Ex. No. 14.                                                            Study of Bacterial diseases

Bacteria: Bacteria are prokaryotic, microscopic, unicellular, rigid cell wall organisms which are achlorophyllous. They are reproduced by binary fission (asexually).

Gram negative bacterium: Xanthomonas, Pseudomonas, Erwinia, Agrobacterium

Gram positive bacterium: Streptomyces, Clavibacter

Disease name	Causal Organism				Symptoms
Bacterial Leaf Blight of rice	Xanthomonas oryzae pv. oryzae				Straw colour necrotic patches with yellow wavy margin are appear
Bacterial leaf streak		Xanthomonas oryzae pv. oryzicola
Black arm of cotton/ Angular leaf spot	Xanthomonas axonopodis  pv. malvacearum (Both internally and externally seed borne)				Black lesions are formed on the leaves and breaking the stem, hang typically a dry black twig to give a characteristic ‘black arm’ symptom
Citrus canker	Xanthomonas citri				Corky outgrowth on the surface of leaves, twigs and fruits with surrounded by yellow halo (except fruits)
Soft rot of carrot	Pectobacterium carotovorum				Softening and disintegration of tissues
Potato Scab	Streptomyces scabies				Bulged lesions  (Soil borne bacterium)
Black rot of cabbage	Xanthomonas campestris pv. campestris (1st seed borne bacterium)				‘V’ Shaped chlorotic regions
Tundu disease of wheat	Corynebacterium tritici				The disease is an example of nematode bacterial complex disease.
Fire blight of apple and pear			Erwinia amylovora( 1878, T.J.Buriill) 1st Bacterial disease in World
Bacterial wilt of cucurbits			Erwinia tracheiphila (E.F.Smith)
Crown gall of apple and pear			Agrobacterium tumefaciens New name is Rhizobium radiobacter (This bacterium is an example plant pathogenic bacterium used for transfer of genetic material from one plant to another plant, Scientist’s best friend)
Moko wilt of Banana			Ralstonia solanacearum (Strain no: 2)
Brown rot of potato			Ralstonia solanacearum (Strain no: 3)
Bacterial wilt of Solanaceous vegetables				Ralstonia solanacearum (Strain no: 1)

Bacterial leaf blight of rice Other name: Bacterial Blight, White withering disease 

Causal organism: Xanthomonas oryzae pv. oryzae Ishiyama

Symptoms: Kresek stage (Nursery stage): At the seedling transplanting stage, the infected plants are wilting

1.       On mature plants, small water soaked lesions are appear

2.       Wavy margin are appear on inner portion of the leaves

3.       Complete death of entire plant is called hama lodoh

4.       Pale yellow discolouration and bacterial ooze out occur

5.       It’s a gram negative bacterium with rod shaped, Single polar flagellum

6.       Mode of spread : Anemochory and Hydrochory

7.       Spray Agrimycin- 50 for manage this disease

Black arm of cotton Other name: Angular leaf spot, Boll rot, Black vein

Causal organism: Xanthomonas axonopodis pv.  malvacearum E.F. Smith

Symptoms: Small dark green water soaked areas develop on the lower surface and turn into reddish brown colour

1.       Blackening of veins and veinlets (necrosis)

2.       On stem there appear elongate grayish to black lesions

3.       Gummosis and Bacterial ooze out also appear

4.       On the bolls, small water soaked lesions are appear and turn brown later

5.       It’s a gram negative bacterium with rod shaped, Single polar flagellum

6.       Rain fallowed by bright sunshine favours the disease

7.       Spray streptomycin for manage this disease

Ex. No. 13                           Dissection specimens  

Guava red rust or Algal spot or Parasitic algal infection 

Causal organism: Cephaleuros spp.  (Cephaleuros virescens, Cephaleuros mycoidea; Cephaleuros parasiticus)

Taxonomic position:

Phylum: Chlorophyta , Order : Trentepohliales,   Division: Trentepohiliaceae,   Genus: Cephaleuros Species: virescens Affected crops: Guava, Mango, Papaya, Citrus, Avocado, Tea, Coffee, Pepper and Sapota.

Symptoms:          Sexual spore : Microzoospore, Asexual spore : Zoospore

1. Orange yellow rust pustules are appear on adaxial surface of the leaves (mostly)                             

 2. Yellow coloured pustules are due to hematochrome                                                                                 

   3. The alga takes up water and minerals from the host by osmosis

Life cycle

1.       Zoospores are biflagellate, and about 30 are produced from each sporangium.

2.       The infection may be initiated by zoospores washed in to the stomata by rain

3.       Zoosporangia are disseminated by the wind (Anemochory)

4.       The end of the rainy season, the disease becomes severe

Management

1.       Avoid heavy application of nitrogen and potassium to reduce the disease incidence.

2.       All badly diseased or dead wood should be removed

3.       Spray Bordeaux mixture or Copper Oxy Chloride at 0.1 per cent

Ground nut Tikka leaf sport 

Causal organism: Cercospora  arachidicola (Mycosphaerella arachidis) (Early leaf spot/ Brown leaf spot )                                     Cercospora  personata (Mycosphaerella berkeleyi) (Late leaf spot/ Black leaf spot)

Symptoms

Characteristics	Early leaf spot	Late leaf spot
Seasonal development	Early season	Late season
Shape of spots	Circular to irregular	Circular
Leaf surface where first, most spores produced	Upper	Lower
Yellow halo	Present	Absent
Colour of spots	Brown (reddish brown)	Black (dark brown)
Conidiophore	Yellowish brown	Olivaceous brown
Conidia	Hyaline, Obclavate	Cylindrical

Epidemiology

1.       25 to 30⁰C with high RH favour for disease development

2.       Heavy application of nitrogen and phosphorus fertilizers increases severity of this disease

Management

Spray Carbendazim 0.5 or Hexaconazole 0.2 percent per cent are effective. Diseased materials are removed from the field.  

Banana black freckle leaf spot

Causal organism: Phyllostictina musarum                                                                                                         Telemorphic stage: Macrophoma musae (Guignardia musae)

Taxonomic position:

Domain: Eukarya, Kingdom: Fungi, Division : : Ascomycota, Class: Dothideomycetes, Order: Botryosphaeriales, Family: Botryosphaeriaceae Genus: Macrophoma

Symptoms:   

                The upper surfaces of older leaves are affected. Dark brown to black spots are appear (Oblong, muddy brown to black dots)

 Pycnidium; It is a flask shaped asexual fruiting body and Psudoparaenchymatous cells are lined with pycnidiophore with an anterior opening called ostiole. Through their ostiole only the pycnidiospores (conidia) are released out or ejected out from the Pycnidium. Conidia are Aseptate, cylindrical. In sexual stage perithecia and ascospores are formed.

Epidemiology: Conidia dispersed through Hydrochory and usually travel through short distance.

Management:                                                                                                                                                                                      1. Removal of infected leaves from the banana.      

               2. Spray Mancozeb at 0.2 per cent

Ex. No. 12                                             Study of foliar, wilt and root rot diseases

Fungi imperfecti, Dust bin fungi, Anamorphic fungi, Asexual fungi, Mitosporic fungi, Residual fungi. Now recent classification point of view they are adopted mostly in Ascomycota and some are in basidiomycota.

Domain: Eukarya, Kingdom: Fungi, Division : : Ascomycota, Sub – division : Pezizomycotina, Class: Dothideomycetes, Order: Pleosporales, Family: Pleosporaceae,  Genus: Cochliobolus

Domain: Eukarya, Kingdom: Fungi, Division : : Ascomycota, Sub – division : Pezizomycotina, Class: Dothideomycetes, Order: Pleosporales, Family: Pleosporaceae,  Genus: Alternaria

Disease name		Causal Organism	Symptoms
Rice blast		Pyricularia oryzae T:Magnaporthe grisea	Spindle shaped spots with grey centre and dark brown margin on leaves, nodes and internodes
Rice brown leaf spot / Sesame leaf spot		Bipolaris oryzae T:Cochliobolus miyabeanus		Brown coloured sesame seed shaped spots on the leaves. Bengal famine (1942-1943)
Banana Sigatoka leaf spot		T: Mycosphaerella musicola Cercospora musae		Initially spots are small, light yellow spots parallel to the side veins of leaves. Later on the spots become enlarge in size and turn brown with light gray centers.
Bhendi Cercospora leaf spot		Cercospora abelmoschi		Black colour powdery patches are appear on underside of the leaves
Sunflower Alternaria blight		Alternaria helianthi                     T: Alternaria is Lewia		Brown colour irregular spots with concentric rings are appear. The concentric rings are due to Alternaric acid – Phytotoxin
Tomato Early blight		Alternaria solani		Brown colour irregular spots with concentric rings are appear
	Banana freckle leaf spot	Phyllostictina musarum		On the leaves numerous, minute dark brown raised spots with a black dots are formed

Vascular Wilts

1.       Fusarium wilt  (Tropical wilt)

Domain: Eukarya, Kingdom: Fungi, Division : : Ascomycota, Sub – division : Pezizomycotina, Class: Sordariomycetes , Order: Hypocreales, Family: Nectriaceae,  Genus: Gibberella (Fusarium sexual stage is Gibberella) (Fusarium oxysporum are not producing sexual stage)

Disease name	Causal Organism	Symptoms
Fusarium wilt of Tomato	Fusarium oxysporum f.sp. lycopersici	Yellowing and Drooping of leaves. Browning and blackening of vascular tissues are appear (Vascular discolouration). Fusarium produces macro conidia, micro conidia and Chlamydospore (resting spore).
Panama wilt of Banana	Fusarium oxysporum f.sp. cubense
Fusarium wilt of cotton	Fusarium oxysporum f.sp. vasinfectum
Foot rot in rice	Fusarium moniliforme

2. Verticillium wilt (Temperate wilt) : Cotton Wilt – Verticiilium dahliae (Tiger stripe symptoms); Tomato Verticillium wilt – Verticillium albo atrum;  Cigar end rot of Banana – Verticillium theobromae

Aganomycetaceae / Mycelia sterlia (In general sterile fungi means Sclerotium producing fungus)

Disease name		Causal Organism	Symptoms
Rice sheath blight		Rhizoctonia solani	Elliptical greenish with irregular blackish brown border spots appear on the leaf sheath near the water level
Pulses root rot	Macrophomina phaseolina Rhizoctonia bataticola		Root portions are decayed. Bark shredding symptoms are appear.
Ground nut collar rot		Sclerotium rolfsii	Reddish brown lesions are appear on the stem near the soil level. Rotten tissues are containing brown mustard shape sclerotia

Anthracnose:  produced sunken spots

Domain: Eukarya, Kingdom: Fungi, Division : : Ascomycota, Sub – division : Pezizomycotina, Class: Sordariomycetes , Order: Glomerales, Family: Glomerellaceae,  Genus: Glomerella (Colletotrichum sexual stage is Glomerella)

Disease name				Causal Organism				Symptoms
Sugarcane red rot		Colletotrichum falcatum				Third or fourth leaf which withers away at the tips along the margins. Reddening of internal tissues with cross white patches. Infected field produce alcoholic odour.
Pulses anthracnose			Colletotrichum lindemuthianum				Sunken brown coloured lesions are appear in the leaves and pods
Fruit rot of chilli	Colletotrichum capsici				A small brown to black coloured spots are appear and spots are having black dots that denotes acervuli.
Mango anthracnose				Colletotrichum  gloeosporioides
Banana anthracnose				Colletorichum musae

Life cycle of Macrophomina phaseolina / Root rot

Kingdom: Fungi ,Division: Eumycota ,Sub – division: Deuteromycotina ,Class: Deuteromycetes ,Order: Aganomycetales

Family: Aganomycetaceae ,Genus: Macrophomina,Species: phaseolina

Disease name: Pulses root rot / Dry root rot

Symptoms: Root portions are decayed. Bark shredding symptoms are appear.

Life cycle: The fungus are having two stages namely Pycnial stage and sclerotial stage.

·         Pycnial stage: Macrophomin phaseolina

·         Sclerotial stage: Rhizoctonia bataticola

·         Sclerotia are black coloured and irregular structures.

·         Infected tissues are having black coloured sclerotia like a coal.

·         The disease is otherwise called charcoal rot. soil borne in nature.

·         In dry and hot conditions the roots are infected

·         The hyphae are inter and intracellular with Septate mycelium.

·         Each Sclerotium size is 100 µ in diameter

·         Later the mycelium are enters to the xylem vessels

Live cycle of Fusarium wilt of banana / Panama wilt of Banana

Kingdom: Fungi ,Division: Eumycota ,Sub – division: Deuteromycotina ,Class: Deuteromycetes ,Order: Moniliales

Family: Tuberculariaceae ,Genus: Fusarium

Species: oxysporum f.sp. cubense

Disease name: Fusarium wilt / Panama wilt of Banana (sudden death)

Symptoms:

1.       Yellowing of leaf blades developing as a band along the margin and spreading towards midrib.

2.       Pseudostem may show longitudinal splitting of outer leaf bases above the soil level

3.       The infected stem smells like rotten fish

Life cycle                                                                      

1.       The fungus produce macro conidia, micro conidia and Chlamydospore

2.       It is a soil borne and producing resting spore Chlamydospore (Hydrochory)

3.       The mycelium are inter and intracellular. Macro conidia are falcate shape, Microconidia are oval and Chlamydospore are globose shaped.

4.       The infection occurs through injured lateral roots

5.       After the entering they are blocking the xylem vessels (formation of gels and tyloses)

6.       Acidic soils are suitable for disease development

7.       They are producing asexual fruiting body is sporodochium

Theories are involved

1.       Tylosis: Vascular vessels mostly xylem are blocking due to wilt fungus

2.       Fusarium fungus are producing Fusaric acid (Vivotoxin)