Further research on the production longevity and infectivity of the zoospores of Leptolegnia chapmanii Seymour Oomycota : Peronosporomycetes

PELIZZA, S. , LOPEZ LASTRA, C.C., BECNEL , J.J. AND GARCÍA , J.J.

JOURNAL OF INVERTEBRATE PATHOLOGY

Academic Press

Lugar: San Franciso; Año: 2008 vol. 98 p. 314 - 319

0022-2011

  The effect of temperature on the production, survival and infectivity of zoospores of an Argentinean iso- 2222 late of Leptolegnia chapmanii was determined under laboratory conditions. Production of zoospores of 23Leptolegnia chapmanii was determined under laboratory conditions. Production of zoospores of 23 L. chapmanii in vitro and in vivo upon first and fourth instars larvae of the mosquito Aedes aegypti was 24and in vivo upon first and fourth instars larvae of the mosquito Aedes aegypti was 24 studied at three different temperatures. Zoospores from infected larvae were infective to mosquito larvae 2525 for 51, 12, and 5 consecutive days whenmaintained at 25, 35, and 10 C, respectively. Maximum zoospore 2626 production in infected fourth-instar larvae was 9.6 ± 1.4 104 zoosp/larva at 48 h at 25 C. The average 27104 zoosp/larva at 48 h at 25 C. The average 27 number of zoospores produced by individual fourth-instar Ae. aegypti larvae infected with L. chapmanii 28Ae. aegypti larvae infected with L. chapmanii 28 was 3.57 ± 0.46 105 zoospores during 6 consecutive days at 25 C. Zoospore production in vitro was also 29105 zoospores during 6 consecutive days at 25 C. Zoospore production in vitro was also 29 affected by temperature with a maximum of zoospores (n = 47,666/ml) produced at 25 C. When zoo- 30(n = 47,666/ml) produced at 25 C. When zoo- 30 spores produced in vitro were used as inoculum against Ae. aegypti larvae at 25 C, larval mortality was 31in vitro were used as inoculum against Ae. aegypti larvae at 25 C, larval mortality was 31 recorded for 5 consecutive weeks. The encystment process for zoospores took 17–20 min; the germina- 32min; the germina- 32 tion of cysts (excystment) occurred 5 min after exposure in water to mosquito larvae. The minimal time 33min after exposure in water to mosquito larvae. The minimal time 33 of contact between zoospores and mosquito larvae to develop infection was two minutes. Infection took 3434 place by zoospore attachment onto and then penetration through the larval cuticle or by ingestion of 3535 cysts as was confirmed by histological studies. Temperature directly affected infectivity and production 3636 of zoospores in vivo and in vitro although L. chapmanii zoospores tolerate a wide range of temperatures. 37in vivo and in vitro although L. chapmanii zoospores tolerate a wide range of temperatures. 37 2008 Published by Elsevier Inc.2008 Published by Elsevier Inc.