3. What is male sterility?
• Male sterility is the failure of plants to produce functional pollen or
• Male sterility is more prevalent than female sterility. The reason is that
the male sporophyte and gametophyte are less protected from the
environment than the ovule and embryo sac.
• Male sterility can arise spontaneously via mutations in nuclear genes
and/or cytoplasmic or cytoplasmic–genetic. The extranuclear genome is
only maternally inherited.
• Male-sterile plants can set seed and propagate. Female-sterile plants
cannot develop seeds and will not propagate.
4. Cytoplasmic male sterility
The pollen sterility which is controlled by cytoplasmic genes or plasmagenes,
is known as cytoplasmic male sterility. It has been reported in different crop
Cytoplasmic male sterility is under extranuclear genetic control
(mitochondrial or plastid genomes). It shows non-Mendelian inheritance,
with male sterility inherited maternally. Generally, there are two types of
cytoplasm, i.e. Normal and Sterile cytoplasms. These types exhibit reciprocal
Plasmogenes– Cytoplasmic male sterility (CMS) is governed by
plasmogenes located in the mt-DNA, which causes pollen abortion in higher
5. Features of cytoplasmic male sterility
• Plants carrying particular type of cytoplasm are male sterile but will
produce seed if pollinators are present.
• The F1 seeds are male sterile, because there cytoplasm is derived entirely
from female gamete.
• System consists of A line and B line. A line is male sterile and B is male
fertile. They are also isogenic.
• CMS is maintained by crossing of A line with B line.
• CMS cannot be utilized for hybrid seed production without the use of
restorer line, because F1 seeds produce only male sterile plants
• CMS is useful for hybrid development in vegetatively propagated and
ornamental crops where grain is not the economic product.
• Not enfluenced by environment such as low or high temperature.
6. Merits Of CMS
Not influenced by environmental condition such as temperature and day
Requires less area
Demerits of CMS
It cannot be used for development of hybrids in those crops where seed
is the economic product.
Can be used only in asexually propagated species such as sugarcane,
potato and forage crops.
Inferior in agronomic performance
Impossible to restore fertility in hybrids
8. HOST-PATHOGEN INTERACTION
Disease is defined as the state of local or
systemic abnormal physiological
functioning of a plant, resulting from the
continuous, prolonged 'irritation' caused by
phytopathogenic organisms (infectious or
biotic disease agents).
Types of pathogen based
Necrotrophy- plant cells
Biotrophy- plant cells
cells initially alive and
• A pathogen that causes disease
is called virulent
• A pathogen that does not
cause diseases is termed
9. Types of pathogen based on effects:
Necrotrophy - plant cells are killed
Biotrophy - plant cells remain alive
Hemibiotrophy - plant cells initially alive and killed later
10. Types of pathogen
Bacteria - Enter through wounds and stomata, live between plant cells.
Fungi - Filamentous growth with specialized structure for penetration,
feeding in cells. Can penetrate directly into plants and move
intercellularly or through cells.
Viruses - Nucleic acid (+ RNA mostly) encapsulated in aprotein coat
separate by plasmodesmata
11. Classes of plant immune responses
Basal responses: Transcription of genes in response to PAMP recognition.
Hypersensitive response (HR): apoptosis of cells at the site of infection
Systemic acquired immunity: The entire plant become resistance to
Jasmonic acid and/ethylene pathway: The entire plant and neighbouring
plants develop resistance to herbivores.
Non host immunity
13. Steps in plant pathogen interaction
RECOGNITION- Depends on generation of elicitors by the pathogen
Transduction- Signal transduction at the cellular level refers to the
movement of signals.
1. PERCEPTION: it is a surface level phenomenon in which elicitors
from the pathogen are recognized by host receptor.
Perception means how pathogen andhost recognize each other. It may
take place directly or indirectly.
After evaluation of nemeroius physiological, biochemical andgenetic
experiment, different models have gained importance as the basic for
all models is the gene for gene relationship between host and
pathogen tiggering race-specific resistence.
Direct intereaction models
Indirect interaction models
15. Direct Interaction models
Four models have been proposed to demonstrate the nature of
recognition reaction and the expression of the defence reaction:
The elicitor – receptor model
The dimer model
The ion channel defence model
The supressor – receptor model.
• The interaction between plant and pathogen are specific, complex
• Signals for activation of various defences initiate response to
• The outcome of interaction dependent on initial sensing of the other
organism via exchange of molecular signal through signaling cascade
and modified gene expression.
• Recognition is the first step by which response is generated which is
involve in defence signal transduction.
• Agrios, G. N. 1997. Plant pathology. Academic Press, San Diego, Calif.
• Birch, P. R. J., and S. Kamoun. 2000. Studying interaction
transcriptomes: coordinated analyses of gene expression during
plant-microorganism interactions, p. 77-82. In R. Wood (ed.), New
technologies for life sciences: a trends guide. Elsevier Science, New
• Caten, C. E., and J. L. Jinks. 1968. Spontaneous variability of single
isolates of Phytophthora infestans. I. Cultural variation. Can. J.