TABLE CONTENTS

TOPIC NINE – POSTER PRESENTATIONS
Effect of Meloidogyne incognita Resistance Genes in Cotton on the
Reproduction of M. mayaguensis
Brito, J.A. (1), R. Kaur (2), R.F. Davis (3) & D.W. Dickson (2)
(1) Nematologist, Division of Plant Industry, Florida Department of Agriculture and Consumer Services, P. O.
Box 147100, Gainesville, FL 32614-7100; (2) Post-Doctoral Associate and Professor, Entomology and
Nematology Department, University of Florida, Gainesville, FL 32611-0620; (3) Research Plant Pathologist,
USDA-ARS, Crop Protection and Management Research Unit, P. O. Box 748, Tifton, GA 31793.
Meloidogyne mayaguensis was first reported in the continental United States in 2002, and
some isolates can reproduce on cotton. Meloidogyne incognita is the single most important
pathogen of cotton in the United States, and efforts to incorporate resistance to M. incognita
into cotton cultivars are ongoing. Our objective was to determine whether resistance to M.
incognita in cotton will also confer resistance to M. mayaguensis. Two greenhouse
experiments showed that gall and egg mass indices, eggs per gram of root, and reproductive
factor (Rf) differed significantly among cotton genotypes resistant or susceptible to M.
incognita when inoculated with M. incognita, but not when inoculated with M. mayaguensis.
Results indicated that resistance to M. incognita in cotton does not confer resistance to M.
mayaguensis; however, on cotton susceptible to M. incognita, inoculation with M.
mayaguensis resulted in gall and egg mass indices, eggs per gram of root, and Rf less than on
plants inoculated with the same number of M. incognita. On cotton resistant to M. incognita,
the two nematode species reproduced similarly.
Variability in Infection and Reproduction of Meloidogyne javanica on
Tomato Rootstocks with the Mi Resistance Gene
Cortada, L. (1), F.J. Sorribas (2), C. Ornat (2), I. Kaloshian (3) & S. Verdejo-Lucas (1)
(1) IRTA. Crta. de Cabrils Km 2. 08348 Cabrils, Barcelona, Spain.; (2) Departament d’Enginyeria
Agroalimentària i Biotecnologia. Universitat Politècnica de Catalunya. Campus Baix Llobregat, Edifici ESAB,
Av. Canal Olímpic 15. 08860 Barcelona, Spain; (3) Department of Nematology, University of California.
Riverside, California, 92521, USA
Grafting became widely used in the late 1990s with the appearance of a disease known as
‘vascular collapse’. Most tomato rootstocks are interspecific hybrids of Solanum
lycopersicum × S. habrochiates or Solanum lycopersicum × Solanum spp. The response of 10
tomato rootstocks with the Mi resistance gene to an initial inoculum of a Mi avirulent
population of Meloidogyne javanica was determined in pot tests conducted in spring and
summer. In a field test, the rootstocks were subjected to continuous exposure to high
population densities of the nematode. The presence of the Mi resistance gene in the
rootstocks was determined using the PCR- based co-dominant markers REX-1, developed to
detect the introgressed Mi region in hybrids of S. lycopersicum × S. peruvianum, and the
Mi23, designed for Solanum hybrids. Nematode infectivity (egg masses), and reproduction
(eggs g -1 root) was highly variable in the spring tests. Rootstocks cvs. PG76, Gladiator, and
MKT-410 consistently responded as highly resistant (Pf/Pi < 1 and reproduction index [RI] <
10%), and were as efficient as the resistant tomato cultivars. The relative resistance levels of
rootstocks cvs. Brigeor, 42851, 43965, Big Power and Heman varied depending on the
susceptible cultivar used for reference or the duration of the test. Rootstocks cvs. PG76 and
5 th International Congress of Nematology, 2008 234