Agriculture 2009 SOLVED PAPER
Q.1. Select the best option/answer and fill in the appropriate box on the Answer Sheet. (20)
(i) White revolution refers to the revolution in:
(a) Rice production (b) Milk production (c) Cotton production (d) None of these (e) All of these
(ii) Organic farming is important because of:
(a) Toxic free plants (b) GMO free (c) Eco friendly (d) Healthy for humans (e) All of these
(iii) Which of the following is not a good source of dietary fiber?
(a) Pasta (b) Brown rice (c) Egg (d) Bread (e) All of these
(iv) The branch of agriculture that deals with rearing of silkworm is called:
(a) Olericulture (b) Sericulture (c) Apiculture (d) Viticulture (e) None of these
(v) Oryza Sativa is the botanical name of:
(a) Rice (b) Wheat (c) Barley (d) Sorghum (e) None of these
(vi) Xanthomonas citri is the disease causal organism of citrus.
(a) Bark splitting (b) Foot rot (c) Canker (d) Citrus decline (e) None of these
(vii) Cholistani, Kali, Damani, Kachi and Bibrik are some of the breeds of:
(a) Goats (b) Camel (c) Buffalo (d) Sheep (e) None of these
(viii) Inflation of mammary glands of milch animals is called:
(a) Johne’s disease (b) Tuberculosis (c) Mastitis (d) Leptospirosis (e) None of these
(ix) Patoto is an example of:
(a) Root crop (b) Legumes (c) Fiber crop (d) Sugar crop (e) None of these
(x) Tobacco is an example of:
(a) Kharif crop (b) Rabi crop (c) Zaid rabi crop (d) Zaid Kharif crop (e) None of these
(xi) Peanuts are:
(a) Roots (b) Grains (c) Legumes (d) Nuts (e) None of these
(xii) Which of the following insects is friendly for an organic farmer?
(a) Stem borer
(b) Root borer
(c) Boll worm
(d) Mango mealy bug
(e) None of these
(xiii) Money maker, Roma, Red top are some of the varieties of:
(e) None of these
(xiv) Swollen underground stem; an organ of food storage and propagation is called:
(e) None of these
(xv) Plants having soft, non woody growth are called:
(e) None of these
(xvi) Removal of exchangeable sodium from the soil is called:
(e) None of these
(xvii) Enzymes are biocatalysts and their nature is:
(e) None of these
(xviii) Khapra beetle is the pest of:
(d) All of these
(e) None of these
(xix) L-113, PR
-100 and BL-4 are the varieties of:
(e) None of these (Sugar cane)
(xx) Which one of the following is non essential amino acid?
(e) None of the above
Q.2. Define biotechnology and discuss in detail the role of biotechnology in crop improvement.
United Nations Convention on Biological Diversity defines biotechnology as:
"Any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use."
Using the techniques of modern biotechnology, one or two genes (Smartstax from Monsanto in collaboration with Dow AgroSciences will use 8, starting in 2010) may be transferred to a highly developed crop variety to impart a new character that would increase its yield. However, while increases in crop yield are the most obvious applications of modern biotechnology in agriculture, it is also the most difficult one. Current genetic engineering techniques work best for effects that are controlled by a single gene. Many of the genetic characteristics associated with yield (e.g., enhanced growth) are controlled by a large number of genes, each of which has a minimal effect on the overall yield. There is, therefore, much scientific work to be done in this area.
Reduced vulnerability of crops to environmental stresses
Crops containing genes that will enable them to withstand biotic and abiotic stresses may be developed. For example, drought and excessively salty soil are two important limiting factors in crop productivity. Biotechnologists are studying plants that can cope with these extreme conditions in the hope of finding the genes that enable them to do so and eventually transferring these genes to the more desirable crops. One of the latest developments is the identification of a plant gene, At-DBF2, from Arabidopsis thaliana, a tiny weed that is often used for plant research because it is very easy to grow and its genetic code is well mapped out. When this gene was inserted into tomato andtobacco cells (see RNA interference), the cells were able to withstand environmental stresses like salt, drought, cold and heat, far more than ordinary cells. If these preliminary results prove successful in larger trials, then At-DBF2 genes can help in engineering crops that can better withstand harsh environments. Researchers have also created transgenic rice plants that are resistant to rice yellow mottle virus (RYMV). In Africa, this virus destroys majority of the rice crops and makes the surviving plants more susceptible to fungal infections.
Increased nutritional qualities
Proteins in foods may be modified to increase their nutritional qualities. Proteins in legumes and cereals may be transformed to provide the amino acids needed by human beings for a balanced diet. A good example is the work of Professors Ingo Potrykus and Peter Beyer in creating Golden rice (discussed below).
Improved taste, texture or appearance of food
Modern biotechnology can be used to slow down the process of spoilage so that fruit can ripen longer on the plant and then be transported to the consumer with a still reasonable shelf life. This alters the taste, texture and appearance of the fruit. More importantly, it could expand the market for farmers in developing countries due to the reduction in spoilage. However, there is sometimes a lack of understanding by researchers in developed countries about the actual needs of prospective beneficiaries in developing countries. For example, engineering soybeans to resist spoilage makes them less suitable for producing tempeh which is a significant source of protein that depends on fermentation. The use of modified soybeans results in a lumpy texture that is less palatable and less convenient when cooking.
The first genetically modified food product was a tomato which was transformed to delay its ripening. Researchers in Indonesia, Malaysia,Thailand, Philippines and Vietnam are currently working on delayed-ripening papaya in collaboration with the University of Nottingham andZeneca.
Biotechnology in cheese production: enzymes produced by micro-organisms provide an alternative to animal rennet – a cheese coagulant – and an alternative supply for cheese makers. This also eliminates possible public concerns with animal-derived material, although there are currently no plans to develop synthetic milk, thus making this argument less compelling. Enzymes offer an animal-friendly alternative to animal rennet. While providing comparable quality, they are theoretically also less expensive.
About 85 million tons of wheat flour is used every year to bake bread. By adding an enzyme called maltogenic amylase to the flour, bread stays fresher longer. Assuming that 10–15% of bread is thrown away as stale, if it could be made to stay fresh another 5–7 days then perhaps 2 million tons of flour per year would be saved. Other enzymes can cause bread to expand to make a lighter loaf, or alter the loaf in a range of ways.
Reduced dependence on fertilizers, pesticides and other agrochemicals
Most of the current commercial applications of modern biotechnology in agriculture are on reducing the dependence of farmers onagrochemicals. For example, Bacillus thuringiensis (Bt) is a soil bacterium that produces a protein with insecticidal qualities. Traditionally, a fermentation process has been used to produce an insecticidal spray from these bacteria. In this form, the Bt toxin occurs as an inactiveprotoxin, which requires digestion by an insect to be effective. There are several Bt toxins and each one is specific to certain target insects. Crop plants have now been engineered to contain and express the genes for Bt toxin, which they produce in its active form. When a susceptible insect ingests the transgenic crop cultivar expressing the Bt protein, it stops feeding and soon thereafter dies as a result of the Bt toxin binding to its gut wall. Bt corn is now commercially available in a number of countries to control corn borer (a lepidopteran insect), which is otherwise controlled by spraying (a more difficult process).
Crops have also been genetically engineered to acquire tolerance to broad-spectrum herbicide. The lack of herbicides with broad-spectrum activity and no crop injury was a consistent limitation in crop weed management. Multiple applications of numerous herbicides were routinely used to control a wide range of weed species detrimental to agronomic crops. Weed management tended to rely on preemergence—that is, herbicide applications were sprayed in response to expected weed infestations rather than in response to actual weeds present. Mechanical cultivation and hand weeding were often necessary to control weeds not controlled by herbicide applications. The introduction of herbicide-tolerant crops has the potential of reducing the number of herbicide active ingredients used for weed management, reducing the number of herbicide applications made during a season, and increasing yield due to improved weed management and less crop injury. Transgenic crops that express tolerance to glyphosate, glufosinate and bromoxynil have been developed. These herbicides can now be sprayed on transgenic crops without inflicting damage on the crops while killing nearby weeds.
From 1996 to 2001, herbicide tolerance was the most dominant trait introduced to commercially available transgenic crops, followed by insect resistance. In 2001, herbicide tolerance deployed in soybean, corn and cotton accounted for 77% of the 626,000 square kilometres planted to transgenic crops; Bt crops accounted for 15%; and "stacked genes" for herbicide tolerance and insect resistance used in both cotton and corn accounted for 8%.
Production of novel substances in crop plants
Biotechnology is being applied for novel uses other than food. For example, oilseed can be modified to produce fatty acids for detergents, substitute fuels and petrochemicals. Potatoes, tomatoes, rice tobacco, lettuce, safflowers, and other plants have been genetically engineered to produce insulin and certain vaccines. If future clinical trials prove successful, the advantages of edible vaccines would be enormous, especially for developing countries. The transgenic plants may be grown locally and cheaply. Homegrown vaccines would also avoid logistical and economic problems posed by having to transport traditional preparations over long distances and keeping them cold while in transit. And since they are edible, they will not need syringes, which are not only an additional expense in the traditional vaccine preparations but also a source of infections if contaminated. In the case of insulin grown in transgenic plants, it is well-established that the gastrointestinal system breaks the protein down therefore this could not currently be administered as an edible protein. However, it might be produced at significantly lower cost than insulin produced in costly bioreactors. For example, Calgary, Canada-based SemBioSys Genetics, Inc. reports that its safflower-produced insulin will reduce unit costs by over 25% or more and approximates a reduction in the capital costs associated with building a commercial-scale insulin manufacturing facility of over $100 million, compared to traditional biomanufacturing facilities
Role of biotechnology for crop improvement in Pakistan
MANKIND HAS been involved in improving the quality and productivity of crops ever since it began using plants as food, fiber, and medicine. At first, early farmers selected the seeds of the “best” plants for replanting. However, when the science of genetics was discovered, the ability to enhance plants was increased significantly. The basis of modern agriculture was born as plants were cross-bred to produce new varieties with desirable characteristics such as higher yields or resistance to diseases. The next advancement in plant improvement came with the development of hybridization of plant species starting in the 1920s. These conventional processes for plant improvement were relatively slow and imprecise. Cross-breeding plants take years of trial and selection to achieve desired characteristics and to eliminate undesired ones.
In the past ten years, science has developed a new way to speed up the process of plant improvement and to make it more precise. While the conventional methods of improving plants through cross-breeding and hybridization attracted little public interest or concern, plants produced using a new technology often called plant biotechnology.
Plant Biotechnology is the application of scientific techniques to modify plants.
Agricultural Biotechnology applies genetic engineering methods to agricultural products. These procedures directly change the DNA of the plant, usually by inserting genetic material from another organism.
Technology developed in the 1970s allowed plant breeders to select genes or traits and incorporate them directly into a plant. Plants developed using this technology is often called “Genetically Modified Organisms” (GMOs), but may be more accurately referred to as transgenic plants.
Biotechnology differs from conventional breeding in two ways. One difference is the selectivity of the gene to be transferred. In the cross-breeding process many other undesirable characteristics from the source plants are also transferred. With biotechnology, only the gene that carries the desired trait is transferred. The second difference is the ability to transfer genetic material from a wider variety of sources to the target plant.
Traditional plant breeding is limited in regards to the species that may be crossed but in plant biotechnology, there is unlimited gene pool.
Use of modern biotechnology started in Pakistan since 1985. Currently, there are 29 biotech centers/institutes in the country. However, few centers have appropriate physical facilities and trained manpower to develop genetically modified (GM) crops. Most of the activities have been on rice and cotton, which are among the top 5 crops of Pakistan. Biotic (virus/bacterial/insect) and abiotic (salt) resistant and quality (male sterility) genes have already been incorporated in some crop plants.
Asia is the home of rice crop varieties. Rice is the staple food of the majority of Asian population; the best quality rice is being cultivated across Asia. Bacterial blight (BB) is a major disease of rice and is widely distributed in most rice growing countries. The use of resistant cultivars has been the most effective and economical way of controlling this disease. In Pakistan this disease can be reduced in basmati and other rice varieties with the help of biotechnology.
Average yield of conventional rice per acre is around 30-45 monds. The Bt Rice can increase yields by 20 to 30 per cent coupled with environmental benefit through substantially reduced insecticides use. This would mean enormous benefits to the rice growers and the economy of Pakistan. However, thanks to the absence of biosafety guidelines the rice farmers will remain deprived of using a useful technology.
Cotton remains the second most important crop of our country after wheat. Pakistan is one of the largest exporters of cotton yarn in the world; almost 65% of Pakistan’s annual export income comes from the textile sector. Therefore, it is absolutely essential for the government and research institutes to intervene in order to minimize the possibilities of pests attack on cotton crops through the adoption of different tools of biotechnology, which results in higher yields, reduction in pesticide use and higher income for the farmers.
Q.3. Discuss the role of environmental factors in the development of infectious diseases in plants and suggest measures to control these diseases
Plant disease is the abnormal growth and development of a plant:
Growth and development of the plant does not live up to the normal expectations. Some standard of “normal” must be assumed.
A diseased plant is incapable of carrying out its normal physiological functions to the best of its genetic potential.
ENVIRONMENTAL FACTORS AFFECTING DISEASE DEVELOPMENT
Important environmental factors that may affect development of plant diseases and determine whether they become epiphytotic include temperature, relative humidity, soil moisture, soil pH, soil type, and soil fertility.
Write details of these factors through your own knowledge.
A. Infectious Diseases (caused by biotic organisms):
c. Viruses and viroids
e. Parasitic Higher Plants
Principles of Plant Disease Control
1. Avoidance Avoiding disease by planting at a time when, or in areas where the pathogen is ineffective, rare or absent.
2. Exclusion Reducing, inactivating, eliminating or destroying the pathogen at the source.
3. Protection Preventing infection by use of a toxicant or other barrier between the host and the pathogen.
4. Disease Resistance Use of plant genetic resistance or tolerance.
5. Therapy Reducing the effect of the pathogen in an already infected plant.
6. Trap Crop Establish plants attractive to insect vectors on the borders or the main crop, then destroy the trap crop and the vector.
Major Plant Disease Control Methods
1. Cultural Control examples:
A. Sanitation pruning, removal of debris, removal of diseased plants, sterilizing tools, washing hands, etc.
B. Use of disease free planting material.
C. Choice of planting location.
D. Time of planting.
E. Choice of irrigation method and schedule.
F. Choice of fertilizer: type, timing, application method, schedule.
G. Crop rotation.
H. Use of green manures or cover crops.
2. Biological Control the use of living organisms that are antagonistic to pathogens.
A. Stimulate beneficial organisms in the environment with soil amendments or other cultural practices.
B. Add beneficial organisms to the soil or plant environment.
3. Resistance or Tolerance host plant genetic control.
A. Generally the most effective means of control when available.
B. Must be continually monitored as pathogens will develop virulence to tolerant plant material.
4. Chemical Control Act to eliminate, reduce or remove the pathogen at the source (eradication); to prevent disease (protection), or to cure disease (therapy).
A. Examples: fungicides, bactericides, nematicides, soil fumigants
B. Chemical used must be less toxic to the plant than to the organism(s) they are designed to control.
C. Most fungicides are actually fungistats, which means that the chemical limits the activity of the fungus, but doesn’t kill it. The disease will return when the chemical is no longer active and the conducive environment for fungal activity reoccurs, Thus, management of diseases with fungicides often requires repeat applications.
D. Effective chemical use depends on:
a. Choosing the right chemical.
b. Applying the chemical in the right way, at the right time, and in the right concentration.
c. Reading and following the label directions very carefully.
Q.4. Describe different methods of pest control in crops with main emphasis on biological control of insect-pests?
Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy.
Types of pest control
Biological pest control
Biological pest control is the control of one through the control and management of naturalpredators and parasites. For example: mosquitoes are often controlled by putting Bt Bacillus thuringiensis ssp. israelensis, a bacterium that infects and kills mosquito larvae, in local water sources. The treatment has no known negative consequences on the remaining ecology and is safe for humans to drink. The point of biological pest control, or any natural pest control, is to eliminate a pest with minimal harm to the ecological balance of the environment in its present form.
Elimination of breeding grounds
Proper waste management and drainage of still water, eliminates the breeding ground of many pests.
Garbage provides food and shelter for many unwanted organisms, as well as an area where still water might collect and be used as a breeding ground by mosquitoes. Communities that have proper garbage collection and disposal, have far less of a problem with rats, cockroaches, mosquitoes, flies and other pests than those that don't.
Open air sewers are ample breeding ground for various pests as well. By building and maintaining a proper sewer system, this problem is eliminated.
Poisoned bait is a common method for controlling rat populations, however is not as effective when there are other food sources around, such as garbage. Poisoned meats have been used for centuries for killing off wolves, birds that were seen to threaten crops, and against other creatures. this tool is also used to manage several caterpillars eg.Spodoptera litura,fruit flies,snails and slugs,crabs etc..
Traditionally, after a sugar cane harvest, the fields are all burned, to kill off any insects or eggs that might be in the fields.
Historically, in some European countries, when stray dogs and cats became too numerous, local populations gathered together to round up all animals that did not appear to have an owner and kill them. In some nations, teams of rat catchers work at chasing rats from the field, and killing them with dogs and simple hand tools. Some communities have in the past employed a bounty system, where a town clerk will pay a set fee for every rat head brought in as proof of a rat killing.
Traps have been used for killing off mice found in houses, for killing wolves, and for capturing raccoons and stray cats and dogs for disposal by town officials.
Spraying poisons by planes, hand held units, or trucks that carry the spraying equipment, is a common method of pest control. Throughout the United States of America, towns often drive a town owned truck around once or twice a week to each street, spraying for mosquitoes. Crop dusters commonly fly over farmland and spray poison to kill off pest that would threaten the crops. Many find spraying poison around their yard, homes, or businesses, far more desirable than allowing insects to thrive there.
A project that involves a structure be covered or sealed airtight followed by the introduction of a penetrating, deadly gas at a killing concentration a long period of time (24-72hrs.). Although expensive, space fumigation targets all life stages of pests.
Residential & commercial building pest control service vehicle, Ypsilanti Township, Michigan
A long term project involving fogging or misting type applicators. Liquid insecticide is dispersed in the atmosphere within a structure. Treatments do not require the evacuation or airtight sealing of a building, allowing most work within the building to continue but at the cost of the penetrating effects. Contact insecticides are generally used, minimizing the long lasting residual effects. On August 10, 1973, the Federal Register printed the definition of Space treatment as defined by theU.S. Environmental Protection Agency (EPA):
“ the dispersal of insecticides into the air by foggers, misters, aerosol devices or vapor dispensers for control of flying insects and exposed crawling insects ”
Laboratory studies conducted with U-5897 (3-chloro-1,2-propanediol) where attempted in the early 1970s although these proved unsuccessful. Research into sterilization bait is ongoing.
Another effective method of soil sterilization is soil steaming. Pest is killed through hot steam which is induced into the soil.
Destruction of infected plants
Forest services sometimes destroy all the trees in an area where some are infected with insects, if seen as necessary to prevent the insect species from spreading. Farms infested with certain insects, have been burned entirely, to prevent the pest from spreading elsewhere.
Natural rodent control
Several wildlife rehabilitation organizations encourage natural form of rodent control through exclusion and predator support and preventing secondary poisoning altogether.
The United States Environmental Protection Agency agrees, noting in its Proposed Risk Mitigation Decision for Nine Rodenticides that “without habitat modification to make areas less attractive to commensal rodents, even eradication will not prevent new populations from recolonizing the habitat.”
Biological control of pests
in agriculture is a method of controlling pests (including insects, mites, weeds and plant diseases) that relies onpredation, parasitism, herbivory, or other natural mechanisms. It can be an important component of integrated pest management (IPM) programs.
Q.5. Discuss in detail the situation of development in agriculture sector in Pakistan and describe strategies to boost agricultural production in the country.
You can write a lot of things on this questions including all the projects related to agriculture sector , ministry of agriculture and all other institutes names and their performances.
Q.6. Enumerate the scope of range management in Pakistan and discuss its role in the development of dairy sector in the country
Range Management Rangelands of Pakistan are fragile ecological resource and provide feed and shelter to animals and fruit, wood, sports hunting and eco-tourism to the human being besides conserving environment provided they are properly managed. Sustainable grazing management and rangeland resource use is a key issue of concern in most rangeland regions of Pakistan, therefore, rangeland research at PARC focuses on assessing the sustainable use of these drought prone rangelands.
• Baseline survey of vegetation cover and composition of Pabbi Hills showed a 34% ground cover. Bermuda grass (Cynodon dactylon) dominated with 11.5% cover, followed by Mesquite (Prosopis juliflora) with 10% cover.
• Dry matter production 3.81 t.ha and higher sprouting rate i.e. (81%) was recorded for blue panic (Panicum antidotale) followed by finger grass (Digitaria swazilandensis) in semi arid conditionsof Pabbi Range.
• A combination of 35% green panic (Panicum m a x i m u m ) a n d 6 5 % cowpeas (Vigna unguiculata) gave highest forage yield. Combination of green pani c and inoculated cowpea produced 13% more forage as compared to combination of green panic and uninoculated cowpeas
• At 100 cm clipping height 35% higher biomass was produced over 10 cm height in double hedgerows of Ipil ipil. Significant increase in wheat yield was observed in alleys of under hedgerows spacing (15 cm) as compared to narrow spacing (5 m).
• Mulberry and Russian Olive plantations were carried out on micro-catchment water harvesting structures at AZRC range area for efficient utilization of rain water and production of forage for livestock.
• As a result of better rainfall distribution during the winter and spring months many new range species were observed.Fodder shrub plantation (Atriplex canescens, A.lentiformis and Salsolavermiculata) on microcatchment water harvesting structures was established w i t h c o m m u n i t y participation at Siddiqabad (Mastung). Shrub survival percentage was 70-80%.Native range vegetation was also improved by protecting the community range area from grazing. During winter and spring months, about 2000 seedlings of different native and exotic species were planted at the site on natural runoff places.Community Fodder shrubs nursery was also established for demonstration and distribution of seedlings to the farmers interested in plantation on range areas.
• Harvesting of Glycyrrhiza glabrea (Malathi) was completed. The harvesting was done after three years of plantation and 80 kg fresh weight of roots was obtained 2 from an area of 9 m .Seeds and seedlings of different exotic medicinal herbs were provided to Women University, Quetta f o r e st a b l is hme n t o f medicinal herb garden for research purpose.
• Of 16 desert flora such as trees, shrubs and grasses species collected from live herbarium, highest seed yield of 3.0 kg/plant was obtained from Acacia ampliceps(Australian Babur) .
Relate the above points with development of dairy sector in Pakistan to complete the answer of the above question.
Q.7. Discuss in detail different techniques used for the asexual propagation of fruit plants
Fruit tree propagation is usually carried out through asexual reproduction by grafting or budding the desired variety onto a suitable rootstock.
Perennial plants can be propagated either by sexual or vegetative means. Sexual reproduction begins when a male germ cell (pollen) from one flower fertilises a female germ cell (ovule, incipient seed) of the same species, initiating the development of a fruitcontaining seeds. Each seed, when germinated, can grow to become a new specimen tree. However, the new tree inherits characteristics of both its parents, and it will not grow 'true' to the variety of either parent from which it came. That is, it will be a fresh individual with an unpredictable combination of characteristics of its own. Although this is desirable in terms of producing novel combinations from the richness of the gene pool of the two parent plants (such sexual recombination is the source of new cultivars), only rarely will the resulting new fruit tree be directly useful or attractive to the tastes of humankind. Most new plants will have characteristics that lie somewhere between those of the two parents.
Therefore, from the orchard grower or gardener's point of view, it is preferable to propagate fruit cultivars vegetatively in order to ensure reliability. This involves taking a cutting (or scion) of wood from a desirable parent tree which is then grown on to produce a new plant or 'clone' of the original. In effect this means that the original Bramley apple tree, for example, was a successful variety grown from a pip, but that every Bramley since then has been propagated by taking cuttings of living matter from that tree, or one of its descendants.
The essentials of our present methods of propagating of fruit trees date from pre-Classical times. Grafting as a technique was first developed in China from where it was imported to Greece and Rome. Classical authors wrote extensively about the technical skills of fruit cultivation, including grafting techniques and rootstock selection. The oldest surviving named varieties of fruits date from classical times.
The simplest method of propagating a tree asexually is rooting. A cutting (a piece of the parent plant) is cut and stuck into soil. Artificial rooting hormones are sometimes used to assure success. If the cutting does not die of desiccation first, roots grow from the buried portion of the cutting to become a complete plant. Though this works well for some plants (such as figs and olives), most fruit trees are unsuited to this method.
Root cuttings (pieces of root induced to grow a new trunk) are used with some kinds of plants. This method also is suitable only for some plants.
A refinement on rooting is layering. This is rooting a piece of a wood that is still attached to its parent and continues to receive nourishment from it. The new plant is severed only after it has successfully grown roots. Layering is the technique most used for propagation of clonal apple rootstocks.
The most common method of propagating fruit trees, suitable for nearly all species, is grafting onto rootstocks. These are varieties selected for characteristics such as their vigour of growth, hardiness, soil tolerance, and compatibility with the desired variety that will form the aerial part of the plant (called the scion). For example, grape rootstocks descended from North American grapes allow European grapes to be grown in areas infested with Phylloxera, a soil-dwelling insect that attacks and kills European grapes when grown on their own roots. Grafting is the process of joining these two varieties, ensuring maximum contact between the cambium tissue (that is, the layer of growing plant material just below the bark) of each so that they grow together successfully. Two of the most common grafting techniques are 'whip and tongue', carried out in spring as the sap rises, and 'budding', which is performed around the end of summer.
1. Cut a slice of bud and bark from the parent tree.
2. Cut a similar sliver off the rootstock, making a little lip at the base to slot the scion into.
3. Join the two together and bind.
4. In time, the scion bud will grow into a shoot, which will develop into the desired tree.
Whip and Tongue grafting
1. Make a sloping cut in the rootstock with a 'tongue
2. Make a matching cut in the scion wood with a 'tongue' pointing downwards.
3. Join the two, ensuring maximum contact of the vascular cambium layers. Bind with raffia or polythene tape or wound around with a 5mm wide strip of elastic band (this is particularly successful because it keeps pressure on the cambium layers to be joined and eventually falls away with out cutting into the bark as the tree grows) and seal with grafting wax.
Q.8. Write short notes on ANY FOUR of the following:
(a) Factors affecting biological nitrogen fixation
2.4.1 Edaphic Factors
2.4.2 Climatic Factors
2.4.3 Biotic Factors
Interactions between the microsymbiont and the plant are complicated by edaphic, climatic, and management factors. A legume-Rhizobium symbiosis might perform well in a loamy soil but not in a sandy soil, in the subhumid region but not in the Sahel, or under tillage but not in no-till plots. These factors affect either the microsymbiont, the host-plant, or both.
2.4.1 Edaphic Factors
Edaphic factors relate to the soil. The six main edaphic factors limiting biological nitrogen fixation are:
• excessive soil moisture,
• soil acidity,
• P deficiency,
• excess mineral N, and
• deficiency of Ca, MO, CO and B.
Excessive moisture and waterlogging prevent the development of root hair and sites of nodulation, and interfere with a normal diffusion of O2 in the root system of plants. Sesbania rostrata and Aeschynomene sp. can actively fix N2 under these conditions because they are located on the plant stems, rather than on the roots.
Drought reduces the number of rhizobia in soils, and inhibits nodulation and N2 fixation. Prolonged drought will promote nodule decay. Deep-rooted legumes exploiting moisture in lower soil layers can continue fixing N2 when the soil is drying. Mycorrhizal infection has also been found to improve tolerance of plants to drought (e.g., Acacia auriculiformis inoculated with the ectomycorrhizal Baletus suillus). Mycorrhiza are symbiotic associations between fungi and plant roots. Some mycorrhizal fungi develop exclusively outside the roots; these are called ectomycorrhiza (e.g., Baletus suillus). Others, called endomycorrhiza, grow inside the roots with their vesicles and arbuscules inside the roots and with their fungal filaments extended outside (e.g., Glamus sp.). These are the vesicular-arbuscular mycorrhiza, usually referred to as VAM.
Soil acidity and related problems of Ca deficiency and aluminum and manganese toxicity adversely affect nodulation, N2fixation and plant growth . Research work on the identification of symbioses adapted to acid soil should focus on the host plant, because effective rhizobia adapted to- soil acidity can be found naturally and can be produced through genetic manipulations.
Phosphorus deficiency is commonplace in tropical Africa and reduces nodulation, N2 fixation and plant growth. Identification of plant species adapted to low-P soils is a good strategy to overcome this soil constraint. The role of mycorrhizal fungi in increasing plant P uptake with beneficial effects on N2 fixation has been reported. Dual inoculation with effective rhizobia and mycorrhizal fungi shows synergistic effects on nodulation and N2 fixation in low P soils*. The use of local rock phosphate has been recommended, particularly in acid soils, as an inexpensive source of P. The addition of P-solubilizing microorganisms, particularly of the general Psemdamaias, Bacillus, Penicillium, and Aspergillus can solubilize rock phosphate and organically bound soil P (which constitutes 95 - 99% of the total phosphate in soils). However, the use of these microorganisms is not widespread. Some reports show nodulation response to K under field conditions. However, other investigators consider the K effect to be indirect, acting through the physiology of the plant.
* Trees are usually infected by mycorrhizal fungi in natural ecosystems in the tropics. The significance of this symbiosis in nature should be better recognised.
Mineral N inhibits the Rhizobium infection process and also inhibits N2 fixation. The former problem probably results from impairment of the recognition mechanisms by nitrates, while the latter is probably due to diversion of photosynthates toward assimilation of nitrates. Some strains of Rhizobium, and particularly stem-nodulating Azarhizobium caulinodans, fix N2actively even when plants are growing in high-N soils (e.g., in the presence of 200 kg fertilizer N ha-1) . Application of large quantities of fertilizer N inhibits N2 fixation, but low doses (<30 kg N ha-1) of fertilizer N can stimulate early growth of legumes and increase their overall N2 fixation. The amount of this starter N must be defined in relation to available soil N.
Various microelements (Cu, Mo, Co, B) are necessary for N2 fixation. Some of these are components of nitrogenase for example Mo.
2.4.2 Climatic Factors
The two important climatic determinants affecting BNF are temperature and light.
Extreme temperatures affect N2 fixation adversely. This is easy to understand because N2 fixation is an enzymatic process. However, there are differences between symbiotic systems in their ability to tolerate high (>35°C) and low (<25°C) temperatures.
The availability of light regulates photosynthesis, upon which biological nitrogen fixation depends. This is demonstrated by diurnal variations in nitrogenase activity. A very few plants can grow and fix N2 under shade (e.g., Flemingia congesta under plantain canopy). In alley farming if hedgerows are not weeded, or if trees are planted with food crops like cassava, their nitrogen fixation and growth will be reduced due to shading. Early growth of legume trees is slow and they cannot compete successfully for light.
2.4.3 Biotic Factors
Among biotic factors, the absence of the required rhizobia species constitute the major constraint in the nitrogen fixation process. The other limiting biotic factors could be:
• excessive defoliation of host plant,
• crop competition, and
• insects and nematodes
Inoculation of Legumes
If specific and effective rhizobia are absent in a soil, or if they are present in low numbers, it is necessary to introduce the rhizobia in that soil to ensure proper nodulation and nitrogen fixation. This is called inoculation. If specific and effective rhizobia are present in a sufficient number, there will be no need to inoculate the legume. In agrisystems, whenever one is not sure of the presence and effectiveness of the native rhizobia, it could be necessary to inoculate the legume with an adequate strain of rhizobia.
How one can determine the need for inoculation? There are some simple tests: Are nodules absent or sparse on an uninoculated young plant growing in a low-N soil? (This is normally accompanied by plant N deficiencies). Or, are nodule sections white or green? (This is an indication of poor effectiveness).
A more accurate relative effectiveness trial will provide more precise information. The trial, in a simple term, consists of growing the legume with and without fertilizer N while controlling all other limiting factors. The relative effectiveness ratio (RE) is then calculated. RE is defined as: dry weight of unfertilized plants × 100/dry weight of fertilized plants. If the value of RE is more than 5, the inoculation is not required.
When the rhizobia in a soil are infective (i.e., capable of colonizing and nodulating a legume) but poorly effective, they constitute a barrier to the successful exploitation of Rhizobium inoculants. Introduced rhizobia must therefore be more aggressive and competitive as nodulators than the native strains. Inoculant rhizobia usually persist in the soil for long periods, particularly when the host is cultivated frequently or is permanent. Persistence of a strain is desirable because it obviates the need for inoculation in subsequent years, assuming inoculant strains maintain their original effectiveness.
Inoculation with rhizobia is usually recommended for newly introduced legumes. Most positive responses to inoculation are confined to crops which have specific requirements for Rhizobium, (e.g., Leucaena leucocephala, American varieties of soybean). Indigenous legumes seldom respond to inoculation with introduced rhizobia because they nodulate with resident strains, even if these native rhizobia are not the most effective ones.
Inoculation with rhizobia should be considered as an exceptional farming practice rather than the rule. In Australia and the USA, inoculation has played a vital role in legume production. But in developing countries, the practice is not widespread. The major drawback to inoculation technology is the wide variability in yield responses in time and space for a given Rhizobium-legume symbiosis. Responses can vary from no response, and sometimes negative responses, to positive yield increases. Response to inoculation with a strain of Rhizobium vary with sites, legume cultivars, and the form of inoculant. Changes in climate, such as Africa's long droughts in recent years, and management factors including cropping systems and inoculant handling will also introduce variability in response to inoculation. Local rhizobia are not necessarily better inoculants than exotic strains.
All these considerations call for a substantial research support system capable of defining the most appropriate inoculants and procedures for each site and probably for each cropping season as well. The use of freely nodulating legumes will be much easier in this respect.
Inoculation procedures are detailed in Volume 1 of this training manual (see Appendices).
Defoliation, Crop Competition, and Pests
Defoliation (e.g., pruning and lopping) decreases the photosynthetic ability of legumes. It impairs N2 fixation and can lead to nodule decay. For perennial legumes, nodule decay sheds a high number of rhizobia in the root zone. When new roots develop in subsequent vegetative cycles, nodulation of the legume is expected to improve. Scientists at IITA have observed that uninoculated Leucaena leucocephala nodulated very sparsely the first year and showed nitrogen deficiency symptoms. After a number of years nodulation improved and N deficiency symptoms disappeared.
Intercropping legumes with non-leguminous crops can result in competition for water and nutrients. This competition can affect N2 fixation negatively. However, it has been shown that when mineral N is depleted in the root zone of the legume component by the non-leguminous intercrops, N2 fixation of legumes may be promoted.
Insects and nematodes have also been reported to interfere with nodule formation, development, and functions.
(b) Soil erosion
Soil is naturally removed by the action of water or wind: such 'background' (or 'geological') soil erosion has been occurring for some 450 million years, since the first land plants formed the first soil. Even before this, natural processes moved loose rock, or regolith, off the Earth's surface, just as has happened on the planet Mars.
In general, background erosion removes soil at roughly the same rate as soil is formed. But 'accelerated' soil erosion — loss of soil at a much faster rate than it is formed — is a far more recent problem. It is always a result of mankind's unwise actions, such as overgrazing or unsuitable cultivation practices. These leave the land unprotected and vulnerable. Then, during times of erosive rainfall or windstorms, soil may be detached, transported, and (possibly travelling a long distance) deposited.
Accelerated soil erosion by water or wind may affect both agricultural areas and the natural environment, and is one of the most widespread of today's environmental problems. It has impacts which are both on-site (at the place where the soil is detached) and off-site (wherever the eroded soil ends up).
More recently still, the use of powerful agricultural implements has, in some parts of the world, led to damaging amounts of soil moving downslope merely under the action of gravity: this is so-called tillage erosion.
Soil erosion is just one form of soil degradation. Other kinds of soil degradation include salinisation, nutrient loss, and compaction.
(c) Crop rotation
Crop rotation is one of the oldest and most effective cultural control strategies. It means the planned order of specific crops planted on the same field. It also means that the succeeding crop belongs to a different family than the previous one. The planned rotation may vary from 2 or 3 year or longer period.
Some insect pests and disease-causing organisms are hosts' specific. For example, rice stem borer feeds mostly on rice. If you don't rotate rice with other crops belonging to a different family, the problem continues as food is always available to the pest. However, if you plant legume as the next crop, then corn, then beans, then bulbs, the insect pest will likely die due to absence of food.
Advantages of crop rotation
1. Prevents soil depletion
2. Maintains soil fertility
3. Reduces soil erosion
4. Controls insect/mite pests. Crop rotation as a means to control to insect pests is most effective when the pests are present before the crop is planted have no wide range of host crops; attack only annual/biennial crops; and do not have the ability to fly from one field to another.
5. Reduces reliance on synthetic chemicals
6. Reduces the pests' build-up
7. Prevents diseases
8. Helps control weeds
(d) Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genomeusing modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest. The introduction of new DNA does not require the use of classical genetic methods, however traditionalbreeding methods are typically used for the propagation of recombinant organisms.
An organism that is generated through the introduction of recombinant DNA is considered to be a genetically modified organism. The first organisms genetically engineered were bacteria in 1973 and then mice in 1974. Insulin-producing bacteria were commercialized in 1982 and genetically modified food has been sold since 1994.
The most common form of genetic engineering involves the insertion of new genetic material at an unspecified location in the host genome. This is accomplished by isolating and copying the genetic material of interest usingmolecular cloning methods to generate a DNA sequence containing the required genetic elements for expression, and then inserting this construct into the host organism. Other forms of genetic engineering include gene targetingand knocking out specific genes via engineered nucleases such as zinc finger nucleases or engineered homing endonucleases.
Genetic engineering techniques have been applied in numerous fields including research, biotechnology, and medicine. Medicines such as insulin and human growth hormone are now produced in bacteria, experimental mice such as the oncomouse and the knockout mouse are being used for research purposes and insect resistant and/or herbicide tolerant crops have been commercialized. Genetically engineered plants and animals capable of producing biotechnology drugs more cheaply than current methods (called pharming) are also being developed and in 2009 the FDA approved the sale of the pharmaceutical protein antithrombin produced in the milk of genetically engineeredgoats.
(e) Effective microorganisms (EM) technology
An effective microorganism refers to any of the predominantly anaerobic organisms blended in commercial agricultural amendments, medicines, and nutritional supplements based on the trademarked product originally marketed as EM-1 Microbial Inoculant, aka Effective Microorganisms and EM Technology. These blends are reported to include:
Lactic acid bacteria: Lactobacillus casei
Photosynthetic bacteria: Rhodopseudomonas palustris
Yeast: Saccharomyces cerevisiae
Others: beneficial microorganisms that exist naturally in the environment may thrive in the mixture.
EM Technology is purported to support sustainable practices in farming and to improve and support human health and hygiene, compost and waste management, disaster clean-up (the Bangkok floods of 2011, the Southeast Asia tsunami of 2004, the Kobe earthquake, andHurricane Katrina remediation projects).
EM has been employed in many agricultural applications, but is also used in the production of several health products in South Africa and the USA
(f) Prospects of meat industry in Pakistan
Following the study entitled “The Competitive Advantage of the Food Processing Industry: Focus on Quality, Safety and Standards”, the CSF was tasked to undertake more specific work on the meat industry. A series of meetings with MINFAL, the Livestock and Dairy Development Board (L&DDB) and the MOF established that development of the meat industry is a critical element in the development of the agricultural economy of Pakistan and the alleviation of poverty. However, whereas much work has been undertaken by various agencies on the dairy sub-sector, little is known about the overall livestock industry and the linkages between live animals, dairy products and meat production. Meat production in particular is an area that has remained largely unexplored and the sub-sector is under-invested. Work on the Action Plan for the Meaty Industry is on-going in September 2007.
You can write the answer of this question by yourself good by adding your knowledge related to live stock demand and supply phenomena in Pakistani market, Potential of meat industry.