Identification of a small core germplasm set representing the available genetic diversity is essential for its proper evaluation and subsequent utilization in rice improvement programmes. For constituting a small diverse mini-core panel of Indian rice germplasm, a representative set of 6912 accessions drawn based on their geographic origin from the whole rice germplasm collection available in the National Gene Bank was genotyped using 36 microsatellite markers. Automated fragment analysis of amplicons yielded a total of 435 alleles, with an average 12.4 and range of 3-29 alleles per locus. Polymorphism information content (PIC) ranged from 0.08 (RGNMS190) to 0.86 (RM552) with an average of 0.528. Based on genotyping data, a mini-core consisting of 98 genotypes was identified. Ninety-four per cent of the alleles present in the core set were present in the mini-core. The identified small but diverse panel will be useful for further intensive trait-specific evaluation and utilization in allele mining.

A protocol was developed for preservation of calli of Oryza rufipogon Griff. in liquid nitrogen (-196°C). Optimal conditions for cryoprotection, pre-freezing and post-thaw recovery of calli were identified. Cryoprotectant treatment at low temperature, pre-freezing in isopropanol bath for 1 h at -70°C, rapid thawing and proper removal of cryoprotectant were critical for post-thaw survival. Genetic fidelity of the R1 plants obtained from cryopreserved, cryoprotectant-treated and untreated calli was assessed by phenotypic and molecular characterization. Comparison of phenotypic characters with seed-derived control plants showed no significant variation in the agronomic characters, but seed physical characters showed significant reduction in all the in vitro generated plants. Molecular data generated using 26 rice simple sequence repeat markers showed 4.78-7.25% change from control. Results suggested that both callus induction and cryopreservation induced heritable variations in O. rufipogon. In addition, a combination of phenotypic and molecular characterization using an appropriate marker provided better insight into genetic fidelity of recovered plants.

On-Farm trail was conducted in Longleng district of Nagaland during the kharif season of 2014-15 and 2015-16 to find out the most suitable nutrient management practices viz. recommended doses of fertilizers (RDF) 80:60:40 kg NPK/ha, locally available weed biomass (Eupatorium @ 10 t/ha) and farmers practices at farmers field of Krishi Vigyan Kendra, Longleng, Nagaland. The experiment was laid out in Completely Randomized Block Design. Result revealed that growth and yield parameters were recorded maximum under RDF and followed by Eupatorium @ 10 t/ha compared to farmers practice. The maximum grain yield (3590 kg/ha) was with RDF closely followed by weed biomass @10t/ha (3270 kg/ha) over the farmer's practices (2730 kg/ha), respectively. Grain yield was increased by 31.5 % in RDF and 11.8 % in Eupatorium @ 10 t/ha compared to the farmer's practices. Similarly, production efficiency was recorded the highest with RDF (28 kg/ha/day) followed by Eupatorium @ 10 t/ha (25.5 kg/ha/day) and farmers practice (21.3 kg/ha/day). With respect to economics, the maximum net returns and benefit: cost ratio (B: C ratio) were recorded with RDF (Rs.18850/ha and 1.91) as compared to other treatments. Economic efficiency was also noted highest under RDF (Rs.147.27/ha/day) followed by Eupatorium @10 t/ha (Rs.128.36/ha/day). Hence, it may be concluded that the farmer’s practices can be replaced with the adoption of RDF or locally available weed biomass (Eupatorium) as a source of nutrition for achieving the higher productivity and profitability of the lowland rice under the mid-hill altitude condition of Nagaland

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