International Journal of Agriculture and Crop Sciences.
Available online at www.ijagcs.com
IJACS/2014/7-11/786-790
ISSN 2227-670X ©2014 IJACS Journal
Effects of damping-off disease caused by
Rhizoctonia solani on growth characteristics of
cotton seedlings
Zahra Khedri1, Asghar Heydari2 , Hossein Azimi2
1. Department of Plant protection, Varamin-Pishva Branch, Islamic Azad University, Varamin, Tehran, Iran
2. Plant Disease Research Department, Iranian Research Institute of Plant Protection, P. O. Box: 1452, Tehran
19395, Iran
Corresponding author email: [email protected]
ABSTRACT: This study was conducted and executed in the greenhouse conditions to investigate the
effects of damping-off disease caused by different isolates of Rhizoctonia solani on some growth
characteristics of cotton seedlings including height, fresh weight and dry weight. Ten Cotton seeds from
four different cultivars were first surface disinfested and were then sown in the field soil inoculated with
four R. solani isolates obtained from cotton and sugar beet. Pots were then placed in a greenhouse with
12 hours photoperiod and were watered as needed. The design of the experiment was completely
randomized and there were four treatments each with four replicates. Sixty days after sowing, two
survived seedlings were removed from each pot and their height, fresh weight and dry weight were
determined and were compared in different treatments. Results showed that all R. solani isolates had
reducing effects on seedling growth characteristic with different rates. For Bakhteghan variety R.s-Co-1
and R.s-Sb-1 isolates caused the most reduction in all three growth factors. In the cause of Mehr variety,
R.s-Sb -2 and R.s-Co-1 were the most reducing isolates on the seedlings growth characteristics. For
Sahel variety, R.s-Sb-2 and R.s-Sb-1 isolates induced the heist reduction in different growth factors of the
seedlings. About the Varamin variety, isolates R.s-Sb-2 and R.s-Co-2 showed the most reducing affects
on all growth characteristics of the cotton seedlings. General result of this study indicate that seedling
damping-off disease of caused by R.solani can significantly reduce the cotton seedling growth.
Key words: Rhizoctonia solani, damping- off, cotton, growth characteristics
INTRODUCTION
Cotton is an important fiber crop which is cultivated in many counties around the word including Iran. Like
many other plants, cotton is also susceptible to several fungal pathogens such as Verticillium dahliea and
Rhizoctonia solani (Javaid 1993). R. solani is a wide- host rang and one of the most important plant pathogens
that causes pre-and post emergence damping - off diseases on many crops including cotton (Watkins 1981;
Heydari et al. 2005).
Pre -emergence damping - off which occurs in the soil before plant emergence is the most common form
of this disease which usually causes seed decay and death of the radicals with in the soil(Watkins 1981; Heydari
et al. 2008). In contrast, there is another form of the disease called post emergences damping -off (Jahanifar et al.
2008). As the name of this disease shows, it happens after the plant emergence and most off the time result in the
death of the seedlings up to 50-60 days after planting in the field conditions. However, in some cases, seedlings
may survive with circular brown lesion (Sore shin) on the steam near the soil line (Mervat 2009; Watkins 1981).
In addition to the above- mentioned symptoms, R. solani and damping - off disease may also cause
negative effects on the vigority and growth of the seed lings (Ardekani et al. 2009). These effects, maybe
induced physically by causing the disease symptoms which result in the growth retardation of the seedlings
(Parmeter 1970 ; Ardekani et al. 2009). The effects could also be physiologically which happens inside the
seedlings root and change the physiology of the cotton plant (Watkins 1981). The changes and redactions in the
growth up seed lings which where decrypted above may and can have negative impacts on the maturity of cotton
plant and reduced the yield significantly (Watkins 1981; Adams 1988).
Intl J Agri Crop Sci. Vol., 7 (11), 786-790, 2014
Different R. solani isolates obtained from various crops and locations may affect the growth of the cotton
seedlings with different rates. In addition, different cotton varieties may not show the same response to R. solani
and damping- off disease. For example, some varieties maybe more tolerant to the disease and show less
changes in their growth factor in comparison with the others (Weller 1988).
Four cotton varieties (Bakhteghan, Mehr, Sahel, Varamin) are commonly cultivated in different parts of
Iran. Doe to the importance of cotton as a major fiber crop and R.solani as an important fungal pathogen of
cotton in Iran, in this study, we decided to in evaluate the effects of four isolates of R.solani obtained from cotton
and sugar beet on the growth of the above-mentioned cotton varieties.
MATERIALS AND METHODS
R. solani isolates
Four isolates of Rhizoctonia solani were tested in this study which are shown in table 1. As this table
indicates, of the total isolates, two belonged to cotton and were obtained from the cotton fields in Golestan province
of Iran. In addition to cotton isolates, two more isolates which were obtained from sugar beet fields in Alborz
provinces where also evaluated in this study (Table 1).
Cotton seeds
Cotton seeds from four domestic varieties which are commonly cultivated in different provinces of Iran
were used in this study. These varieties included Bakhtegan, Mehr, Sahel and Varamin. The seeds where
obtained from Iranian Cotton Research institute.
Soil preparation
Soil used in this study was obtained from cotton fields in different provinces of Iran where the abovementioned cotton variety are planted. Obtained soil were transferred to the experimental greenhouse at Iranian
Research Institute of Plant Protection and were pasteurized using a steam heater. Plastic pots where then filled
whit the Pasteurized soil at the rate of 4 kg per pot.
R. solani inoculums preparation
R. solani inoculum was prepared by autoclaving 500 g of wheat seeds which was placed in a flask and
inoculated with five 1-cm diameter mycelial plugs of a fresh culture of
R. solani grown on potato dextrose agar
(PDA) culture medium. The flask were then incubated for 3 weeks at 25 C until the fungal mycelia covered the
whole grain surface. The flask was then evacuated and its content was air dried, blended, and used as inoculum
in the greenhouse experiment.
Greenhouse experiment
Sixty days after sowing, two seedlings where removed from each pot, placed in a plastic bag and where
transferred to the laboratory. The effects of Different R. solani isolates (Table 1) on three growth factors of cotton
seedlings (height, fresh weight and dry weight) were investigated four different treatments by measuring and
determining the above - mentioned growth characteristics of all removed seedlings. The determined growth
factors four different treatments where then compared in the different treatments two evaluate their effects.
Table 1. Characteristics of Rhizoctonia solani isolates used in the study.
Isolate code
Isolate description
Isolation host
Isolation location
R.s-Co-1
R.s-Co-2
Rhizoctonia solani (AG-4)
Rhizoctonia solani (AG-4)
Cotton
Cotton
Golestan province
Golestan province
R.s-Sb-1
Rhizoctonia solani (AG-4)
Sugar beet
Alborz province
R.s-Sb-2
Rhizoctonia solani (AG-4)
Sugar beet
Alborz province
787
Intl J Agri Crop Sci. Vol., 7 (11), 786-790, 2014
Statistical analyses of the data
All data obtained in greenhouse experiments were subjected to analysis of variance (ANOVA) and means
were compared by Duncan Multiple Range Test using CO-STAT statistical soft ware (Cohort, CA, USA). Level of
significance was determined at 5% probability level.
RESULTS
The results of this study are presented in Tables 2-5. Table 2 shows the effects of R.solani isolates on
the growth characteristic of Bakhtegan cotton variety. As the Table indicates, R.s-Co-1 had the most negative
effect on the seedlings height fallowed by R.s-Sb-1, R.s -Sb-2 and R.s-Co-2 respectively (Table 2). For the
seedlings fresh weight, again, R.s-Co-1 caused the most reduction in the fresh weight fallowed by R.s-Sb-1, R.s Co-2 and R.s- Sb-2 respectively (Table 2). For the derivate the most reduction was induced by R.s-Co-1, R.s-Sb2 ,R.s-Sb-1 and R.s-Co-2 respectively (Table 2).
The effects of R.solani isolates on the growth factors of Mehr cotton variety are indicated in Table 3.
According to this table, R.s-Sb-2 showed the height reduction in the seedlings height fallowed by R.s-Co-1, R.s-Sb1 and R.s-Co-2 respectively (Table3). For seedlings fresh weight, the most reduction was caused by R.s-Co-1,
R.s-Sb-2, R.s-Co-2 and R.s-Sb-1 respectively(Table3). In the cased of dry weight, the highest negative effect was
mediated by R.s-Sb-1 fallowed by R.s-Sb-2, R.s-Co-1 and R.s-Co-2 respectively (Table3).
Table 4 shows growth factors of Sahel variety affected by different R.solani isolates. As the Table
indicates, R.s-Sb-2 caused the highest reduction in the seedlings height fallowed by R.s-Sb-1, R.s-Co-1 and R.sCo-2 respectively (Table4). In the cased of fresh weight, the most reducing effect was mediated by R.s-Sb-1, R.sSb-2, R.s-Co-1and R.s-Co-2 respectively(Table4). For seedlings dry weight, isolates R.s-Sb-1 showed the highest
reduction in the seedlings dry weight fallowed by R.s-Sb-1, R.s-Sb-2, R.s-Co-2 and R.s-Co-1 respectively(Table4).
The effects of R.solani isolates on the growth characteristics of Varamin cotton variety are presented in
Table 5. According to this table, R.s-Sb-2 resulted in the highest reduction in the seedlings height fallowed by R.sCo-2, R.s-Sb-1 and R.s-Co-1 respectively (Table5). About the seedlings fresh weight, isolates R.s-Sb-2, R.s-Co-2,
R.s-Sb-1and R.s-Co-1 mediated the most reducing effects respectively (Table5). In the case of seedlings dry
weight, R.s-Co-2 was the most effective in reducing seedlings dry weight, followed by R.s-Sb-2, R.s-Sb-1 and
R.s-Co-1 respectively (Table5).
Table 2. Effects of different Rhizoctonia solani isolates on the growth characteristics of Bakhtegan cotton variety 60 days after
sowing under greenhouse conditions
treatment code
Treatment description
Seedling height (cm)
R.S-Co-1
Seeds sown in soil inoculated with
R. solani (isolate 1 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from cotton)
R.S-Co-2
R.S-Sb-1
R.S-Sb-2
Seeds sown in soil inoculated with
R. solani (isolate 2 from sugar beet)
Seeds sown in soil inoculated with
R. solani (isolate 3 from sugar beet)
Seeds sown in soil
59.29 c
Seedling fresh weight
(g)
36.27 b
Seedling dry weight
(g)
5.87 a
91.53 a
47.88 a
7.37 a
63.39 c
42.63 ab
7.02 a
73.73 b
50.95 a
6.20 a
Values in the columns marked with the same letter(s) are not statistically different (P>0.05)
788
Intl J Agri Crop Sci. Vol., 7 (11), 786-790, 2014
Table3. Effects of different Rhizoctonia solani isolates on the growth characteristics of Mehr cotton variety 60 days after sowing
under greenhouse conditions
treatment code
Treatment description
Seedling height (cm)
R.S-Co-1
Seeds sown in soil inoculated with
R. solani (isolate 1 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from sugar beet)
Seeds sown in soil inoculated with
R. solani (isolate 3 from sugar beet)
Seeds sown in soil
R.S-Co-2
R.S-Sb-1
R.S-Sb-2
45.43 b
Seedling fresh weight
(g)
12.65 bc
Seedling dry weight
(g)
3.75 b
66.55 a
35.53 a
13.20 a
60.26 a
37.80 a
3.20 b
35.50 b
19.17 b
3.45 b
Values in the columns marked with the same letter(s) are not statistically different (P>0.05)
Table 4. Effects of different Rhizoctonia solani isolates on the growth characteristics of Sahel cotton variety 60 days after
sowing under greenhouse conditions
treatment code
Treatment description
Seedling height (cm)
R.S-Co-1
Seeds sown in soil inoculated with
R. solani (isolate 1 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from cotton)
R.S-Co-2
R.S-Sb-1
R.S-Sb-2
Seeds sown in soil inoculated with
R. solani (isolate 2 from sugar beet)
Seeds sown in soil inoculated with
R. solani (isolate 3 from sugar beet)
Seeds sown in soil
57.42 a
Seedling fresh weight
(g)
40.73 b
Seedling dry weight
(g)
9.80 a
62.50 a
49.65 a
9.32 a
55.03 a
23.90 c
3.12 b
48.47 ab
26.08 c
4.97 b
Values in the columns marked with the same letter(s) are not statistically different (P>0.05)
Table 5. Effects of different Rhizoctonia solani isolates on the growth characteristics of Varamin cotton variety 60 days after
sowing under greenhouse conditions
treatment code
Treatment description
Seedling height (cm)
R.S-Co-1
Seeds sown in soil inoculated with
R. solani (isolate 1 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from cotton)
Seeds sown in soil inoculated with
R. solani (isolate 2 from sugar beet)
Seeds sown in soil inoculated with
R. solani (isolate 3 from sugar beet)
Seeds sown in soil
R.S-Co-2
R.S-Sb-1
R.S-Sb-2
69.75 a
Seedling fresh weight
(g)
40.30 a
Seedling dry weight
(g)
5.42 a
46.48 b
26.83 b
2.22 b
60.71 a
35.00 b
5.35 a
27.24 c
13.05 d
2.32 b
Values in the columns marked with the same letter(s) are not statistically different (P>0.05)
789
Intl J Agri Crop Sci. Vol., 7 (11), 786-790, 2014
DISCUSSION
The results of this study in general, indicate that almost are isolates of Rhizoctonia solani had negative
and reducing effects on growth characteristics of different cotton varieties. As was mentioned in the introduction
section, the effects of a certain fungal pathogen on the growth of a certain plant could be direct or indirect (Hydari
and Misaghi 1998). The direct effects include the chances in the phenology and the growth process of the plants
which is usually related to the alteration of plant physiology (Khadga et al. 1963; Watkins 1981; Hydari and Misaghi
1998). Indirect effects, however, are those chances in the vigority of the plants caused by the pathogen and the
disease it causes(Heydari and Missaghi ,1998).
In our study, four domestic cotton varieties were used which showed different growth responses to the R.
solani isolates which were obtained from cotton and sugar beet. The different effects of the fungal pathogen in the
growth factors of are varieties could be related to boat plant and pathogen. For example, the differences in the
genetic traits of the cotton plant may have played important role in their responses to R. solani isolates. On the
other hand, the virulence, genetic diversity and host plant of R. solani isolates may also have affected
interactions with different cotton variety.
The results of the present study are compare able to those of some previous research on
The interaction among R. solani and crop plants including cotton and potato (Asran and Batson 2001). In their
study related to cotton, there results were somehow similar to those of our research and showed that different
cotton varieties showed various growth responses to different R. solani isolates (Aqil et al. 1999; Mikhail et al.
2009).
In another previous study, the growth response of different potato varieties were evaluated to some
isolates of R. solani (Bienkowski et al. 2010). Like our study, the results of the above- mentioned research also
showed that the effects of R. solani isolates on the potato growth were variable among different varieties.
The overall results obtained in our study are promising and can be use in the control and management of
damping-off disease on the cotton which is a serious and important disease in the cotton field around the world
including Iran which can result in the promotion of cotton growth and increase of the yield .
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