الفهرس 
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Abstract
6.SUMMARY AND CONCLUSION
Potato (Solanum tuberosum L.) is the fourth main crop in the
world after wheat, rice, and maize. Since the past two decades, the
potato sector in Egypt has undergone rapid changes in potato
industry. However, large amount of potato are kept under ordinary
storage conditions. This frequently lead to many problems among
which is tuber dry rot disease which causes a greater loss of potatoes
than any other post-harvest diseases. Assessing disease status of
stored potatoes allows for better disease management. Disease
control strategies could eventually integrate use of alternative
methods like physical. Safe chemical compounds and microbial
antagonists.
The objectives of the research reported here were: (i) to
isolate the fungal species causing dry rot and determine the extent of
co-ioculation of such isolates on storability of tubers. (ii) to identify
specific treatments to suppress dry rot. Results could be
summarized as follows:
1. The three potato cultivars (Desriee, Annabelle, and
Spunta), collected from El-Deer village, Sheibin El-
Kanater, Kalyubia Governorate during winter season 2012,
and stored in pored cartoon boxes under room temberature
and refrigerator for two monthes showed dry rot disease
during storage.
2. All stored potato tubers of cultivar Annabelle were rotted
with appearance of white mycelial mats; while tubers of
Spunta cv showed 50% of rot signs and 10% of Desiree cv.
tubers showed various rot degrees when stored in pored
carton boxes under room temperature, for 2 months.
SUMMARY AND CONCLUSION
Ola B. Abd El-Hafez, M.Sc., 2014
76
3. Twenty- two fungal isolates were isolated included five
genera, being (Fusarium, Penicillium, Altenaria,
Drechslera, and Chaetomium).
4. Frequency of isolated the fungi from the rotted potato tubers
indicated that 64% of isolated fungi belong to Fusarium
spp, Penicillium sp. (14%) , Drechslera sp.(4%) , and
Chaetomium sp. (4%).
5. Only one isolate of each Cyanobacteria , Fusarium sp. and
Bacillus sp. were isolated from soil-adhered to potato
tuber.
6. Identification of isolated Fusaria indicate that they belong to
three species i.e. F. solani, F. sambucinum and F.
oxysporum. Frequency of these species indicates that 86%
belong to F. solani, 7% belong to F. sambucinum and 7%
belong to F. oxysporum.
7. The pathogenicity of 14 isolates of Fusarium spp. showed
varied reactions on potato tuber discs Spunta cv., and F.
sambucinum (F4) was more pathogenic compared to F.
solani and F. oxysporum.
8. Three Penicillium isolates were more vigorous on potato
tubers in comparison to isolate of F. solani. Subculturing of
Penicillium sp. isolates caused losses of their pathogencity
on potato tuber discs. Therefore, pectinase and cellulase
activity of Penicillium cultured on Pectin or CMC
indicated the ability of the tested isolate to hydrolyze both
pectin or CMC
9. Alternaria sp., Drechslera sp., Cheatomium sp. were not
pathogenic to potato tuber discs of Spunta cultivars.
SUMMARY AND CONCLUSION
Ola B. Abd El-Hafez, M.Sc., 2014
77
10. The co-inoculation between F. solani and Penicillium sp.,
Alternaria sp., and Drechslera sp. were tested on the dry rot
disease.
11. The co-inoculation between Fusarium sp. and Penicillium
sp. caused that the sporulation of Penicillium sp. was more
than the control rotted discs although it lost its
pathogenicity.
12. The co-inoculation between F. solani and both fungal
isolates Drechselra sp. and Alternaria sp. had no significant
effect on dry rot., and it showed reduced in the sporulation
of the first fungi, and the sporulation of the second and the
third fungi were completely absent.
13. Chloroform soil extract greatly suppressed all figures of dry
rot disease for F. solani (2), while it suppressed the rot
completely in the in the weak isolates (IC4, IE8lab).
14. All figures of disease due to severely pathogenic isolate
were non affected due to the presence of Bacillus sp., while
disease caused by moderately and weak Fusarium isolate
significally affected and all figures of disease were
decreased to a very great extent.
15. The culture filtrate of cyanobactria (Nostoc sp.) has a less
effect on dry rot disease, and it suppressed the sporulation.
The polar fraction of culture filtrate have not any affect on
dry rot disease and the non polar fraction effected on all
figures of dry rot in moderately and weak isolates.
16. The exposure of potato tuber discs to warm shock (42ºC for
5 min.) and cold shock (10 ºC) before inoculation with F.
solani led to significantly decrease all disease figures
17. Four chemical compounds (N-acetylcysteine, chitosan,
hydrogen peroxide, and calcium chloride) were used for
studying their effect on the dry rot disease.
SUMMARY AND CONCLUSION
Ola B. Abd El-Hafez, M.Sc., 2014
78
18. N-acetylcysteine (0.04%) reduced the weight of the rotted
tissues and fungal sporulation
19. Chitosan (1%) significantly reduced all figures of disease
severity
20. H2O2 (4%) significantly effected on all figures of disease
while the all concentration of H2O2 effected on the
sporulation of the disease
21. CaCl2 especially at 1% or 2% significantly reduced
percentage of the rotted area and the weight of rotted
tissues. All tested concentrations significantly suppressed
F. solani sporulation especially 1%.
22. The three tested agents i.e. warm water (42ºC),
acetylcysteine at 0.4mg/ml and chitosan increased the PO
activity over control (non-treated inoculated discs).
Meanwhile, the other three tested agents reduced PO
activity below control discs i.e. cold water (10ºC), H2O2
(4%) and calcium chloride (1%).