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.

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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.

Abstract.A potyvirus was isolated from diseased Cymbidium pendulum and C. tigrinum epiphytic orchids collected from Sikkim in northern India. ELISA, RT-PCR and Northern blot analysis revealed the association of potyvirus infection with disease symptoms. The sequencing of a RT-PCR-amplified amplicon using potyvirus group-specific primers showed that this virus is distinct but most closely related to Calanthe mild mosaic virus. This paper reports the occurrence of potyvirus in wild orchids especially in Cymbidium spp.

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.

The variability in the coat protein (CP) gene sequence of Cymbidium mosaic virus (CymMV) that naturally infects orchids worldwide was investigated. Samples were collected from different regions of India, and the gene encoding the CP of nine isolates was specifically amplified by reverse-transcription polymerase chain reaction. The amplified product obtained was cloned, sequenced and multiple sequence alignment of deduced amino acid (aa) sequences revealed considerable homology to CymMV isolates from other countries. The nucleotide sequences and the amino acid sequences were found to be 85-100% identical and 65-100% respectively. Such high sequence conservation suggests that the CymMV CP gene is highly conserved and is a suitable candidate for the development of diagnostic procedures and to provide transgenic resistance to orchids cultivated in different geographical locations. Although recombination is not common among CymMV isolates, one isolate from Cymbidium was found to be a recombinant between a Korean and a Thai isolate of the virus. IHBT communication no: 0451.

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