cytoplasmic male sterility in minor crop - sorghum

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UNIVERSITY COLLEGE OF AGRICULTURE

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BY ISHTIAQ SHARIQ

ROLL # 2 SEMESTER 8th

PLANT BREEDING AND GENETICS B. Sc. (Hons.) Agriculture

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KINGDOM Plantae

ORDER Poales

FAMILY Poaceae

GENUS Sorghum Moench

SPECIE Sorghum bicolor L.

Moench

BINOMIAL NAME

Sorghum bicolor L. Moench

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• Sorghum is cultivated in the semi-arid tropics in 86 countries.

• Prodcution was 120,800 tonnes (FAO Stats 2012-13)

• Diverse origin and probably arose from S. Verticilliflorum

• Domestication began around 3000 BCE

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PAKISTAN

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2011-12

Area ('000'Ha) Production ('000' ton)

YIELD

(Kgs/ Ha) (Mds/Acre)

213.5 137.1 642.2 7

The Ministry of National Food Security and Research (NFS&R)

• The cultivated sorghum taxa have been classified into five basic races (bicolor, caudatum, durra, guinea, and kafir),

• 10 hybrid races (e.g., bicolor-caudatum)

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• When sterility is due to the failure of functional anthers or pollen, it is

termed male sterility (Poehlman 4th ed.)

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• Genetic male sterility is manifested through the action of nuclear genes inhibiting normal development of anthers and pollen

• Precise stage where pollen development is interupted, varies specie to specie or specific male sterelity gene.

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• Expression of gene may be:

–Complete

–Partial

–Varying with environment

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• Male sterelity conditioned by recessive allele (ms)

• Normal anther and pollen because of (Ms) allele

• Diploid species would have constitution:

–Male sterile = msms

–Male fertile = Msms, MsMs

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• Maintainance of male sterile gene in population is very necessary

• A pure population of genetically male sterile plant is impossible

• Male sterile gene is maintained if seeds from the male sterile plants only are harvested and used to plant the next generation.

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• Seed from a male sterile plant (rosins) may be pollinated by either homozygous

(MsMs) or heterozygous (Msms) male fertile plants.)

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msms Msms X

ms ms Ms

50 % Msms 50 % msms

CASE 1

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msms MsMs X

ms Ms

100 % Male fertile Msms

CASE 2

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msms MsMs X

Msms (self)

X

F1

F2 25 % msms

F3 33 % msms

25 % MsMs 50 % Msms

66 % Msms

CASE 2, FURTHER GENERATIONS, ONLY MALE STERILE HARVESTED IN F2 AND ONWARD

• Eliminate emasculation in hybridization

• Increase natural crosspollination in selfpollinated crops

• Facilitate commercial hybrid seed production.

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UTILIZATION IN A BREEDING PROGRAM

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CYTOPLASMIC MALE STERELITY

• Cytoplasmic male sterility is controlled by the cytoplasm, but may be influenced by genes in chromosomes

• Cytoplasm causing sterelity referred as (sterile cytoplasm (S) or (CMS)

• Cytoplasm developing functional anthers and pollens designated (N)

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• Sterile cytoplasm results when nuclear chromosome introduced in foreign cytoplasm.

• For example, cytoplasmic male sterility in sorghum was obtained by transferring kafir chromosomes into cytoplasm of

milo.

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• Male sterility is not expressed when the milo chromosomes are in milo cytoplasm.

• The kafir chromosomes were introduced into milo cytoplasm by pollination of a milo plant with kafir pollen, and successively crossing the progeny as the female back to kafir as the male, until the entire set of kafir chromosomes were recovered.

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• Similar procedures to obtain obtain cytoplasmic male sterile in wheat

and other crops

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• Because the cytoplasm is transferred through the egg only, the sperm

contributing an insignificantly small bit of cytoplasm to the zygote, cytoplasmic

male sterility is transmitted only through the female plant

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CONCEPTUAL POINT

• The action of cytoplasmically controlled male sterility may be modified by the action of fertility restoring genes located in the chromosomes.

• RfRf = Sterile cyto. Becomes inoperative

• rfrf = (Cytoplasm is sterile) Sterility is expressed

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• The parent with the sterile cytoplasm necessarily is used as the female and the fertility restoring genes are contributed by the male parent

• The nuclear genes and cytoplasm interact to produce male sterileand male fertile plants

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CMS rfrf

MALE STERILE MALE FERTILE

CMS Rfrf

MALE FERTILE CMS RfRf

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N rfrf

MALE FERTILE MALE FERTILE

N Rfrf

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CMS rfrf RfRf N or CMS

Rf rf CMS

Rfrf CMS OFFSPRING

SPERM NO CYTO

FEMALE MALE

EGG

• The restorers should be taller than male steriles usually by 0.1 to 0.8m, and

possess good pollen shedding ability

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CONCLUSION

• The milo cytoplasm male-sterility system still remains the most widely used because the hybrids based on this

cytoplasm produce sufficient heterosis (20–30%) over the best available pure

lines in sorghum

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