Thermal requirements for the embryonic development and life cycle of Meloidogyne hispanica

The life cycle of a Portuguese Meloidogyne hispanica isolate on susceptible cv. Easypeel and resistant (Mi-1.2 gene) cv. Rossol tomato plants was studied in growth chambers at constant temperatures (1035 degrees C). The development within the egg and hatching were compared to those of a Portuguese M. arenaria isolate. The base temperature was 10.11 and 8.31 degrees C with 179.5 and 235.3 thermal units for M. hispanica and M. arenaria, respectively, suggesting better potential adaptation to low temperatures by M. arenaria than M. hispanica. No egg development occurred at 10 or 35 degrees C. An increase in invasion of tomato roots by M. hispanica second-stage juveniles (J2s) was correlated with an increase in temperature on both tomato cultivars. Tomato cv. Rossol limited M. hispanica development at 20, 25 and 30 degrees C, but not at 35 degrees C, indicating that these high temperatures blocked the resistance mechanism provided by the Mi-1.2 gene. At 15 degrees C, J2s penetrated tomato cv. Rossol roots, but failed to develop and establish feeding sites. On tomato cv. Easypeel, nematode development and reproduction occurred at 20, 25 and 30 degrees C, but at 20 degrees C the life cycle was 1.5 and 2.0 times longer than at 25 and 30 degrees C, respectively. No egg production was observed at 15 degrees C. The results of this study showed that M. hispanica is most suited to soil temperatures around 25 degrees C. Predicted climate change might favour the spread of this nematode species into southern Europe and northwards. The thermal requirements for M. hispanica development are analysed and compared with those of M. arenaria, M. hapla, M. incognita and M. javanica.