The Science of Plants in Agriculture

1

The Science of Plants in Agriculture

Plant Science 102

Study Notes for Test #3

Genes, Mendel and Meiosis

What is a gene?

What is the central dogma of genetics?

What are the components of a gene?

What are alleles?

What is the difference between homozygous and heterozygous alleles?

What is the difference between a recessive allele and a dominant allele?

What are the two divisions of meiosis?

What are Mendel’s two laws of genetics?

Plant Breeding

What is the difference between a self-pollinating species and an out-pollinatingspecies:

What types of cultivar can be developed?

What are the major characteristics of species from which the following cultivar types are developed? And, provide an example crop where that cultivar type is developed

What factors would you consider when designing a breeding scheme?

How can breeders develop crops with improved profitability?

What are the two operations in cultivar development?

How do breeders produce genetic variability?

What are most commonly used mutagens in plant breeding?

What types of mutation can occur?

What would be the genotypic and phenotypic segregation in the F2 generation after a cross between a tall two-row barley (TTss) and a short six-row barley (ttSS), given that the tall gene (T) gene is dominant to the short gene (t) gene and the siz-row gene (S) is dominant to the two-row gene (s)?

If a plant breeder makes a cross between a tall homozygous barley parent (TT) and a short homozygous (dwarf) barley parent (tt). Where the tall gene (T) is completely dominant over the recessive dwarf gene (t). If the first generation (F1) is self pollinated and 800 second generation (F2) plants were grown out in the field. At harvest all the dwarf plants (short) are discarded and a single seed from each of the tall selected plants were grown out in the F3 generation. How many of the F3 plants would you expect to be short (dwarfs)?

What is heritability?

The phenotypic variance for seed weight in an F2 population is 200 kg2 and the genetic variance in that population is 150 kg2. What is the heritability for seed weight?

Plant diseases and insects

Which pests affect crop plants?

What are the major characteristics of the following plant pests?

Provide examples of the following pest types.

What effect do plant pests have on our crops?

In what sector of the ‘disease triangle’ might you expect to have disease?

Given that plants are resistant to a pathotype differentiated disease because they have at least one copies of dominant resistance gene (locks), which can only be overcome, and hence the plant become susceptible to the disease, if the disease pathotype has two copies of the appropriate recessive virulence gene (keys). Given that plant resistance genes are donated as capital letters (A, B and C) with susceptible genes as lower case letters (a, b, or c), and that disease virulent genes are donated as a’, b’ or c’ with disease avirulent genes donated as A’, B’, or C’, would the following plants be resistant or susceptible to the associated disease pathotype?

With respect to disease resistance what is meant by hypersensitivity?

Explain the following plant resistance mechanisms:(1) Antibiosis(2) Antixenosis(3) Escape

What is the difference between vertical and horizontal plant resistance?

Weed control

How do weeds impact crop plants?

How can weeds be controlled in crops?

Describe the mode of action of the following herbicide groups.

Why is herbicide mode of action important when considering herbicides resistant weeds?

What is meant by the term "plant back restriction"?

What does IPM stand for?

What techniques are utilized in IPM systems?

Biotechnology – molecular markers and plant transformation

What are bacteriophages?

What are restriction enzymes?

What are molecular markers used for?

What can be achieved by plant transformation techniques that are not possible with traditional plant breeding methods?

What plant characters have been developed through plant transformation?

What vectors can be used to insert genes into plants?

How does Agrobacterium tumefacians cause crown galls in plants?

Describe (briefly) the process of plant transformation.