BIOSCI 108: Lecture 22 - Plant Domestication & Breeding

Steps of Cultivation

1. The gathering of wild uzeful plants as populations travelled around

2. The semi settling of populations as they purposefully moved to find these wild plants again

3. The permanent settlement of populations of where they found those wild plants and the cultivation of them

This was very important to kickstart the development of civilisations.

Artificial Selection & Domestication

After cultivation, humans would, over time, artificially select traits in plants by choosing to breed and continue cultivating plants with desirable traits.

This led to the domestication of crops

Desirable Traits

Traits that increases yield, fruit size, longer-lasting fruit, tastier plants, faster growing, easy to grow, made it easier to eat/use, and so on.

Maize Domestication

The wild ancestor of maize is teosinte, a shorter plant with only a few rows of hard kernels.

A scientist suspected that it could be a wild ancestor of maize and proved it by being able to cross them.

• Through this, he discovered 5 main regulatory gene differences:

• tb1, a gene controlling branching patterns and number of kernels

• tga1, a gene affecting structure of outer casing of seeds

The differences in gene expression and regulation caused morphologi al differences:

• Corn having a cebtral stalk with corn having many rows of softer kernels

These changes accumulated as humans cultivated teosinte and selected the most diserable teosinte (within natural variation) to continue cultivating.

• This would continue until we see the homogenous corn we see today

Staple Crops

Many of our staple crops arose because of how humans have artificially selected and domesticated their wild counterparts:

• Some wild ancestors may be the ancestors of many modern day staple crops

Despite having a variety of staple crops, we really only focus on and eat a few major plant families:

• Poaceae

• Fabaceae

• Solanaceae

Poaceae

Grass Family, crops such aa rice, wheat, rye, cereals, maize, sorghum, and so on

Fabaceae

Legume Family, crops such as beans, peas, lentills, soybeans, and so on

Solanaceae

Nightshade Family, crops such as potatoes, tomatoes, eggplants, pepper, tobacco, and so on

Adapating to the World’s Growing Food Demand

To be support the growing population, we must change and adapt our processes

• Diversifying our diets, focusing on underutilised foods to reduce the demand and stress on staple crops

• Alternative farming methods such as vertical farming and indoor farming (more space & water efficient methods)

• Technological innovations that allow us to better breed crops that lead to better crops

“Natural” Foods

There is a misconception that foods can be “natural” as if they appear like that in the wild.

We know that many of the plants we eat today are the results of deliberate decisions and changes over time than has modified them to what they are today.

Traditional Breeding

The crossing of plants with desirable traits and selection of offspring with said traits to cultivate

This tends to affect a few genes or even the entire genome. It is unregulated

Mutagenesis

Inducing mutations in plants by exposing them to radiation.

This tends to have a lot of changss in the plant’s genome (could be beneficial or detrimental). Tends to be unregulated

Transgenics

Inserting selectsd genes from other crops or species into a target crop using recombinant DNA methods. This is our GMO crops.

Typically is precise affecting a few genes. Tends to be highly regulated

Gene Editing

The delection or addition of target DNA, or a single nucleotide, to improve crops. This is done with CRISPR, which allows us to precisely edit genes.

This tends to affect one gene. It has mixed regulation