Somnath Roy

Bio: Somnath Roy is an academic researcher from Rice University. The author has contributed to research in topics: Population & Germplasm. The author has an hindex of 12, co-authored 78 publications receiving 472 citations. Previous affiliations of Somnath Roy include Bidhan Chandra Krishi Viswavidyalaya & Indian Council of Agricultural Research.

Genetic Diversity and Population Structure in Aromatic and Quality Rice (Oryza sativa L.) Landraces from North-Eastern India.

Abstract: The North-eastern (NE) India, comprising of Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim and Tripura, possess diverse array of locally adapted non-Basmati aromatic germplasm. The germplasm collections from this region could serve as valuable resources in breeding for abiotic stress tolerance, grain yield and cooking/eating quality. To utilize such collections, however, breeders need information about the extent and distribution of genetic diversity present within collections. In this study, we report the result of population genetic analysis of 107 aromatic and quality rice accessions collected from different parts of NE India, as well as classified these accessions in the context of a set of structured global rice cultivars. A total of 322 alleles were amplified by 40 simple sequence repeat (SSR) markers with an average of 8.03 alleles per locus. Average gene diversity was 0.67. Population structure analysis revealed that NE Indian aromatic rice can be subdivided into three genetically distinct population clusters: P1, joha rice accessions from Assam, tai rices from Mizoram and those from Sikkim; P2, chakhao rice germplasm from Manipur; and P3, aromatic rice accessions from Nagaland. Pair-wise FST between three groups varied from 0.223 (P1 vs P2) to 0.453 (P2 vs P3). With reference to the global classification of rice cultivars, two major groups (Indica and Japonica) were identified in NE Indian germplasm. The aromatic accessions from Assam, Manipur and Sikkim were assigned to the Indica group, while the accessions from Nagaland exhibited close association with Japonica. The tai accessions of Mizoram along with few chakhao accessions collected from the hill districts of Manipur were identified as admixed. The results highlight the importance of regional genetic studies for understanding diversification of aromatic rice in India. The data also suggest that there is scope for exploiting the genetic diversity of aromatic and quality rice germplasm of NE India for rice improvement.

Genetic diversity and structure in hill rice ( Oryza sativa L.) landraces from the North-Eastern Himalayas of India

Abstract: Hill rices (Oryza sativa L.) are direct seeded rices grown on hill slopes of different gradients. These landraces have evolved under rainfed and harsh environmental conditions and may possess genes governing adaptation traits such as tolerance to cold and moisture stress. In this study, 64 hill rice landraces were collected from the state of Arunachal Pradesh of North-Eastern region of India, and assessed by agro-morphological variability and microsatellite markers polymorphism. Our aim was to use phenotypic and genetic diversity data to understand the basis of farmers’ classification of hill rice landraces into two groups: umte and tening. Another goal was to understand the genetic differentiation of hill rices into Indica or japonica subspecies. According to farmers’ classification, hill rices were categorized into two groups: umte (large-grained, late maturing) and tening (small-grained, early maturing). We did not find significant difference in days to 50 % flowering between the groups. Principal component analysis revealed that two groups can be distinguished on the basis of kernel length-to-width ration (KLW), kernel length (KL), grain length (GrL), grain length-to-width ration (GrLW) and plant height (Ht). Stepwise canonical discriminant analysis identified KL and Ht as the main discriminatory characters between the cultivar groups. Genetic diversity analysis with 35 SSR markers revealed considerable genetic diversity in the hill rice germplasm (gene diversity: 0.66; polymorphism information content: 0.62). Pair-wise allelic difference between umte and tening groups was not statistically significant. The model-based population structure analysis showed that the hill rices were clustered into two broad groups corresponding to Indica and Japonica. The geographic distribution and cultivars grouping of hill rices were not congruent in genetic clusters. Both distance- and model-based approaches indicated that the hill rices were predominantly japonica or admixture among the groups within the subspecies. These findings were further supported by combined analysis hill rices with 150 reference rice accessions representing major genetic groups of rice. This study collected a valuable set of hill rice germplasm for rice breeding and for evolutionary studies. It also generated a new set of information on genetic and phenotypic diversity of hill rice landraces in North-Eastern region of India. The collected hill rices were mostly japonica or admixture among the subpopulations of Indica or Japonica. The findings are useful for utilization and conservation of hill rice germplasm.

Rice bean: a lesser known pulse with well-recognized potential

Abstract: Required genetic resources for the improvement of agronomic, nutritional and economic value of rice bean are available in the world collection. International cooperative effort is required to utilize and conserve them. Rice bean [Vigna umbellata (Thunb.) Ohwi and Ohashi], a lesser known pulse among the Asiatic Vigna, has long been considered as a food security crop of small and marginal farmers of Southeast Asia. Considered as a nutritionally rich food and fodder, it is also a source of genes for biotic and abiotic stress tolerance including drought, soil acidity and storage pest. Although it spread from its centre of domestication in the Indo-China region to other parts around the world, it never became an important crop anywhere probably because of agronomic disadvantages. Crop improvement for determinate nature, good yield, less variable seed colour, pleasant organoleptic properties and lower antinutrients is required. Scanning of scientific literature indicates that genetic resources with desirable agronomic and nutritional traits exist within the current collection but are spread across countries. Genomic studies in the species indicate that except for insect resistance and aluminium toxicity tolerance, not much attention has been paid to decipher and utilize other stress tolerance and nutritional quality traits. Collaborative efforts towards improving farming, food, trade value and off-farm conservation of rice bean would not only help marginal farmers but will also help to preserve the yet to be explored genomic resources available in this sturdy pulse.

Heterosis for yield and quality traits in rice

Abstract: Twenty rice hybrids developed through a line× tester crossing programme involving five high yielding lines and four superior grain quality testers were evaluated for yield and quality characters. Significant heterosis for grain yield and quality traits were observed in most of the hybrids. Higher magnitude of heterosis against all yield and quality traits were not expressed in a single hybrid combination which varied from cross to cross due to diverse genetic background of their parents. Most of the heterotic crosses for grain yield plant−1were accompanied by heterosis for two or more component traits. The cross combinations IET 5656×Kalonunia, IET 8002×Dudheswar, IET 5656 × Dudheswar and IR 62×Sambamahsuri were identified for their superior yield and grain quality characters. In general heterosis was found to be low for quality traits as compared to yield and yield components.

Strong Room-Temperature Ferromagnetism in Co2+-Doped TiO2 made from Colloidal Nanocrystals

Abstract: Colloidal cobalt-doped TiO2 (anatase) nanocrystals were synthesized and studied by electronic absorption, magnetic circular dichroism, transmission electron microscopy, magnetic susceptibility, cobalt K-shell X-ray absorption spectroscopy, and extended X-ray absorption fine structure measurements. The nanocrystals were paramagnetic when isolated by surface-passivating ligands, weakly ferromagnetic (Ms = 1.5 x 10-3 mB/Co2+ at 300 K) when aggregated, and strongly ferromagnetic (up to Ms = 1.9 mB/Co2+ at 300 K) when spin-coated into nanocrystalline films. X-ray absorption data reveal that cobalt is in the Co2+ oxidation state in all samples. In addition to providing strong experimental support for the existence of intrinsic ferromagnetism in cobalt-doped TiO2, these results demonstrate the possibility of using colloidal TiO2 diluted magnetic semiconductor nanocrystals as building blocks for assembly of ferromagnetic semiconductor nanostructures with potential spintronics applications.