G×E Interaction and Stability Analysis for Salinity and Sodicity Tolerance in Rice at Reproductive Stage.

Not AvailableRice (Oryza sativa L.) is the most import cereal crop in the South Asian countries and unfortunately, it is sensitive to salinity. Breeding for salt tolerant varieties is the cost-effective way of addressing this problem. The development and dissemination of these high yielding and salinity tolerant varieties to different agro-ecological zones of the country involves conducting multi-location trials. In the current study, one such trial was conducted using 44 genotypes which were tested across seven salt stress environments during Kharif, 2014. The data recorded for days to 50% flowering and grain yield were analyzed through both Genotype and Genotype × Environment interaction (GGE) and Additive Main Effects and Multiplicative Interactions(AMMI) analyses. GGE biplots accounted for 92.5% and 87.5% of the interaction variance, whereas AMMI biplots could explain 95.7% and 88.5% for days to 50% flowering and grain yield, respectively. The location Aligarh (ENV6) was found the most discriminating for both the characters. Furthermore, it was found the most favorable environment. For days to 50% flowering, two mega environments were identified while for grain yield one mega-environment through GGE biplot and three through AMMI biplot could be demarcated. Both AMMI and GGE have led to similar conclusions with minor differences. However, the GGE biplot was found comparatively more advantageous over AMMI. The genotypes RP 5898-18-5-2-1-1, Bulk 18, NDRK 50043, CSR 11-121, CSR 23, RP 5898-38-7-2-1-1 and CSR 55 were found stable with above average yields across saline and sodic soils. These rice lines could be used for commercial cultivation for improve the productivity in salt affected soils.Not Availabl

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Not AvailableRice is sensitive to heat stress at gametogenesis and anthesis stages. For sustaining rice yields under the predicted threat of reproductive stage heat stress (RSHS), identification of tolerant donors as well as mapping of genes governing tolerance is crucial. Recently a NERICA (NEwRIce for AfriCA) rice genotype, NL44 has been reported tolerant to RSHS. The present study aims to survey a recombinant inbred line (RIL) population developed from the cross, Pusa Basmati 1 (PB1)/NL44 using markers linked to 54 RSHS quantitative trait loci (QTLs) through phenotypic and genotypic characterization. When exposed to RSHS, the susceptible parent PB1 and several RILs showed significant reduction for spikelet fertility and grain yield plant−1 relative to NL44. Both these traits and the estimated stress tolerance index (STI) showed a quantitative pattern of inheritance. Out of the 116 SSR markers surveyed, 31 markers were polymorphic between PB1 and NL44. No discernible associations could be found through a preliminary bulked segregant analysis with these markers. A subsequent single marker analysis revealed five minor QTLs, four for spikelet fertility under heat stress and two for STI-spikelet fertility, of which one QTL was mapped for both the traits. These QTLs, however, could explain a very low level of total phenotypic variation. Additionally, the cumulative additive effect of these QTLs could account only for a possible 30% of the contrast between PB1 and NL44. Thus, the study clearly establishes that NL44 has novel genomic regions for RSHS tolerance.Not Availabl

Photosynthetic machinery under salinity stress: Trepidations and adaptive mechanisms

Chloroplasts and photosynthesis are the physiologically fateful arenas of salinity stress. Morphological and anatomical alterations in the leaf tissue, ultrastructural changes in the chloroplast, compromise in the integrity of the three-layered chloroplast membrane system, and defects in the light and dark reactions during the osmotic, ionic, and oxidative phases of salt stress are conversed in detail to bring the salinity-mediated physiological alterations in the chloroplast on to a single platform. Chloroplasts of salt-tolerant plants have evolved highly regulated salt-responsive pathways. Thylakoid membrane remodeling, ion homeostasis, osmoprotection, upregulation of chloroplast membrane and stromal proteins, chloroplast ROS scavenging, efficient retrograde signalling, and differential gene and metabolite abundance are the key attributes of optimal photosynthesis in tolerant species. This review throws light into the comparative mechanism of chloroplast and photosynthetic response to salinity in sensitive and tolerant plant species