Effects of storage temperature on survival and infectivity of three indigenous entomopathogenic nematodes strains (Steinernematidae and Heterorhabditidae) from Meghalaya, India

Abstract

Three locally isolated strains of entomopathogenic nematodes (EPNs), viz. Heterorhabditis indica, Steinernema thermophilum and Steinernema glaseri, from Meghalaya, India were characterized in terms of storage temperature and survival and infectivity of their infective juveniles (IJs). The survival and infectivity of nematode IJs was studied at, 5 ± 2 and 25 ± 2°C, for a period of 120 days, using deionized water as storage medium. The viability of nematode IJs was checked by mobility criterion at different storage periods, while the infectivity of nematode IJs was ascertained on the basis of establishment of IJs, using Galleria mellonella larva mortality tests in petridishes. The results of this study revealed that storage temperature markedly affects the survival as well as the establishment of nematode IJs of the three EPN species. At 5°C, comparatively higher rate of IJ's survival (i.e. 74-86 %) was observed for 15 days of storage, but the same reduced drastically to 28-32 % after 30 days of storage for H. indica and S. thermophilum. On the other hand, at 25°C, the survival of nematode IJs was observed till 120 days for all the three studied EPNs. In case of S. thermophilum and S. glaseri, higher rate of IJs survival ([75 %) was observed respectively at 15 and 30 days of observation. The study also showed that the establishment of IJs of the three EPN species declines with increase in storage periods, at both the test temperatures. In general, the nematodes stored at 25°C showed comparatively better establishment than those stored at 5°C. Among the three EPN studied, the establishment of S. glaseri was comparatively better than the rest of the species at both the temperatures and for different storage durations. In conclusion, our study adds further valuable information about the effect of storage temperature on survival and infectivity of three indigenous EPN species of Meghalaya, India which appears to be promising biocontrol agents of local insect pests.

NATURAL ENEMIES OF HERBIVORES MAINTAIN THEIR BIOLOGICAL CONTROL POTENTIAL UNDER FUTURE CO2, TEMPERATURE AND PRECIPITATION PATTERNS

“…Investigating the impact of single and combined climate related drivers onto EPN survival and efficacy revealed no interaction between elevated temperature, CO 2, and decreased precipitation. While temperature is known to be a major driver of EPN survival and infectivity (Pervez et al 2015;Lalramliana & Yadav 2016;Aatif et al 2020), we did not find any impact of warming in our study. This discrepancy may be explained by the low range of temperature used in our study (19.6 -23°C) compared to the described beneficial temperature range (25 -30 °C) (Pervez et al 2015).…”

Bioactive Excreted/Secreted Products of Entomopathogenic Nematode Heterorhabditis bacteriophora Inhibit the Phenoloxidase Activity during the Infection

“…The negative effect of age on virulence is supported by a study by Lalramliana et al [ 56 ], who reported that the highest virulence of S. thermophilum and S. glaseri toward G. mellonella was observed in the first month of storage at 25 °C. After 3 and 4 months of storage, virulence began to significantly decrease, in both S. thermophilum and S. glaseri , respectively.…”

“…An explanation for the differences in virulence observed in the above-mentioned studies remains unknown. However, the virulence and insect killing effectivity of EPNs can be affected by many others factors, e.g., temperature [ 52 , 56 , 58 , 59 ], UV radiation [ 60 ], and others. Therefore, it is necessary to always specify IJs age and storage parameters in the experimental design.…”

EPNs Exhibit Repulsion to Prenol in Pluronic Gel Assays

“…In agricultural use, it is not uncommon for EPNs to endure extended storage times. It has been previously demonstrated that storage temperature may affect both the survival and infectivity of EPNs [ 23 , 24 ]. Since previous work had demonstrated that the response of some EPNs to prenol were affected by moderate storage times [ 5 , 18 ], we wondered how longer time periods of storage/aging would impact the IJs’ behavior.…”