RESUMEN

Banana bunchy top disease is one of the major prevailing virus diseases associated with banana cultivation, spreading rapidly within a small scale of time. Till date there are only few extensive reports of completely sequenced isolates in India. A study was conducted to detect BBTV infection across 12 districts in West Bengal (WB) where extensive prevalence of the disease was ascertained. In silico characterization of the six genome components were accomplished which showed 84.90-99.86% similarity with other BBTV isolates reported worldwide. The phylogenetic analysis based upon DNA R and DNA S suggested formation of monophyletic cluster of majority of the WB isolates and its close association with Tripura, Manipur, Australia and Africa isolates indicating diversion from geographical differentiation. Dynamics of evolutionary pattern such as genetic diversity including Tajima's D test and Fu Li's Fs test, average number of nucleotide differences (K), Polymorphic sites (S); Fst distance; Mismatch distribution plot; Haplotype network, and selection pressure were performed based upon geographical distribution of the virus. Population genetics analysis of both Pacific Indian Ocean group and South East Asian group of the global BBTV population revealed low nucleotide diversity, high haplotype diversity, high gene flow within the group, and negative or purifying selection constraint indicating recent population expansion. Hence, this study portrays Indian subcontinent as the possible hotspot for rapid demographic expansion from a small virus population size, contributing valuable addition to the currently available information on BBTV worldwide. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00815-0.

RESUMEN

BACKGROUND: The invasive and calamitous polyphagous pest Spodoptera frugiperda or commonly known as fall armyworm (FAW) poses serious menace to the global agricultural production. Owing to the revamped invasion of FAW in 2018 in India, present study was undertaken for precise assessment of its genetic identity and pesticide resistance to aid in pest-management strategies. RESULTS: To evaluate the diversity in FAW population across Eastern India, mitochondrial COI sequences were used which revealed a low nucleotide diversity. Analysis of molecular variance indicated significant genetic variation between four global geographical FAW populations with lowest differentiation between India and Africa suggesting a present-day and shared origin of FAW. The study demonstrated existence of two different strains ('R' strain and 'C' strain) based on COI gene marker. However, discrepancies between COI marker and host plant association of FAW was observed. Characterization of Tpi gene revealed abundance of TpiCa1a followed by TpiCa2b and TpiR1a strains respectively. The FAW population showed higher susceptibility towards chlorantraniliprole and spinetoram than cypermethrin. Insecticide resistance genes depicted marked upregulation although with lot of variance. Chlorantraniliprole resistance ratio (RR) exhibited significant correlation with 1950 (Glutathione S-transferase, GST), 9131 (Cytochrome P450, CYP) and 9360 (CYP) genes, while spinetoram and cypermethrin RR was found to correlate with 1950 (GST) and 9360 (CYP) genes. CONCLUSION: This study manifests Indian subcontinent as the potential new hotspot for the growth and distribution of FAW population that can be effectively controlled using chlorantraniliprole and spinetoram. This study also adds novel significant information on FAW population across Eastern India for developing a comprehensive pest management approach for S. frugiperda.

Asunto(s)

RESUMEN

Bemisia tabaci (whitefly) is one of the most detrimental agricultural insect pests and vectors of many plant viruses distributed worldwide. Knowledge of the distribution patterns and insecticide resistance of this cryptic species is crucial for its management. In this study, genetic variation of mitochondrial cytochrome oxidase subunit 1 (MtCoI) gene of B. tabaci was analyzed followed by a study of the infection profile of various endosymbionts in 26 whitefly populations collected from West Bengal, India. Phylogenetic analysis revealed Asia I as the major cryptic species (65.38%), followed by Asia II 5, China 3, and Asia II 7, which were diversified into 20 different haplotypes. In addition to the primary endosymbiont (C. poriera), each of the four whitefly species showed a variable population of three secondary endosymbionts, majorly Arsenophonus with the highest infection rate (73.07%), followed by Wolbachia and Rickettsia. Further phylogenetic analyses revealed the presence of two subgroups of Arsenophonus, viz., A1 and A2, and one each in Wolbachia (W1) and Rickettsia (R3). Resistance to thiamethoxam, imidacloprid, and acetamiprid insecticides was analyzed for a clear picture of pesticide resistance status. The highest susceptibility was noted toward thiamethoxam (LC50 = 5.36 mg/L), followed by imidacloprid and acetamiprid. The whitefly population from Purulia and Hooghly districts bearing Asia II 7 and Asia II 5 cryptic species, respectively, shows maximum resistance. The differences in mean relative titer of four symbiotic bacteria among field populations varied considerably; however, a significant positive linear correlation was observed between the resistance level and relative titer of Arsenophonus and Wolbachia in the case of imidacloprid and thiamethoxam, while only Wolbachia was found in case of acetamiprid. Expression analysis demonstrated differential upregulation of insecticide resistance genes with Purulia and Hooghly populations showing maximally upregulated P450 genes. Moreover, thiamethoxam and imidacloprid resistance ratio (RR) showed a significant correlation with CYP6CM1, CYP6DZ7, and CYP4C64 genes, while acetamiprid RR correlated with CYP6CX1, CYP6DW2, CYP6DZ7, and CYP4C64 genes. Taken together, these findings suggested that P450 mono-oxygenase and symbiotic bacteria together affected whitefly resistance to neonicotinoids. Hence, a symbiont-oriented management programme could be a better alternative to control or delay resistance development in whitefly and can be used for pesticide clean-up in an agricultural field.

RESUMEN

The whitefly, B.tabaci is a major pest of agricultural crops which transmits begomovirus in a species-specific manner. Yellow vein mosaic disease (YVMD) and okra leaf curl disease (OLCD) caused by distinct begomovirus are a major limitation to production of okra in India. In this framework the present investigation reports, for the first time, comparative study of begomovirus species viz. yellow vein mosaic virus (YVMV) and okra enation leaf curl virus (OELCuV) ingested and egested by two cryptic species (Asia I and Asia II 5) of B.tabaci at different time interval using detached leaf assay. A gradual increase of both virus copies were observed with increased feeding exposure in Asia I and Asia II 5. Both the genetic groups of whitefly could acquire the viruses within just 5 minutes of active feeding however, a significant amount of variation was noted in virus uptake by the both. At 24 hours of active feeding Asia II 5 acquired more of YVMV whereas, Asia I ingested more OELCuV. Similarly, the genetic group acquiring higher titre of virus egested higher amount during inoculation period. On the whole, it can be presumed that Asia I is a more effective transmitter of OELCuV whereas, Asia II 5 of YVMV further suggesting increased risk of virus pandemics (both YVMV and OELCuV) in regions where Asia I and Asia II 5 is dominant.

Asunto(s)

RESUMEN

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.

RESUMEN

The silverleaf whitefly, Bemisia tabaci (Gennadius, Hemiptera: Aleyrodidae), is a major threat to field and horticultural crops worldwide. Persistent use of insecticides for the management of this pest is a lingering problem. In the present study, the status of sensitivity of B. tabaci to two neonicotinoids, imidacloprid and thiamethoxam, was evaluated. The expression pattern of two cytochrome P450 (cyp) genes and changes in the relative amount of symbionts in insecticide-treated B. tabaci were also assessed. Quantitative PCR (qPCR) studies indicate that the CYP6CM1 and CYP6CX1 genes were always expressed higher in imidacloprid-treated whitefly, suggesting a correlation between gene expression and the insect's ability to detoxify toxic compounds such as insecticides. In addition, the thiamethoxam-treated population harbored higher Portiera and lower Rickettsia titers, whereas the imidacloprid-treated population harbored more Rickettsia at different time intervals. Interestingly, we also examined that an increase in exposure to both the insecticides resulted in a reduction in the mutualistic partners from their insect host. These differential responses of endosymbionts to insecticide exposure imply the complex interactions among the symbionts inside the host insect. The results also provide a deeper understanding of the molecular mechanism of resistance development that might be useful for formulating effective management strategies to control B. tabaci by manipulating symbionts and detoxifying genes.

RESUMEN

Fall armyworm (FAW), Spodoptera frugiperda a recent invasive pest in India is reported to cause significant damage by feeding voraciously on maize and other economic crops from tropical to temperate provinces. It is becoming an arduous challenge to control the pest as it can survive in a wide range of temperature conditions and is already said to develop resistance towards certain insecticides. The small Heat shock proteins (hereafter, sHsps) are known to play an important role in adaptation of insects under such stress conditions. Our present study involved characterization of the three sHsps genes (sHsp19.74, sHsp20.7 and sHsp19.07) which encoded proteins of about 175, 176 and 165 amino acids with a conserved α-crystalline domain. Phylogenetic analysis of deduced amino acid sequences of the three genes showed strong similarity with the other lepidopteran sHsps. The effect of different growth stages on the expression profile of these stress proteins has also been studied and the Quantitative real time PCR (qRT-PCR) analysis revealed that the transcript level of sHsp19.07 and sHsp20.7 were significantly upregulated under extreme heat (44 °C) and cold (5 °C) stress. However, sHsp19.74 responded only to heat treatment but not to the cold treatment. In addition, the expression profile of all three sHsps was significantly lower in the larval stage (5th instar). Chlorantraniliprole treatment resulted in maximum expression of sHsp19.07 and sHsp20.7 after 12hr of exposure to the insecticide. Meanwhile, the same expression was observed after 8hr of exposure in case of sHsp19.74. These results proved that the sHsp genes of S. frugiperda were induced and modulated in response to abiotic stress, thus influencing the physiological function leading to survival of FAW in diversified climate in India.

RESUMEN

ABSTRACT Amorphophallus (elephant foot yam) is an herbaceous edible aroid crop which belongs to the family Araceae. The study was undertaken to identify the efficient SSR primer that could differentiate a set of 12 elephant foot yam genotypes. Various efficiency parameters, namely, Polymorphism Information Content (PIC), Marker Index (MI), Resolving Power (RP) and Diversity Index (DI) were studied for 11 primers. The relationship between the parameters was studied using Spearman rank correlation coefficient. Discrimination analysis was done to find out the most effective parameter. Finally Principal Coordinate Analysis (PCoA) and dendrogram was done to find out the genetic diversity among the germplasm. The SSR markers under this investigation will facilitate further studies in population genetics and utilization of A. paeoniifolius.

Asunto(s)

RESUMEN

Rice tungro bacilliform virus (RTBV) is a plant pararetrovirus. The large intergenic region (LIGR) of RTBV having a single transcriptional promoter produces more than genome length pregenomic RNA (pgRNA) which directs synthesis of circular double-stranded viral DNA and serves as a polycistronic mRNA. By computer-aided analysis of LIGR, the 11 RTBV isolates sequenced so far were compared with respect to structural organization of promoter and pgRNA 5'-leader. The results revealed only 74.90% identity at LIGR between 'Southeast Asian' (SEA) and 'South Asian' (SA) isolates of RTBV indicating considerable variation between two groups which was also reflected during analysis of promoter and leader sequence. The predicted promoter region of SA isolates exhibited major variations in terms of transcription start site and consensus sequences of cis motifs expecting further exploitation of promoter region of SA isolates. The reduced length of leader sequence along with less numbers and different arrangements of small open reading frames (sORFs) in case of SA isolates might have some alterations in the control of expression of ORF II and III between the two groups. In spite of these variations, the leader sequence of both SEA and SA type isolates showed formation of stable secondary or stem-loop structure having identical features for efficient translation. The conservation of sORF1 at seven nucleotides upstream of stable stem-loop, CU-rich sequence following the sORF1 stop codon and AU-rich shunt landing sequence immediately downstream of the secondary structure suggested conservation of ribosomal shunt mechanism in all RTBV isolates irrespective of their geographical distribution.

Asunto(s)

RESUMEN

A new isolate of Rice tungro bacilliform virus (RTBV) was collected from Chinsura, West Bengal, India. The full genome was sequenced and deposited to GenBank designating the new one as Chinsura isolate. The four open reading frames (ORFs) of the new isolate were compared with those of previously reported 'South-east Asian' (SEA) and 'South Asian' (SA) isolates emphasizing the ORF3, which is the largest and functionally most important gene of RTBV. In the ORFs, Chinsura isolate shared 90.0-100.0% identity at amino acid level with SA isolates, but only 58.76-88.63% identity with SEA isolates for the same. Similarly, the amino acid identity of ORFs between SEA and SA isolates ranged from 58.77 to 88.64, whereas within each group the corresponding value was >96.0%. The phylogenetic analysis based on nucleotide and amino acid sequences of each ORF made two broad clusters of SEA- and SA-types including Chinsura isolate within SA cluster. Moreover, the relative positions and length of functional domains corresponding to movement protein (MP), coat protein (CP), aspartate protease (PR) and reverse transcriptase/ribonuclease H (RT/RNase H) of ORF3 of Chinsura isolate were completely identical with SA isolates. The clustering pattern indicated strong influence of geographical habitat on genomic evolution. Comparison of ORF3 among all the isolates revealed major variations at non-functional regions in between the functional domains and at the hypervariable 3'-terminal end of ORF3, while PR appeared to have evolved differentially in SA isolates expecting further characterization.

Asunto(s)

RESUMEN

In this study, attention was paid to investigate the effect of organophosphate insecticides, profenofos 40% EC, methyl parathion (metacid) 50% EC, and neem-based product nimbecidine 0.03% EC (from Azadirachta indica) on somatic chromosomal behavior, level of leaf protein, and activity of antioxidant enzymes in Lathyrus sativus L., the leguminous herb. The experiments on somatic chromosomes of root tip cells of L. sativus L. revealed that most common type of abnormalities were anaphase bridge, chromosome fragment, breaks, giant interphase, etc. Also, the mitotic index reduced and abnormality index enhanced, which were directly proportional to the rise in concentration as well as time period of exposure of chemicals. The profenofos and metacid induced drastic changes in mitotic index when compared with nimbecidine. The electrophoretic studies of leaf protein of L. sativus L. showed alteration of some major and minor protein bands subjected to spraying of organophosphate insecticides and induced to synthesize additional high molecular mass protein compared to untreated control. Analysis of SOD, EST, and POD activity by non-denaturing polyacrylamide gel electrophoresis showed different patterns of the isoforms. Complete inhibition of EST was observed in profenofos-treated plants, while with metacid- and nimbecidine-treated plants EST was suppressed. Induction and/or increased activities of SOD and POD were generally enhanced. Our present study not only provides the important information for better understanding of the toxic and tolerance mechanisms, but as well can be used as a bio-indicator for contamination by pesticides, which could cause genetic instabilities of natural plant populations and in crop varieties.

Asunto(s)