Sudip Kumar Dutta

Identification and characterization of a distinct banana bunchy top virus isolate of Pacific-Indian Oceans group from North-East India

Banana bunch top virus (BBTV) is considered to be a serious threat to banana production. A new isolate of the virus (BBTV-Umiam) was identified and characterized from local banana mats growing in mid-hills of Meghalaya in North-East India. The complete nucleotide sequence analysis revealed the presence of six full-length ssDNA components (DNA R, DNA U3, DNA S, DNA M, DNA C and DNA N) sharing major common region (CR-M) and a stem-loop common region (CR-SL). BBTV-Umiam showed a unique deletion of 20 nucleotides in the intergenic region of DNA R, the absence of predicted open reading frame (ORF) in DNA U3 and probability for a small ORF in DNA U3 expecting functional evidence at transcriptional level. Phylogenetic analysis based on 88 complete nucleotide sequence of BBTV DNA R available in GenBank generated two broad clusters of Pacific-Indian Oceans (PIO) and South-East Asian (SEA) groups including BBTV-Umiam within PIO cluster. However, BBTV-Umiam was identified as the most distinct member of the PIO group with 100% bootstrap support. This was further supported by the phylogenetic grouping of each genomic component of BBTV-Umiam at the distant end of PIO group during clustering of 21 complete BBTV sequences. BBTV-Umiam shared relatively less nucleotide identity with PIO group for each genomic component (85.0-95.4%) and corresponding ORF (93.8-97.5%) than that of earlier PIO isolates (91.5-99.6% and 96.0-99.3%, respectively). Recombination analysis revealed two intra-component and five inter-component recombination events in BBTV-Umiam, but none of them was unique. Moreover, the isolate was identified as major parental sequence for intra-component recombination event spanning the replication-associated protein encoding region in Tongan BBTV DNA R. The current study indicated differential evolution of BBTV in North-East India (Meghalaya). The natural occurrence of hybrids of Musa balbisiana and M. acuminata in this geographically isolated region could be the contributing factor in accumulating genetic distinctiveness in BBTV-Umiam which need further characterization.

Impact of postburn jhum agriculture on soil carbon pools in the north-eastern Himalayan region of India

Land-use change, particularly soil organic carbon (SOC) loss induced by shifting cultivation (jhum) is a common land degradation issue in the hilly tracts of the humid tropics. The SOC concentration comprises different pools (labile and recalcitrant fractions), and each fraction responds to temporal dynamics of adopted management practices at varying magnitudes, such as deforestation followed by cultivation. However, information on the variation of different SOC pools due to cultural practices of vegetation burning and postburn agricultural practices (crop production) associated with shifting cultivation remains inadequate. In the present investigation, we examined the effect of burning and postburning cultivation on SOC pools across different forest fallow periods at Kolasib district, Mizoram state of the north-eastern Himalayan Region of India. Results revealed increase in the soil C stocks and total organic carbon (TOC) due to the increase in the length of fallow periods ranging from 3 to 23 years. The TOC decreased significantly compared with antecedent concentrations before vegetation burning. This was mostly attributed to the reduction in contribution of active pools (very labile and labile) to TOC from 69% to 60%. However, contribution of passive pools (less labile and nonlabile) to TOC concentration increased from 31% to 40%. Postburn cultivation also resulted in reduction of TOC as well as considerable variation in the proportion of different SOC pools to TOC concentration. Among the different pools of SOC, the very labile C pool was most sensitive to land-use change induced by shifting cultivation (phytomass burning and postburn cultivation). The labile SOC pools can act as a sensitive indicator for devising suitable location specific management practices for restoration of soil health through SOC dynamics in degraded jhum lands in hilly ecosystems.

Bioactivity and traditional uses of 26 underutilized ethno-medicinal fruit species of North-East Himalaya, India

North-Eastern hill (NEH) region of India is considered as an agro-biodiversity hotspot, which has rich diversity of less-known, underutilized and ethno-medicinally important fruit crops. Since these fruits are ethno-medicinally and nutritionally important, we attempted to quantify the bioactive and antioxidant compounds of these underutilized fruit crops. The antioxidant properties were assayed by scavenging abilities using diphenyl-2-picrylhydrazyl (DPPH), azinobisethylbenzothiazoline-6-sulphonic acid (ABTS), assay of ferric reducing antioxidant power (FRAP), and determining total phenolics (TP) and total flavonoids (TF) contents. Soapberry (Sapindus mukorossi Gaertn.), Bengal quince (Aegle marmelos (Correa) Linn.), Elephant apple (Dillenia indica L.), Burmese grape (Baccaurea ramiflora Lour.), Amla (Emblica officinalis Gaertn.) and Chapalish (Artocarpus chama Buch.-Ham.) were high source of TP content; Elephant apple (D. indica L.) and Amla (E. officinalis Gaertn.) were found to be high source of TF. Highest DPPH, ABTS and FRAP activity of underutilized fruit crops were discussed. Significant positive correlation was detected among TF–FRAP, TF–ABTS, ABTS–FRAP, DPPH–FRAP and DPPH–ABTS assays. Principal component analysis was found an effective technique in grouping the local underutilized fruits based on their antioxidant contents. Results signify that, these underutilised fruits must be promoted for cultivation, pharmaceutical and processing use in large scale.

Collection and phenotypic characterisation of pole-type common bean (Phaseolus vulgaris L.) landraces from Mizoram

Common beans are one of the many important food legumes grown in India. In the hilly regions of north-eastern India farmers mostly grow the pole-type beans by intercropping beans with maize, and in backyardsand kitchen gardens. In this study, we characterized a set of 52 pole-type common bean landraces collectedfrom the state of Mizoram for 23 agro-morphological and quality traits. Remarkable variability was observedfor almost all the traits. Wide range of variability was found for the traits such as leaf length (7.5–18.0 cm), leafbreadth (6.2–12.8 cm) days to flowering (33–70 days), pods per plant (7.7–24.0), pod length (8.1–14.6 cm), podyield per plant (61.5–182.3 g), seeds per pod (4.6–8.0), 100-seed weight (23.0–50.1 g) and crude protein content(20–33.8%). Positively significant correlation coefficients were observed between 100-seed weight and daysto flowering; number of pods per plant and pod yield per plant. The patterns of morphological variation wereassessed using multivariate approaches. Five morphologically distinct clusters were identified within thecollected germplasm. The evolutionary grouping of the common bean landraces has been discussed consideringthe morphological features.

Temporal modeling for forecasting of the incidence of litchi stink bug using ARIMAX analysis

The litchi, Litchi chinensis Sonn. is an important sub-tropical evergreen fruit crop. Among various insect pests of litchi, stink bug, Tessaratoma papillosa (Drury) is a major one causing extensive damage in Mizoram. The forecasting model to predict stink bug incidence in litchi was developed by ARIMAX model of weekly casesand weather factors. In exploring different prediction models by fitting covariates to the time series data, model ×(mean maximum and minimum temperature, morning and evening relative humidity and rainfall) was found bestmodel for predicting the stink bug incidence; all covariates were found significant predictors except evening RH, which did not have any significant covariates as predictor of stink bug incidence.