Isolation of VAM fungi:Four VAM fungi were isolated from Healthy roots taken from
onion (Allium cepa), broad bean (Vicia faba), the ornamental Swiss cheese
(Monstera deliciose) and maize (Zea mays) plants were used for isolation of VAM
fungi. The isolated VAM fungi formed terminal sporangia (varied in diameter) contained
rounded hyaline 1-celled sporangiospores in addition to apical, intercalary
chlamydospores formed singly and/or in chains. Zygospore formation was noticed only
in onion-isolate.Inoculation with VAM fungi significantly improved most of the examined
growth criteria of maize seedlings comparing with the control (non-inoculated). Typical
VA-mycorrhizal infection structures (arbuscules, vesicles and aseptate hyphae grow
mainly between and rarely across cells in root cortex were clearly seen in mycorhizal
(inoculated) and non-mycorhizal roots of maize seedlings. Roots of inoculated
seedlings showed no any detectable changes in their external morphology when
compared with those of control treatment. Among detected DNA bands, Similarity
between the 4 VAM fungal isolates (in cultures) was ranged between 87.27-100.00%.
As for mycorrhizal roots (inoculated with any VAM isolate including Glomus sp.) and
non-mycorhizal roots, percentage similarity was ranged between 77.39-85.03%.
Physiological studies on the isolated VAM fungi: The isolated VAM fungi could
grow and sporulate on different nutritive media. Bushnell’s medium was the superior.
Bushnell’s medium, were sharply increased as temperature increased from 5°C to 28
or 31°C, depended on VAM isolate, then appreciably decreased by raising temperature
up to 33°C. However, these parameters were significantly decreased as R.H.%
increased from 14% to 100% comparing with the control (un-controlled humidity
conditions). The yeast extract, beef extract and aspragine were the best N-sources for
growth and sporulation of the isolated VAM fungi. As for carbon sources, growth and
sporulation of all isolates were completely stopped on citric acid and inositol. In
general, glucose produces the highest growth dry weight followed by galactose,
fructose, starch, maltose, arabinose and sucrose, respectively and significantly
increased as pH increased from pH 5.0 to pH 7.0 then gradually decreased by
elevating pH value up to 7.6, 8.0, 8.6 or 9.0, respectively and in the hyaline light was
the best for growth dry weight and spore formation followed by the green, blue, yellow,
red light waves and dark, respectively.
Evaluation of the isolated VAM fungi under greenhouse conditions: All VAM
isolates, particularly in the second sowing, significantly increased % survival in the
pathogen-infested soil compared with the control. Inoculation with VAM-4 was the
superior in this respect followed by VAM-1, VAM-3 and VAM 2, respectively. All VAM
isolates significantly increased the shoot length, stem diameter, the number of
leaves/plant, both total fresh and dry weights/plant,the photosynthetic pigments
(chlorophyll and carotenoids) and increase in the pH value in the rhizosphere region
compared with their controls.
Evaluation of the isolated VAM fungi for their effects on seed germination and
controlling the most familiar diseases affecting maize plants and on some
growth parameters of maize plants under field conditions: Inoculation with
different levels of VAM fungi significantly increased seed germination, significantly
decreased wilt disease, caused the highest decrease in the common smut disease
incidence and significantly decreased percentage of stunt disease incidence
compared with P fertilizer in both 2002 and 2003 seasons. Inoculation with VAM
significantly increased plant height, increasing total fresh and dry weights/plant,
significantly better for increasing the fresh weight of roots (FWR)/plant, significantly
increased dry weight of roots (DWR)/plant more than compared with P fertilizer. The
isolate VAM-1 recorded the highest significant increases in ear weight and significant
increases in the grain yield/plant.Applying VAM inoculation at any level alone or
combined with N fertilizer significantly increased weight of 100-kernels compared
with application of P and N fertilizers, respectively. Using Using N fertilization + VAM-
1 (high level), VAM-2 (middle level) or VAM-4 (low and the middle levels) in 2002
season and N fertilizer + VAM-3 and VAM-1 (high level) in 2003 season produced
the highest CP content. VAM inoculation at different levels alone or combined with N
fertilizer significantly increased phosphorous (P) and potassium (K) content in the
corn kernels in maize kernels compared with P and N fertilizers, respectively.
Keywords:
1- VAM fungi
2- maize (Zea mays) plants
Original Material: Roots taken from onion (Allium cepa), broad bean (Vicia faba),
the ornamental Swiss cheese (Monstera deliciose) and maize (Zea mays) plants.
Modified MS-agar medium*(After Murashige and Skoog, 1962).** (After El-Fiki et al.,
1999a & b), Chemicals and Laboratory. Greenhouse, pathogenic fungi Rhizoctmia solani,
Cephalosporium maydis and Fusarium monioliforme. Field and P and N fertilizer. |
