agriculture2

Question 1

Plant breeding is

Answer 1

an art and science of improving the heredity
of plants for the benefit of mankind

Question 2

n i vavilov

Answer 2

“Studies on the Origin
of
Cultivated Plants”

Question 3

A center of origin (or centre of diversity)

Answer 3

is a geographical area
where a group of organisms, either domesticated or wild, first
developed its distinctive properties.

Question 4

1.crop plants evolved from
wild species in the areas showing great diversity and termed
them as Primary centres of origin.

Answer 4

Main features of these centres are given below:
1. They have wide genetic diversity.
2.Have large number of dominant genes.
3.Mostly have wild characters.
4. Exhibit less crossing over.
5. Natural selection operates

Question 5

2.crop species show considerable diversity of
forms although they did not originate there; such areas are
known as Secondary centres of origin.
E.g. Sorghum. The primary centre of origin for this crop is
Africa but India exhibits maximum diversity for this crop

Answer 5

main features.
1. Have lesser genetic diversity than primary centres.
2. Have large number of recessive genes.
3. Mostly have desirable characters.
4. Exhibit more crossing over
5. Both natural and artificial selections operate.

Question 6

3. Microcenters:J. R. Harlon made exploration to turkey and
   added micro centres.
   *In some case, small areas within the centres of
   diversity exhibit tremendous genetic diversity of
   some crop plants.

Answer 6

main features of micro centres are
1.They represent small areas within the centres of diversity.
2.Exhibit tremendous genetic diversity.
3.The rate of natural evolution is faster than larger areas.
4.They are important sites for the study of crop evolution.

Question 7

CoO

Answer 7

central america - corn &chily
south america- potato &peanut
mediteran- olive and cabbae
west asia - wheat&barley
hornafrica- coffee
india- chickpea &apple
china - soybean
southeast asia- sugarcane &rice

Question 8

Law of homologous series of variation.
* Vavilov also developed the concept of parallel series of
variation or Law of homologous series of variation.

Answer 8

• This concept states that a particular variation observed in a crop
  species is also expected to be available in its another related
  species

Question 9

OBJECTIONS TO VAVILOV’S THEORY

Answer 9

• According to Vavilov whenever a crop plant exhibits
  maximum diversity, that place is the centre of origin for that
  crop. But this view is no longer valid. E.g. maize and tomato.
• For maize the centre of diversity is Peru but
  archeological evidence shows Mexico as centre of origin.
• For tomato, South America is considered to be primary centre
  of origin but it is Mexico as per archeological evidence.
• Secondly Vavilov stated that primary centre is marked by a
  high frequency of dominant genes in the centre and recessive
  genes towards the periphery. But it is not so. E.g. Wheat,
  maize, oil palm
• Vavilov’s claim that centre of origin confined to mountainous
  regions only. But this is not the case. For E.g. Maize exhibits
  maximum diversity in plains
• Many crops have more than one centre of origin E.g. Balsam,
  Sorghum. In some crops centre of domestication cannot be
  determined for want of suitable evidence.
• Vavilov could not adequately cover Africa.
• Australia was not at all covered.
• These two continents have tremendous wealth of crop
  genetic diversity of several crop plants

Question 10

Megagene centre and Microgene centres

Answer 10

*Zhukovsky, in 1965, recognised 12 mega-gene centres of
crop plant diversity.
*Mega gene centres were the places where cultivated
plant species exhibit diversity
*micro gene centre is the place where wild species
occur.
The cultivated forms are believed to have first
originated in these microgene centres.
*These centres may not be the centres of origin of the
species concerned, but they are the areas of the maximum
diversity of these species.

Question 11

PLANT GENETIC RESOURCES - GERMPLASM
genetic resources or
gene pool or
genetic stock

Answer 11

The sum total of hereditary material i.e. all the
alleles of various genes, present in a crop species
and its wild relatives is referred to as germplasm.

Question 12

Components/Types of germplasm

Answer 12

a. Landraces (J.R.Harlan, 1975) : Primitive cultivars selected and
cultivated by farmers for many generations.
Main features
* These were not bred like modern cultivars and evolved
under subsistence agriculture
* Have high level of genetic diversity with high degree of
resistance to biotic and abiotic stresses
* Have broad genetic base with wider adaptability and
protection from epidemic pests and diseases
* They have recognizable morphology, name, nutritive value
* They are genetically diverse and balanced populations
4
Components/Types of germplasm (contd.,)
b. Obsolete cultivars
*Improved varieties of recent past
*These were popular earlier and now have been replaced by new
varieties
*These have desirable characters and constitute an important part in
gene pool
*Eg. Wheat varieties K65, K68, Pb 591
*(Popular traditional tall varieties, have attractive grain colour and
chapatti making quality and good genetic resources and widely
used in wheat breeding programes for improvement of grain
quality)
5
Components/Types of germplasm (contd.,)
c. Modern cultivars
*Currently cultivated high yielding varieties
*High yielding and uniformity and constitute a major part of working
collections and used as parents in breeding programmes
*However, these have narrow genetic base and low adaptability
compared to land races
d. Advanced breeding lines
*Pre-released plants which have been developed by plant breeders for
use in modern scientific plant breeding and are valuable part of gene
pool
6
Components/Types of germplasm (contd.,)
e. Wild forms of cultivated species
*Have high degree of resistance to biotic and abiotic stresses
*These are utilized in breeding programs
f. Wild relatives
*Those naturally occurring plant sps. which have common
ancestry with crops and can cross with crop sps.
*These are important sources of resistance to stresses
7
Components/Types of germplasm (contd.,)
g. Mutants
*Through mutation breeding, extra variability is created in
cultivated sps.
Eg. Mutant gene pool Dee-Geo-Woo-Gen in rice and Norin 10
in wheat proved to be valuable genetic resources in
development of high yielding and semi dwarf varieties in the
respective cro

Question 13

Gene pool concept
Proposed by Harlan and De Wet in 1971.
Gene pool consists of all the genes and their alleles
present in all such individuals, which hybridize with
each other

Answer 13

Classification of gene pool on the basis
1. Area of collection
a)Indigenous (collected within the country)
b)exotic (collected from other country)
2. Domestication
a)Cultivated (germplasm of domesticated species)
b)Wild (germplasm of uncultivated species)

Question 14

genepool classifi

Answer 14

3. Duration of conservation
   1.Base collection, 2. Active collection 3. Working collection
   Base collection
   *Plant materials which are meant for long term storage
   *Regeneration is carried out after a long time dep. on viability
   *Seed viability should not drop to 95% before regeneration
   *Seeds with 5 ± 1% moisture content and stored at -18 to -20˚C
   10
   Active collection
   *Meant for medium term storage (10-15 years)
   *Subjected
   to
   regeneration,
   multiplication,
   distribution, documentation after every 10-15 years
   *Stored at zero ˚C and moisture should be around 8%
   *Routine germination after every 5-10 years
   Working collection
   *Stored for short term (3 to 5 years)
   *Regularly used in crop improvement programmes
   * No need to grow such materials every year
   *Stored at 5-10˚C with moisture content of 8-10%
4. Crossability
5. Primary gene pool
6. Secondary gene pool
7. Tertiary gene pool
   evaluation,
   11
   Primary gene pool (GP1)
   * Crossing is easy and leads to production of fertile hybrids.
   * Includes plants of the same species or closely related sps.
   * Genes can be exchanged b/w lines by normal crosses
   Secondary gene pool (GP2)
   * Leads to partial fertility on crossing with GP1
   * Includes plants belonging to related sps.
   * on crossing with GP1, resultant hybrids are sterile and
   some are fertile
   * Transfer of gene from such material to GP1 is possible
   but
   difficult
   Tertiary gene pool (GP3)
   * Leads to production of sterile hybrids on crossing with
   GP1
   * Includes material which can be crossed with GP1 but
   hybrids are sterile
   12
   * Transfer of genes from GP3 to GP1 is possible with help

Question 15

Genetic erosion

Answer 15

The gradual loss of variability from cultivated species,
and their wild forms and wild relatives is called genetic
erosion.
Main causes of genetic erosion
*Replacement of genetically variable land races by the
improved genetically uniform pureline or hybrids
*Improved crop management practices have eliminated the
weedy forms of many crops
*Increasing human needs have extended farming and
grazing into forests, the habitats of most wild species
*Development activities like hydroelectric projects, roads,
industrial areas, railways, buildings, etc. have disturbed
the wild habitat
*Introduction of a weedy species may result in the
invasion of wild habitats by this species and lead to the
elimination of the native wild relatives of crops

Question 16

Activities in Germplasm Maintenance

Answer 16

1.Exploration and collection
2.Conservation
3.Evaluation
4.Documentation
5.Distribution
6.Utilization

Question 17

1.Germplasm Conservation
Conservation refers to protection of genetic diversity of
crop plants from genetic erosion.
Two important methods of germpalsm conservation
i) In-situ conservation ii) ex situ conservation.

Answer 17

i) In - situ conservation:
Conservation of germplasm under natural conditions is
referred to as in situ conservation. This is achieved by
protecting the area from human interference.
Such an area is often called natural park, biosphere reserve
or gene sanctuary. NBPGR, New Delhi has established gene
sanctuaries in Meghalaya for citrus, North Eastern regions
for musa, citrus, oryza and saccharum.
16
Advantage and disadvantages of In - situ conservation
Merit:
The wild species and the complete natural or
semi natural ecosystems are preserved together.
Demerits:
*Each protected area will cover only very small portion of
total diversity of a crop species, hence several areas will
have to be conserved for a single species.
*The management of such areas also poses several
problems.
*This is a costly method of germplasm conservation.
17
ii) Ex - situ conservation:
It refers to preservation of germplasm in gene
banks. This is the most practical method of germplasm
conservation.
Advantages
* It is possible to preserve entire genetic diversity of a
crop species at one place.
* Handling of germplasm is also easy.
* This is a cheap method of germplams conservation.
This type of conservation can be achieved in 5 ways.
a) Seed banks:
Germplam is stored as seeds of various genotypes.
Seed conservation is quite easy, relatively safe and
needs minimum space .
Seeds are classified on the basis of their storability
into two major groups.
1) Orthodox 2) Recalcitrant
18
Orthodox seeds: Seeds which can be dried to low
moisture content (5%) and stored at low temperature
without losing their viability for long periods of time is
known as orthodox seeds. (eg.) Seeds of corn, wheat, rice,
carrot, papaya, pepper, chickpea, cotton, sunflower.
Recalcitrant: Seeds which show very drastic loss in
viability with a decrease in moisture content below 12 to
13% are known as recalcitrant seeds. (e.g) citrus, cocoa,
coffee, rubber, oilpalm, mango, jack fruit etc.
Seed storage:
Based on duration of storage, seed bank collections
are classified into three groups. (1) Base collections (2)
Active collections and (3) Working collection.
19
b. Plant Bank: ( Field gene bank )
It is an orchard or a field in which accessions of fruit trees or
vegetatively propagated crops are grown and maintained.
Limitations: 1. Require large areas
2. Expensive to establish and maintain.
3. Prone to damage from disease, insect attacks
4. Man – made
5. Natural disasters
6. Human errors in handling
c. Cell and organ banks:
A
germplasm collection based on cryopreservation
(at – 196OC in liquid nitrogen) in the form of embryogenic cell
cultures, somatic/ zygotic embryos.
d.DNA banks:
In these banks, DNA segments from the genomes of
germplasm accessions are maintained and conserved.
20
e. Shoot tip banks:
Germplasm is conserved as slow growth cultures of
shoot-tips and nodal segments.
Advantages
* Each genotype can be conserved indefinitely free from
virus or other pathogens.
* It is advantageous for vegetatively propagated crops like
potato, sweet potato, cassava etc., because seed
production in these crops is poor
* Vegetatively propagated material can be saved from
natural disasters or pathogen attack.
* Long regeneration cycle can be envisaged from meristem
cultures.
* Regeneration of meristerms is extremely easy.
* Plant species having recalcitrant seeds can be easily
conserved by meristem cultures.

Answer 18

Central tuber crops research
Institute(CTCRI), - Tuber crops other
than potato

Thiruvananthapuram
Central Rice Research Institute,
(CRRI)Cuttack- Rice
Central Institute for Cotton
Research (CICR), Nagpur
2 Central Plantation Crops Research
Institute(CPCRI), Kasargod
3 Central Potato Research Institute,
Shimla
IRRI
CIMMYT
ICRISAT

Question 19

2. NBPGR (National Bureau of Plant Genetic Resources),
   New Delhi - Established by ICAR in 1976

Answer 19

Basic function is to conduct research and promote
collection, conservation, evaluation, documentation and
utilization of crop genetic resources in India

Main functions of NBPGR
* Sole agency in India for export and import of plant genetic
resources and helps in exchange of germplasm
*Promotes national genetic resources activities
* Five stations in India 1.Shimla,HP 2.Jodhpur,Rajastan
3. Akola,Maharastra 4. Kanyakumari 5. Shillong, Meghalaya
*Organizes national and intl. explorations to collect GP
*Provides guidance about cold storage facilities for medium
and short term conservation of germplasm
*Takes decision about setting up of gene sanctuaries for
endangered species in India
15
Activities of NBPGR
*Introduces required germplasm from its other agencies in other
countries
*Explorations inside and outside the country to collect valuable
germplasm
*Testing, multiplication and maintenance of germplasm obtained
*Supplies germplasm to various institutions on request
*Supplies germplasm to its counterparts or other agencies in other
countries
*Maintains records of plant name, variety name, propagating
material, special characteristics, source, date and other
information about germplam
*Publishes its exchange and collection lists.
*Sets up the natural gene sanctuaries of plant
*Looks after improvement of certain plants like medicinal and
aromatic plants

Question 20

Mechanisms promoting self-pollination

Answer 20

1. Cleistogamy
   In this case, flower does not open at all. This ensures
   complete self- pollination since foreign pollen cannot reach
   the stigma of a closed flower. Cleistogamy occurs in some
   varieties of wheat (Triticum sp.), oats (Avena sp.) barley (H.
   vulgare) and in a number of other grasses.
2. Chasmogamy
   In some species, the flowers open, but only after
   pollination has taken place. This occurs in many cereals,
   such as, wheat, barley, rice and oats. Since the flower does
   open, some cross-pollination may occur.
3. In crops like tomato (L. esculentum) and brinjal
   (S. melongena) the stigmas are closely surrounded by
   anther. Pollination generally occurs after the flowers open.
   But the position of anthers in relation to stigmas ensures
   self-pollination.
   25
4. In some species, flowers open but the stamens and the
   sigma are hidden by other floral organs. In several
   legumes, e.g., pea (P. sativum), mung (V. radiate), urd
   (V.mungo), soybean (G. max) and gram (C.arietinum), the
   stamens and the stigma are enclosed by the two petals
   forming a keel.
5. In a few species, stigmas become receptive and
   elongate through the staminal columns. This ensures
   predominant self-pollination.

Question 21

echanism promoting cross pollination

Answer 21

1.Dicliny or unisexality is a condition, in which the flowers are
either staminate (male) or pistillate (female)
1(a). Monoecy. Staminate and pistillate flowers occur in the
same plant, either in the same inflorescence, e.g., castor,
mango (Mangifera indica), banana(Musa sapientum) and
coconut or in separate inflorescences, e.g, maize.
1(b). Dioecy. The male and female flowers are present at
different plants, i.e., the plants in such species are either male
or female, e.g, papaya (C. papaya), datepalm, palmsugar

2. Dichogamy
   Stamens and pistils of hermaphrodite flowers may
   mature at different times facilitating cross-pollination.
   2a. Protogyny In crop species like bajra, pistils mature
   before stamens. Eg. Cumbu
   2b. Protandry In crop like maize and sugarbeets, stamens
   mature before pistils. Eg. Maize
3. In Lucerne or alfalfa, stigmas are covered with a waxy film.
   The stigma does not become receptive until this waxy film is
   broken. The waxy membrane is broken by the visit of honey
   bees, which also effect cross-pollination.
4. A combination of two or more of the above mechanisms
   may occur in some species. This improves cross-pollination.
   Eg. maize exhibits both monoecy and protandry.

• 5) Heterostyly: Different length of style and
  filaments E.g Linseed.
• 6) Herkogamy: Presence of physical barrier or
  mechanical obstacles between the anther and
  stigma ensures cross pollination. E.g.
  (Calotropic gigantia).
  7. Self- incompatibility. It refers to the inability of viable pollen
  to fertilize the same flower or other flowers on the same plant.
  Self-incompatibility is of two types: sporophytic and
  gametophytic. In both the case, flowers do not set seed on
  selfing. Self-incompatibility is common in several specie of
  Brassica (mustard, cauliflower) some species of Nicotiana,
  radish, rye and many grasses. It is highly effective in
  preventing self-pollination.
  8. Male Sterility. Male sterility refers to the absence of
  functional pollen grains in otherwise hermaphrodite flowers.

Question 22

Genetic Consequences of
Cross Pollination

Answer 22

1) It preserves and promotes heterozygosity in
population.
2) Cross pollinated species shows inbreeding depression
and considerable heterosis.
3) Usually hybrid and synthetics without reducing
heterozygosity

Question 23

Self – Incompatibility: It refers to the failure of pollen grain to fertilize
the same flower or other flower on the same plants.

Answer 23

• Incompatibility may occur due to the lot of reason.
• 1) Pollen grain fails to germinate on the stigma.
  2) Pollen grain germinates but the pollen tube fails to enter the stigma.
  3) Sometimes pollen tube enters the style but growth is very slow to
  effect fertilization.
  4) Pollen tube enters the ovule but there is no fertilization due to
  degeneration of egg cell.
  5) Fertilization is effected but embryo degenerate at very early stage.

Question 24

Main features of self incompatibility

Answer 24

1. Self incompatibility is an important outbreeding
   mechanism which prevents autogamy and promotes
   allogamy
2. Self incompatible species do not produce seed on self
   pollination but lead to normal seed set on cross
   pollination
3. It maintains high degree of heterozygosity in a species
   due to outbreeding and reduces homozygosity due to
   elimination of inbreeding or selfing
4. Self incompatibility results due to morphological, genetic,
   physiological and biochemical causes. It is not under
   simple genetic control

Question 25

Measures to overcome self incompatibility

Answer 25

1.Bud pollination
Pollination of immature buds with mature pollens has been
successful in the production of large quantity of self seed in
Brassica, Nicotiana. This method is now used for the
development of inbred lines for hybrid seed production in
Brassica species. The bud pollination should be done 2 to 4
days before flower opening
2. Delayed pollination
Pollination of aged pistils several days after maturity with
normal incompatible pollen resulted in some degree of self
fertilization in Brassica and Linum
29
3.Late season pollination
Self pollination at the end of flowering season also leads to
seed set in Nicotiana. This may be due to loss of capacity to
produce active incompatibility substances at the end of
flowering.
4.Irradiation
Irradiation of style with x-rays immediately before selfing
resulted in breakdown of self incompatibility in Petunia.
Gamma irradiation significantly increased seed setting upon
selfing in Nicotiana alata.
5. High temperature
Treatment of style at temperatures ranging from 30˚C to 60˚C
leads to breakdown of self incompatibility in Pyrus, Prunus.
Heat treatment inactivates the substance or enzyme which
causes self incompatibility.
30
6. Mutilation of style
Removal of stigma with steel wire brush during
pollination in species having stigmatic self incompatibility
results in certain amount of seed production in Brassica.
7. In vitro fertilization
Placing of pollen grains in direct contact with ovule
resulted in breakdown of self incompatibility in crop
species like Petunia. This indicates that restriction of
interference from the stigma, the style or the ovary leads
to breakdown of self incompatibility.
Mixed Pollination:Pollen from a compatible donor plant is mixed with pollen from the self-incompatible plant and applied to the stigma. The compatible pollen can sometimes trigger the acceptance of the self-pollen.
- Example: This method is occasionally used in some vegetable crops like cabbage.
3. Artificial Pollination: Physical methods, such as rubbing or brushing, are used to force pollen onto the stigma, bypassing the self-incompatibility mechanism.
- Example: Used in breeding programs for crops like alfalfa.
Genetic Modification: Genetic engineering techniques are used to modify or disable the self-incompatibility genes.
- Example: Transgenic approaches in crops like tobacco have shown success in overcoming self-incompatibility.
6. Chemical Treatments: Application of certain chemicals to the stigma can inhibit the self-incompatibility response, allowing self-pollination.
- Example: In some cases, chemicals like calcium chloride have been used to facilitate self-pollination in certain plants.
7. Grafting: Grafting a self-compatible plant or part (like a branch) onto a self-incompatible plant can bypass the self-incompatibility mechanism.
- Example: Commonly used in fruit tree breeding, such as in cherries and almonds.

Question 26

SI appln

Answer 26

Utilization in plant breeding
*Production of hybrids
Self incompatibility provides a way for hybrid seed
production without emasculation (Brassica and sunflower).
The harvest from both SI lines sown adjacent to each other
would be hybrid seed
*Combining Desirable genes
Self incompatibility system permits combining of desirable
genes in a single genotype from two or more different
sources through natural cross pollination which is not
possible in self compatible species
Limitations of self incompatibility
*It is very difficult to produce homozygous inbred lines
in a self incompatible species. Bud pollination has to
be made to maintain the parental lines.
*It is affected by environomental factors such as
temperature and humidity. Incompatibility is reduced
or broken down at high temperature and humidity.
*Sometimes, bees visit only one parental line in the
seed production plot resulting in sib mating. This also
poses problems in the use of self incompatibility in
hybrid seed production programmes

Question 27

Mechanisms of Self-Incompatibility

Answer 27

1. Gametophytic Self-Incompatibility (GSI)
   - In GSI, the self-incompatibility response is determined by the genotype of the pollen grain (the gametophyte).
   - The recognition of self-pollen occurs in the style of the flower.
   - When pollen from the same plant or a genetically similar plant lands on the stigma, specific proteins in the style recognize the self-pollen.
   - These proteins typically include S-RNases and other proteins that degrade the RNA of self-pollen tubes, preventing them from growing and reaching the ovary.
   - Solanaceae: Tomato (Solanum lycopersicum), Petunia (Petunia spp.)
   - Rosaceae: Apple (Malus domestica), Pear (Pyrus spp.)
   - Papaveraceae: Poppy (Papaver rhoeas)
   #### 2. Sporophytic Self-Incompatibility (SSI)
   - In SSI, the self-incompatibility response is determined by the genotype of the pollen-producing plant (the sporophyte).
   - Recognition occurs on the stigma surface.
   - The stigma contains specific receptor proteins that interact with proteins on the pollen coat.
   - If the pollen is recognized as self-pollen, the interaction triggers a signal transduction pathway that inhibits pollen germination or pollen tube growth.
   - Brassicaceae: Cabbage (Brassica oleracea), Mustard (Brassica juncea),
   - Asteraceae: Sunflower (Helianthus annuus), Lettuce (Lactuca sativa)

Question 28

Male Sterility

Answer 28

• Male sterility is characterized by nonfunctional pollen grains,
  while female gametes function normally.
• Inability to produce or to release viable or functional pollen as
  a result of failure of formation or development of functional
  stamens, microspores or gametes

Question 29

Why Male Sterility ???

Answer 29

*Reduced the cost of hybrid seed production.
*Production of large scale of F1 seeds.
*Avoids enormous manual work of emasculation and
pollination.
*Speed up the hybridization programme.
5
*Commercial exploitation of hybrid vigour

Question 30

MS

Answer 30

Genetic Male Sterility (GMS)
* Also called as nuclear male sterility
* Mostly governed by single recessive gene (ms) but dominant gene
* governing male sterility (safflower).
* Origin: Spontaneous mutation or artificial mutations (Gamma rays,
EMS) are common
* ‘ms’ alleles may affect staminal initiation, stamen or anther sac
development, PMC formation, meiosis, pollen formation,
maturation and dehiscence.
* This type of male sterility is used in Redgram and Castor for
production of hybrids. 9
Genetic structure :
A line
ms
ms
In Redgram there are number of GMS lines are
available. E.g. Ms Co5, Ms T21
10
Inheritance & Maintenance Of Male Sterile Line
11
Nuclear male sterility and hybrid seed production
12
DIFFICULTIES IN USE OF GMS
* Maintenance of GMS requires skilled labour to identify
fertile and sterile line.
* Labelling is time consuming and costly
* In hybrid seed production plot identification of fertile line and
removing them is costly.
* Use of double the seed rate of GMS line is costly.
* In crops like castor high temperature leads to break down of
male sterility.
13
Cytoplasmic Male Sterility (CMS)
*Determined by the cytoplasm (mitochondrial or chloroplast genes).
*Result of mutation in mitochondrial genome (mtDNA)- Mitochondrial
dysfunction.
*Progenies would always be male sterile since the cytoplasm comes
primarily from female gamete only.
*Nuclear genotype of male sterile line is almost identical to that of
the recurrent pollinator strain.
*Male fertile line (maintainer line or B line) is used to maintain the
male sterile line (A line).
*CMS is not influenced by environmental factors (temperature) so is
stable.
14
Utilization of CMS in Plant Breeding
* CMS can used in hybrid seed production of certain ornamental
species or in species where a vegetative part is of economic
value.
* But not for crop plants where seed is the economic part
because the hybrid progeny would be male sterile.
* This type of male sterility found in onion, fodder jowar,
cabbage etc.
15
Use of CMS lines
16
Transfer of CMS to new strains (Diversification)
17
Cytoplasmic Genetic Male Sterility (CGMS)
* CGMS is also known as nucleoplasmic male sterility.
* In Case of CMS, where a nuclear gene (R) for restoring fertility
in male sterile line is known.
* R (restorer gene) is generally dominant can be transferred
from related strains or species.
* This system is known in maize, jowar, bajra, sunflower and
rice
18
Requirements for 3 Lines in CGMS System
A-line (Male sterile line)
1)Stable Sterility
2)Well developed floral traits for outcrossing
3)Easily, wide-spectum, & strongly to be restored
B-line (Maintainer line)
1)Well developed floral traits with large pollen load
2)Good combining ability
R-line (Restorer line)
1)Strong restore ability
2)Good combining ability
3)Taller than A-line
4)Large pollen load, normal flowering traits and timing
19
Hybrid seed production using CGMS system
20
Transfer of Restorer gene ‘R’ to non restorer strain
21
Sources of CMS & Restorer genes in some Crops
22
Sources of CMS & Restorer genes in some Crops(contd.,)
23
Male Sterility based Hybrids in Important Crops
24
Limitations of CGMS lines
* Fertility restoration is a problem. E.g. Rice.
* Seed set will be low in crops like Rice where special techniques
are to be adopted to increase seed set.
* Break down of male sterility at higher temperature.
* In crops like wheat having a polyploidy series it is difficult to
develop effective R line.
* Undesirable effect of cytoplasm. E.g.Texas cytoplasm in
maize became susceptible to Helminthasporium. In bajra
Tift 23 A cytoplasm became susceptible to downy mildew.
* Modifier genes may reduce effectiveness of cytoplasmic male
sterility.

Sources of male sterility
*Spontaneous mutations
*Induced mutations
Physical & chemical mutagens
*Interspecific crosses (wild x cultivated)
29
Utilization of male sterility in plant breeding
Development of hybrids
GMS
Development of commercial hybrids in both seed
propagated and vegetatively propagated plants.
CMS
Development of hybrids in vegetatiively propagated
plants, forage and ornamental plants where vegetative
part is the economic product.
CGMS
Development of commercial hybrids in both seed
propagated and vegetatively propagated plants.
30
Significance of male Sterility in Plant Breeding
* Male sterility a primary tool to avoid emasculation in
hybridization.
* Hybrid production requires a female plant in which no viable
pollens are borne. Inefficient emasculation may produce some
self fertile progenies.
* GMS is being exploited (Eg.USA-Castor, India-Arhar).
* CMS/ CGMS are routinely used in Hybrid seed production in
corn, sorghum, sunflower and sugarbeet, ornamental plants.
* Saves lot of time, money and labour.
31
Limitations in using Male Sterile line
* Existence and maintenance of A, B & R Lines is laborious and
difficult.
* If exotic lines are not suitable to our conditions, the
native/adaptive lines have to be converted into MS lines.
* Adequate cross pollination should be there between A and R lines
for good seed set.
* Synchronization of flowering should be there between A & R
lines.
* Fertility restoration should be complete otherwise the F1 seed
will be sterile. Isolation is needed for maintenance of parental
lines and for producing hybrid seed

Question 31

Types of Male Sterility with Examples

Answer 31

1. Genetic Male Sterility (GMS)Controlled by nuclear genes, often following Mendelian inheritance patterns.
   
   • Example: In maize (Zea mays), male sterility can be controlled by the ms (male sterile) genes, such as ms1, ms2, etc.
2. Cytoplasmic Male Sterility (CMS) Controlled by the plant’s cytoplasmic (usually mitochondrial) genome and is maternally inherited.
   
   • Example: In rice (Oryza sativa), the CMS-WA (wild abortive) system is widely used for hybrid seed production.
3. Genetic-Cytoplasmic Male Sterility (GCMS) Involves both nuclear and cytoplasmic genes, where the nuclear genes interact with the cytoplasmic factors to cause male sterility.
   
   • Example: Sunflower (Helianthus annuus) uses PET1 cytoplasm combined with specific nuclear restorer genes to manage male sterility.
4. Thermosensitive Genetic Male Sterility (TGMS) Male sterility is induced by high or low temperatures, and fertility can be restored by changing the temperature.
   
   • Example: In rice, the TGMS line “Pei’ai 64S” becomes sterile at higher temperatures and fertile at lower temperatures.
5. Photoperiod-sensitive Genetic Male Sterility (PGMS) Male sterility is influenced by the length of day (photoperiod), with sterility induced under specific light conditions.
   
   • Example: In rice, the PGMS line “Nongken 58S” becomes sterile under long-day conditions and fertile under short-day conditions.
6. Chemically Induced Male Sterility (CIMS) Male sterility is induced by chemical treatments that prevent the development of functional pollen.or ethydium bromide
   
   • Example: In wheat (Triticum aestivum), chemicals like ethrel or sodium methyl arsenate can be used to induce male sterility temporarily.
7. Transgenic male sterility-Barnase/Barstar System in Brassica napus (Canola)

Question 32

Advantages of PGMS & TGMS systems in twoline breeding

Answer 32

• There is no need for maintainer line; hence, procedure for
  development of hybrids is simpler.
• Any genotype can be utilized as male parent; there is no
  need that it should possess restorer genes; hence, the
  chances of development of heterotic hybrids are greatly
  increased.
• Negative effects associated with sterility inducing
  cytoplasm are avoided.
• Seed production programme is simple and more efficient.
• Roguing of male fertile plants from the female line is costly
  as a result of which the cost of hybrid seed is higher. Use of
  TGMS or PGMS eliminates this problem.

Question 33

Chemical Induced Male Sterility
* CHA is a chemical that induces artificial, non-genetic male sterility
in plants so that they can be effectively used as female parent in
hybrid seed production.
* Also called as Male gametocides, male sterilants, selective male
sterilants, pollen suppressants, pollenocide, androcide etc.

Answer 33

Properties of an Ideal CHA
*Must be highly male or female selective.
*Should be easily applicable and economic in use.
*Time of application should be flexible.
*Must not be mutagenic.
*Must not be carried over in F1 seeds.
*Must consistently produce >95% male sterility.
*Must cause minimum reduction in seed set.
*Should not affect out crossing.
*Should not be hazardous to the environment
Hybrid Seed Production based on CHAs
Conditions required:
1.Proper environmental conditions (Rain, Sunshine, temp, RH
etc.)
2.Synchronisation of flowering of Male & Female parents.
3.Effective chemical emasculation and cross pollination
4.CHA at precise stage and with recommended dose
5.GA3 spray to promote stigma exertion.
6.Supplementary pollination to maximise seed set
7.Avoid CHA spray on pollinator row.

Advantages of CHAs
*Any line can be used as female parent.
*Choice of parents is flexible.
*Rapid method of developing male sterile line.
*No need of maintaining A,B&R lines.
*Hybrid seed production is based on only 2 line system.
*Maintenance of parental line is possible by self pollination.
*CHA based F2 hybridsarefully fertile as compared to
few sterile hybrids in case of CMS or GMS.

Limitations of CHAs
*Expression and duration of CHA is stage specific.
*Sensitive to environmental conditions.
*Incomplete male sterility produce selfed seeds.
*Many CHAs are toxic to plants and animals.
*Possess carryover residual effects in F1 seeds.
*Interfere with cell division.
*Affect human health.
*Genotype, dose application stage specific.

Question 34

apomixix

Answer 34

Apomixis - Parts of a flower
*Seeds are formed and embryos develop without
fertilization.
*Plants resulting from apomixis are identical in
genotype to the female parent .
*When sexual reproduction does occur, apomixis
is termed as facultative.
*When sexual reproduction is absent, it is
referred as obligate.
3
Apomixis
* Apomixis is very common in angiosperms and
pteridophytes, but was so far not detected in
gymnosperms.
* It is widespread in some grasses (Poa), Rosacea
(Rubus, Sorbus), Compositae (Achillea, Crepis,
Hieracium, Taraxacum), and Rutaceae (Citrus).
4
* Agamospermy is asexual seed formation.
Asexual reproduction in which seeds are produced
from unfertilized ovules
* Agamospermy and vegetative propagation are
collectively also called apomixis
5
*When embryos arise from hapliod cells, apomixis is
termed as nonrecurrent because the progeny so
obtained cannot be maintained further.
*But when embryos arise from diploid cells, it is
called recurrent as the progeny so obtained can be
perpetuated indefinitely.
*Genetics of apomixis :It is governed by one or two
genes, which may be either dominant or recessive.
6
Apomixis classification
1. Adventive embryony
2. Gametophytic embryony
i. Apospory
ii. Diplospory
a. Parthenogenesis
b. Apogamy
7
OVULE
8
*1. Adventive embryony
Embryos develop directly from vegetative
cells of the ovule such as nucellus, integument
and chalaza.
Embryosac is not produced
Eg. mango. Citrus, etc.
9
Classification of Apomixis
1. Adventive embryony
2. Gametophytic embryony
i. Apospory
ii. Diplospory
a. Parthenogenesis
b. Apogamy
*Embryos develop without fertilization from egg cell or
other cells of embryo sacs.
*In recurrent apomixis, unreduced embryo sacs are
produced by a process of apomeiosis
*Apomeiosis - “Without meiosis”; usually meaning the
production of a meiotically unreduced gametophyte.
2. Gametophytic Apomixis :
10
1. Adventive embryony
2. Gametophytic embryony
i. Apospory
ii. Diplospory
a. Parthenogenesis
b. Apogamy
2. Gametophytic Apomixis :
i. Apospory
Some vegetative cell of the ovule develop into
unreduced embryo sac through a series of mitotic
division.
Embryo develop from the egg cell or other cell of
the embryo sac.
Eg. Hieraceum, Malus, Crepis, Orchids, Ranunculus,
etc
11
1. Adventive embryony
2. Gametophytic embryony
i. Apospory
ii. Diplospory
a. Parthenogenesis
b. Apogamy
ii. Diplospory
Embryosac is produced from megaspore, which remains diploid,
occassionally haploid. Diplospory leads to parthenogenesis or apogamy
❖ Parthenogenesis: Embryo develops from egg cell without fertilisation.
Haploid parthenogenesis: Nicotiana, Crepis,Solanum nigrum, maize
Diploid parthenogenesis: Taraxacum
* Apogamy : Synergids or antipodal cells develop into an embryo.
Apogamy may be haploid or diploid depending on the state of
embryosac.
Diploid apogamy occurs in Allium,Antennaria, Alchemilla
12
1. Adventive embryony
2. Gametophytic embryony
i. Apospory
ii. Diplospory
a. Parthenogenesis
b. Apogamy
13
* Pseudogamy(centrogamy)
* Pollination is necessary for embryo development, but fertilization
of the egg cell does not take place. Fertilization of the secondary
nucleus, however, occurs and is necessary for endosperm
development. It is of two types 1. gonial pseudogamy 2. somatic
pseudogamy
* 1. Gonial pseudogamy: embryos develop from egg cell
* 2. Somatic pseudogamy: embryos arise from some other cell of
the embryo sac other than the egg cell.
14
* Androgamy :
* It is the development of embryo neither from egg cell
nor from synergids or antipodals, but from one of the
male gametes itself, inside or outside the embryo-sac.
Since it is haploid, it is non-recurrent apomixis.
* Parthenocarpy, development of fruits without
fertilization. It is the phenomenon of fruiting without the
union of male and female gametes. The lack of
fertilization results seedless fruits.
* Seedless grapes
15
Types of parthenocarpy
* stimulative parthenocarpy: In some plants, pollination or
other stimulation is required for parthenocarpy. This is
termed stimulative parthenocarpy. Eg. Seedless
watermelon , seedless banana
* vegetative parthenocarpy : Plants that do not require
pollination or other stimulation to produce parthenocarpic
fruit. Eg. Seedless cucumbers
16
* Seedless fruits can be developed in two ways:
* either they can be developed by parthenocarpy or
stenospermocarpy.
* In parthenocarpy, fruits develop without any fertilization.
* In stenospermocarpy, fruit development is triggered by
pollination, but the ovules or embryo abort and do not
produce mature seeds. Eg. Seedless grapes variety
Thomson seedless
17
* Development of apomictic lines
1. Gene transfer from wild species
2. Induced mutations
3. Isolation
of
apomictic
interpsecific crosses
recombinants
from
18
Applications of apomixis
It is used to achieve
1.Fixation of heterosis
Where apomixis is dominant, a sexually reproducing line is used as the female
parent and an obligate apomictic line is used as the male parent to produce the
hybrid that is apomictic. The hybrid will produce only apomictic seeds, which are
used for maintenance, multiplication and cultivations of the hybrid variety.
sexually reproducing line x obligate apomictic line
↓
Apomictic hybrid
2. Rapid production of pure lines or homozygous lines
3. Development of phenotypically stable populations called vybrids
A Vybrid is the progeny obtained from a cross between two facultative
apomicts.
4. exploitation of maternal effect, if present, is possible from generation to
generation.
19
Significance of Apomixis
* It is of great help when breeder desires to
maintain varieties.
* Once a desirable genotype was selected, it can
be maintained and multiplied apomitically.
* It is used in fixing heterosis
* Reduced cost of hybrid seed production
* It is a nuisance when breeder desires for sexual
progeny or selfs.
20
Advantage of apomixis
1.Apomictic hybrids can be produced by crossing an obligate
apomictic line as male parent with a sexual line. Farmers can
resow the seeds produced by apomictic hybrids generation after
generation.
2.The new hybrid variety could be multiplied from few hybrid seeds
in a manner as are purelines. This greatly simplifies seed
production.
3.Even such parents that flower at different times may be crossed
in a green house to obtain few hybrid seeds, which can be used
to establish the new hybrid variety .

Question 35

drought resistance

Answer 35

** CR Dhan 801 **(2018 ) pyramided with
genes, Sub1, qDTY1.1, qDTY2.1, qDTY3.1 and
**CR Dhan 802 **(2018) pyramided with genes, Sub1, qDTY1.1 were released by
NRRI, Cuttack are resistant to both drought and submergence
drought resistant- Embryo Rescue Technique
interspecific hybrid in sunflower **(Helianthus annuus ×
Helianthus argophyllus; **
* Wheat (Triticum durum × Aegilops tauschii;
* drought guard- maize dought resistance line-transgenic
* tnau cumbu co10- composite
*MAS- Several
drought QTLs such as qDTY2.2 and qDTY4.1 were introgressed
in IR64 background, resulting in higher grain yield under
reproductive stage drought stress and was released by IIRR,
Hyderabad as IR64drt.

Answer 36

Black gram variety, ADT 5 is a Pureline selection from
Kanpur variety which is suited to rice fallow and YMV
resistant
Blackgram variety, **VBN (G) 5 (Vamban 1 x UK 17) is YMV **
resistant
MAS-Rice variety, CR Dhan 800, is resistant to both blight and
submergence, pyramided with genes, Sub1, xa5, xa13, Xa21
mutant-MCU 10 cotton, a resistant variety to bacterial blight

Question 37

mutation

Answer 37

Wheat :Sharbathi sonara (gamma rays)
* Castor :** Aruna (th.N)**
* Rice
:Jagannath (x-rays), Prabhavathy (EMS)**