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Effect of the mechanical wounding of green bean roots on the severity of disease complex causes by Meloidogyne javanica and Macrophomina phaseolina
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Al-Nadhari S. N.1, A. S. Al-Hazmi2, F. A. Al-Yahya2, Younis Y. Mawlan2,
Ahmed A. M. Dawabah2, Mahmoud H. El-Komy2 and Hamzeh A. Lafi2
1Plant Production Department, College of Agricultural, Ibb University, Yemen.
2Plant Protection Department, College of Food and Agricultural Sciences, King Saud University, Saudi Arabia.
Introduction
TABLE 1. Effect of the mechanical wounding of green bean roots with Meloidogyne javanica and Macrophomina phaseolina on the growth of green bean "cv. Contender", 60 days after inoculation under greenhouse conditions.
TABLE 2. Effect of the mechanical wounding of green bean roots with Meloidogyne javanica and Macrophomina phaseolina on the no. galls/roots system of green bean "cv. Contender", 60 days after inoculation under greenhouse conditions.
Green bean, Phaseolus vulgaris L., is an important vegetable crop in Saudi Arabia. Meloidogyne javanica and Macrophomina phaseolina are often associated simultaneously with the roots of green beans under field conditions (Al-Hazmi, 1985). Joint infection by both root-knot nematodes and root-rot fungi can cause a disease complex with more serious damaging effects, compared to each pathogen alone (Assuncao and Moura, 1981; France and Abawi, 1994; Singh et al., 1981).
There are many factors affect the severity of the disease complex caused by M. javanica and M. phaseolina, such as initial inoculums of the nematodes (Al-Hazmi, 1985; Ibrahim, 2002; Kofoid and White, 1919; Treub, 1885), time of infection (Asmaa Mokbel, et al., 2007; Al-Hazmi. 1985; Reddy, et al., 1979), soil humidity (Ali and Ghaffar, 1991), plant aging (Tu and cheng, 1971) and soil texture (Al-Hazmi, et al., 1995). Diomande and Beute (1981) reported that the mechanical wounding in the apical meristem region before inoculation with two microsclerotial of Cylindrocladium crotalariae led to more infections than when roots were either unwounded or wounded further from the growth zone.
Treatment
Fresh weight (g)
Root size (cm3)
Shoot system
Root System
Whole Plant
Non-inoculated
Check
19.80 a
11.66 a
31.50 a
11.06 a
Nematode
M. javanica
(10000 eggs/pot)
14.58 b
12.58 a
27.16 b
11.76 a
Fungus
M. phaseolina
(1000 sclerotia/pot)
15.00 b
10.10 b
25.16 c
9.90 b
Both nematode & Fungus
with wounding
8.10 d
6.40 d
14.48 e
6.74 d
without wounding
10.02 c
7.86 c
17.88 d
7.92 c
LSD0.05
1.2
1.07
1.57
0.83
Treatment
No. galls/ root system
% change*
No. galls/g fresh root
gall index
(0-5)**
Non-inoculated Check -
Nematode
M. javanica
(10000 eggs/pot)
234.2 c
18.59 c
5.0
Fungus
M. phaseolina
(1000 sclerotia/pot)
Both nematode & Fungus with wounding
341.8 a
+ 67.6
53.73 a
Both nematode & Fungus without wounding
301.8 b
38.85 b
LSD0.05
32.37
6.19
Values are the mean of five replicates each.
Values in the same column followed by the same letter(s) are not significant different (P ≤ 0.05)
Values in the same column followed by the same letter(s) are not significant different (P ≤ 0.05).
*compared to Nematode treatment.
**gall index: 0= 0, 1= 1-2, 2= 3-10, 3= 11-30, 4= , 5= ›100 galls/root system.
Objectives
This study aimed to determine the effect of mechanical wounding on the development and severity of the disease complex (Root rot-root knot) on green beans.
TABLE 3. Effect of the mechanical wounding of green bean roots with Meloidogyne javanica and Macrophomina phaseolina on the severity of charcoal rot disease and fungus colonization of the roots of green bean "cv. Contender", 60 days after inoculation under greenhouse conditions.
TABLE 4. Effect of the mechanical wounding of green bean roots with Meloidogyne javanica and Macrophomina phaseolina on the reproduction of M. javanica in the roots of green bean "cv. Contender", 60 days after inoculation under greenhouse conditions.
Materials and Methods
Treatment
Charcoal rot index
(0-10)*
% Charcoal severity**
% re- isolation from root
Non-inoculated Check -
Nematode
M. javanica
(10000 eggs/pot)
Fungus
M. phaseolina
(1000 sclerotia/pot)
4.80 b 48
35.00 c
Both nematode & Fungus with wounding
6.80 a 68
60.00 b
Both nematode & Fungus without wounding
7.40 a 74
80.00 a
LSD0.05
1.04
17.79
Treatment
No. eggmasses /root system
No. eggs /root system
(×1000)
No. eggs / g fresh root (×1000)
Reproductive factor (RF)*
Non-inoculated Check -
Nematode
M. javanica
(10000 eggs/pot)
227.8
53.76 a
4.27 c
5.38 a
Fungus
M. phaseolina
(1000 sclerotia/pot)
Both nematode & Fungus with wounding
242.2
46.08 b
7.36 a
4.61 b
Both nematode & Fungus without wounding
238.2
45.62 b
5.89 b
4.56 b
LSD0.05
31.93
6.30
1.05
0.63
Plastic pots (15 cm diam.) Were filled with an autoclaved soil mixture (1 sandy loam: 1 sand), Pots were then sown with green bean seeds cv. Contender, susceptible cultivar to both nematode M. javanica (Rajan, et. al., 1990) and fungus M. phaseolina (Ibrahim, et. al., 2009). After emergence, plants were thinned to one plant/pot and pots were arranged on a bench in the greenhouse (25 ± 2°C) in a randomized complete block design (RCBD) with five replicates of each treatment.
Treatments included: 1) Control (Non-inoculated), 2) Nematode inoculation M. javanica (10000 eggs/pot), 3) Fungus inoculation M. phaseolina (10000 sclerotia/pot), 4) M. javanica + M. phaseolina without root wounding, 5) M. javanica + M. phaseolina with root wounding. Sixty days after inoculation, plants were re-potted, and washed with a gently stream of tap water. All parameters were taken and then subjected to ANOVA, and means were separated using Fishers' protected LSD.
Values are the mean of five replicates each.
Values in the same column followed by the same letter(s) are not significant different (P ≤ 0.05).
*Charcoal rot index: 0= 0, 1= 1-10, 2= 11-20, 3= 21-30, 4= 31-40, 5= 41-50, 6= 51-60, 7= 61-70, 8= 71-80, 9= 81-90, 10= % of the root system rotted.
** % Charcoal severity = [∑disease index × no. inoculated plants in each index/ maximum index × total no. of inoculated grass samples] × 100.
Values are the mean of five replicates each.
Values in the same column followed by the same letter(s) are not significant different (P ≤ 0.05)
*Nematode reproduction factor (RF) = nematode final population (Pf)/initial population (Pi).
Results
Discussion
Infection of green bean roots with both M. javanica and M. phaseolina had a negatively impact on plant growth, as well as roots damaging. Significantly, plant damaging increased when the process of joint infection was done directly after roots wounding, could be due to the fact that the process of mechanical wounding facilitated the entry of the pathogens into the tissues of the root, compared with the untreated control. Furthermore, the process of root wounding might have a physiological effect by predisposition the roots to infection. Diomande and Beute (1981) studied the incidence of the fungus C. crotalariae on peanuts. They indicated an increase in the incidence of the fungus C. crotalariae on peanuts with root wounding and reached 100%, compared with 10% with unwounding roots.
The process of roots wounding with the joint infection of nematode and fungus has led to increase the synergistic relation between nematodes and fungi, thus they had a negatively impact on the infected plants that have been wounded. This process increases the damage to the plant, the severity of disease complex and the reproduction of both nematodes and fungus.
References
FIGURE 1. Effect of different treatments of the infection with Meloidogyne javanica and Macrophomina phaseolina on the roots of green bean "cv. Contender".
A total of 15 references listed in this research.