Comparison of phenotypic and genotypic frequency of phosphine resistance in select field populations of Tribolium castaneum from India.

BACKGROUND: Tribolium castaneum causes substantial damage to stored grains, leading to economic losses. The present study evaluates phosphine resistance in adult and larval stages of T. castaneum from north and northeast India, where continuous and long-term phosphine use in large-scale storage conditions intensifies resistance, posing risks to grain quality, safety, and industry profitability. METHODS AND RESULTS: This study utilized T. castaneum bioassays and CAPS markers restriction digestion methodology to assess resistance. The phenotypic results indicated a lower LC50 value in larvae compared to adults, while the resistance ratio remained consistent across both stages. Similarly, the genotypic analysis revealed comparable resistance levels regardless of the developmental stage. We categorized the freshly collected populations based on resistance ratios, with Shillong showing weak resistance, Delhi and Sonipat displaying moderate resistance, and Karnal, Hapur, Moga, and Patiala exhibiting strong resistance to phosphine. Further validation by accessing findings and exploring the relationship between phenotypic and genotypic variations using Principal Component Analysis (PCA). This comprehensive study enhances our understanding of T. castaneum resistance levels, providing valuable insights for the development of targeted pest management strategies. CONCLUSION: This study provides insights into the current phenotypic and genotypic resistance levels of T. castaneum in North and North East India. Understanding this is crucial for developing effective pest management strategies and future research on biological and physiological aspects of phosphine resistance in insects, enabling the formulation of effective management practices. Addressing phosphine resistance is vital for sustainable pest management and the long-term viability of the agricultural and food industries.

Transcription dynamics of heat-shock proteins (Hsps) and endosymbiont titres in response to thermal stress in whitefly, Bemisia tabaci (Asia-I).

The sweet potato whitefly, Bemisia tabaci (Gennadius), is one of the several species complexes of whitefly that are currently significant agricultural pests. Bemisia tabaci infests more than 600 plant species and thrives under a wide range of temperature conditions. In addition to the direct damage caused by sucking plant sap, it vectors several plant viruses. Heat-shock proteins play a pivotal role in enabling the insect to extend its geographical location, survival, and reproduction under different stress conditions. B. tabaci harbours several endosymbionts under the genera Portiera, Rickettsia, Hamiltonella, Wolbachia, Arsenophonus, Cardinium, and Fritschea that directly or indirectly affect its fitness. By accelerating cuticle biosynthesis and sclerotisation, symbiotic microbes can reduce or enhance tolerance to extreme temperatures and detoxify heavy metals. Thus, symbionts or microbial communities can expand or constrain the abiotic niche space of their host and affect its ability to adapt to changing conditions. The present study delineates the effect of thermal stress on the expression of heat-shock genes and endosymbionts in B. tabaci. Studies of the expression level of heat-shock proteins with the help of quantitative real-time polymerase chain reaction (qRT-PCR) showed that heat- and cold-shock treatment fuels the increased expression of heat-shock proteins (Hsp40 and Hsp70). However, Hsp90 was not induced by a heat- and cold-shock treatment. A significant decrease in the relative titre of secondary endosymbionts, such as Rickettsia, Arsenophonus, and Wolbachia, were recorded in B. tabaci upon heat treatment. However, the titre of the primary symbiont, C. Portiera, was relatively unaffected by both cold and heat treatments. These results are indicative of the fact that Hsp genes and endosymbionts in B. tabaci are modulated in response to thermal stress, and this might be responsible for the adaptation of whitefly under changing climatic scenario.