANKS Storing genetic diversity as seed is the best researched, most widely used and most convenient method of ex situ conservation. Much is known about the optimum treatment of the seed of most of the major food crops.  EX SITU : SEED BANKS Requirements include adequate: – thorough drying, i.e. seed moisture contents as low as 3 % for oily seeds and ca 5 % for starchy seeds – appropriate storage temperature (-18°C) is recommended for long-term storage), and – careful production and regeneration of quality seed to ensure greatest longevity (Rao and Jackson, 1996).  EX SITU : SEED BANKS Seeds of many plant species, especially tropical shrubs and trees, lose viability if dried (‘recalcitrant’ seeds). Seeds of some species can be dried to some extent but cannot survive low-temp storage and have intermediate storage characteristics. This category includes coffee, citrus species, rubber and others.  EX SITU : SEED BANKS Seeds of wild relatives do not always behave as those of domesticates, hence optimal storage conditions have to be individually determined. EX SITU : SEED BANKS  EX SITU : SEED BANKS Most national genebanks now rely on cold storage facilities for seed maintenance. However, these depend on electricity supply, which not reliable in some countries.  EX SITU : SEED BANKS To overcome this problem, alternative approaches to low temp storage have been developed, including the so-called ‘ultra-dry seed’ technology. Drying seeds to a moisture content as low as 1 % (oily seeds) or approx. 3 % (starchy seeds) and hermetic packaging allows storage for long periods at room temp. Care must be taken to prevent over-drying of the seeds (Walters and Engels, 1998).  EX SITU : SEED BANKS Materials conserved in seed banks can be placed in 3 main categories: a. Base collection b. Active collection c. Working collection  EX SITU : SEED BANKS 1. Base collection A collection of genetic resource samples which is kept for long-term, secure conservation and is not to be used as a routine distribution source. ▪ Seed materials are dried to 3 % to 7 % moisture content, packed in sealed containers and stored at -10 to -20oC.  EX SITU : SEED BANKS Base collection … ▪ Vegetative materials are either maintained on the field or cryopreserved. ▪ Materials are only removed from a base collection for infrequent regeneration when seed viability has started to decline below an acceptable regeneration standard, or when stocks of an accession are no longer available from an active collection.  EX SITU : SEED BANKS Active collection: A collection of accessions maintained for medium-term viability (about 30 years), stored between 0oC and 15oC, and 3-7 % moisture content. Normally larger than base collection in both number of accessions and amount of seed.  EX SITU : SEED BANKS Active collection: Usually contains material in the process of being evaluated and characterized, as well as material represented in base collections. Ideally, all accessions in an active collection should be maintained in sufficient quantity to be available on request.  EX SITU : SEED BANKS Working collection: A collection of accessions usually used by a breeder for crop improvement, or by researchers. The accessions are stored under ambient temp in aircon rooms They are comprehensively tested and used in character selection, crossing and hybridization SVALBARD GLOBAL SEED VAULT Also known as “Doomsday” seed vault It is a secure seed bank located on the Norwegian island of Spitsbergen ca 1,300 km from North Pole. The facility preserves a wide variety of plant seeds in an underground cavern. SVALBARD GLOBAL SEED VAULT The seeds are duplicate samples, or "spare" copies, of seeds held in genebanks worldwide. The seed vault provides insurance against loss of seeds in genebanks, Also as a refuge for seeds in case of large scale regional or global crises.  SVALBARD GLOBAL SEED VAULT The seed bank is constructed 120 m (390 ft) inside a sandstone mountain at Svalbard on Spitsbergen Island. Has robust security systems. Seeds are packaged in special four- ply packets and heat sealed to exclude moisture.  SVALBARD GLOBAL SEED VAULT Facility managed by the Nordic Genetic Resource Center (NordGen). Funded entirely by Gov. of Norway as a service to the world. Operational costs paid by Norway and Global Crop Diversity Trust. Storage of seeds in the seed vault is free of charge. SVALBARD GLOBAL SEED VAULT … Spitsbergen was considered ideal due to its lack of tectonic activity and its permafrost which will aid preservation. Location of 130 m (430 ft) above sea level ensures site remains dry even if the icecaps melt. SVALBARD GLOBAL SEED VAULT … Locally mined coal provides power for refrigeration units that further cool the seeds to the internationally recommended standard (−18 °C). Even if the equipment fails, at least several weeks will elapse before the temperature rises to the −3 °C of the surrounding sandstone bedrock. SVALBARD GLOBAL SEED VAULT … The Vault opened officially on Feb. 26, 2008 but first seeds arrived in Jan. 2008. Approx. 1.5 million distinct seed samples of agricultural crops are thought to exist. Facility has capacity for 4.5 million samples.  SVALBARD GLOBAL SEED VAULT … Deposit of samples in Svalbard does not constitute a legal transfer of genetic resources. Ownership remains with depositor, who has sole right of access to those materials in seed vault. In genebank terminology this is called a "black box" arrangement. Each depositor signs a Deposit Agreement with NordGen, acting on behalf of Norway.  SVALBARD GLOBAL SEED VAULT … Researchers, plant breeders and other groups wishing to access seed samples cannot do so through the seed vault; instead they must request samples from the depositing genebanks Entrance to seed vault Rendered visualization of seed vault Design of Seed vault Seed samples from Africa Rice Centre in vault EX SITU METHODS: POLLEN STORAGE Pollen might represent an interesting alternative for the long-term conservation of problematic species (IPGRI, 1996). Technique for pollen storage is close to that for seed storage, since pollen can be dried to less than 5 % moisture content on a dry weight basis and stored below 0°C.  DISADVANTAGES OF POLLEN STORAGE Pollen has relatively short life compared with seeds (although varies significantly with species) Testing for pollen viability time- consuming and uneconomical. Small amount of pollen produced by many species  DISADVANTAGES OF POLLEN STORAGE Organelle genomes not carried via pollen Loss of sex-linked genes in dioecious species General inability to regenerate into plants.  ADVANTAGES OF POLLEN STORAGE Pests and diseases are rarely transferred by pollen (except some virus diseases). Hence safer movement and exchange of germplasm as pollen. EX SITU METHODS: DNA STORAGE DNA storage: This more recently developed technique is increasing in importance. DNA from the nuclei, mitochondria and chloroplasts is now routinely extracted and stored. For the purpose of analysis, DNA is often immobilized on nitrocellulose sheets where it can be probed. EX SITU METHODS: DNA STORAGE DNA cloning technology has further facilitated efficient use of DNA sequences. The advantage of storing DNA is that it is efficient and simple and overcomes many physical limitations that characterize other forms of storage. The disadvantage lies in problems with subsequent gene isolation, cloning and transfer, but, most importantly, it does not allow the regeneration of live organisms.  EX SITU : IN VITRO STORAGE In vitro conservation involves maintenance of explants in a sterile, pathogen-free environment. Widely used for conservation and multiplication of species that: – produce recalcitrant seeds, – or do not produce seeds – as well as Genetically Engineered Materials  EX SITU METHODS: IN VITRO STORAGE For short- and medium-term storage Aims at increasing intervals between subcultures by reducing growth. Achieved by modifying environmental conditions, including culture medium, to realize slow-growth conservation.  EX SITU METHODS: IN VITRO STORAGE The most widely applied technique is temp reduction – 0–5°C for cold tolerant species – 9–18°C for tropical species Can be combined with decrease in light intensity or dark storage and adjustment of growth medium – especially inclusion of growth retardants like mannitol or sorbitol. Plants growing under in vitro conditions  EX SITU: CONSERVATION Conservation of germplasm outside their natural habitats Most relied upon method of germplasm conservation Mostly materials in seed form Also plant cells, tissues or organs 100  EX SITU: CONSERVATION Short term or long term conservation If long term: Usually termed PRESERVATION Preservation requires adequate and suitable conditions for maintenance and periodic regeneration of materials 101  RECALCITRANT SEEDS Also known as unorthodox seeds Do not survive drying or freezing during ex-situ conservation Can’t resist freezing below 10 °C 102  RECALCITRANT SEEDS Cannot be stored for long periods bcos they lose viability soon after harvest Examples: mango, cocoa, avocado 103 WAYS OF IN VITRO CONSERVATION 3 MAIN WAYS Low-pressure and low- oxygen storage Cold storage Deep freeze preservation (Cryopreservation) 104 1. LOW-PRESSURE STORAGE (LPS) ❖Reducing atmospheric pressure surrounding plant material ❖Decreases partial pressure exerted by gases around germplasm. ❖Lowered partial pressure reduces in vitro growth of plants 105 LOW-PRESSURE STORAGE contd. ❖Useful for short-term and long- term storage of plant materials. ❖Particularly useful in short-term storage ❖Increases shelf life of many plant materials e.g. fruits, vegetables, plant cuttings and cut flowers 106  LOW-PRESSURE STORAGE Germplasm grown in cultures can store for long under low pressure LPS also reduces activity of pathogenic organisms and inhibits spore germination in plant culture systems. 107  LOW-OXYGEN STORAGE (LOS) Suitable for storage of green plant tissues O2 concentration reduced, but atmospheric pressure (260 mm Hg) maintained by addition of inert gases (N2) 108  LOW-OXYGEN STORAGE (LOS) Partial pressure of O2 < 50 mm Hg reduces plant tissue growth –Bcos reduced O2 results in reduced CO2 production –Consequently photosynthetic activity is reduced –Thereby inhibiting plant tissue growth 109  2. COLD STORAGE Germplasm conservation at low but non-freezing temps (10 – 1°C) Plant material growth slowed down drastically Hence referred to as slow growth germplasm conservation 110  MAJOR ADVANTAGE OF COLD STORAGE Plant material (cells/tissues) not subjected to cryogenic injuries. 111 3. IN VITRO CRYOPRESERVATION Storage of germplasm at extremely low temps Intended to halt plant cell and tissue activity to a zero metabolic or non-dividing state 112  IN VITRO CRYOPRESERVATION... 1. On solid CO2 (at -79 °C) 2. Low temp freezing (at -80 °C) 3. In vapour phase N2 (at -150 °C) 4. In liquid nitrogen (at -196 °C) 113  IN VITRO CRYOPRESERVATION... Preservation in liquid nitrogen (at -196°C) most commonly used Cells stay completely inactive therefore germplasm can be preserved for long periods. 114  ABSOLUTE ZERO Definition: point where no more heat can be removed from a system. Corresponds to: 0°K, or -273.15°C, or -459.67°F 115  ADVANTAGES OF IN VITRO CONSERVATION Large quantities stored in small space. Can be preserved in a-septic environ (free from pathogens) Protected from natural hazards 116  ADVANTAGES OF IN VITRO CONSERVATION Large number of plants can be obtained whenever needed. Less quarantine restrictions during international transport (as germplasm is maintained under a-septic conditions). 117  Cryopreservation process C A B D Progressive chemical Excision of treatment to remove Freezing in Preculture meristems LN freezable water in the cell F Post-culture for survival E and plant regeneration Thawing/Rewarming Plunging samples into LN for cryopreservation Liquid nitrogen tanks for cryopreservation Arrangement of materials in liquid nitrogen tank Materials in liquid nitrogen  EX SITU IN VIVO CONSERVATION Conservation of germplasm in its natural form but away from its natural environment. Usually in seed/gene/germplasm reservatories or banks 123  EX SITU IN VIVO CONSERVATION... Tree crops planted in habitats where conditions are close to natural e.g. Arboretums Seed gardens 124  COMPONENTS OF GERMPLASM CONSERVATION ▪ Assembly of germplasm Exploration collection characterisation ▪ Multiplication or rejuvenation ▪ Documentation ▪ Preservation ▪ Distribution/exchange 125  TYPES OF GERMPLASM Three main types of germplasm targeted for collection 1. Products of scientific breeding programs 2. Varieties of traditional agriculture 3. Wild and weedy relatives of crops  TYPES OF GERMPLASM 1. Products of scientific breeding programs a. Modern cultivars: High yielding modern varieties including F1 hybrids, composites and synthetics. Most have been selected for high uniformity and performance in intensive agricultural systems.  TYPES OF GERMPLASM 1. Products of scientific breeding programs b. Obsolete cultivars: Ecostrains of obsolete cultivars that may be found in some areas. c. Other products of plant breeding or genetic studies, i.e. advanced breeding lines, stocks, mutants and gene markers.  TYPES OF GERMPLASM … 2. Varieties of traditional agriculture a. Landraces – showing great diversity. – Inherent diversity is a unique feature of landraces. – Many are varietal mixtures (Chang, 1985). b. Primitive cultivars: – Crop forms grown under traditional agricultural systems, which have not undergone much improvement and which, in many cases, have developed from landraces selected by farmers  TYPES OF GERMPLASM … 2. Varieties of traditional agriculture c. Special-purpose types: – Special types from the areas of diversity which are adapted to specific ecological niches or provide special dietary or religious needs.  TYPES OF GERMPLASM … 3.Wild and weedy relatives Wild and weedy forms (species) of same genus May include related genera. All mostly found in primary centre of diversity (true origin)  TYPES OF GERMPLASM … 3.Wild and weedy relatives Region of true origin identified by presence of wild relatives, primitive characteristics and high frequencies of dominant alleles (IBPGR, 1991). All of these categories should be collected and conserved as germplasm.  TYPES OF GERMPLASM … ❖Landraces characterized by high levels of genetic variability ❖Variability is found within and between sites and populations ❖Their genetic diversity expressed over space and time provides improved protection against climatic extremes and epidemics.  TYPES OF GERMPLASM … ❖Wild species and weedy races are good sources of: – resistance to diseases and insect pests, – tolerance to stress environments, – cytoplasmic sterility, – adaptability to different growing conditions, – high nutritional value, – improved quality, etc.  GERMPLASM CONSERVATION METHODS ❖Germplasm conservation can be done: – on-site (in situ) – off-site (ex situ).  GERMPLASM CONSERVATION METHODS … ❖In situ conservation includes the following strategies: a. Protected areas b. On-farms and c. Home gardens  IN SITU : PROTECTED AREAS a. Protected areas Involves natural reserves created to conserve species in natural habitats. This type also called dynamic evolutionary conservation. Plants and animals conserved in entire biomes and free to evolve through natural selection. Protected areas are widely regarded as instrumental for in situ conservation of wild relatives.  IN SITU: PROTECTED AREAS Disadvantages of protected areas: – Conserved material is not readily available for agricultural use. – Limited opportunity for management – Little characterization and evaluation of the germplasm, restricting its use as a genetic resource. – The number of varieties present in protected area sets the upper limit to the genetic variability especially if the plant species is self-pollinating. IN SITU : ON-FARM CONSERVATION Farmers worldwide have been practicing on-farm conservation for as long as agriculture has existed, as a necessary part of crop prod’cn. In addition to crops, wild and weedy species occur that are associated with farming. The traditional farming systems, allow for continued survival and evolution of landraces and wild and weedy species  IN SITU : HOME GARDENS Home gardens are a reservoir of diversity for fruits, vegetables and small domestic livestock. Proximity to homes allows detailed selection of variants, as well as generation of vast morphological variation that exists in many domesticated species. A community of gardens may need to be included, as the intraspecific diversity within an individual garden is often limited, whereas the variation among gardens is often substantial  LONG-TERM IN VITRO STORAGE ❖ The principal objective of any in vitro storage scheme is to limit the number of sub-cultures and also retain the genetic diversity of a species in a sterile condition without compromising its genetic integrity. ❖ This therefore necessitates long-term in vitro conservation that significantly reduces frequent sun-culturing, which could be highly labour intensive. ❖ Long-term in vitro storage is practicable through cryopreservation, which is the storage of biological living materials at ultra-low temperature, usually by using liquid nitrogen (-196°C). ❖ At this temperature all cellular divisions and metabolic processes are virtually halted. ❖ Consequently, plant material can be stored without alteration or modification theoretically indefinitely.  GERMPLASM CONSERVATION AS SEEDS Seeds most common and convenient form of conservation – Many plants propagated through seeds – Seeds retain viability even under ambient conditions for long – Seeds occupy relatively small space. – Seeds can be easily transported to various places without damage or loss. 142  LIMITATIONS TO CONSERVATION OF SEEDS Seeds lose viability with time. Susceptible to insect or pathogen attack, often leading to their destruction. 143  LIMITATIONS TO CONSERVATION OF SEEDS… ❖Exclusively for seed propagating plants –not suitable for vegetatively propagated plants like cassava and yams ❖Difficult to maintain clones through seed conservation. 144  LIMITATIONS TO CONSERVATION OF SEEDS… Certain seeds are heterogeneous and therefore, not suitable for true genotype maintenance. 145 QUESTIONS AND FEEDBACK ????? 146