Insight into the Role of Arbuscular Mycorrhizal Fungi in Sustainable Agriculture - Environmental Sustainability: Role of Green Technologies - page 18

fungi, soil organisms and cultural practices on the
introduced fungi could be more clearly under-
stood. Factors that should be considered when
assessing the potential role and introduction of
AM fungi in agroecosystems include:

species may differ with the cultivars as well as
with the AM fungal species involved (Table 2 ;
Figs. 5 and 6 ).

4.7.2 Inoculum Density, Rate
and Extent of AM Colonization
Rapid and extensive spread of AM fungal coloni-
zation is a crucial factor for effectively enhancing
plant growth and ably competing with indigenous
AM fungi. Therefore, the formation of entry
points is important, and their number is con-
trolled by inoculum level, more specifi cally by
inoculum density, that is, the number of propa-
gules per given unit of soil. Experiments are pre-
formed either with unknown quantities of AM
fungal inoculum or state only the spore numbers.
However, the spore numbers alone do not consti-
tute total propagules, as dried root bits, sporo-
carps, soil hyphae and mycorrhizal roots can also
act as propagules. Therefore, currently, the total

4.7.1 Mycorrhizal Growth Response
(MGR) and Mycorrhizal
Dependency (MD)
of the Host Crop
Mycorrhizal growth response (MGR) is the
responsiveness of change in the total biomass of
mycorrhizal (M) versus non-mycorrhizal (NM)
crop plants from the symbiosis (Hetrick et al.
1992 ):

( )

MGR =− ⊣ M NM / NM ⊦ × 100

Mycorrhizal dependency (MD) is defi ned as the
growth response of the total dry matter in mycor-
rhizal (M) versus non-mycorrhizal (NM) plants
at a given phosphorus level (Plenchette et al.
1983 ):

Table 2 Mycorrhizal dependency of agricultural crops
under low soil P
Mycorrhizal
dependency Agricultural crops
Strong Cassava, onion, legumes, peppers
Medium Soya, wheat, barley, cowpea, grain
legumes, tomatoes
Weak Potato, rice, melon, sunfl ower,
beans, maize, sorghum
After Jeffries and Dodd ( 1991 ) with permission

( )

MD =− ⊣ M NM / M ⊦ × 100

All mycorrhizal agricultural crops are not equally
benefi tted from the association. Generally, coarse-
rooted plants like legumes benefi t more from AM
symbiosis than fi ne-rooted cereals (Jeffries and
Dodd 1991 ). Mycorrhizal dependency of a crop

12

10

8

6

Fig. 5 Relative mycorrhizal
dependency of four Musa
cultivars ( GN Grande Naine,
GM Gros Michel, PJB ,
Pisang Jari Buaya, YKm5 ,
Yangambi Km5) inoculated
with Funneliformis mosseae
(Data from Elsen et al. 2003 ,
with permission)

4

2

0

GN GM PJB YKm5

Accession