d(GC) - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and Pharmacy
Vol. 6 (2) 173-182 April 2012, ISSN 0973-8916 (Print), 2230-7303 (Online)
Analysis of Population Structure of Magnaporthe grisea
Using Genome Specific Microsatellite Markers
K. Madhan Mohan 1* , M. Sheshu Madhav 2 , M. Srinivas Prasad 1 , S. J. S. Rama Devi 2 , G. Ram Kumar 2
and B. C. Viraktamath 3
1 Department of Plant Pathology, Directorate of Rice Research, Crop Protection Division, Rajendranagar,
Hyderabad, Andhra Pradesh 500030, India
2 Department of Biotechnology, Directorate of Rice Research, Crop Improvement Division, Rajendranagar,
Hyderabad, Andhra Pradesh 500030, India
3 Project Director, Directorate of Rice Research, Rajendranagar, Hyderabad,
Andhra Pradesh 500030, India
*For Correspondence - madanmohan.kolluru@gmail.com
Abstract
In order to understand the pathogen’s
genetic diversity and dynamics of fungal
populations, 34 rice blast isolates collected from
various blast endemic areas of India were
analyzed using Magnaporthe grisea genome
specific microsatellite markers (MGM) and repeat
element based Pot2 primer. All the blast isolates
showed average pair wise similarities in the range
of 0.15 to 0.9 and suggested the large variations
with in the isolates collected from the different
places. To know the genetic relationship among
the blast isolates, a dendogram was generated
based on analysis of MGM and Pot2 primers
separately and in combination using SHAN/
UPGMA program. The cluster analysis grouped
all the blast isolates in to different clusters mostly
based on the location, from where they were
collected. Based on International blast differential
lines containing single resistance genes, it was
identified that AVR Pi-k gene was present
predominantly in isolate collected from Nellore
in costal Andhra Pradesh; and AVR Pi-2 and AVR
Pi-4 genes in isolates collected from Mandya
(Karnataka). The isolates collected from Almora,
Ranchi and Nawagam showed the presence of
AVR Pi-1 and AVR Pi-4a genes. The present
study helped us to understand the population
diversity and their AVR genes spectra in the blast
hotspot regions of India, which can be useful in
173
deployment strategies for blast resistance genes
in rice improvement programmes.
Key words: Avr genes, Blast resistance genes,
Cultivars, Pathosystem, Repetitive DNA
sequences.
Introduction
Rice blast disease is caused by a heterothallic
ascomycetes fungus Pyricularia grisea
(Teleomorph: Magnaporthe grisea (Hebert) Barr).
Among all the biotic stresses of rice, blast disease
alone causes yield loss of about 50 % (1). The
fungus grows in all rice-growing areas across the
world and attacks almost all the aerial parts of
rice plant typically, leaves and panicles. Sesma
and Osbourn (2) revealed that the foliar blast
pathogen also invades roots using a typical rootspecific
pathway. It is estimated that the loss due
to this disease is over 70 % in the USA (3). Neck
blast is the most destructive form of the disease,
which causes the maximum damage to the yield.
Though chemicals are available to combat this
disease, deployment of resistant cultivars is the
best alternative method, which is economically
viable and environmentally safe. But, high
mutation rate of this fungus can overcome the
resistance within a short time after the release
of a new cultivar thus making the breeding for
resistance to blast a constant challenge. To
Analysis of Population Structure of Magnaporthe grisea