Presentacion de 11th Asian Maize Conference which took place in Beijing, China from November 7 – 11, 2011.

1. Genetic and Morphological Diversity in Exserohilum
Turcicum, Incitant of Turcicum Leaf Blight in Maize
Sangit Kumar, Meena Shekhar, Archana Sharma, B. M. Prasanna
Directorate of Maize Research, Pusa Campus IARI, New Delhi,
110012 India

2. 1. Turcicum leaf blight or northern corn leaf blight
(TLB) is incited by the fungus Exserohilium
turcicum (Pass) Leonard and Sugs. (Synonyms;
Drechslera turcica (Pass.), Shoemaker.
Helminthosporium turcicum (Pass.)
2. It is a ubiquitous foliar disease of maize (Renfro
and Ullstrup 1976). TLB has worldwide
distribution.
3. Loss in grain yield range from 27.6 to 97.5% and
this loss was directly proportionate to the
intensity of the disease.
4. Two hot spots (Nagenahalli & Almora) for
Turcicum leaf blight identified for screening for
resistance in Peninsular India & Northern hills.

3. Turcicum leaf blight
• Distribution – Jammu & Kashmir, Himachal Pradesh, Sikkim,
West Bengal, Meghalaya, Tripura, Assam, Rajasthan, Uttar
akhand, Uttar pradesh (Rabi), Bihar (Rabi), Madhya Pradesh,
Gujrat, Maharastra, Andhra Pradesh, Karnataka, Tamil Nadu
• Symptoms – Long, elliptical, grayish-green or tan lesions
ranging from 2.5 to 15 cm in length develop on leaves. They
may appear first on the lower leaves and later on the diseases
progresses upward on the plant. The disease can develop
rapidly after anthesis resulting in complete blighting of leaves.
• Predisposing Factors – cool/moderate humid conditions
(18-27ºC) favors disease developments. When infection occurs
prior to and at silking stage and conditions are optimum, it
may cause significant economic damage.

4.  The extent of morphological and genetic diversity
among a set of isolates of E. turcicum, collected
from two distinct agro climatic zones (Northern
hill region and southern peninsular zone) in three
different years from different maize cultivars were
investigated.
 For developing location specific disease
management strategy, understanding the genetic
variability among isolates of E. turcicum is
essential.

5. Details of isolates used in present investigation
S. Isolate Year of Location
No. collection
1 A05 2005 Almora (Hawalbagh -Him-4)
2 A05a 2005 Almora (Hawalbagh -Vivek-9)
3 A05b 2005 Almora (Hawalbagh -CML-142)
4 A05c 2005 Almora (Hawalbagh -DMR-617)
5 A06 2006 Almora (Sheetlakhet)
6 A08 2008 Almora (Hawalbagh)
7 N05 2005 Naganenhalli
8 N06 2006 Naganenhalli
9 N08 2008 Naganenhalli

6. Morphological variability in the isolates of E. turcicum
Isolates N08 NO6 N05 A08 A06 A05 AO5a AO5b AO5c
Para.
Col. of Mouse Light Mouse Light Mouse Light grey Light grey
culture grey grey grey grey br. grey grey brown grey brown
br.
Culture Radia Radia Radia Irre Radi Radia Radia Radia Irregu.
orien. ting ting ting gular ating ting ting ting
Conidia Less High high Mod. Less Less high Mod. Suppre
intensity ssed
Mod.
Br. – Brown,
Orien. – Orientation
Mod. - Moderate

7. Isolates N08 NO6 N05 A08 A06 A05 AO5a AO5b AO5c
Para.
Conidia 1-7 1-10 1-11 1-9 1-7 1-9 1-10 1-11 1-10
speta
Color of stra Dark light Dark straw dark dark dark dark
conidia w straw straw straw straw straw straw straw
Conidia 35X 20X90 35X120 20X90 20X90 20X90 20X70 20X90 20X90
(µm) 120
Conidia Sligh Straig. Slight. Straig. straight Slight Slight. Slight. Slight.
shape tly curv. curv. curv. curv. curv.
curv. Long
beak
Chlamy high Mod. high Mod. Mod. Mod. Less High Less
dospore
intensity

8. Cultural characteristics of the colonies of different isolates of E. turcicum
10 days old Cultures grown in PDA

9. Spore germination in different isolates of
Exserohilum turcicum
S. No Isolate Germination Germination
after 2 hours after 4 hours
1 NO8 - +
2 NO6 - +
3 NO5 - +
4 AO8 - +
5 AO6 + +
6 AO5 + +
7 AO5a + +
8 AO5b + +
9 AO5c + +

10. 1. The isolates of E. turcirum exhibited variation in
mycelium color, with isolates N08, N05, A06 (mouse
grey) while isolates N06, A08 (light grey brown) and
isolates A05, A05a, A05b and A05c being light grey
to grey brown.
2. They varied significantly in their cultural,
morphological and physiological traits of colony
color shape, texture, conidia size and radial mycelia
growth on culture media. The optimum temperature
for the mycelia radial growth was 25°C and the
fungus was grown well in potato dextrose agar
(PDA).

11.  Spore germination data revealed that
Almora isolates were more prolific in
comparison to Nagenahalli isolates in
terms of germ tube production. Though
the Nagenahalli isolates possessed higher
number of spores in culture media (PDA).
 Progressive mycelial growth on culture
media revealed maximum coefficient of
variation in A05c while minimum in A05b
isolates.

12.  The morphological observation showed that
all the isolates of E. turcicum had different
conidial traits.
 Among them N05 sporulated better on PDA
medium. The mean length and breadth of
conidia ranged from 20x70 µm and (A05a,
A05c) and 35X120 µm (N05, N08), respectively.
 Mean septa of conidia was maximum in isolate
N05, A05b and minimum in isolate A06 and
N08.
 The highest mean radial growth was observed
in isolate N05 followed by N08 and the lowest
was observed in isolate A05c.

13. Dendrogram of isolates of Exserohilum turcicum based on
morphological traits
• Phenotypically all isolates belonged to four clusters
• maximum similarity of 64% in A05a and A05c
• N08and A06 again belonged to same cluster as in RAPD analysis.

14. L N08 N06 N05 A08 A06 A05 A05a A05b A05c L N08 N06 N05 A08 A06 A05 A05a A05b A05c
(a)
L N08 N06 N05 A08 A06 A05 A05aA05bA05c L N08 N06 N05 A08 A06 A05 A05a A05bA05c
(b)
L N08 N06 N05 A08 A06 A05 A05a A05b A05c L N08 N06 N05 A08 A06 A05 A05a A05b
A05c
(c)
characterization of exserohilum turcicum with different primers; (a) OPP-10,
OPS-1, (b) OPO-10, OPO-12 (c) OPS-3, OPS-10

15. Dendrogram of isolates of E. turcicum based on RAPD analysis

16. Results
1. Thirty two primers out of eighty (40%) produced
reproducible PCR banding pattern with a total of
205 bands.
2. Each primer produced an average of six bands
ranging in size between 0.025-0.1 kb. Five percent of
the amplified bands were common to all individual
isolates, while 90% were polymorphic being specific to
more than one isolates.
3. These were considered “phylogenetically
informative” since they were useful for inferring
clustering relationships.
4.The most divergent isolate was N05 from Nagenahalli
with only 12% similarity with other isolates.

17. 5. Isolates from Nagenahalli, N08 & Almora A06
are very similar to each other with 85%
similarity.
6. The morphological variability was observed
among these isolates.
7. The highest mean radial growth was
observed in isolate N05 followed by N08 and
the lowest was observed in isolate A05c.
8. Isolates belonging to same year from similar
location (A05, A05a, A05b and A05c) exhibited
enormous cultural variation in respect to
cultural characteristics & spore characters.

18. Conclusions
1. Dendrogram based on morphological traits
revealed diversity within the isolates collected
from the same geographical locations as well
from Nagenahalli and Almora.
2. Only a single isolate from Nagenhalli 05 was
out grouped with only 12% similarity with other
isolates. Isolate from Nagenahalli N08 and
Almora A06, are closely related with 85%
similarity. Gowda (1993) has reported that the
isolates from Almora and Nagenahalli belong to
race IV.

19. 3. Genotypic and phenotypic variability
were not correlated from two locations.
4. Phenotypically all isolates were grouped
into four groups as compared to three
groups at genotypic level.
5. Further study with more number of
isolates is needed to establish the
relationship between genetic and
morphological traits.

20. Acknowledgement
The authors gratefully acknowledge
with thanks the contribution of Dr. K. T.
Pandurangegowda, Professor, UAS,
Bangalore and Dr. S. K. Pant, Sr.
Scientist Plant Pathology for providing
the isolates and infected samples from
Nagenahalli (Karnataka) and Almora
(Uttarakhand) in India respectively for
present study.