Plant Pathologist's Diary: Practical 7: Phyto bacteriology

Practical 7: Phyto bacteriology

Introduction

Bacteria are a group of microorganisms classified as prokaryote. They have cell walls which are consisted of peptidoglycan layers. Bacteria are smaller than fungal spores and can only be seen clearly using the highest magnification of a light microscope. The classification of bacteria depends on the shape, composition of cell wall and mobility. According to shape, bacteria can be divided into 3 main types it is coccus, Bacillus, and spiral. Gram satin divides bacteria into 2 groups according to the composition of cell wall it is gram positive (with peptidoglycan layer) and gram-negative (with peptidoglycan and an additional outer membrane)

Objective

i. To study the taxonomy and pathological important of bacteriology.
ii. To learn the characteristics are shown by each of bacterial and microorganisms.
iii. To observer the disease cycles by bacterial microorganisms.

Method and material

1. Morphology

a) Observe the slide of bacteria.

b) Draw the shape of bacteria on the Petri plates provided.

c) Draw the shape of bacteria colonies produced on NA using dilution streak plate.

d) Observe the color of Gram bacteria positive and negative (purple and red).

2. Disease symptom

a) Take it the picture

b) Observe the symptom by bacteria

3. Disease cycle

a) Take the picture.

b) Observe the cycle of various bacteria.

4. Bacterial isolation

a) Wipe a knife, alcohol and Clorox

b) Cut out canker spot from disease tissue. (direct isolation)

c) Cut out disease from (b) above is distilled water 10 min (dilution streak)

d) Sterilize the cut tissue and place on the provided NYGA and NA.

e) Incubate the petri plate at temperature 27- 30 ˚C for 24- 48 hours.

5. Diagnostic test using cut plant tissue.

a) Wash the potato and peel off the skin.

b) Cut out two potato slices of 7-9 mm thick aseptically.

c) Cut ‘V’ shape of two potatoes on slices.

d) Put a drop of sterile water on it. (control)

e) Inoculate it with Erwinia caratovora subspecies on the ‘V’.

f) Incubate both plates for 24-48 hours at 30˚C.

g) Observe for symptom developed.

Result and discussion

Morphology

1	NYGA
2	NA

Disease symptom

Types of disease symptom	Description	Disease
Local necrosis scab	Scab is a serious disease of all lemon varieties the disease also affects Rangpur lime and rough lemon rootstocks. Scab is caused by the fungus Elsinoe fawcettii. Symptoms. Citrus scab attacks the fruit, leaves, and twigs, producing slightly raised, irregular scabby.
Local necrosis Leave spot	Leaf spot is a common descriptive term applied to a number of diseases affecting the foliage of ornamentals and shade trees. The majority of leaf spots caused by bacteria. Some insects also cause damage that appears like a leaf spot disease
Local necrosis Downy mildew	It is caused by the fungus-like water mold Pseudoperonospora cubensis. Once established in a region, the disease can spread rapidly, causing significant loss of fruit quality and yield. Downy mildew symptoms on cucumber leaves.
Local necrosis Canker	Citrus canker is a disease affecting Citrus species caused by the bacterium Xanthomonas. The infection causes lesions on the leaves, stems, and fruit of citrus trees
Local necrosis Powdery mildew	Powdery mildew, mainly caused by the Erysiphe cichoracearum, infects all cucurbits, including muskmelons, squash, cucumbers, gourds, watermelons, and pumpkins. In severe cases, powdery mildew can cause the premature death of leaves, and reduce yield and fruit quality.
Hypertrophy Hyperplasia-gall	Crown gall is a common plant disease caused by the soil-borne bacterium Agrobacterium tumefaciens. It is found throughout the world and occurs on woody shrubs and herbaceous plants including grapes, raspberries, blackberries and roses.
General necrosis Soft rot	Bacterial soft rots are caused by several types of bacteria, but most commonly by species of gram-negative bacteria, Erwinia, Pectobacterium, and Pseudomonas. It is a destructive disease of fruit, vegetables and others.
Local necrosis Rust leaf	Rust on the leaf are very easy to identify on the plant. The disease can be characterized by a rust color on plant leaves and stems. The rust will start out as flecks and will eventually grow into bumps. The plant rust will most likely appear on the underside of the leaves of the plant.