PLANT BREEDING AGR 3204

Plant Reproduction

System

PLANT BREEDINGAGR 3204

PLANT REPRODUCTION SYSTEMThe reproduction mechanism of a

particular plant species or the way it reproduces determines

its genetic characteristicsthe breeding approach.

1. SEXUAL REPRODUCTION Using sex organs to form next generation / to produce seeds.

Important steps:

1. Production of gametes (gametogenesis)

2. Pollination – Transfer of pollen from anther (male organ) to the stigma (female organ).

3. Fertilization – The union of male and female gametes to produce new genotypes.

1. SEXUAL REPRODUCTION (CONT.)

POLLINATIONTransfer of pollen from anther

(male organ) to the stigma (female organ).

Two kinds of pollination, Self pollinationCross pollination

Transfer of pollen from anther to stigma of the same flower / plant

SELF POLLINATION

Natural mechanisms that encourages self pollination:

1. Cleistogamy Pollination happens when

flower is still closed. Example: Rice

SELF POLLINATION

2. Stigma protected by anther

Anthesis and pollination occur instantaneously once the flower blooms.

Many pollen are produced, covering the stigma, hence preventing pollination by pollen from outside. Example: lime, tomato and chilli

SELF POLLINATION (CONT.)

Chilli flower

3. Stigma and anther protected by other parts of flower.

Male (stamen) and female (pistil) organs covered by keel, i.e. two fused petals.

Example: Leguminosae family, sub-family Papilionoideae.

SELF POLLINATION (CONT.)

Transfer of pollen from anther to stigma of flower of different plant.

CROSS POLLINATION

Natural mechanisms to promote cross pollination:

1. Dieocious Male and female flowers are formed on different plants. Have male and female

plants. Example: Papaya, salak

CROSS POLLINATION(CONT.)

Male salak flower

Female salak flower

2. Monoecious

Male and female flowers are in separate positions on the same plant but mature at slightly different times. Example: Oil palm, corn

and rubber.

CROSS POLLINATION(CONT.)

3. Dichogamy Anther and stigma from hemaphrodite flower or flower of monoecious plant mature at different times. Protogyne

Stigma (female flower) matures before anther (male flower).Example: Potato, cassava and cashew.

CROSS POLLINATION(CONT.)

Protogyne: Potato flower

CROSS POLLINATION(CONT.)3. Dichogamy (cont.)

ProtandryAnther (male flower) matures before stigma (female flower).Example: Starfruit and rubber.

Protandry: Starfruit flower

4. Self-incompatibility

Pollens are unable to fertilize ovule (female gamete) of the same flower/plant due to genetic factor (self incompatibility gene)

Example: Potato, passion fruit and starfruit.

CROSS POLLINATION(CONT.)

In some species, there are more than one mechanism to promote cross pollination:

1. Rubber and corn: monoecious and protandry.

2. Potato, Sweet potato: Self-incompatibility and protogyne

3. Starfruit & passion fruit: Self-incompatibility and protandry

CROSS POLLINATION(CONT.)

METHODS TO DETERMINE MODES OF POLLINATION

1. Identify flower formation system. 2. Isolate plants.

No fruit/seed cross pollinatedFruit set/seed set self pollinated and possibly cross pollinated

3. Selfing. To observe the effects of inbreeding.Present cross pollinated.Absent / minimal self pollinated.

2. ASEXUAL REPRODUCTION Does not involve sex or union

of male and female gametes.

Mechanisms:-1. Vegetative reproduction2. Apomixis

VEGETATIVE REPRODUCTIONo Stem/branch/root cuttings e.g.

cassavao Grafting e.g. rubber, rambutan

& duriano Rhizome e.g. tumeric & gingero Stolon e.g. grasso Tuber e.g. potato & sweet

potatoo Tiller e.g. pineapple ,

sugarcane & banana

APOMIXISFormation of seeds without union of gametes, i.e. fertilization.

APOMIXIS (CONT.) Apogamy – Embryo formation from synergids

or antipodals

Apospory Embryo develops from somatic cell such as nucellus and integument.

Diplospory Embryo develops from megasporocyte.

Adventitious embryo Embryo develops directly from nucellus and integument cells without involving embryo sac cells.

Parthenogenesis Embryo develops from unfertilized eggs.

APOMIXIS (CONT.)

1. Obligate apomixis Apomixis reproduction

is the main method of reproduction.

Example: mangosteen

APOMIXIS (CONT.)

2. Facultative apomixis

Both apomixis and sexual reproduction occur.

Example: Guinea grass (Panicum maximum), Citrus sp.

CHARACTERISTICS OF CROSS POLLINATED, SELF POLLINATED AND ASEXUAL PLANTS

Characteristic Cross pollinated Self pollinated Asexual

Population Heterogeneous Homogeneous Homogeneous

Genotype Heterozygous Homozygous Heterozygous

Gamete Different Similar Different

Progeny Different & heterozygous

Similar & homozygous

Similar & heterozygous

Inbreeding depression

Present Absent Present

Incompatibility Present Absent Present