Domestication In Crop Plants GPB 202

Dr. NAVEENKUMAR K.L
Assistant Professor
Dept. Of Genetics and Plant Breeding

1. Dr. NAVEENKUMAR K.L Assistant Professor Dept. Of Genetics and Plant Breeding UAHS Shivamogga DOMESTICATION

2. What is domestication..? Domestication is the process of bringing wild species under human management. Plant domestication is the genetic modification of a wild species to create a new form of a plant altered to meet human needs ( Doebley et al., 2006 ) Present day cultivated plants have been derived from wild weedy species. The process by which humans actively interfere with and direct crop evolution. Individuals that exhibit desirable traits are selected to be bred, and these desirable traits are then passed along to future generations

3. How much domestication About 5000 species have been grown for human food – less than 1% of all plant species thought to exist Today about 150 species are commercially grown for food (not including spices) About 50 very productive species supply almost all of our caloric needs. Benefits of Domestication- 10,000 years ago, before agriculture began, the world’s total human population was about 5 million. There was one person for every 25 square kilometers. Today we have more than 7 billion people, with a density of just over 25 people per square kilometer. As agriculture developed humans selected for: Plants that provide enough calories to meet our basic energy needs. We also selected for a balanced nutritional intake - this tends to develop in any system where the cultivator eats and depends upon on what he/she grows.

4. Types of Domestication Incidental Didn’t happen on purpose. Hunter/gatherers dropped seeds, scared off natural herbivores, disrupted natural environments so that plants could grow. 2. Directed Humans and plants became dependent on each other, so better plants helped people get healthier, planting more (and maybe improved) plants, etc. 3. Agriculture Human intervention in crop Husbandry , Cultivation and Selection.

5. Selection under Domestication Selection: When different genotypes present in a population reproduce at different rates, it is called selection . A population may be simply defined as the group of individuals, which mate or can mate freely with each other. Selection is grouped into two types, on the basis of the agency responsible for it Natural selection A rtificial selection

6. Natural Selection The selection that occurs due to natural forces like climate, soil, biological factors (e.g., diseases, insect pests, etc.) and other factors of the environment is called natural selection. In 1962, Nichlson proposed that natural selection may be seen to operate through two mechanisms, viz.; (l) Environmental selection (2) Competition. Environmental selection acts against all such genotypes that are unable to cope with the environmental stresses . It is through competition occurs in crop populations where a plant takes up more water, nutrients or light than another at the expense of the other.

7. Artificial Selection It is carried out by man and is confined to domesticated species. It allows only the selected plants to reproduce, ordinarily makes plants more useful to man and generally leads to a marked decline in genetic variability in the selected progenies/populations. Types of Selection- 1 ) Directional selection, 2 ) Stabilizing selection 3) Disruptive selection.

8. Directional Selection: When individuals having the extreme phenotype for a trait or a group of traits are selected for, it is called directional selection. Stabilizing Selection: When selection favours the intermediate phenotype and acts against the extreme phenotypes, it is termed as stabilizing selection . Disruptive Selection: In each 'ecological niche' a different 'phenotypic optima' is selected for so that the population ultimately consists of two or more recognizable forms; such a selection is called disruptive selection .

9. Changes in plant species under domestication Elimination of or reduction in shattering of pods spikes etc in cultivated species (Pulses) Elimination of dormancy (Barely, wheat, Mung ) Decrease in toxins (cucurbitaceous plants) Decreased plant height (cereals, millets) I ncreased plant height (sugarcane, jute, fodder grasses) Life cycle has become shorter (cotton, arhar ) Increased economic yield Variability within the a variety has drastically decreased under domestication.

10. Domestication syndrome The domestication syndrome can be defined as the characteristic collection of phenotypic traits associated with the genetic change to a domesticated form of an organism from a wild progenitor form.

11. Effect of selection during domestication A selective sweep is the reduction or elimination of variation among the nucleotides in neighboring DNA of a mutation as the result of recent and strong positive natural selection