Genetics & Plant Breeding Study Important Point
Subject:- Genetics & Plant Breeding
Genetics & Plant Breeding Study Important Table
1.Types of Polyploid & Their Definition
| Polyploid | Definition/brief description |
| Autopolyploidy | |
| Autotriploidy | Three copies of the same genome (3x) |
| Autotetraploidy | Four copies of the same genome (4x) |
| Autopentaploidy | Five copies of the same genome (5x) |
| Autohexaploidy | Six copies of the same genome (6X) |
| Allopolyploidy | |
| Allotetraploidy | Two copies each of two distinct genomes (2x1+ 2x2) |
| Allohexaploidy | Two copies each of three distinct genomes (2x1+ 2x2 +2x3) |
| Allooctaploidy | Two copies each of four distinct genomes (2x1 + 2x2+ 2x3 + 2x4) |
- Autopolyploidy:– Multiplication of the same genome.
- Allopolyploidy:- A condition in which complete genomes of two or more species combine together.
2.Types of Polyploid & Crops
| Polyploidy | Crops |
| Autopolyploidy (more vigour, robust) | |
| Auto triploids | Banana, water melon |
| Auto tetraploids | Potato, groundnut, coffee, barseem, Rye |
| Auto hexaploid | Sweet potato |
| Allopolyploidy (50% of plants evolved) | |
| Allohexaploid | Wheat, Triticale |
| Allotetraploid | Cotton, Tobacco |
3.Type of cross & hybrids Varieties of Crops
| Crops | Type of cross | Name of hybrids released |
| Cross pollinated crops | ||
| Maize | Double and three way crosses | Ganga 2, Ganga 5, Ganga 11, Makka 1 and VL 42 |
| Pearl-millet | Single cross | HB 3, BJ 104, MBH 110, BK 560, MH 179 |
| Sunflower | Single cross | BSH 1, HSFH 1, MSFH 10, KBSH 1 and KBSH 11 |
| Castor | Single cross | GCH 2, GCH 3, Gauchi and GCH 4 |
| Cucumber | Single cross | Pusa Sanyog |
| Often cross pollinated crops | ||
| Sorghum | Single cross | CSH1, CSH5, CSH6,CHS9,CSH10, CSNH |
| Cotton | Intra specific | H 4 H 6, H8, H 10, JKHY 1, JKHY 2, PKVHY 2, PKVHY 3, PKVHY 4 |
| Cotton | Inster specific tetraploid hybrids | Varalaxmi, DCH 32, HB2 24, TCHB 213, DHB 105, Sruthiv |
| Cotton | Inter specific diploid | DH 7, DH 9, DDH 2 |
| Cotton | Intra – arboreum | LDH II |
| Pigeon pea | Single cross | ICPH 8 from ICRISAT |
| Self pollinated crops | ||
| Tomato | Single cross | Hybrid Tomato F1 |
| Brinjal | Single cross | Vijay, Pusa Kranti. Arka Sheel, Arka Navneet and Azad Kranti |
| Jute | Single cross | Hybrid C |
4.Similarities Between Synthetic & Composite Cultivars
| Particulars | Synthetic Cultivars | Composite Cultivars |
| Equilibrium | Allo – gamous Species | Allo gamous Species |
| Relevant to | Allogamous Species | Allo gamous Species |
| Genetic Constitution | Hetero – geneous, mixture of several homo – zygotes and hetero-zygotes | Hetero geneous, mixture of several homo – zygotes and hetero-zygotes |
| Adaptation | Wide, due to broad genetic base | Wide, due to broad genetic base |
5.Dissimilarities Between Synthetic & Composite Cultivars
| Particulars | Synthetic Cultivars | Composite Cultivars |
| Base Material | Inbred or clones | Open pollinated varieties or any other hetero – zygous Source |
| Component Genotypes | Two to eight | Two to many |
| Evaluation for General Combining Ability (GCA) | Always done | Usually not done |
| Seed Replacement | After 4-5 years | After 3-4 years |
| Exact Reconstitution | Possible | Not Possible |
6.Commonly used physical mutagens radiation their properties and mode of action
| Type of radiation | Main properties | Mode of action or changes caused |
| X-rays | S.I., penetrating and non- particulate | Induce mutations by forming free radicals and ions. Cause addition, deletion, transitions and transversions |
| Gamma Rays | S.I., penetrating and non- particulate | Induce mutations by ejecting atoms from the tissues. Cause all types of changes as above. |
| Alpha Particles | D.I., particulate, less penetrating and positively charged. | Act by ionization and excitation. Cause chromosomal and gene mutations. |
| Beta Rays Particles | S.I., particulate, more penetrating than alpha particles and negatively charged | Act by ionization and excitation. Cause chromosomal and gene mutations. |
| Fast and Thermal Neutrons | D.I., particulate, neutral particles, highly penetrating. | Cause chromosomal breakage and mutations. |
| Ultra Violet Rays | Non-ionizing, low rays mutations. | Cause chromosomal breakage and gene |
7.Some commonly used chemical mutagens and their mode of action
| Name of chemical | Mode of action |
| Alkylating agents | |
| Ethyl methane Sulphonate | AT <-> GC Transitions |
| Methyl methane Sulphonate | Transitions |
| Ethyl ethane Sulphonate | GC <-> AT Transitions |
| Ethylene lmines | Transitions |
| Base analogues | |
| 5 Bromo Uracil | AT <-> GC Transitions |
| Amino Purine | AT <-> GC Transitions |
| Acridine dyes | |
| Acriflavin, Proflavin | Deletion addition and Frame shifts |
| Deamination agent | |
| Ethidium bromide | |
| Others | |
| Nitrous Acid | AT <-> GC Transitions |
| Hydroxy lamine | GC <-> AT Transitions |
| Sodium Azide | Transitions |
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