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POPULATION STRUCTURE OF RHIZOCTONIA SOLANI AG-1-IA, THE RICE
SHEATH BLIGHT PATHOGEN, FROM THE NORTH OF IRAN
J. Zad A , S. Jafarpour B and M. Javan-Nikkhah B
A Department of Agriculture, Islamic Azad University, Karaj branch 3187644511, Iran.Email:sjmycology@Gmail.com.BDepartment of Plant
Protection, University College of Agriculture and Natural Resources, University of Tehran, Karaj 31587-11167
ABSTRACT. Rhizoctonia solani (Kuhn) is an important soil born pathogen of rice and the most widespread plant pathogenic
fungi in many rice growing regions including the north of Iran. Very limited studies on the genetic diversity of this fungus
have been carried out so far in Iran. This fungus was isolated from stubbles and sheath blight lesions on plant in different
fields from northern rice-growing regions of Iran. Genetic diversity among 30 isolates belonged to AG-1-IA were determined
by analyzing RAPD-PCR using five random primers. RAPD fingerprinting analysis of the isolates determined three
fingerprinting groups at 85% similarity level. No correlation was observed between RAPD clustering and geographical
origins and Very distantly separate isolates showed high level of similarity in banding pattern. Considering to the high level
of similarity among isolates of rice sheath blight populations, the asexual stage is probably viewed as predominant in the life
cycle of the organism in Iran.
INTRODUCTION
Rice sheath blight caused by Rhizoctonia solani AG-1-IA is
an important rice disease complex occurring in most riceproducing
areas of the world including Iran. It has been the
subject of several population studies measuring variation
based on, RFLP (Rosewish et al., 1999; Linde et al., 2005),
rep-PCR (Linde et al., 2005), ITS-5.8s rDNA (Ciampi et al.,
2005), RAPD (Pascual et al., 2000). Very limited studies,
on the genetic diversity of rice sheath blight pathogen have
been carried out So far in Iran. The aims of this study were
to investigate the diversity of R. solani within anastomosis
group AG-1-IA field populations on rice using RAPD
markers to obtain a clear picture of relationship between
Iranian isolates and to assess the sensitivity of this marker
for studies at this taxonomic level.
MATERIALS AND METHODS
Rhizoctonia solani specimens were collected from different
fields in Northern rice growing areas of Iran, Guilan and
Mazandaran provinces. Sampling was carried out randomly
from each selected fields. Both of mentioned provinces are
characterized by humid weather. Two anastomosis tester
isolates from each subgroup AG-1-IA and IC were used for
genetic comparison with rice recovered isolates. Hyphal
anastomosis reactions of Iranian field isolates with tester
strain AG-1-IA were assessed according to categories
described by carling et al., (1996).. Genomic DNA of each
30 isolates from Guilan and Mazandaran provinces with two
AG-1-IA and AG-1-IC was extracted according to Pascual
et al., (2000) with some modifications. The RAPD–reaction
was carried out using five random primers:OPR-06-5′-
GTCTACGGCA-3′,OPR-04-5′-CCCGTAGCAC-3′,RC09-
5′-GATAACGAGCA-3′,R-28-5′ATGGATCCGC-3′ ,P14-
5′-CCACAGCACG-3′
RESULTS AND DISCUSSION
PCR reaction with the five random primers gave
amplification products that generated reproducible
monomorphic and polymorphic DNA pattern in the size
range of 0.4-1.9 Kb.UPGMA clustering analysis of the
isolates allowed grouping of AG-1-IA, IC into distinct
clusters and resolved three distinct groups of AG-1-IA at the
85% similarity level. More than 90% of Rice isolates
clustered in one group (n = 28) and just two other rice
isolates in two distinct clusters. There was no considerable
polymorphism within AG-1-IA of R. solani, as detected by
RAPD analysis, in Northern regions of Iran.All of the
isolates in our study have been obtained exclusively from
rice and from the same weather conditions. Both
Mazandaran and Guilan provinces have humid weather
therefore it can lead to this high level of similarity among
the isolates and No correlation was observed between
RAPD clustering and geographical origins. The most
important observation from our research was high level of
similarity found among isolates of rice sheath blight
population in Iran. This fungus from rice survives and
disseminated primarily by the asexual reproduction of
sclerotia and vegetative mycelia in crop debris. The asexual
stage is conventionally viewed as predominant in the life
cycle of the organism (Ciampi et al., 2005; Rosewish et al.,
1999).These observations suggest the need, in future
studies, for enlarging the sample size, using another
techniques and host range of this fungus to advance
understanding of genetic diversity within subgroup IA in
Iran. For better evaluation of population variation that exists
in population of the pathogen, the analysis of the other
markers is necessary.
REFERENCES
1. Ciampi, M. B., Huramae E. E., Fenille R. C., Meyer M.
C., Souza N. L., Cerecini P. C. (2005). Intraspecific
evaluation of Rhizoctonia solani associated with
soybean and rice in Brazil based on polymorphism at
ITS-5.8S rDNA operon. European Journal of Plant
Pathology 113: 183-196.
2. Linde C. C., Zala, M., Paulraj R. S. D., MacDonald B.
A., Gnanamanickam S. S., (2005). Population structure
of Rice sheath blight pathogen Rhizoctonia solani AG-
1-IA from India. European Journal of Plant Pathology
112: 113-121.
3. Pascual C.B., Toda T., Raymondo A.D., Hyakumachi
M., 2000. Characterization by conventional techniques
and PCR of Rhizoctonia solani isolates causing banded
leaf sheath blight in maize. Plant Pathology 49: 108-
118.
4. Rosewich U. L., Pettway R. E., McDonald B. A., Kistler
H. C. (1999). High levels of gene flow and heterozygote
excess characterize Rhizoctonia solani AG-1-1A
(Thanatephorus cucumeris) from Texas. Fungal
Genetics and Biology 28: 148–159.
7th Australasian Soilborne Diseases Symposium 77