Pathology

1. Cassava mosaic –
Cassava mosaic virus
Vector - Whitefly, Bemisia tabaci
This is characterized by severe mosaic
symptoms on leaves. The affected leaves may
show mosaic mottling in beginning after which
the young leaves show more severe symptoms
such as distortion of leaves, malformation and
puckering.
Cassava mosaic

2. Redgram sterility mosaic :
Pigeon pea sterility mosaic virus
Vector – Mite, Aceria cajani
The characteristic symptoms comprise
the pale green colour of plants,
absence of flower
s and stunted growth.

3. Blackgram and greengram yellow
mosaic:
yellow mosaic virus
Vector - Whitefly, Bemisia tabaci
The infection begins when the plant is in
young stage. Small greenish yellow
patches are seen on young leaves which
are limited by veins. Spots are
translucent, light yellow margin is also
seen.

4. Bhendi vein clearing –
Yellow vein mosaic virus
Vector – Whitefly, Bemisia tabaci
Main symptoms are vein clearing
and veinal chlorosis of leaves. The
yellow network of veins is very
conspicuous and the veins and
veinlets are thickened. Fruits
become small, malformed and
yellowish green.

5. Tomato/ Tobacco/ Papaya leaf curl :
leaf curl virus
.Vector – Whitefly, Bemisia tabaci
Crinkling, curling, puckering of leaves. The plant is
stunted, reduction in the length of internodes etc.

6. Leaf crinkle of black gram and green gram
Leaf crinkle virus
Seed borne, sap transmissible and
Vector – Whitefly, Bemisia tabaci
Crinkling and curling of the leaflets. The petioles and the
internodes are shortened. The infected plants gives a
stunted appearance. Malformed flower buds fail to open.

7. •Banana bract mosaic virus
•Pinkish to reddish spindle shaped streaks on the pseudostem, midrib,
peduncle, bract
•Clustering of leaves at crown with “travelers palm” appearance in Nendran
variety
•The virus is transmitted by Pentalonia nigronervosa
On Stem
On inflorescens

8. Papaya ring spot
Papaya ring spot virus (PRSV)
Vector – Aphid, Aphis gossypii
Myzus persicae
Shoe string symptoms on leaves. Oily streak on
papaya stem. Ring spot pattern on fruits and
distortion of fruits.

9. Citrus tristeza
Citrus tristeza virus
Vector – Brown citrus aphid, Aphis gossypii
Decline includes chlorotic leaves
general dieback of the infected tree.
Stem-pitting in the trunk and stem
Seedling yellows-yellowing of foliage and
general dieback.

10. Rice tungro
Rice tungro virus
Vector - Leaf hopper,
Nephotettix virescens
Plants stunted .Yellow to orange discolouration of
leaves. Interveinal chlorosis.

11. Bunchy top of banana –
Musa virus 1 or Banana Virus
Vector – Aphid, Pentalonia
nigronervosa
In badly infected plants leaves
are typically bunched together
at the apex forming a dense
rosette, hence the name
bunchy top. Younger infected
plants are stunted showing
more erect leaves than
normal. Green streaks appear
on secondary veins on the
underside of lamina, midrib
and petiole.

12. Tomato spotted wilt -
Tomato spotted wilt virus
Vector – Thrips, Scirtothrips dorsalis
The plant becomes stunted with leaves reduced in size,
bronzing of veins. Necrotic regions or rings on leaves with
necrotic streaks on petioles and stem. Concentric rings of
mosaic mottling on fruits

13. Bud necrosis of groundnut
Vector – Thrips, Frankliniella schultzii,
Thrips tabaci, Scirtothrips dorsalis
chlorotic spots on young leaflets as faint that may
develop into chlorotic or necrotic rings and streaks.
Terminal buds of plants are affected
Leaflets produced on auxilary shoots show a wide
range of symptoms including reduced size, distortion
of the lamina, mosaic and general chlorosis, stunting
of plants, seeds produced by early-infected plants are
small, shriveled, and with spots.

14. Viroids and prions
Viroids- are covalently closed, circular, single-stranded RNA molecules without
protein coat.
Eg. Potato spindle tube disease- potato spindle tuber virus
Citrus exocortis:
Chrysanthemum stunt
Coconut cadang cadang
Prions- unfolded infectious proteins and have no nucleic acids.
virusoids:- viroid like RNA enclosed in a virus particle/virion/virus. Thus viron
contains viroid like RNAs besides its own RNA

15. SYMPTOMS OF ALGAL PARASITE
RED RUST DISEASE- Cephaleuros sp
SYMPTOMS:
1. The disease caused by algae in plant is called as red rust disease.
2. It affect Guava, Mango, Sapota, Citrus, Tea, Coffee etc.
3. The symptoms will be reddish brown to Orange circular raised spots with
filamentous margins appear on both surfaces of the leaves.
4. These spots coalesce and infected leaf become yellow and dried with Pre-
mature leaf shedding.

16. PATHOGEN:
1. Cephaleuros species consist of branched filaments that comprise a
thallus in the form of irregular discs. The thallus grows below the
cuticle or sometimes below the epidermis of the host plant.
2. This thallus is pigmented (orange to red-brown) consists of a
vegetative filaments and sporangiophores. They are erect which
may be fertile or sterile.
3. The sporangiophores bear one or more head cells with Sterigmata.
Each sterigmata bears single gametangium.

17. Ascus development
Ascus (Asci; pl): sac-like structure containing ascospores (typically eight) and usually
borne in a sexual fruiting body of the ascomycota fungi
Ascospores : a haploid (1N) sexual spore borne in an ascus. They are produced
by ascomycota fungi
Mitosis in crozier

18. Ascus development
1. Mycelium produce antherium and ascogonium
2. Male nuclei reaches ascogonium through Trichogyne and form dikaryotic state
3. Small protuberance appear on the ascogonium and later forms ascogenous hyphae
4. Dikaryons multiply by conjugative divisions in the ascogenous hyphae and septa are
laid down in such a way that each cell is dikaryotic except the terminal cells which has
single nucelus.
5. penultimate cell of the ascogenous hyphae bends to form crozier like cell called
Crook cell. Two nuclei in the crook cell divide mitotically in a such as way that two
daughter nuclei lin in the bend of the hook. Other two parental nuclei, one lies at the
base and another at the tip.
6. The penultimate cell acts as ascus initial cell. Karyogamy takes place in the ascus initial
cells form diploid, followed by meiosis leading to the production of 4 nuclei, followed
by mitosis resulting in 8 nuclei.
7. Wall is formed around each nucleus with some cytoplasmic material resulting in
ascopores
8. The basal and the apical cells present near the the ascus initial cells later fuse and
form the new the ascus initial cells leading to the production of ascoposre

19. Character Black rust/stem rust Leaf /brown/orange
rust
Yellow or stripe rust
Causal organism P. graminis tritici P. recondita P. striiformis
symptom Mainly on stem,
brown pustutle
initially and later
turns to black
On leaves initially
brown later turn to
orange
On leaves, yellow
pustules in rows
Uredospores Brown, oval, with 4
germpores
Brown, spherical, 7-
10 germpores
Yellow, spherical to
oval
Teliospores Black, two celled,
pointed apex
Brown, two celled,
round apex
Brown, two celled,
flat apex
Alternate host Berberis, mahonia Thalictrum Unknown
Distinguishing features of wheat rust diseases