Vol.5, No.11, 1189-1192 (2013) Natural Science
http://dx.doi.org/10.4236/ns.2013.511145
Assessment on early blight of potato in order to
compare the two methods in vitro using pathogenic
fungi Alternaria solani
Hamid Reza Mirkarimi1*, Ahmad Abasi-Moghadam2, Javad Mozafari2
1Department of Plant breeding, Faculty of Agriculture, Science and Research Branch, Islamic Azad University of Tehran, Tehran,
Iran; *Corresponding Author: rezamirkarimi21@gmail.com
2Department of Genetics & National Plant Gene-Bank, Seed and Plant Improvement Institute, Karaj, Iran
Received 14 September 2013; revised 14 October 2013; accepted 21 October 2013
Copyright © 2013 Hamid Reza Mirkarimi et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Potato (Solanum tuberosum) early blight, caus-
ed by Alternaria solani is one of the most de-
structive fungal foliar diseases. This research
was done in order to study methods comparison
of evaluation by culture filtrate of A. solani in in
vitro condition for selecting resistance cultivars
to early blight. Plantlets of potato viruse free
were obtained from the National plant gene bank
of Iran, and were inoculated in vitro methods
with a culture filtrate of A. solani. In in vitro se-
lection by droplet of culture filtrate method,
leaflet received a 10 µl droplet of the A. solani
culture filtrate and in in vitro selection by direct
using of culture filtrate method, plantlets were
placed in test tubes that include 5 µl A. solani
culture filtrate. The experimental design was
factorial on basis of completely randomized de-
sign (CRD) with two factors, three replications
and six genotypes. During droplet method assay,
the A. solani symptoms appeared 1 - 2 days until
6 days and during direct method they appeared
2 - 3 days until 6 days. The AUDPC values were
submitted to the analysis of varience (ANOVA)
and AUDPC means were compared by using
Duncan test (α = 0.01%). In each method, sig-
nificant difference among potato cultivars was
observed for disease to early blight (p < 0.01).
Results show that casmos cultivar is suscepti-
ble for resistance to early blight and in vitro
methods experiment had the same result.
Keywords: E arly Blight; AUDPC; Resistance;
Alternaria solani; Potato
1. INTRODUCTION
Early blight is a very common disease of both potato
and tomato. It causes leaf spots and tuber blight on po-
tato, and leaf spots, fruit rot and stem lesions on tomato
[1]. The disease can occur over a wide range of climatic
conditions and can be very destructive if it is left uncon-
trolled. Infection can cause serious yield losses in sus-
ceptible cultivars [2,3]. Potato plants are susceptible to a
wide variety of diseases that can severely reduce yield,
quality and storability of tubers. Diseases can occur in
the field or in storage and are caused by infectious bacte-
ria, fungi, viruses and other related organisms. Early
blight, caused by the A. solani fungus, is one of the main
diseases of potatoes in tropical climates, especially
where potato es are grown under irr igation , causing yield-
losses through defoliation of the plants. The fungicides
used to control the disease are expensive and frequently
inefficient [4]. Potato resistance to early blight is a quan-
titative trait, and obtaining successful resistant cultivars
is not simple [5-7]. It has been observed that resistance to
early blight is age-related: early-maturing cultivars are
more susceptible than late-maturing cultivars. A droplet
inoculation method was used for evaluation of tomato
resistance to early blight, caused by Alternaria solani
(Ellis & Martin) Sorauer. In this experiment method,
leaflets are inoculated with small droplets of a conidial
suspension in water or culture filtrate [8,9]. This method
was first introduced by Locke (1948) to find sources of
resistance to early blight (Locke, 1949). The droplet in-
oculation method has been used to evaluate early blight
resistance components (O’Leary and Shoemaker, 1983).
The direct method was described by [9,10]. Plantlets
were inoculated in a 18 × 2 cm test tube, containing 5 ml
of A. solani culture filtrate. Severity values were plotted
against time and the area under the disease progress
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