Doubling a haploid genome yields fully homozygous plants in a single step, useful for developing pure breeding lines.
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16Which term describes the direct formation of embryos from cultured microspores or anthers?
to isolate and inoculate anthers for haploid production
Easy
A.Androgenic embryogenesis
B.Micropropagation of shoots
C.Somatic hybridization
D.Protoplast fusion
Correct Answer: Androgenic embryogenesis
Explanation:
When microspores develop directly into embryos, the process is called androgenic (pollen) embryogenesis.
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17Which of the following crops is classically used as a model for successful anther culture?
to isolate and inoculate anthers for haploid production
Easy
A.Banana
B.Mango
C.Tobacco (Nicotiana tabacum)
D.Coconut
Correct Answer: Tobacco (Nicotiana tabacum)
Explanation:
Tobacco was among the first plants in which haploids were produced through anther culture and remains a classic model.
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18After inoculation, anther cultures are typically incubated:
to isolate and inoculate anthers for haploid production
Easy
A.Under controlled temperature with a suitable light regime
B.In complete darkness at
C.In direct outdoor sunlight without control
D.In boiling water
Correct Answer: Under controlled temperature with a suitable light regime
Explanation:
Cultures are maintained in a growth room at controlled temperature (around ) with an appropriate photoperiod for development.
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19A major advantage of using anther culture in plant breeding programmes is that it:
to isolate and inoculate anthers for haploid production
Easy
A.Guarantees polyploid seeds
B.Eliminates the need for any medium
C.Shortens the time needed to obtain homozygous lines
D.Produces only male sterile plants
Correct Answer: Shortens the time needed to obtain homozygous lines
Explanation:
By producing haploids that are doubled to homozygous diploids in one generation, anther culture drastically reduces breeding time compared to repeated selfing.
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20An undesirable outcome sometimes seen in anther culture, where regenerated plants are not uniformly haploid, is due to:
to isolate and inoculate anthers for haploid production
Easy
A.Cold pretreatment of buds
B.Use of MS medium
C.Excess sterilization of the medium
D.Regeneration from diploid anther wall tissue
Correct Answer: Regeneration from diploid anther wall tissue
Explanation:
Diploid somatic cells of the anther wall can also regenerate, producing diploid or mixed-ploidy plants alongside the desired haploids.
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21During anther culture, haploid plants develop primarily because the cultured cells originate from which structure?
to isolate and inoculate anthers for haploid production
Medium
Androgenesis redirects the developmental pathway of the haploid microspores (immature pollen) toward embryogenesis, yielding haploid plants.
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22Why is the correct developmental stage of the microspore considered the single most critical factor for successful anther culture?
to isolate and inoculate anthers for haploid production
Medium
A.Older microspores contain more auxin for callus growth
B.Mature pollen divides faster and gives more embryos
C.The tapetum is thickest at the mature stage and nourishes embryos
D.Only microspores at the uninucleate stage can be reprogrammed toward embryogenesis
Correct Answer: Only microspores at the uninucleate stage can be reprogrammed toward embryogenesis
Explanation:
Microspores are most responsive around the mid-to-late uninucleate stage, when their gene expression can still be switched from gametophytic to sporophytic development.
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23A researcher wants to quickly estimate microspore stage before culture. Which practical correlation is most commonly used in the field?
to isolate and inoculate anthers for haploid production
Medium
A.Anther colour after autoclaving indicates the stage
B.Root length of the donor plant predicts the stage
C.Number of stamens per flower reflects ploidy
D.Flower bud length or petal-to-sepal ratio correlates with microspore stage
Correct Answer: Flower bud length or petal-to-sepal ratio correlates with microspore stage
Explanation:
External bud morphology (length, petal/sepal position) reliably correlates with internal microspore stage, allowing rapid selection without dissection of every bud.
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24Before inoculation, flower buds are commonly surface sterilized and then held at low temperature (around ) for a few days. What is the main purpose of this cold pretreatment?
to isolate and inoculate anthers for haploid production
Medium
A.It sterilizes the anthers by killing surface bacteria
B.It doubles the chromosome number directly
C.It acts as a stress trigger that diverts microspores toward the sporophytic (embryogenic) pathway
D.It causes the anthers to release more nectar
Correct Answer: It acts as a stress trigger that diverts microspores toward the sporophytic (embryogenic) pathway
Explanation:
Cold (and other stresses such as heat or starvation) reprogram microspores away from normal pollen development toward embryogenesis, increasing haploid yield.
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25While excising anthers, a technician often discards buds where filaments are long and anthers have dehisced. Why?
to isolate and inoculate anthers for haploid production
Medium
A.Long filaments carry more contaminating fungi
B.Long filaments block absorption of medium
C.Dehisced anthers are diploid and cannot form haploids
D.Dehisced anthers contain mature pollen that rarely responds to culture
Correct Answer: Dehisced anthers contain mature pollen that rarely responds to culture
Explanation:
Once anthers dehisce, the pollen is mature (bi- or tri-nucleate) and has largely lost the capacity to switch to embryogenic development.
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26During excision, care is taken to remove the filament completely before placing anthers on medium. What is the main reason?
to isolate and inoculate anthers for haploid production
Medium
A.Filament (somatic diploid tissue) can proliferate and give diploid callus, masking haploid regenerants
B.Removing the filament reduces the anther's water content
C.The filament is the site of pollen tube growth
D.The filament secretes ethylene that inhibits growth
Correct Answer: Filament (somatic diploid tissue) can proliferate and give diploid callus, masking haploid regenerants
Explanation:
Filament tissue is diploid somatic tissue; if left attached it may form callus and produce diploid plants, defeating the aim of obtaining haploids.
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27In a routine protocol, buds are surface sterilized rather than the individual anthers. Which reasoning best supports this practice?
to isolate and inoculate anthers for haploid production
Medium
A.Buds must be sterilized to trigger dehiscence
B.The enclosed anthers stay sterile inside the bud, so sterilizing the intact bud avoids damaging the delicate anthers
C.Individual anthers absorb too much sterilant and become diploid
D.Anthers are resistant to sterilants and cannot be cleaned individually
Correct Answer: The enclosed anthers stay sterile inside the bud, so sterilizing the intact bud avoids damaging the delicate anthers
Explanation:
Anthers within an unopened bud are naturally protected; sterilizing the whole bud keeps them undamaged while ensuring an aseptic explant.
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28A student obtains many plants from anther culture but finds most are diploid, not haploid. What is the most likely explanation?
to isolate and inoculate anthers for haploid production
Medium
A.Regeneration occurred from diploid anther wall/connective tissue rather than microspores
B.The buds were too young
C.The cold pretreatment was too long
D.The medium contained too much sucrose
Correct Answer: Regeneration occurred from diploid anther wall/connective tissue rather than microspores
Explanation:
Somatic (2n) tissues of the anther can regenerate; if microspore-derived structures are not favoured, diploid plants of somatic origin dominate.
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29Which combination of plant growth regulators is typically effective for inducing androgenesis in many species?
to isolate and inoculate anthers for haploid production
Medium
A.Ethephon combined with ethylene
B.Abscisic acid alone
C.A balance of an auxin and a cytokinin, adjusted per species
D.Only gibberellic acid at high concentration
Correct Answer: A balance of an auxin and a cytokinin, adjusted per species
Explanation:
Most anther culture media use an auxin:cytokinin balance to induce microspore-derived callus or embryos; the exact ratio is optimized for each species.
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30Haploid plants regenerated from anther culture are often treated with colchicine. What is the objective?
to isolate and inoculate anthers for haploid production
Medium
A.To sterilize the plantlets against fungal infection
B.To double the chromosome number and obtain homozygous diploid (doubled haploid) plants
C.To induce flowering earlier
D.To convert diploids back into haploids
Correct Answer: To double the chromosome number and obtain homozygous diploid (doubled haploid) plants
Explanation:
Colchicine blocks spindle formation, doubling the haploid genome to yield completely homozygous diploids, valuable in breeding.
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31In anther culture, activated charcoal is sometimes added to the medium. Its main role is to:
to isolate and inoculate anthers for haploid production
Medium
A.Increase the osmotic pressure of the medium
B.Provide a carbon source for microspore growth
C.Supply nitrogen for embryo development
D.Adsorb inhibitory phenolics and browning compounds released by the anthers
Correct Answer: Adsorb inhibitory phenolics and browning compounds released by the anthers
Explanation:
Activated charcoal absorbs toxic phenolic exudates and other inhibitors, reducing browning and improving embryogenic response.
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32Which cytological verification is most direct for confirming that regenerated plantlets are haploid?
to isolate and inoculate anthers for haploid production
Medium
A.Observing flower colour
B.Weighing the fresh biomass
C.Measuring plant height
D.Counting chromosome number in root-tip mitotic cells
Correct Answer: Counting chromosome number in root-tip mitotic cells
Explanation:
Chromosome counting from actively dividing root-tip cells (or flow cytometry) directly confirms the ploidy level of regenerants.
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33Why is the physiological condition of the donor plant important for anther culture success?
to isolate and inoculate anthers for haploid production
Medium
A.Healthy, well-grown donor plants under optimal conditions yield more responsive microspores
B.Donor age has no effect on microspore response
C.Only diseased plants produce embryogenic anthers
D.Water-stressed plants always give the highest yields
Correct Answer: Healthy, well-grown donor plants under optimal conditions yield more responsive microspores
Explanation:
Donor plant genotype, age, nutrition and growth environment strongly influence microspore embryogenic competence and overall culture success.
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34A key advantage of doubled haploids produced via anther culture over conventional inbreeding is that:
to isolate and inoculate anthers for haploid production
Medium
A.No genetic variation is ever produced
B.The plants are always triploid and sterile
C.Complete homozygosity is achieved in a single generation instead of many
D.They eliminate the need for a donor plant
Correct Answer: Complete homozygosity is achieved in a single generation instead of many
Explanation:
Doubling a haploid genome gives instant, fully homozygous lines, saving several generations of selfing required in traditional breeding.
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35In some protocols microspores are isolated from anthers and cultured directly (isolated microspore culture) instead of whole anthers. One major benefit is:
to isolate and inoculate anthers for haploid production
Medium
Spontaneous chromosome doubling and endoreduplication during culture can create mixoploid regenerants containing cells of different ploidy levels.
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39Why are low light or dark conditions often used during the early induction phase of anther culture?
to isolate and inoculate anthers for haploid production
Medium
A.Darkness supplies carbon to the microspores
B.Light is completely lethal to all anthers
C.They reduce phenolic browning and favour the switch to embryogenesis
D.Light causes immediate chromosome doubling
Correct Answer: They reduce phenolic browning and favour the switch to embryogenesis
Explanation:
Initial dark or dim conditions minimise light-induced phenolic oxidation and browning, improving early induction; light is introduced later for greening.
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40A breeder crosses two parents, then uses anther culture on the F hybrid. What is the main strategic advantage?
to isolate and inoculate anthers for haploid production
Medium
A.It converts the F directly into a stable triploid crop
B.It prevents any recombination between parental genes
C.It removes the need to make the initial cross
D.Recombinant gametes are fixed instantly as homozygous doubled-haploid lines for selection
Correct Answer: Recombinant gametes are fixed instantly as homozygous doubled-haploid lines for selection
Explanation:
Anther culture of F hybrids captures recombined gametes and fixes them as homozygous doubled haploids, greatly speeding up line development.
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41During anther culture, a researcher observes that anthers inoculated at the late uninucleate to early binucleate microspore stage give the highest androgenic response, while anthers taken at the mature pollen stage fail completely. What is the primary reason for this stage-dependence?
to isolate and inoculate anthers for haploid production
Hard
A.Only microspores at this developmental window can be diverted from the gametophytic pathway to the sporophytic (embryogenic) pathway
B.The anther wall at the mature stage secretes ethylene which is toxic to the surrounding culture medium
C.Late uninucleate microspores possess thicker exine that mechanically protects them during dissection and plating
D.Mature pollen grains contain higher concentrations of endogenous cytokinins that block callus induction on the medium
Correct Answer: Only microspores at this developmental window can be diverted from the gametophytic pathway to the sporophytic (embryogenic) pathway
Explanation:
Androgenesis requires reprogramming the microspore from its normal gametophytic (pollen-forming) fate to a sporophytic (embryo-forming) fate. This switch is only possible when the microspore is still developmentally plastic, at the late uninucleate to early binucleate stage. Once pollen matures, the cell is committed and cannot be redirected.
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42A cold pretreatment (e.g., for several days) of flower buds prior to anther inoculation frequently increases embryo yield. Which mechanism best explains this stress-induced enhancement?
to isolate and inoculate anthers for haploid production
Hard
A.Cold stress promotes symmetric division of the microspore and blocks the vegetative-generative asymmetry that leads to pollen
B.Cold triggers rapid endoreduplication so that all microspores become spontaneously diploid before plating
C.Cold pretreatment sterilizes the buds, reducing the fungal contamination that otherwise destroys cultures
D.Cold stress permanently kills the tapetum, releasing large amounts of stored sucrose into the anther locule
Correct Answer: Cold stress promotes symmetric division of the microspore and blocks the vegetative-generative asymmetry that leads to pollen
Explanation:
Stress pretreatments such as cold divert the first pollen mitosis from an asymmetric (vegetative + generative cell) division toward a symmetric division, initiating the embryogenic sporophytic pathway. This reprogramming is the key event in androgenesis, not sterilization or spontaneous diploidization.
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43In an anther culture experiment, a large fraction of the regenerated plants turn out to be diploid rather than the expected haploid. Assuming the microspores were correctly staged, what is the most likely source of these diploids?
to isolate and inoculate anthers for haploid production
Hard
A.Use of an excessively high sucrose concentration that induced polyploidy in the microspores
B.Contamination of the medium with -D which doubles the ploidy of any explant it contacts
C.Regeneration from the diploid somatic tissue of the anther wall or connective rather than from the microspores
D.Fusion of two adjacent haploid microspores inside the anther locule during plating
Correct Answer: Regeneration from the diploid somatic tissue of the anther wall or connective rather than from the microspores
Explanation:
A major limitation of anther (versus isolated microspore) culture is that the surrounding diploid somatic tissues—anther wall, connective, filament—can also regenerate plants. These give diploids of somatic origin, contaminating the haploid population. Careful staging does not prevent somatic-tissue regeneration.
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44To confirm that a regenerated plantlet from anther culture is genuinely of microspore (gametic) origin and not somatic, which approach is most rigorous?
to isolate and inoculate anthers for haploid production
Hard
A.Counting chromosomes to confirm the plant is diploid rather than tetraploid
B.Observing whether the plantlet forms roots faster than a seed-derived control
C.Molecular marker analysis showing homozygosity/hemizygosity at heterozygous parental loci
D.Measuring the height of the regenerated plant relative to the donor plant
Correct Answer: Molecular marker analysis showing homozygosity/hemizygosity at heterozygous parental loci
Explanation:
Gametic (microspore-derived) plants carry only one allele at loci that are heterozygous in the donor, so molecular markers reveal homozygosity or a single allele. Somatic-derived plants remain heterozygous like the donor. Chromosome counts alone cannot distinguish origin because a somatic diploid and a chromosome-doubled haploid both appear diploid.
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45A protocol calls for surface sterilization of intact flower buds rather than isolated anthers before dissection. What is the principal rationale for sterilizing the whole bud?
to isolate and inoculate anthers for haploid production
Hard
A.The sterilant chemically induces the microspore reprogramming needed for embryogenesis
B.Whole buds retain more moisture, preventing the anthers from desiccating during sterilization
C.Isolated anthers cannot withstand any contact with sterilant, so the bud must absorb it first
D.The enclosed anthers inside an intact bud are already aseptic, so only the outer bud surface needs treatment
Correct Answer: The enclosed anthers inside an intact bud are already aseptic, so only the outer bud surface needs treatment
Explanation:
Anthers within an unopened bud are naturally protected and sterile. By surface-sterilizing the intact bud and then dissecting anthers under aseptic conditions, the anthers themselves need no direct sterilant exposure, avoiding chemical damage to the delicate microspores.
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46When inoculating anthers, technicians are warned to avoid damaging or breaking the anther during dissection. Why is an intact, undamaged anther important for androgenesis (as opposed to callus from wounding)?
to isolate and inoculate anthers for haploid production
Hard
A.Damaged anthers lose their pigmentation, making it impossible to track developmental stage
Wounding stimulates callus/regeneration from the injured diploid somatic cells of the anther wall, boosting the proportion of unwanted diploid plants of somatic origin. Keeping the anther intact favors response from the microspores and reduces somatic-tissue interference.
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47A researcher wants to determine the correct microspore stage without sacrificing the anthers to be cultured. Which practical correlation is most commonly exploited for staging?
to isolate and inoculate anthers for haploid production
Hard
A.The ratio of petal length to sepal length, or bud size/position, correlated to microspore stage by prior cytological calibration
B.The number of anthers per flower, which decreases as microspores mature
C.The pH of the anther locule fluid measured with indicator paper before plating
D.The intensity of green color in the anther, which directly indicates uninucleate microspores
Correct Answer: The ratio of petal length to sepal length, or bud size/position, correlated to microspore stage by prior cytological calibration
Explanation:
Because microspore stage cannot be seen externally, researchers first calibrate an easily measured external morphological marker—typically bud size or the petal-to-sepal length ratio—against acetocarmine-stained microspore stages. Then buds of the correct size can be selected non-destructively for culture.
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48In many dicots, anther-culture-derived haploids spontaneously double to diploid, whereas in cereals colchicine treatment is often required. What underlies this need for artificial chromosome doubling?
to isolate and inoculate anthers for haploid production
Hard
A.A substantial fraction of embryos/plants remain haploid and sterile, requiring doubling to restore fertility and homozygous diploidy
B.Dicot haploids are always sterile while cereal haploids are always fertile without treatment
C.Colchicine is the auxin required specifically by monocot microspores to begin dividing
D.Cereal haploids are lethal and can only survive if immediately treated with colchicine at plating
Correct Answer: A substantial fraction of embryos/plants remain haploid and sterile, requiring doubling to restore fertility and homozygous diploidy
Explanation:
Haploid plants are typically sterile because they lack homologous chromosomes for normal meiosis. To obtain fertile, completely homozygous doubled-haploid lines, the chromosome number must be doubled—often via colchicine when spontaneous doubling is insufficient, as is common in cereals.
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49Adding activated charcoal to the anther culture medium often improves androgenic embryo formation. Which explanation is best supported?
to isolate and inoculate anthers for haploid production
Hard
A.It emits far-red light that specifically triggers the sporophytic switch in microspores
B.It provides a carbon source that microspores metabolize directly in place of sucrose
C.It adsorbs inhibitory phenolics and browning compounds released by the anther, and may adsorb excess growth regulators
D.It raises the osmotic potential of the medium, forcing microspores to divide symmetrically
Correct Answer: It adsorbs inhibitory phenolics and browning compounds released by the anther, and may adsorb excess growth regulators
Explanation:
Anthers release phenolic and browning substances that inhibit growth. Activated charcoal adsorbs these toxic exudates (and can sequester excess hormones), creating a more favorable environment for microspore-derived embryo development.
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50A comparison shows that isolated microspore culture generally yields a higher frequency of true haploids than intact anther culture. What is the fundamental advantage of the isolated-microspore approach?
to isolate and inoculate anthers for haploid production
Hard
A.It removes the diploid somatic anther tissues, so regenerants arise almost exclusively from gametic cells
B.Isolation eliminates the requirement for sterile technique because single cells resist contamination
C.Isolated microspores no longer need any developmental staging before culture
D.Microspores in isolation absorb colchicine automatically, doubling without treatment
Correct Answer: It removes the diploid somatic anther tissues, so regenerants arise almost exclusively from gametic cells
Explanation:
By physically separating microspores from the anther wall and connective, isolated microspore culture eliminates the diploid somatic tissue that causes somatic-origin escapes. Nearly all regenerants therefore derive from gametic cells, giving cleaner haploid populations.
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51In an experiment, anthers plated on a medium with a high auxin:cytokinin ratio produced abundant callus, but the callus mostly regenerated diploid plants. What is the best interpretation?
to isolate and inoculate anthers for haploid production
Hard
A.Callus phase increases genetic instability and favors proliferation of diploid somatic cells, promoting somatic escapes and variation
B.Callus formation is impossible from microspores, so the plants must be from seeds
C.Cytokinin was completely absent, so no microspores could survive to form embryos
D.High auxin directly converts every haploid nucleus into a diploid nucleus
Correct Answer: Callus phase increases genetic instability and favors proliferation of diploid somatic cells, promoting somatic escapes and variation
Explanation:
Routing regeneration through a callus (indirect) phase introduces genetic instability (somaclonal variation, ploidy changes) and gives the diploid somatic tissues opportunity to proliferate. Direct embryogenesis from microspores is preferred for reliable haploid recovery.
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52Two donor-plant batches of identical genotype give very different androgenic responses; one had been grown under short days with high light, the other under stressful low-nutrient conditions. Which conclusion about anther culture is most valid?
to isolate and inoculate anthers for haploid production
Hard
A.Genotype is the only factor determining androgenesis, so the difference must be a plating error
B.Microspore competence is fixed at meiosis and cannot be influenced by donor growth conditions
C.The physiological condition and growing environment of the donor plant strongly influence androgenic competence of its microspores
D.Donor-plant condition affects only contamination rates, not embryo yield
Correct Answer: The physiological condition and growing environment of the donor plant strongly influence androgenic competence of its microspores
Explanation:
Beyond genotype, the growth conditions and physiological state of the donor plant (light, temperature, nutrition, age) markedly affect how responsive its microspores are to androgenic induction. Well-maintained donor plants under optimal conditions typically give the best response.
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53Why is the term 'androgenesis' specifically appropriate for anther/microspore culture, and how does it contrast with gynogenesis?
to isolate and inoculate anthers for haploid production
Hard
A.Androgenesis yields diploids and gynogenesis yields haploids by definition
B.Androgenesis produces haploids from the male gametophyte (microspores/pollen), whereas gynogenesis produces them from the female gametophyte (unfertilized ovule/egg)
C.Androgenesis uses only male (dioecious) plants, while gynogenesis uses only female plants
D.Androgenesis requires fertilization by male gametes, while gynogenesis avoids fertilization
Correct Answer: Androgenesis produces haploids from the male gametophyte (microspores/pollen), whereas gynogenesis produces them from the female gametophyte (unfertilized ovule/egg)
Explanation:
Androgenesis is haploid production from the male gametophyte (microspores in anther/microspore culture). Gynogenesis is the parallel process from the female gametophyte (unfertilized ovary/ovule culture). Both bypass fertilization to yield gametic haploids.
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54A worker reports that anthers dehisced (split open) during dissection and pollen was released onto the medium; subsequent cultures failed. What is the most likely reason for failure?
to isolate and inoculate anthers for haploid production
Hard
A.Dehiscence proves the buds were fungally infected before dissection
B.Dehiscence indicates the pollen was already mature, past the responsive uninucleate/early-binucleate stage
C.Open anthers lower the medium pH to lethal levels within minutes
D.Released pollen instantly fertilizes the medium, forming inhibitory zygotes
Correct Answer: Dehiscence indicates the pollen was already mature, past the responsive uninucleate/early-binucleate stage
Explanation:
Anther dehiscence and free pollen release are signs of anther maturity. At this point microspores have matured into pollen and lost the developmental plasticity needed for androgenesis, so cultures typically fail. Responsive anthers are dissected from younger, unopened buds.
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55In doubling-haploid breeding, why are anther-culture-derived doubled haploids especially valuable compared with conventional inbreeding to homozygosity?
to isolate and inoculate anthers for haploid production
Hard
A.They avoid the need for any field selection because all traits are dominant
B.They achieve complete homozygosity in a single generation, versus many generations of selfing
C.They are always polyploid, giving larger fruit than inbred lines
D.They guarantee heterozygous vigor that inbreeding can never produce
Correct Answer: They achieve complete homozygosity in a single generation, versus many generations of selfing
Explanation:
A haploid derived from a single gamete already carries one allele per locus; doubling it produces a fully homozygous diploid instantly. Conventional inbreeding requires six or more selfing generations to approach this level of homozygosity, so doubled haploids dramatically accelerate breeding.
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56Which combination of pretreatment plus medium condition would most rationally be chosen to maximize the sporophytic switch while minimizing somatic-tissue regeneration in a recalcitrant cereal?
to isolate and inoculate anthers for haploid production
Hard
A.Cold/starvation stress pretreatment of buds combined with a low-auxin medium favoring direct microspore embryogenesis
B.Prolonged heat pretreatment combined with a very high -D concentration to force callus
C.No pretreatment combined with high cytokinin to keep anther walls dividing
D.High-sucrose osmotic shock combined with continuous bright light to mature the pollen faster
Correct Answer: Cold/starvation stress pretreatment of buds combined with a low-auxin medium favoring direct microspore embryogenesis
Explanation:
A stress pretreatment (cold or sugar starvation) triggers the microspore's sporophytic switch, while a low-auxin medium that promotes direct embryogenesis (rather than callus) minimizes proliferation of diploid somatic tissue. This combination targets gametic embryos and reduces somatic escapes.
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57'Albino plant' regeneration is a well-known problem in cereal anther culture. What does the frequent recovery of albinos indicate about the process?
to isolate and inoculate anthers for haploid production
Hard
A.Albino plants form only when colchicine is applied too early during doubling
B.Albinism proves the plants are diploid somatic escapes rather than haploids
C.Albinism results from excess activated charcoal blocking all light in the culture vessel
D.Microspore-derived cells often carry plastid/chloroplast genome deletions or defects, so regenerants lack functional chloroplasts
Correct Answer: Microspore-derived cells often carry plastid/chloroplast genome deletions or defects, so regenerants lack functional chloroplasts
Explanation:
In cereals, a high frequency of anther-derived plants are albino due to deletions or rearrangements in the plastid (chloroplast) genome arising during the culture process. These albinos cannot photosynthesize and are a major limitation, distinct from ploidy or somatic-origin issues.
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58If a heterozygous donor plant is used for anther culture, what genotypic outcome is expected among the (chromosome-doubled) haploid regenerants, ignoring linkage?
to isolate and inoculate anthers for haploid production
Hard
A.Only heterozygotes, identical to the donor plant
B.Only and in a ratio
C.Four homozygous classes—, , , —each in equal proportion
D.A continuous range of partially heterozygous genotypes
Correct Answer: Four homozygous classes—, , , —each in equal proportion
Explanation:
Each microspore is a product of meiosis carrying one allele per gene; for two independent genes the gametes are , , , in equal frequency. Chromosome doubling makes each fully homozygous, giving the four homozygous classes in equal proportions—a key benefit for fixing recombinant lines.
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59A lab wants to verify microspore stage rapidly at the bench during dissection. Which staining method is the standard choice for visualizing the nucleus/nuclei to confirm the uninucleate stage?
to isolate and inoculate anthers for haploid production
Hard
A.Gram staining of the anther smear to distinguish nuclear membranes
B.Acetocarmine (or DAPI) squash of a sample anther to count microspore nuclei
C.Iodine (I-KI) staining to detect starch in mature pollen only
D.Trypan blue exclusion to confirm microspore viability rather than stage
Correct Answer: Acetocarmine (or DAPI) squash of a sample anther to count microspore nuclei
Explanation:
Acetocarmine (or fluorescent DAPI) staining of a squashed sample anther allows the nuclei to be seen so the microspore stage can be scored (one nucleus = uninucleate). A representative anther from the same bud is sampled while sibling anthers of the correct stage are cultured.
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60A researcher obtains many embryo-like structures from anther culture but they arrest before forming shoots. Which manipulation is the most logical next step to promote conversion to plantlets?
to isolate and inoculate anthers for haploid production
Hard
A.Increase the -D concentration greatly to force the embryos into more callus
B.Return the cultures to prolonged cold to restart the sporophytic switch
C.Transfer embryos to a fresh regeneration medium with an adjusted cytokinin:auxin balance favoring shoot organogenesis
D.Add colchicine immediately to double the arrested embryos before any shoot forms
Correct Answer: Transfer embryos to a fresh regeneration medium with an adjusted cytokinin:auxin balance favoring shoot organogenesis
Explanation:
Microspore-derived embryos often require transfer from the induction medium to a regeneration medium with a cytokinin-favoring hormone balance to complete shoot and plantlet development. Adding more -D would push toward callus, and cold or colchicine do not solve the conversion block.
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