MALE STERILITY IN PLANTS

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Male Sterility in Plants Presented by – Pudhuvai Baveesh . M.Sc (Genetics & Plant Breeding) Lovely Professional University Punjab 144411 INDIA

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Content - - Introduction- - features- - Types of Male Sterility- - List of male gametocides - -Comparison of 3 Types of Male Sterility in plants- - Utilizatio n of Male sterility - - Limitations of Male sterility - - Hybrid seed production in Rice using CGMS-

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Introduction It refers to a condition in which the plants are unable to produce or release the functional pollen grain as a result of failure of formation or development of pollen, stamens or gametes . Koelreuter ,1763 There are 3 types of sterility based on phenotypic characters : “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.

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Tranverse section of the anther wall

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Features of Male sterility Male sterility is an important outbreeding device which prevents Autogamy (Self pollination) and permits Allogamy (Cross pollination). Presence of male sterility leads to heterozygosity in a species as it promotes outbreeding and reduces homozygosity due to elimination of inbreeding. Male sterility results from the action of nuclear genes or cytoplasmic genes or both. Male sterility caused due to pollen or anther abortion. Male sterility occur in nature through spontaneous mutations as well as can be induced artificially by chemical or physical mutagens. Male sporophyte and gametophyte less protected from environment than ovule and embryo sac.

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Types of Male sterility Based upon the Inheritance or Origin, Male sterility is classified into 4 types. I Genetic male sterility (GMS). * Temperature-sensitive genetic (TGMS) * Photoperiod-sensitive genetic (PGMS) * Transgenic male sterility II Cytoplasmic male sterility (CMS ). III Cytoplasmic genetic male sterility (CGMS ). IV Chemically-induced male sterility.

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Genetic male sterility (GMS). The pollen sterility, which is caused by nuclear genes, is termed as genic or genetic male sterility. It is usually governed by a single recessive gene ms or ‘s’ with monogenic inheritance. A male sterile line may be maintained by crossing it with heterozygous male fertile plant, such a mating produces 1:1 male sterile and male fertile plants.

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Advantages and Disadvantages GMS is usually recessive and monogenic . Hence fertility restoration in the hybrid and the crossing plans are relatively easy. GMS can be used for the production of hybrid seed in both seed propagated crops and vegetatively propagated species. It requires less area and labour because the breeder has to maintain only A and B lines. It is less stable . GMS can some times become fertile at low temperature. Ex: In Rice the sterile plants become fertile at temp. below 23 o C. The sterility which is influenced by the temp. is called as Thermo-sensitive male sterility.

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Temperature-sensitive genetic (TGMS) The complete male sterility is produced by the ms gene at higher temperatures (23.3˚C or higher for rice TGMS line Pei-Ai645), but at temperatures below this critical point it exhibits normal fertility . Photoperiod has a limited effect in determination the lowest temperatures at which complete sterility is produced. This type of genetic male sterility is being used to develop hybrid rice in China.

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Photoperiod-sensitive genetic (PGMS) Expression of ms gene drastically affected by the prevailing photoperiod , provided the temperature is within a critical range ( 23-29˚C for Rice PGMS). Within this temperature range , complete sterility is obtained in rice plants grown under long-day conditions (day length more then 13 hr 45 min ) but under short day condition almost normal fertility is obtained.

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Transgenic Male Sterility Principle of BARSTAR- BARNASE system TA29 Barnase gene Bar gene Barnase gene produce RNase Endothecium Middle layer Tapetum Tapetum layer promoter Herbicide resistant ( Phopothricin ) Tapetum degenerates PMC’s/ Pollens become S terile Bacillus amyloliquefaciens Barstar gene (Fertility restorer )

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Principle of BARSTAR- BARNASE system TA29 Barnase gene Bar gene Barnase gene produce RNase Endothecium Middle layer Tapetum Tapetum layer promoter Herbicide resistant ( Phopothricin ) Tapetum Persistant PMC’s/ Pollens are Fertile Bacillus amyloliquefaciens Barstar gene

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Barnase BARSTAR Interaction (Binding) Male sterile Herbicide resistant Barnase Male Fertile Herbicide Sensitive

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Cytoplasmic male sterility (CMS). The pollen sterility which is controlled by cytoplasmic genes is known as cytoplasmic male sterility (CMS). Usually the cytoplasm of zygote comes primarily from the eggs cell and due to this progeny of such male sterile plants would always be male sterile . CMS is maintained by crossing A line with B line . CMS can be used for development of hybrids in vegetatively propagated crops and ornamental crops . The male sterile line is maintained by crossing it with pollinator strain used as a recurrent parent in backcross, since the nuclear genotype of the pollinator is identical with that of the new male sterile line. Such a male fertile line is known as maintainer line or ‘B’ line and ‘male sterility is also known as ‘A ‘ line. Cytoplasmic male sterile is not influenced by environmental factor and it resides in maize in mitochondria.

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Advantages and Disadvantages Merits - CMS is highly stable and not influenced by environmental factors i.e. low & high temperature. - A cross between A and B lines will always male sterile F1 , t herefore CMS requires less area because the breeder has to maintains A and B lines only. Demerits – CMS governed by plasma genes , therefore it is impossible to restore fertility in the hybrid.

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Inhertance of CMS

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Cytoplasmic genetic male sterility (CGMS) When-pollen sterility is controlled by both cytoplasmic and nuclear genes is known as CGMS. - CGMS was first discovered by Jones and Davis (1944) in onion. - This male sterility is controlled by the interaction of cytoplasm and nuclear genes. - This system include A, B and R lines . A is male sterile line, B is male fertile line and R is restorer line.

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Advantages and Disadvantages Merits CGMS is widely used for hybrid seed production in both seed propagated species and vegetatively propagated species. CGMS is highly stable and reliable. It is not affected by environmental effect. Demerits - It requires more area and labour because the breeder has to maintain three types of materials viz. A, B and R lines .

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Inhertance of CGMS

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Chemical Induced Male sterility Induced by use Chemicals ( Male Gametocides ) GA ( Gibberillic acid) NAA ( Napthalene Acetic acid) MH ( Malic Hydrazide ) Etheral Examples CHEMICAL CROP Etheral Rice, Sugarbeet ,Wheat FW 450 Cotton, Groundnut, Tomato GA ( Gibberillic acid) Lettuce, Maize, Onion, Rice MH ( Malic Hydrazide ) Cucurbits, Onion, Tomato, Wheat NAA ( Napthalene Acetic acid) Cucurbits Sodium Methyl Arsenate Rice Zinc Methyl Arsenate Rice

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No . Particulars GMS CMS CGMS 1 Control It is controlled by Nuclear genes. Controlled by Cytoplasmic genes. Controlled by both Nuclear and Cytoplasmic genes. 2 Material included Consist of A and B lines. Consist of A and B lines. Consist of A, B & R lines. 3. Effect of temperature May become fertile at low temp . No effect of temp. No effect of temp. 4. Maintenance Maintained by mating sterile plants with heterozygous male fertile plants. Maintained by crossing of A line with B line . Maintained by crossing of A line with B line . 5. Uses Production of hybrids in both seed and vegetatively propagated crops. hybrid in vegetatively propagated crops both seed propagated and vegatatively propagated species. 6. Demerits The male sterile and fertile plants are observed in 1:1 ratio. The fertile plants have to be removed in hybrid seed production. It can be used in seed propagated plants because the F1 is sterile. It require handling of 3 types of material. i.e. A,B and R lines . 7 Examples Barley, Wheat, Lucerne, Watermelon, Pumpkin, Rice, Cotton, Tomato, Tobacco, Sunflower etc. Onion, Sugarcane, Forage crops etc. Pearlmillet , Sorghum, Cotton, Wheat, Maize, Rice, Sugar beet. Comparison of 3 types of male sterility in plants

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Utilization of male Sterility Male sterility has important application in the development of hybrids in plant breeding. All three types of male sterility are used in crop improvement programmes . GMS can be used for the development of commercial hybrids in both seed propagated and vegetatively propagated crop plants. CMS can be used for the development of vegetatively propagated crop plants, forage and ornamental plants. CGMS can be used for the development of commercial hybrids in both seed propagated and vegetatively propagated crop plants

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Limitations of male Sterility It is very difficult to identify the male sterile line (when controlled by nuclear genes) before anthesis . Male sterility can not be effectively used in those crops in which efficient natural pollen dispersal mechanism is lacking and flower morphology is not suitable for cross pollination. In some cases GMS line becomes fertile under low or high temperature conditions.

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Hybrid seed production in Rice by using CGMS Father of Hybrid Rice Dr. Yuen long ping The breeding method in which mating or crosses are made between two plants or lines of different genotype is known as hybridization. The seeds as well as the progeny obtained from hybridization is known as hybrid or F1.

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Three line breeding or CGMS In this system, three lines are used that’s why this system is called three line breeding. These line are:- 1 Cytoplasmic Genetic Male Sterile line (CGMS Line) or A-Line 2 Maintainer Line or B-Line, and 3 Restorer line or R-Line. In hybrid seed production A–Line is crossed with R–Line. As R–Line possesses fertility restorer gene in dominant condition, though the cytoplasm contributed by A-Line is sterility inducing one. As a resultant, F1 which is used as commercial hybrid is fertile one. A–Line and B–Line are exactly same genetically but they differ only in respect of cytoplasm content. A–Line has sterility inducing enzyme whereas, B–Line has normal cytoplasm. The R-Line possesses fertility restorer genes in dominant condition. The R-Line will be always fertile with respect to the cytoplasm either it is sterile or fertile.

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A = Cytoplasmic male sterile B = male fertile or maintainer R = genetic male fertile (Restores fertility)

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Thank you….!

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