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The relevance of VAM fungal diversity to the
functioning of mycorrhizae in the field is not yet
known.
Data from normal conditions of
field grown citrus inoculated with different
communities of VAM fungi on plant growth
and physiology is lacking (Graham, 1982).
VAM fungal species, and geographic isolates
of the same species, can vary with respect to
their ability to colonize roots and improve plant
growth (Camprubi and Calvet, 1996).
Thus, the objective of this study is to test
the hypothesis that VAM fungal communities
differentially affect citrus growth.
OBJECTIVES
The objectives of the study are the
following:
1. to collect and taxonomically identify existing
mycorrhizae in citrus plantations
2. to analyze the diversity of indigenous VAM
fungi in citrus plantations
3. to investigate the in-vivo compatibility and
colonization of each VAM species in citrus
root system
4. to study the nutrient uptake of citrus seedlings
inoculated with indigenous VAM
5. to determine the growth characteristics of
citrus seedlings inoculated with indigenous
VAM.
The study will limit its scope using
mycorrhiza which is VAM fungi which was
inoculated in pre-germinated citrus seedlings
and three (3) month old citrus seedlings. The
study was conducted from February 2008
to June 2009. Collection of VAM fungi were
conducted at Kongkong Valley, Muta and
Malabing Valley, Kasibu, Nueva Vizcaya and
in-vivo and in-vitro preparation of seedlings
were conducted at NVSU Research Laboratory,
NVSU, Bayombong, Nueva Vizcaya.
MATERIALS AND METHODS
Area of Collection
A total of 201 soil samples were
collected in March, 2008 from 120 Satsuma
citrus plantations located in the valleys of
Kongkong, Muta and Malabing, Kasibu, Nueva
Vizcaya. Exact location of the sampling sites
was taken with the use of GPS (Technica).
Predominant soil types were clay loam soil.
Average air temperatures ranged from 21ºC to
26ºC in Kongkong and Muta Valley and 19ºC to
22ºC in Malabing Valley.
Satsuma citrus ages ranged from
3.8 to 4 years. Soil fertilization and chemical
control of pests and diseases were common
in all sampling site. Samples were taken from
homogeneous areas in terms of landscape,
crop age at each site, by collecting seven (7)
to 10 single samples consisting of 0.5 dm3 of
soil and roots of each plant as follows: each
single sample was composed by two subsamples,
collected in opposite positions under
the plant canopy, 30-50 cm from the stem and
0 to 20 cm deep. Single samples were pooled
to form one compound sample of 0.5 dm3 of
soil per location. Soil samples were analyzed
for available Phosphorous, pH, organic matter
and texture and total counts of VAM fungal
spores. Roots were gently separated from the
soil, washed and stained with 0.05% trypan
blue (Philips and Hayman, 1970). Roots were
scored for VAM root colonization (Amber and
Young, 1977) if there is existing colonization of
indigenous VAM in citrus roots.
In order to multiply native VAM fungal
spores for accurate identification, and to
establish single isolate cultures, soil samples
were used to set up trap cultures by growing
Sorghum bicolor (L.) Moench as host plants.
Trap cultures were established by disposing 0.2
L of sterile sand on the bottom of 1 L plastic pots
and covering with 0.6 L of a mixture of native
soil + sterile sand + garden soil (2:1:1, v:v:v).
Trap plant seeds were sown over this mixture
and covered with a third layer of 0.2 L of sterile
2 Diversity Studies and Utilization of Indigenous Vescular.......