1. MALE-STERILITY

2. Several forms of pollination control
Manual emasculation
Use of male sterility
Use of self-incompatibility
Use of male gametocides
Use of genetically engineered “pollen killer” genetic system

3. Male-sterility
Plant that do not produce viable, functional pollen grains
An inability to produce or to release functional pollen as a result of failure of formation or development of functional stamens, microspores or gametes

4. Phenotypic classes of sterility
“Pollen sterility” in which male sterile individuals differ from normal only in the absence or extreme scarcity of functional pollen grains (the most common and the only one that has played a major role in plant breeding)
“Structural or staminal male sterility” in which male flowers or stamen are malformed and non functional or completely absent
“Functional male sterility” in which perfectly good and viable pollen is trapped in indehiscent anther and thus prevented from functioning

5. Types of Male-sterility
Genetic male sterility
Cytoplasmic male sterility
Environment sensitive genetic male sterility
Chemical induced male sterility
Genetically engineered male sterility

6. Cytoplasmic male-sterility
CMS is the result of mutation in the mitochondrial genome (mtDNA), which leads to mitochondrial dysfunction.
Stamen (anther and filament) and pollen grains are affected

7. Cytoplasmic male-sterility
The nuclear genetic control of CMS is predominantly governed by one or more recessive genes, but can be also dominant genes as well as polygenes
The different mtDNA restriction endonuclease digestion patterns are reflections of aberrant intra- or inter molecular DNA recombination events in the mitochondrial genome which have either modified existing genes or related new genes some of which are more or less related to the male sterile phenotypes

8. Cytoplasmic male-sterility
Origins:
1. Intergeneric crosses
2. Interspecific crosses
3. Intraspecific crosses
4. Mutagens (EMS, EtBr)
5. antibiotic (streptomycin and Mitomycin)
6. Spontaneus

9. CMS Characterization
It has been traditionally characterized by the restore genes required to overcome the CMS and to provide male sterile progeny in the male sterile system
CMS restoration is by nuclear genes, frequently dominant in action, in many cases, few in number
The CMS restore genes temporarily suppress the expression of the CMS permitting normal or near-normal pollen production

10. Types
a. Autoplasmic CMS has arisen within a species as a result of spontaneous mutational changes in the cytoplasm, most likely in the mitochondrial genome b. Alloplasmic CMS has arisen from intergeneric, interpecific or occasionally intraspecific crosses and where the male sterility can be interpreted as being due to incompatibility or poor co-operation between nuclear genome of one species and the organellar genome another CMS can be a result of interspecific protoplast fusion

11. CMS mechanism of action
Abnormal behavior of the tapetum in the anther
Genetic determinant of CMS reside in mitochondria
Nuclear gene control the expression of CMS

12. CMS Limitations
Pleiotropic negative effect of the CMS on agronomic quality performance of plants in the CMS cytoplasm
Enhanced disease susceptibility
Complex and environmentally unstable maintenance of male sterility and/or male fertility restoration
Inability to produce commercial quantities of hybrid seed economically because of poor floral characteristic of cross pollination

13. CMS Utilization
It provides a possible mechanism of pollination control in plants to permit the easy production of commercial quantities of hybrid seeds
It consists of a male sterile line (the A-line), an isogenic maintainer line (The B line), and if necessary also restore line (the R-line)
A lines are developed by back-crossing selected B-lines to a CMS A-line for 4 – 6 times to generate a new A-line, B and R-lines are developed by similar back cross procedures using a CMS R-line as female in the original cross and a new line as the recurrent parent in 4 – 6 backcrosses

14. CMS Utilization
Selfing the last backcross generation two successive times and selection of pure breeding male fertility restore line is required to complete the development of the new R-lines developed in the CMS
Current commercial hybrid seed production relies entirely on the block method (alternating strips of female and male genotypes

15. Fertility restoration in maize

16. Simple hybrid with cms and restorationrr S rr F
CMS line (A-line)
CMS, rfrf x
Maintainer line (B-line)
N, rfrf
Large amounts
of CMS line rr S F x RR
Male line (C-line)
N and RfRf Rr S
Fertile F1 hybrid
CMS, Rfrf

17. Nuclear male sterility
Originated through spontaneous mutation or mutation by ionizing radiation and chemical mutagens such as ethyl methane sulphonate (EMS) and ethyl imine (EI) or by genetic engineering, protoplast fusion
can probably be found in all diploid species
Usually controlled by mutations in genes in the single recessive genes affect stamen and pollen development, but it can be regulated also by dominant genes

18. Morphology
Variable (complete absence of male reproductive organs to the formation of normal stamen with viable pollen that fail to dehisce)
It is not distinguishable from parent fertile plants with the exception of flower structure
Male sterile flowers are commonly smaller in size in comparison to the fertile
The size of stamens is generally reduced

19. Determining factor Temperature (TGMS) Photoperiod (PGMS)
Changing the optimal temperature can induce sterility (23°C)
Photoperiod (PGMS)
It has a strong influence (Photoperiod sensitive)
Changing the growth habit can stimulate the sterility
(23°C - 29°C)

20. Cytological Changes
Breakdown in microsporogenesis can occur at a number of pre-or postmeiotic stages
The abnormalities can involve aberration during the process of meiosis, in the formation of tetrads, during the release of tetrad (the dissolution of callose), at the vacuolate microspore stage or at mature or near-mature pollen stage

21. Use of genic male sterility in hybrid programs
Male sterile plants of monoecious or hermaprodite crops are potentially useful in hybrid program because they eliminate the labor intensive process of flower emasculation

22. Hybrid seed production with GMS and restoration
Male sterile line X Male fertile line
msms MsMs
Male sterile line X Maintainer line
msms Msms
Seed for harvested in bulk from male sterile line

23. Maintenance plot Hybrid seed production plot
Plants with Msms and msms genotypes
Female rows male rows Female rows
Msms & msms Msms & msms
Harvest seed only from sterile plants
Remove fertile plants from rows before anthesis, harvest seed from sterile plants

24. Cytoplasmic-genetic male sterility
A case of cytoplasmic male sterility where a nuclear gene for restoring fertility in the male sterile line is known.
The fertility restorer gene R is dominant.

25. Various Genotypes and Phenotypesrr S
Cytoplasm sterile
Nuclear gene non restorer rr F
Cytoplasm fertile
Nuclear gene non restorer RR S
Cytoplasm sterile (Male fertile)
Nuclear gene restorer in homozygous RR or heterozygous Rr state
The effect of sterile cytoplasm is negated by the restorer gene Rr S

26. CHEMICAL INDUCED MALE-STERILE

27. Biochemical means of producing male sterile plants
Feminizing hormones
Inhibitors of anther or pollen development
Inhibitors of pollen fertility

28. Chemical hybridizing agent (CHA)
Could be used in the large scale commercial production of hybrid seed
Are applied to plant only at certain critical stage of male gametophyte development

29. The logic of chemical hybridization
High degree of efficacy and developmental selectivity
Persistence during the development of flower or spikes
Low cost
Acceptable levels of toxicity to people and the environment
Low general phytotoxicity
Agronomic performance of hybrid seed produced is not inferior to equivalent crosses produced by genetic methods

30. CHAs and pollen development
There are at least 4 classes of chemical agents:
a. Plant growth regulators and substances that disrupt floral development
b. Metabolic inhibitors
c. inhibitors of microspore development
d. inhibitors of pollen fertility

31. Plant growth regulators and substances that disrupt floral development
Plant hormones/hormones antagonists
a. auxins and auxin antagonists (NAA, IBA, 2,4-D, TIBA, MH)
b. Gibberellins and antagonist (GA3, GA4+7, CCC: 2-chloroethyl-trimethyl ammonium chloride)
c. Abscisic acid
Other substances
a. LY195259
b. TD1123

32. Metabolic Inhibitors
There are halogenated aliphatic acids (alpha, beta-dichloroisobutyrate and 2,2-dichloropropionate salts) and arsenicals (methanearsonate salts)
They affect mitochondrial protein by reducing the efficiency of normal metabolic processes

33. Inhibitors of microspore development
Copper chelators
Ethylene
Fenridazon
Phenylcinnoline carboxylates (SC-1058, SC-1271 and SC-2053)

34. Inhibitors of pollen fertility
Azetidine-3-carboxylate (A3C, CHA™)