Microbes in Agriculture

Question 1

What are the three main causal agents of disease in crops plants?

Answer 1

Bacteria, oomycetes and viruses.

Question 2

What are some examples of microbes which have beneficial effects on the plant?

Answer 2

• Rhizobiaceae
• AMF fungi
• tolerance to salinity
• aiding nutrient absorption
• bioremediation
• phytoremediation

Question 3

What is the name of the most destructive pathogen of the potato?

Answer 3

Phytophthora infestans.

Rapid production of genetically resistant cultivars.

Question 4

How does the phytophthora blight spread?

Answer 4

In water, splashing rain and irrigation.
Infected plant dies - pathogen remains in the debris
Mating types present = oospores (can survive for yrs)

Question 5

What do infected phytophthora blight plants produce a lot of ?

Answer 5

Millions of asexual sporangia.

Each sporangium produces 20-40 swimming zoospores called capsici.

Question 6

What are some symptoms of plant infection?

Answer 6

Wilt
Necrosis of the leaves
Maceration
Dark spots on leaves

Question 7

What is the name of the fungal pathogen which affects rice and interacts similarly to AMF hyphae?

Answer 7

Magnaporthe Oryzae; M.oryzae

Question 8

How are M.oryzae spread?

Answer 8

In the field, sporolates at nodes on the rice stem and rots the neck of the mature rice plants.
Sporolates from lesions and spores are dispersed by drewdrop splash.

Question 9

What is the name of the dome shaped infection site on the rice lead surface?

Answer 9

Appressorium - this can generate enormous turgor of up to 8MPa to rupture the rice leaf surface.

Question 10

What is an example of a GP bacterium which results in potato scab?

Answer 10

Streptomyces scabies

Question 11

What is an example of a GN bacterium which results in the bacterial blight for example?

Answer 11

Xanthomonas Oryzae

Question 12

Are there any benefits associated with viral pathogens and plants?

Answer 12

The tulip virus offers a variety of plant colours.

Question 13

Which auxin produces a suspension responsible for growth promotion in the plant?

Answer 13

Pseudomonas Corrugata

Question 14

In which ways can rhizobacteria promote plant growth?

Answer 14

• prod of plant hormones IAA
• Increasing availability of S, P and N
• restriction of entry for pathogens around plant roots - RECRUITED by plant to do this.

Question 15

Name three ways in which bacteria transform plant nutrients:

Answer 15

• Carbon - decomp & photosynthesis
• Sulphur - P insoluble in soil, bacteria make it available for plant
• phosphorous “”

Question 16

What is the causal agent in the early damping off disease in sugar beet?

Answer 16

Pythium Ultimum, an oomycete.

Question 17

What is ISR?

Answer 17

This is induced systemic resistance.

Ex: the primed feature of bacterial application to the plant roots to confer pathogen resistance.

Question 18

Which pseudomonas is beneficial to plants?

Answer 18

Fluorescent pseudomonads - in soil.

Question 19

What are 2 types of antibiotics which are involved in plant growth promotion?

Answer 19

HCN - hydrogen cyanide

Lytic enzymes

Question 20

What are 2 examples of indirect plant growth promotion mechanisms?

Answer 20

• antifungal metabolites production

- ISR responses (induced systemic response)