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Papaya ringspot virus (PRSV) is one of the important pathogens responsible for damage of the papaya crop and causes significant yield loss of fruits and vegetable worldwide and hence a serious threat. In this study, PRSV-infected plant samples collected from different locations in North 24 Parganas districts of West Bengal, were tested with potyvirus specific ELISA and further confirmed with potyvirus group specific degenerate primers by RT PCR, TEM and sequence analysis. Our result indicates that the disease symptoms occurred in 80–100% of the plant in the field surveyed. The complete sequence of PRSV isolate WB was determined from RT-PCR products with specific primer pairs designed covering the whole genome and confirmed by next-generation sequencing. The whole genome of the PRSV was determined and submitted to GenBank as accession no. LC482263. The sequence of PRSV-WB (10,340 bp) was found to share upto 90% and 93%, identity with other PRSV isolates at the nucleotide and amino acid levels respectively. Based on phylogenetic analysis, PRSV- WB was found to be most closely related to PRSV-BD2 (MH397222) from papaya in Bangladesh (geographically close).

The state West Bengal, India was thoroughly investigated and a total of ten specimens belonging to the genus Chlorophyllum was collected. Detailed morphological and molecular studies revealed that the collected specimens were distributed over three species among which two viz. Chlorophyllum hortense and C. molybdites were previously known from the region, and one, Chlorophyllum squamulosum sp. nov., is described herein as new to science. The new species is distinguished by its small plate-like squamules over the pileus coloured greyish brown to reddish brown or dark brown; truncate, hyaline basidiospores with a prominent germ-pore; relatively small (17–25 × 7.5–11.5 μm), clavate or spheropedunculate cheilocystidia; and a tightly packed hymeniderm type pileus covering. A comprehensive morphological description, field photographs of the basidiocarps, comparisons with phenotypically similar and phylogenetically related species and a phylogram showing the placement of each of the collected species are provided. Besides, earlier records of Chlorophyllum species from West Bengal as well as in India are consulted and information related to diversity of the genus in the country are discussed with notes on the previous records. An artificial dichotomous key is provided to aid in the identification of the presently available Chlorophyllum species in India.

Arsenic (As) contamination of soil and ground water poses serious threats to agricultural food production. MicroRNAs (miRNAs), a class of small non-coding RNAs play essential role in plant responses to environmental stress. In this study, we constructed two small RNA (sRNA) libraries from control and arsenate (50 μM AsV) treated maize leaves to identify AsV stress-responsive miRNAs. Using deep sequencing, we identified 22 (16 conserved and 6 novel) up- and 35 (33 conserved and 2 novel) down-regulated miRNAs from AsV challenged leaves. Gene ontology (GO) analyses reveal that predicted target genes of arsenic responsive miRNAs are associated with diverse biological processes such as plant growth and developmental (miR156s, miR166e-3p, miR166m, miR319b-3p), metabolic processes (miR159b-5p.3, zma_460, zma_468, zma_469), ROS generation (miR167d) and hormone signalling pathways (miR167d, miR159e.2, miR319b-3p). Moreover, we validated the expression patterns of selected miRNAs and their target genes by qRT-PCR. The miR319b-3p mediated down-regulation of GAMYB and low ARF3 transcript level might result in restricted shoot growth under AsV stress. The present work adds new insights into the underlying mechanisms of plant responses to arsenate stress at post-transcriptional level.

β-Aminobutyric acid (BABA), a potent chemical priming agent, induces plant resistance to a broad spectrum of biotic and abiotic stresses. Nevertheless, the molecular mechanisms underlying this phenomenon remain poorly understood. Therefore, this study aims to identify rare and differentially expressed transcripts in BABA-primed maize (Zea mays L.) using a suppression subtractive hybridization strategy. Forward subtraction was performed using the cDNA prepared from a BABA primed leaf as a tester and cDNA from the control leaf as the driver. For reverse subtraction, tester cDNA was synthesized from control leaf and driver cDNA from the BABA primed leaf. A total of 626 clones were picked randomly. In total 192 and 204 high quality expressed sequence tags (ESTs) were generated from forward (ZmSF) and reverse SSH library (ZmSR) respectively. Contigs analyses revealed 27 unigenes from the forward subtracted library and 4 unigenes from the reverse subtracted library. The ESTs encoding alpha amylase, inositol monophosphatase 3, tocopherol cyclase, thioredoxin H-type, aspartic proteinase, NADP-malic enzyme and PEP carboxykinase were expressed predominantly in BABA-primed leaf and found to be predominantly associated with major metabolic and biosynthesis events along with seed germination, developmental processes and adaptive responses to environmental stimuli such as drought, salinity, osmotic stress and pathogen attack. In this study, we present the first report of transcriptome analysis of maize leaf exposed to BABA. The expression profiles of candidate genes from subtracted libraries were checked using semi quantitative RT-PCR and further validated by qRT-PCR. Expression profiles largely corroborated the quality and functional diversity of both libraries. In ZmSF, 130 ESTs (67.70%) did not show any significant similarity to any protein in the NCBI database, indicating a significant fraction of novel and rare expressed transcripts that were rapidly and strongly induced in response to BABA. Further research needs to be done for these novel transcripts to elucidate their function in a BABA-potentiated stress adaptation mechanism. Overall, our study adds new insights into the BABA potentiated defense mechanisms in plants, and strengthens the available transcriptome database of maize.

The present study assesses the impact of arsenate (AsV) stress on maize ( Zea mays L.) seedlings. Three different levels of AsV stress (25, 50 and 100 μM Na 2 HAsO 4 ·7H 2 O) were imposed and seedling growth performances were studied at 2d and 4d of experiment. Arsenate induced modulation of antioxidant enzymes of ascorbate-glutathione cycle along with antioxidant molecules (glutathione and ascorbate) were monitored. Dose and time dependent decline in shoot biomass along with yellowing and drying of leaf tips were observed in AsV treated seedlings. Comparatively high phytochelatin synthesis in roots appears to restrict arsenic translocation from root to aboveground tissues as evident from low arsenic concentration in leaves as compared to roots. Increased uptake of Evans blue by AsV stressed roots indicates loss of root cells viability. Histochamical staining with NBT and DAB revealed dark blue and brown spots respectively on the leaves under AsV stress, which indicated oxidative burst. CM-H2DCFDA and DHE staining of AsV stressed roots further indicated enhanced formation of ROS. Western blot and real-time qRT-PCR analyses revealed high GR expression at protein and transcript levels respectively in presence of high AsV concentration. However, increased GR activity coupled with high GSH/GSSG ratio and enhanced GST activity does not seem to prevent cells from oxidative damages, as evident from high MDA level in leaves of 50 and 100 μM AsV stressed seedlings. Marked decrease in DHAR and MDAR render the stressed cells in futile recycling of ascorbate pool which might contribute to increased susceptibility towards high AsV dose.

During a survey from March 2013 to October 2015, in Barasat, West Bengal, India, symptoms suggestive of begomovirus infection were observed in Malachra capitata. The occurrence of begomovirus on M. capitata was confirmed by symptomatology, polymerase chain reaction (PCR), Southern blot analysis and nucleotide analysis of the whole genome sequence. Sequence analysis showed that the virus had 90.6% identity with available sequences of Tomato leaf curl New Delhi virus (ToLCNDV). We propose that the new begomovirus be named Malachra yellow mosaic virus (MalYMV). To the best of our knowledge, this is the first time the complete genome of the MalYMV, infecting M. capitata in West Bengal, India, has been sequenced.

The complete nucleotide sequence of an Indian strain of Cymbidium mosaic virus (CymMV) was determined and compared with other potexviruses. Phylogenetic analyses on the basis of RNA-dependent RNA polymerase (RdRp), triple gene block protein and coat protein (CP) amino acid sequences revealed that CymMV is closely related to the Narcissus mosaic virus (NMV), Scallion virus X (SVX), Pepino mosaic virus (PepMV) and Potato aucuba mosaic virus (PAMV). Different sets of primers were used for the amplification of different regions of the genome through RT-PCR and the amplified genes were cloned in a suitable vector. The full genome of the Indian isolate of CymMV from Phaius tankervilliae shares 96–97% similarity with isolates reported from other countries. It was found that the CP gene of CymMV shares a high similarity with each other and other potexviruses. One of the Indian isolates seems to be a recombinant formed by the intermolecular recombination of two other CymMV isolates. The phylogenetic analyses, Recombination Detection Program (RDP2) analyses and sequence alignment survey provided evidence for the occurrence of a recombination between an Indian isolate (AM055720) as the major parent, and a Korean type-2 isolate (AF016914) as the minor parent. Recombination was also observed between a Singapore isolate (U62963) as the major parent, and a Taiwan CymMV (AY571289) as the minor parent.

The present study highlights the role of β-aminobutyric acid (BABA) in alleviating drought stress effects in maize (Zea mays L.). Chemical priming was imposed by pretreating 1-week-old plants with 600 μM BABA prior to applying drought stress. Specific activities of key antioxidant enzymes and metabolites (ascorbate and glutathione) levels of ascorbate-glutathione cycle were studied to unravel the priming-induced modulation of plant defense system. Furthermore, changes in endogenous ABA and JA concentrations as well as mRNA expressions of key genes involved in their respective biosynthesis pathways were monitored in BABA-primed (BABA+) and non-primed (BABA-) leaves of drought-challenged plants to better understand the mechanistic insights into the BABA-induced hormonal regulation of plant response to water-deficit stress. Accelerated stomatal closure, high relative water content, and less membrane damage were observed in BABA-primed leaves under water-deficit condition. Elevated APX and SOD activity in non-primed leaves found to be insufficient to scavenge all H2O2 and O2 (·-) resulting in oxidative burst as evident after histochemical staining with NBT and DAB. A higher proline accumulation in non-primed leaves also does not give much protection against drought stress. Increased GR activity supported with the enhanced mRNA and protein expressions might help the BABA-primed plants to maintain a high GSH pool essential for sustaining balanced redox status to counter drought-induced oxidative stress damages. Hormonal analysis suggests that in maize, BABA-potentiated drought tolerance is primarily mediated through JA-dependent pathway by the activation of antioxidant defense systems while ABA biosynthesis pathway also plays an important role in fine-tuning of drought stress response.