© Benaki Phytopathological Institute
Hellenic Plant Protection Journal
8:
1-11, 2015
DOI 10.1515/hppj-2015-0001
1
Department of Plant Protection, Faculty of Agricultur-
al Sciences, University of Guilan, P.O. Box: 41635-1314,
Rasht, Iran
2
Department of Plant Protection, Rice Research Insti-
tute of Iran, P.O. Box: 1658, Rasht, Iran
* Corresponding author:
Evaluation of the virulence of
Sclerotium rolfsii
isolates on
Arachis hypogaea
and screening for resistant genotypes in
greenhouse conditions
A.A. Eslami
1
, S.A. Khodaparast
1
, S. Mousanejad
1*
, F. Padasht Dehkaei
2
Summary
Sclerotium rolfsii
is a soil borne pathogen responsible for root and stem rot on a wide range
of crops. This study was conducted to identify the virulence of different
S. rolfsii
isolates on a suscepti-
ble local peanut germplasm and determine the resistance of 20 peanut genotypes to the most virulent
isolate and also the relationship between virulence and mycelial compatibility groups (MCGs). Seven-
ty eight isolates of this fungus from 10 host plants and six known MCGs were used in the experiment.
The experiment was done in greenhouse conditions (25±5
o
C) using a complete randomized block de-
sign with three replications. Pots containing sterile soil (pH=6.7) were inoculated with barley seeds col-
onized by each isolate separately before being seeded with the peanut germplasm. Disease severity
was assessed by scoring the wilting, yellowing or death of plants, mycelia or sclerotia production on
the soil surface or on plant stem, stem area affected (%) and stem lesion length, at the stage of plant
maturity. Also, shoot wet weight and plant height were recorded at this stage. According to the results
of the pathogenicity tests, all of the isolates were virulent on the susceptible peanut germplasm and
the virulence differed significantly between the isolates (P≤0.01). There was no relationship between
the virulence of the five groups of isolates identified in the present study and the MCGs. The peanut
genotype 140, which was better than the others based on seed size, plant height and the canopy size,
was also the most resistant one.
Additional keywords
: diversity, groundnut, pathogenicity, southern blight, stem rot
Introduction
Sclerotium rolfsii
Sacc. (teleomorph:
Athe-
lia rolfsii
(Curzi) Tu & Kimbrough) is one of
those soil borne plant pathogenic fungi that
are prevalent in warm temperate and sub-
tropical regions of the world (Punja
et al
.,
1984). This pathogen has a host range of
over 500 plant species mostly of dicotyle-
donous plants. A wide range of symptoms
are produced by this pathogen on its hosts
including crown and root rot, stem can-
ker and damping-off and resulting diseas-
es called southern wilt, blight or stem rot
(Punja, 1985). The pathogen is of great im-
portance especially when the disease sever-
ity is high in the fields. The crop loss may be
between 10-25% or even more than 81% in
some fields (Mehan
et al
., 1995).
Groundnut or peanut (
Arachis hypogaea
L.) is an annual legume crop cultivated in
more than 80 countries in the tropics, sub-
tropics and warm temperate zones (Ham-
mons, 1994). It is a major source of edible oil,
vitamins and amino acids and is used exten-
sively for feed and food (Savage and Keenan,
1994). Groundnut is also a main crop in Gui-
lan province of Iran with about 3500 hect-
ares cultivation area.
Southernblight, stemrot or whitemould,
caused by
S. rolfsii
, is one of the most impor-
tant diseases of peanut. The disease appears
in peanut growing areas and causes great
yield losses when climatic conditions, such
as soil temperature and humidity, are favor-
able for fungal development and the dis-
