Date palm (Phoenix dactylifera L.) for commercial plantations, is always propagated through offshoots (suckers). This is the only commercial method of vegetative clonal propagation used to multiply the best varieties. Offshoots are produced from axillary buds situated on the base of the trunk during the juvenile life of the palm. However, they develop slowly and the numbers produced per tree are limited. Furthermore, suckers are produced only within a certain period in the mother palm’s life. Thus, during the lifetime of an individual plant, only a low number of transplantable offshoots is available.
Fungal root rot diseases of date palm are causing direct and indirect losses in orchards and nurseries in Egypt (Baraka et al., 2011a).
Temperature and relative humidity percent (Rh %) play important role in fungal diseases development of plants. Results of temperature and relative humidity studies were in Fig. (2): Pathogenicity test on different cultivars seedling of date palm.
5
6.67 1.67 11.11 2.78 15.56 3.89 20 22.22 5.56
BARTAMODA SAKOTY SIWEY SAMMANY ZAGHLOUL CONTROL Disease incidence % Disease severity %
Governorates Associated fungi% Disease
incidence% Disease severity%
L. theo. R. s. F. spp.
Bani-suef 50 30 20 20 13
Behara 70 20 10 40 25.5
Kaluobia 60 30 10 30 14.5
Table (1): Frequency of fungi associated with root rot disease of date palm offshoots in different governorates.
L. theo= Lasiodiplodia theobromae / R. s.= Rhizoctonia solan / F.= Fusarium
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THE BLESSED TREE DECEMBER 2013
Table (2): Effect of temperature on linear growth of the fungus Lasiodiplodia theobromae
Table (3): Effect of relative humidity on linear growth of the fungus Lasiodiplodia theobromae
L.S.D. at 5% Degree= 4.76
L.S.D. at 5% Degree= 5.23
agreement with that of (Abdul et al., 2011; Arafat, 2011) reported that the optimum temperature for mycelial growth of L. theobromae is 30–35ºC and optimum temperature degree for infection is 30ºC. While, the optimum relative humidity for mycelial growth is 60-70% and optimum for infection is 60%. In addition, Banik et al. (1988) studied the effect of temperature, relative humidity and rainfall on the colony growth of Lasiodiplodia
theobromae and he found that the colony growth L. theobromae was maximum at the temperature level of 32ºC. The colony growth of this fungus was maximum at the temperature level of 25ºC according to the results of Patil and Phatak (1993). Temperature and relative humidity are effective on pathogenic fungi and disease severity of date palm seedlings for all cultivars (Arafat, 2011).
Water salinity is the important factor
effective on disease incidence and severity of date palm seedlings root rot disease caused by L. theobromae for all cultivars tested. Water salinity at all levels tested were increased the disease incidence and severity. In vitro salinity negligible effective on rate mycelial growth of L. theobromae, but maybe effective on root system of date palm, this results agreement with (Suleman et al., 2001; Arafat, 2011) whose suggested that the salinity of irrigation water could lead to opportunistic pathogens becoming more aggressive or could predispose healthy plants to these pathogens.
Rashed et al. (2006) reported that increasing irrigation water salinity increased the root rot of date palm caused by Phytophthora palmivora in all salt concentrations tested. In addition, results indicated that high salinity levels might be a factor in root rot development leading to higher disease incidence.
The effect of five root exudates on the mycelial growth of L. theobromae evaluated was significantly differ between the extracts from five cultivars of date palm and the all concentrations tested. The highest activity was found in Bartamoda cv. followed by Sakoty, Siwey, Sammany and Zaghloul, respectively.
The exudation of this compound’s has been highly dependent on the
Treatment Degree Linear growth (mm)
Temperature degrees (ºC)
25 63.30c
30 71.70b
35 90.00a
40 53.40d
Treatment Degree Linear growth (mm)
Relative humidity (Rh%)
60 83.33b
70 90.00a
80 79.70b
90 63.93c
Table (5): Effect of relative humidity on disease incidence and severity
T.- Treatment / D.-Degree / B.-Bartamoda / S.-Sakoty / Si.-Siwey / Sa.-Sammany / Z.-Zaghloul L.S.D. at 5% for Disease severity
Degree (D) = 0.78 / Cultivars (V) = 0.87 / D X V= ns.
T. D. Cultivars
B. S. Si. Sa. Z.
D.I.% D.S.% D.I.% D.S.% D.I.% D.S.% D.I.% D.S.% D.I.% D.S.%
Rh% 60a 26.67 6.67 28.89 7.22 35.56 8.89 46.67 11.67 51.11 12.78
70b 22.22 5.56 24.44 6.11 28.89 7.22 35.56 8.89 42.22 10.56
80c 17.78 4.44 22.22 5.56 24.44 6.11 28.89 7.22 37.78 9.44
90d 11.11 2.78 15.56 3.89 22.22 5.56 28.89 7.22 31.11 7.78
Mean 4.86d 5.70d 6.95c 8.76b 10.14a
52
KHALIFA INTERNATIONAL DATE PALM AWARDcultivars, which indicates that all exudation process is determined by genetic factors (Wu, 2005). This could be explain the differences found in the five date palm cultivars tested. The efficacy of different biological control
agents (Marjoram crude extract, Jojoba oil and Plant guard commercial product) against L. theobromae were tested in vitro and in greenhouse.
The results showed that all bioagents were significantly (P≤0.05) inhibited
the linear growth of the fungus tested with inhibition varying from one to another. On the other hand, Jojoba oil was the most effect in vitro and in greenhouse, followed by Plant guard and Marjoram. These results Table (7): Effect of water salinity on disease incidence and severity of date palm cultivars
L.S.D. at 5% for disease severity (D.S.)
Concentration (C) = 0.98 / Cultivars (V) = 0.98 / C X V = ns.
Concentration ECw (ds/m2)
Cultivars
Bartamoda Sakoty Siwey Sammany Zaghloul
D.I.% D.S.% D.I.% D.S.% D.I.% D.S.% D.I.% D.S.% D.I.% D.S.%
1.4e 8.89 2.22 13.33 3.33 15.56 3.89 17.78 4.44 20.00 5.00
6.9d 22.22 5.56 24.40 6.11 28.89 7.22 33.33 8.33 37.78 9.44
12.9c 24.44 6.11 28.89 7.22 33.33 8.33 42.22 10.56 48.89 12.22
18.4b 31.11 7.78 37.78 9.44 42.22 10.56 48.89 12.22 60.00 15.00
26.5a 33.33 8.33 44.44 11.11 57.78 14.44 62.22 15.56 66.62 16.67
Mean 6.00e 7.44d 8.89c 10.22b 11.67a
Table (8): Effect of root exudates of date palm cultivars on reduction of linear growth of L. theobromae
Cultivars
Concentration of root exudates %
0 1 2.5 5 10
Reduction of linear growth (%) Mean
Bartamoda 00.00 32.43 34.43 37.17 41.30 29.09a
Sakoty 00.00 26.67 30.63 33.67 38.23 25.84b
Siwey 00.00 15.70 18.93 21.17 27.67 16.69c
Sammany 00.00 9.60 14.33 18.87 20.60 12.68d
Zaghloul 00.00 5.43 9.07 11.93 15.90 8.47e
Mean 00.00e 17.97d 21.50c 24.56b 28.74a 18.55
L.S.D. at 5%
Cultivars (V) = 2.27 / Concentration (C) = 2.27 / V X C = 5.41
Table (6): Effect of water salinity on reduction linear growth of L. theobromae
Treatment Concentration
ECw (ds/m2) % Reduction of linear growth
Water salinity
1.40 0.00e
6.25 6.86d
9.38 8.99c
12.50 13.97b
15.63 17.03a
L.S.D. at 5% / Concentration= 0.43
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THE BLESSED TREE DECEMBER 2013
agrees with the finding of Baraka et al. (2011b) they reported that the bioagents (biotic and abiotic) were effective in inhibition the linear growth of soil borne pathogenic fungi, and decreased the disease incidence and severity root rot of date palm seedlings
in all cultivars tested. Kaufman et al. (1999) they reported that the plant natural products containing the chemical natural substance could use against pathogenic fungi.
Biological control agents may use a variety of inhibitory and suppressive
mechanisms (Etebarian et al., 2000;
Whipps, 2001; Arafat et al., 2012).