Genetics in Agriculture

Farming goals

• A need to improve air, water, and soil quality

• Plant Breeding• A. Breeding Methods Using

Sexually Compatible Germplasm• 1. Strategies– Self pollinating– Cross pollinating

• 2. Germplasm Collection and Gene Banks

Self pollinating

• 1. homozygous all genes come from the same parent

• Include: wheat, rice, oats, barley, peas, beans, tomatoes, and peppers

• Some fruit trees: apricots, nectarines, peaches, and citrus

• These plants have undergone a significant amount of inbreeding

Pure line selection

• Take seeds from each of several plants (A,B,C,D) and planting them in rows (A,B,C,D)

• Then select the most desirable row • Use the seeds from those plants for your crop

or go through the process again

Rice plants

• Seeds harvested from an inbred variety can be used for the succeeding plant seasons without losing their varietal identity, provided cross-pollination with other varieties is avoided.

• Cross between normal wheat and dwarf wheat has created dwarf varieties where more energy is used for seed production and not stalk elongation. This gives a higher yields

Pollination

Cross pollinators

• Highbred plants• Highly heterozygous• A hybrid is the product of a cross between two

genetically distinct parents. When the right parents are selected, the hybrid will have both greater vigor and yield than either of the parents.

Advantages and disadvantages

• Increased yield• Increased vigor (which makes them more competitive with

weeds)• Increased resistance to diseases and insects• Seed is expensive• Farmers can not use their seed from the past season like

they can with inbred plants• Seeds harvested from the hybrid plant are not

recommended for replanting because the hybrid vigor is lost because of segregation which results in a lower yield, so farmers must buy new hybrid seeds every year

From the lab book

• The probability of event A is the number of ways event A can occur divided by the total number of possible outcomes.

• Flip the coin

• 4 X number of flips of a given genotype = ratio Total number of flips

Cross in Corn

• F2 generation• Cross between homozygous yellow and

homozygous white parents• What does the F1 generation look like

Terms

• Back cross: cross a plant from the F1 generation with one of the parents

• Test cross: cross a plant with unknown parentage with a homozygous recessive plant

Dihybrid Cross in Red corn

• Ears of corn that demonstrated two traits in the F2 kernels, red and white colors and smooth and wrinkled shape were analogized. A tabulation of 135 individual kernels gave the following results:

(red smooth = 75, white smooth = 28, red wrinkled = 24, white wrinkled = 8)

• According to the Punnett square, the predicted results should have been 9/16 purple smooth (56.3%), 3/16 purple wrinkled (18.8%), 3/16 white smooth (18.8%), and 1/16 white wrinkled (6.3%).

• Do the corn kernels from above compare in number exactly to the predicted number?