Efeito da temperatura na multiplicação celular, no desenvolvimento embrionário e na eclosão de juvenis do segundo estádio de Meloidogyne javanica

Abstract

Abiotic factors affect the embryonic development, survival and hatching of second-stage juvenile (J2) of Meloidogyne spp. The effect of constant temperature has been studied with various species and populations of Meloidogyne spp. However, the temperature fluctuation which predominates in the field between day and night or during periods of predominance of polar cold front, has not been well studied. Thus, this work aimed to study the effect of temperature fluctuation on egg of M. javanica with standardized embryo development. When eggs with formed juveniles inside were used, highest percentage of hatching occurred at fixed temperature of 28°C. The reduction of the exposure time at 28°C reduced hatching. The eggs exposed for 10 hours at 10°C and complemented by 14 hours at 28°C resulted in greater J2 hatching as compared to 10 hours at 5°C complemented by 14 hours at 28°C. The incubation at fixed temperature of 10°C rendered lowest hatching. When eggs at the two-cell stage were used and incubated at 28°C the cell multiplication and embryonic development were speeded up. At constant temperature of 10°C for egg incubation during 12 days only cell multiplication occurred. However, when the incubation temperatures varied with period of 10 hours at 10°C and complemented by 14 hours at 28°C, juveniles were formed inside the eggs and hatched but significantly lower than those at constant temperature of 28°C. At alternated temperatures of 10 hours at 5°C, complemented by 14 hours at 28°C, with the same incubation time, juveniles were not formed. In the eggs occurred only the pluricelular, gastrula and tadpole stages occurred. Therefore, the constant temperature of 10°C allows only the cellular multiplication, and the temperature interval of 5°C and 10°C affect drastically several processes involved in embryo development of M. javanica.