TABLE CONTENTS

Evaluation of Tobacco Germplasm for Resistance to Meloidogyne Species
in Diverse Regions of the World
Fortnum, B. & F. Bremm
(1) Department of Entomology Soils and Plant Sciences, Clemson University, Pee Dee Research and Education
Center, 2200 Pocket Road, Florence, South Carolina USA 29506. (2) Departamento de Producao Agricola,
CTA- Continental Tobaccos Alliance S/A
Root-knot nematodes (Meloidogyne species) are a diverse group of plant parasites and are
found across temperate and tropical regions of the world. Use of nematicides has reduced the
losses to root-knot nematodes on tobacco (Nicotiana tabacum L.) in some countries but
nematicides are not available or rarely used in many developing countries. Worldwide losses
are estimated to reach 15% of production. Use of fumigant nematicides, reduce root-knot
nematode losses, but are an increasing environmental concern. The most reliable and least
costly method of nematode control is host resistance. Ninety-five percent of all nematode
damage on tobacco is causes by one of four major species of root-knot nematodes: namely,
M. incognita races 1-4, M. arenaria races 1 and 2, M. javanica and M. hapla. Tobacco
germplasm is available with reported resistance to some populations of root-knot nematodes
however, comprehensive testing of tobacco germplasm for host reaction to a diversity of
Meloidogyne spp., races and populations has not be conducted. Tobacco germplasm (11
entries), reported to be resistant to one or more Meloidogyne spp. was obtained from
commercial breeders in southern Africa, USA and Brazil and evaluated for resistance to M.
incognita races 1,3,4, M. arenaria races 1 and 2, M. javanica and M. hapla in a controlled
greenhouse trial. The tested entries included: NC 95, CC13, CC33, RJR 35, PVEH 270,
PVEH 272, NC 119, Okinawa, STNCB 2-28, K RK 26, K 30R and a susceptible control.
The germplasm was evaluated for nematode reproduction under field conditions in replicated
field trials in Malawi, Zambia, Tanzania, Brazil (3 locations) USA (2 locations) and France.
At least one tobacco cultivar significantly lowered root galling or egg mass production within
each nematode species or across each field location (P = 0.05). The status of breeding for
resistance in N. tabacum will be discussed.
Introgressing Root-knot Nematode Resistance into Local Maize Genotypes
Fourie, H., A.H. Mc Donald & G.A. Venter
Plant Protection Division, Nematology Unit, ARC – Grain Crops Institute, Private Bag X1251, Potchefstroom,
2520, South Africa
Local maize production is hampered by parasitism of economically important root-knot
nematodes (Meloidogyne spp.). The demand for the identification of resistant maize
germplasm is growing, since chemical control is seldom cost-effective, especially under dry
land production conditions and most crop rotation practices favour the build-up of high rootknot
nematode populations. Two acquired maize lines have been identified with resistance to
M. javanica (RF-values < 1) in a greenhouse trial. The resistance of these two lines, together
with that of the F 1 progeny resulting from crosses between the resistant and susceptible
parents was subsequently verified in a field trial, where a mixed population of M. javanica
and M. incognita was established artificially. Consequently six F 2 populations resulting from
these crosses were evaluated for resistance to this mixed root-knot nematode population.
Root-knot nematode numbers were generally low in the roots of the majority of F 2 plants
from population 1 (0 to 113 17 per 50 g roots). Fifty-one percent of these F 2 plants
maintained between 0 and 100 root-knot nematodes individuals per 50 g roots. Although
5 th International Congress of Nematology, 2008 236