Apart from the infection, nematode development and
reproduction were significantly affected by P. indica colonization
in the –3 treatment. On the one hand, reduced J2
vitality and nematode infection ability lead to a decline in
the number of developing adults. On the other hand, the
development rate after 14 days was relatively more strongly
affected than the infection rate in the first 3 days in the –3
P. indica-treated plants. These results indicate that not only
infection and migration of J2s but also later stages of nematode
development are affected by P. indica. Accordingly, syncytium
size was reduced in –3 treatment plants. The current
analysis suggests that mechanical barriers may play a minor
role in syncytium size reduction. Microscopic observation
showed that hyphae of P. indica were not able to penetrate
and thus irritate syncytial protoplast. Although the microscopic
analysis showed the evidence of vessel colonization by
P. indica hyphae following nematode infection, a clear relationship
with the state of syncytial protoplasts could not be
found. Syncytia with electron-translucent and necrotizing
protoplasts were found next to vessels with hyphae as well as
next to vessels without hyphae inside their lumen. There are
also too few data for statistical evaluation of the possible role
of fungal parasitism and hyphae penetration into nematode
bodies, and it was not clear if alive or dead nematodes were
successfully infected. Therefore, nematode as well as syncytium
development appear to be primarily affected by fungusderived
chemical compounds. Accordingly, development and
reproduction of H. schachtii as well as syncytium expansion
were significantly affected when only CF and even more when
only CWE were added onto the roots and no direct fungus–
root–nematode interaction occurred. The composition
of both extracts is currently unknown. CWE may contain
active chitinases that were demonstrated to coincide with the
development of resistance against the root-knot nematode
M. incognita in AMF-colonized roots (Li et al., 2006).