Bioassays for Root-knot Nematodes
Gall Index Systems
From Barker, K. R. 1985. Nematode extraction and bioassays.
In Barker, Carter and Sasser
(eds) An Advanced Treatise on
Meloidogyne Vol II. Methodology.
Various index systems have been developed. Their relationship to
degree of root galling is indicated below:
Gall Index Systems % root system galled
0-4 0-5 1-6 0-10
0 0 1 0 0
1 2 1 10
2 3 2 20
1 25
3 30
4 40
2 3 4 5 50
6 60
7 70
3 75
4 5 8 80
9 90
4 5 6 10 100
Assessment of degree of galling of indicator plants
(from Daulton and Nusbaum, 1961; Nematologica)
Infection Index Description of Index Value
Class Value
0 0 Free from galls.
1 1 Trace, less than 5 galls.
2 5 Very slight, trace to 25 galls.
3 10 Slight, 26 to 100 galls.
4 25 Moderate, galls numerous,
mostly discrete.
5 50 Moderately heavy, galls
numerous, many coalesced.
6 75 Heavy, galls very numerous, mostly
coalesced, root growth slightly
retarded.
7 90 Very heavy, mass invasion, slight root
growth.
8 100 Extremely heavy, mass invasion, no root
development.
References:
Barker, K. R. 1985. Nematode extraction and bioassays.
In Barker, Carter and Sasser
(eds) An Advanced Treatise on
Meloidogyne Vol II. Methodology.
Daulton, R.A.C. and C.J. Nusbaum. 1961. The effect of soil temperature on the survival of the root-knot nematodes Meloidogyne javanica and M. hapla. Nematologica 6:280-294.