Increased Catalase Activity and Maintenance of Photosystem II Distinguishes High-Yield Mutants From Low-Yield Mutants of Rice var. Nagina22 Under Low-Phosphorus Stress

An upland rice variety, Nagina22 (N22) and its 137 ethyl methanesulfonate (EMS)-induced mutants, along with a sensitive variety, Jaya, was screened both in low phosphorus (P) field (Olsen P 1.8) and in normal field (Olsen P 24) during dry season. Based on the grain yield (YLD) of plants in normal field and plants in low P field, 27 gain of function (high-YLD represented as hy) and 9 loss of function (low-YLD represented as ly) mutants were selected and compared with N22 for physiological and genotyping studies. In low P field, hy mutants showed higher P concentration in roots, leaves, grains, and in the whole plant than in ly mutants at harvest. In low P conditions, Fv/Fm and qN were 24% higher in hy mutants than in ly mutants. In comparison with ly mutants, the superoxide dismutase (SOD) activity in the roots and leaves of hy mutants in low P fields was 9% and 41% higher at the vegetative stage, respectively, but 51% and 14% lower in the roots and leaves at the reproductive stage, respectively. However, in comparison with ly mutants, the catalase (CAT) activity in the roots and leaves of hy mutants in low P fields was 35% higher at the vegetative stage and 15% and 17% higher at the reproductive stage, respectively. Similarly, hy mutants in low P field showed 20% and 80% higher peroxidase (POD) activity in the roots and leaves at the vegetative stage, respectively, but showed 14% and 16% lower POD activity at the reproductive stage in the roots and leaves, respectively. Marker trait association analysis using 48 simple sequence repeat (SSR) markers and 10 Pup1 gene markers showed that RM3648 and RM451 in chromosome 4 were significantly associated with grain YLD, tiller number (TN), SOD, and POD activities in both the roots and leaves in low P conditions only. Similarly, RM3334 and RM6300 in chromosome 5 were associated with CAT activity in leaves in low P conditions. Notably, grain YLD was positively and significantly correlated with CAT activity in the roots and shoots, Fv/Fm and qN in low P conditions, and the shoots’ P concentration and qN in normal conditions. Furthermore, CAT activity in shoots was positively and significantly correlated with TN in both low P and normal conditions. Thus, chromosomal regions and physiological traits that have a role in imparting tolerance to low P in the field were identified

Biocompatible small molecules that enhance silica solubilization under ambient conditions: chemical profile of such complexes, possible mechanism for enhancement, and their effect on the growth and protection from pests in the rice plant (Oryza sativa L.)

Recent studies suggest that the depletion of silicon available to plants may be a major reason for the yield decline observed for rice cultivation. In the present article, a novel strategy is explored to identify small biocompatible molecules (carriers) that would enhance the solubility of sand (SiO 2. nH 2 O) (here after named silica) in water under ambient conditions. All considerations, notably biocompatibility, make the 20 proteinous amino acids and their simplified analogs the first choice. Among the proteinous amino acids, notable enhancement of silica solubility was seen at 1000 μ mole.L-1 : Blank: 1; glutamine: 3.5; histidine: 3; alanine: 2.9. Based on the assumption that the observed enhancement is related to proclivity for hydrogen bond formation with water, a large number of varied biocompatible substrates were examined. Among these, notable enhancement of silica solubilization at 1000 μ mole.L-1 was seen as exemplified with Blank: 1; imidazole: 5; inositol: 4.5; mannitol: 3.9; 3, 4-dihydroxy phenylalanine (DOPA): 3.5. A complementary gravimetric protocol coupled with thermogravimetric analysis (TGA) enabled the estimation of an approximate empirical formula for few of the carrier-silica complexes. A possible mechanism for the interaction of the carrier at the silica-water interface is suggested. Field experiments (reported separately) with selected carriers, monitored in the stem extract by colorimetry and in the leaf by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis showed enhanced levels of silica and were significantly beneficial for the growth and protection from predators of the rice plant

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Not AvailableImprovement of photosynthetic traits is a promising strategy to break the yield potential barrier of major food crops. Leaf photosynthetic traits were evaluated in a set of high yielding Oryza sativa, cv. Swarna 9 Oryza nivara backcross introgression lines (BILs) along with recurrent parent Swarna, both in wet (Kharif) and dry(Rabi) seasons in normal irrigated field conditions. Net photosynthesis (PN) ranged from 15.37 to 23.25 µmol(CO2) m-2 s-1 in the BILs. Significant difference in PN was observed across the seasons and genotypes. Six BILs showed high photosynthesis compared with recurrent parent in both seasons. Chlorophyll content showed minimum variation across the seasons for any specific BIL but significant variation was observed among BILs. Significant positive association between photosynthetic traits and yieldtraits was observed, but this association was not consistent across seasons mainly due to contrasting weather parameters in both seasons. BILs 166s and 248s with high and consistent photosynthetic rate exhibited stable high yield levels in both the seasons compared to the recurrent parent Swarna. There is scope to exploit photosynthetic efficiency of wild and weedy rice to identify genes for improvement of photosynthetic rate in cultivars.Not Availabl

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Not AvailableHeat is one of the major factors that considerably limit rice production. Nagina 22 (N22) is a deep-rooted, drought and heat tolerant aus rice cultivar. This study reports the characterization of a previously isolated dark green leaf mutant N22-H-dgl219 (NH219) which showed reduced accumulation of reactive oxygen species in leaf under 40°C heat conditions. The mutant was characterized for several traits in field under ambient (38°C) and heat stress (44°C) conditions by raising temperature artificially from flowering stage till maturity by covering plants with polythene sheets during dry season 2011. Yield traits were mapped in 70 F2 segregants of IR64 × NH219 and 36 F2 segregants of its reciprocal cross.Not Availabl