TABLE CONTENTS

TOPIC TWO – MORPHOLOGY AND DEVELOPMENT
Influence of Temperature on the Life Cycle of the Root-knot Nematode,
Meloidogyne hispanica
Maleita, C.M. (1), M.C. Vieira dos Santos (1), R.H.C. Curtis (2) & I.M. de O. Abrantes (1)
(1) IMAR – CIC and Departamento de Zoologia, Faculdade de Ciências e Tecnologia, Universidade de
Coimbra, 3004-517 Coimbra, Portugal; (2) Nematode Interactions Unit, Plant Pathology and Microbiology
Department, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, United Kingdom.
Global warming has the potential to influence the occurrence and distribution of plant
diseases. Meloidogyne hispanica is a virulent pathogen of a variety of plant hosts and has
been reported in Africa, Asia, Europe, North, Central and South America and Australia.
Development and generation times of M. hispanica in susceptible tomato plants cv. Easypeel
were studied at 15, 20, 25, 30 and 35ºC in growth chambers. Three-week-old seedlings were
inoculated with 150 second-stage juveniles (J2). Three/seven days after inoculation (DAI),
the seedlings were uprooted and the roots washed to remove all J2 outside the roots. They
were then transplanted into Petri dishes with sterilized soil. Nematodes were dissected out
from roots and their developmental stages and sex recorded daily for the period between 3-10
DAI; every two days for 10-30 DAI and every 5 days after 30 DAI until the completion of the
life cycle. The life cycle (from J2 to J2) was shorter at 25 and 30ºC (34 and 26 days,
respectively). At 20ºC, the life cycle was twice as long as that at 25ºC (70 days). At 15ºC,
females were only found at 75 DAI and egg production was not observed until 80 DAI, this is
probably related to the unfavourable conditions of plant growth at this temperature. Eggs
were laid after 22 DAI at 35ºC, but no hatching occurred at this temperature indicating the
upper temperature limit for life cycle completion. At higher temperatures (30 and 35ºC)
development of J2 into females decreased slightly, but the number of males increased. Thus
M. hispanica is most suited to soil temperatures around 25 o C and predicted climate change
indicates that this nematode will spread in Southern Europe.
Developmental Biology of the White-tip Nematode Aphelenchoides besseyi
Mochiji, N., K. Hasegawa & J. Miwa
Graduate School of Bioscience and Biotechnology, Chubu University, 1200 Matsumoto,Kasugai 487-8501
Japan
The white-tip nematode Aphelenchoides besseyi is the causal agent of white tip disease of
rice, and the disease occurrence and nematode distribution have been reported in almost
every rice-growing region of the world. Although we have observed that this nematode has
two sexes, male and female, it has been reported to have a strongly biased sex ratio or even to
reproduce parthenogenetically. We have studied the early embryogenesis of A .besseyi HM-
M (a strain isolated in Hiroshima, Japan; a gift from Dr. K. Togashi) from fertilization to the
4-cell stage under Nomarski optics and examined the chromosome structure by DAPI
staining. After passing through the spermatheca, an oocyte is fertilized by sperm, the eggshell
is formed, the egg is deposited, and the male and female pronuclei are reconstructed. The
male pronucleus moves toward the female pronucleus, they meet and move to the center of
the egg where they rotate 90° and fuse. The embryo then divides unequally to form an
anterior and larger cell and a posterior and smaller cell.
5 th International Congress of Nematology, 2008 192