Desiccation tolerance of dauers of entomopathogenic nematodes of the genus Steinernema

Abstract

For transport of entomopathogenic nematodes to the user, developmentally arrested dauer juveniles (DJ) are mixed with inert carriers at high density. If quiescence is not induced, DJ will quickly lose energy reserves and die. To induce quiescence DJ can be moderately desiccated. This study investigated the desiccation tolerance by measurement of water activity (ow-value) tolerated by 50% of populations (WA50) of different Steinernema species and strains. DJ were tested with or without prior adaptation to desiccation stress. Stress conditions were produced by exposure to various concentrations of poly(ethylene glycol) 600. Significant differences in desiccation tolerance were recorded between strains and species, but, except for Steinernema abbasi, not within strains of one species. Without adaptation to stress conditions, the most tolerant species was S. carpocapsae (WA50 = 0.836) followed by S. abbasi (0.86). Adaption to stress by exposure to an Ow-value of 0.95 for 48 h increased tolerance to 0.68 and 0.66, respectively. The least tolerant species were S. kraussei, S. giaseri and S. ethiopiense. Tolerance recorded would allow storage at a water activity that would inhibit growth of bacteria but not of fungi. Analysis of water activity tolerated by only 10% of the population indicated potential for genetic improvement by selective breeding for S. carpocapsae, S. abbasi and 5. arenarium to reach water activity levels that would also inhibit fungal growth.

Formulation of Entomopathogenic Nematodes for the Control of Key Pests of Grapevine: A Review

“…Ellenby (1968) and Wharton (2002) suggest that the main factor contributing to the survival of desiccated anhydrobiotic nematodes is the controlled rate of body water loss. Different species adapt to anhydrobiosis in a variety of ways: the survival ability of S. carpocapsae is enhanced by a fast rate of water loss, whereas S. glaseri survives well with a low rate of water loss Nimkingrat et al, 2013). Recently, Cortés-Martínez et al (2017) reported the importance of pre-acclimatisation on S. glaseri when producing pellets to prolong survival time.…”

Moisture Evaporation from Granular Biopesticides Containing Quiescent Entomopathogenic Nematodes

“…S. carpocapsae IJs survive well at high rate of water removal and S. glaseri IJs survive better at low rate of water removal [10,11]. Therefore, the major cause of nematode survival to desiccation in anhydrobiosis is the controlled rate of water removal from the IJs [12].…”

Genomics of Entomopathogenic Nematodes and Implications for Pest Control

“…Storage stability is essential for EPN longevity in the soil and in commercial production and distribution. Artificial selection and hybridization can enhance desiccation tolerance [32–34], but removal of selection pressure ultimately results in loss of the desired traits [32, 33]. Deep knowledge of EPN genomes [27, 28], especially the genetic regulatory networks controlling the traits, coupled with improvements in genetic engineering for EPNs may provide new means to stabilize enhanced traits.…”