LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – PLANT BIOLOGY & PLANT BIO-TECH.

SIXTH SEMESTER – APRIL 2011

PB 6608/PB 6604 – PLANT DISEASES AND MANAGEMENT

 

 

 

Date : 05-04-2011              Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

PART – A  (20 marks)

 

ANSWER ALL THE QUESTIONS

 

I.CHOOSE THE CORRECT ANSWER :                                                (5 x 1 = 5 marks)

 

1. Which one of the following is not produced by the pathogen ?

[a]  Toxins         [b] Enzymes        [c] Phytoalexins         [d] Growth regulators

 

1. Which one of the symptoms is  produced by viral pathogens?

[a] Chlorosis           [b] Canker        [c] Rot              [d] Wilt

 

1. The causal organism of the club root of cabbage is:

[a] Pernospora parasitica                 [b] Phytophthora infestans

[c] Plasmodiophora brassicae          [d] Fusarium oxysporum

 

1. Tobacco Mosaic Virus can be controlled by

[a] spraying chemicals                  [b] controlling insect vectors

[c] growing resistant varieties       [d] clipping diseased plant parts.

 

1. Which one of the following is an organic mercurial fungicide ?

[a] Agrosan        [b] Bavistin      [c] Captan        [d] Maneb

 

 

1. STATE WHETHER THE FOLLOWING STATEMENTS ARE TRUE OR FALSE :

(5 x 1 = 5 marks)

1. Fungal pathogens penetrate the host by producing appressorium.
2. Horizontal resistance is usually polygenic in inheritance.
3. Damping off is a symptom seen in branch tips.
4. Root knot of potato is caused by nematodes.
5. The ‘safener’ in Bordeaux mixture is copper.

 

III. COMPLETE THE FOLLOWING :                                                                        (5 x 1 = 5 marks)

 

1. Removing the source of inoculum and  preventing the spread of infection is achieved

through —————–.

1. Secondary metabolites of host plant produced in response to pathogen attack are called ————.
2. Red rot of sugarcane is caused by —————— ——————-.
3. Little leaf of brinjal is caused by ———————.
4. Plant quarantine  measures help in preventing —————–.

 

1. ANSWER THE FOLLOWING, EACH WITHIN 50 WORDS:        (5 x 1 = 5 marks)

 

1. Define inoculum potential.
2. What is hypersensitive reaction?
3. What is an alternate host?
4. How are insect galls produced?
5. What is biological control ?

PART – B

 

ANSWER ALL QUESTIONS, EACH WITHIN 500 WORDS, DRAW DIAGRAMS WHEREVER  NECESSARY :                                                                                                           ( 5 x 7 = 35 marks)

 

1. a)  Explain the molecular basis of infection.

(OR)

1. b) What are the various toxins produced by fungal pathogens ?

Point out their role in infection.

 

1. a) What are the induced defence mechanisms seen in host plants ?

(OR)

1. b) Explain the role of environmental factors in the onset of disease.

 

1. a) Give the causal organism, symptoms and control measures for Tikka disease of

groundnut.

(OR)

1. b) Describe the Downy mildew disease of grapes.

 

1. a) Give an account of a disease caused by mycoplasma.

(OR)

1. b) Give an account of angiospermic plant parasite.

 

1. a) Give a concise account of  chemicals used for plant protection.

(OR)

1. b) Write notes on bacterial biopesticide.

 

PART C

 

ANSWER ANY THREE QUESTIONS IN NOT MORE THAN 1200 W0RDS EACH. DRAW DIAGRAMS WHEREVER NECESSARY.                                                       (3 x 15 = 45 marks)

 

1. Elaborate on the concepts in the process of infection.
2. Explain the innate defence mechanisms  encountered in host plants.
3. Discuss the causal organism, symptom and control measures of Rust of wheat.
4. Give a brief account of the diseases of paddy crop –fungal, bacterial and viral.
5. Highlight the role of engineered resistance in plant disease control.

 

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