Salt stress is one of the most severe environmental stresses limiting the productivity of crops, including rice. However, there is a lack of information on how salt-stress sensitivity varies across different developmental stages in rice. In view of this, a comparative evaluation of contrasting rice varieties CSR36 (salt tolerant) and Jaya (salt sensitive) was conducted, wherein NaCl stress (50 mM) was independently given either at seedling (S-stage), tillering (T-stage), flowering (F-stage), seed-setting (SS-stage) or throughout plant growth, from seedling till maturity. Except for S-stage, CSR36 exhibited improved NaCl stress tolerance than Jaya, at all other tested stages. Principal component analysis (PCA) revealed that the improved NaCl stress tolerance in CSR36 coincided with enhanced activities/levels of enzymatic/non-enzymatic antioxidants (root ascorbate peroxidase for T- (2.74-fold) and S+T- (2.12-fold) stages and root catalase for F- (5.22-fold), S+T- (2.10-fold) and S+T+F- (2.61-fold) stages) and higher accumulation of osmolytes (shoot proline for F-stage (5.82-fold) and S+T+F- (2.31-fold) stage), indicating better antioxidant capacitance and osmotic adjustment, respectively. In contrast, higher shoot accumulation of Na⁺ (14.25-fold) and consequent increase in Na⁺/K⁺ (14.56-fold), Na⁺/Mg⁺² (13.09-fold) and Na⁺/Ca⁺² (8.38-fold) ratio in shoot, were identified as major variables associated with S-stage salinity in Jaya. Higher root Na⁺ and their associated ratio were major deriving force for other stage specific and combined stage salinity in Jaya. In addition, CSR36 exhibited higher levels of Fe³⁺, Mn²⁺ and Co³⁺ and lower Cl⁻ and SO₄²⁻, suggesting its potential to discriminate essential and non-essential nutrients, which might contribute to NaCl stress tolerance. Taken together, the findings provided the framework for stage-specific salinity responses in rice, which will facilitate crop-improvement programs for specific ecological niches, including coastal regions.

Rice crop, a staple food for a majority of population across the world, holds a significant role to play in alleviating the global hunger problem. Enhancement of genetic diversity of rice will serve to overcome constraints in sustained and ecologically effective improvement in the production of quality rice, challenged by erratic patterns of global climate, changing pest dynamics, resource availability in proportion to growing population etc. Proton ion beam has sprung up as a promising novel mutagen in the mutation breeding of crop plants, by virtue of its higher LET values, causing higher frequency of mutations. Dose optimization is pre-requisite to obtain a range of phenotypic mutants, without drastic reduction in survival and growth subsequently. This study was undertaken to standardize proton beam irradiation dose rate post the evaluation of in-vitro germination, growth and survival of rice variety IBD-1, with doses ranging from 0–500Gy. Doses between 152.47Gy253.53Gy were found suitable for mutagenesis, without drastically impairing growth and survival.

A total of 132 Farmers’ Varieties (FVs) of rice have been grouped into different classes based on the colour of basal leaf, days to 50% flowering, length of the stem (excluding panicle), length of decorticated grain, shape of decorticated grain (in lateral view), colour of decorticated grain, amylose content of endosperm and aroma of decorticated grain. Basal leaf colour of the most of the FVs was green. Based on the days to 50% flowering most of the FVs were classified under late to very late category. Again majority of the FVs were categorized into moderate and long in respect of length of the stem (excluding panicle). The rice genotypes with long slender decorticated grain have importance in international market. The FVs Uttar Banga Local-18, Birali-selection, Uttar Banga Local-17, Tulaipanji, Uttar Banga Local-14, Dudheswar-AD, Uttar Banga Local-16, Malbati, Rampha, Biroi, Uttar Banga Local-19, Kalturey, Tulaipanji-AD were classified as long slender. Decorticated coloured rice is reported to be potent sources of antioxidants and their consumption is encouraged. Decorticated grain colour of the FVs Chakhao Poireiton, Chakhao Angangbi, Chakhao Amubi, Chakhao-Selection-2, Sadabhatkalo were dark purple. Most of the FVs were non-aromatic, only 25 cultivars were found to have strong aroma on cooking and 23 were found to have mild aroma. The FVs which have been classified under desirable groups may be used for further improvement of rice based on specific character of donor.