Identification of mega-environments and rice genotypes for general and specific adaptation to saline and alkaline stresses in India.

In the present study, a total of 53 promising salt-tolerant genotypes were tested across 18 salt-affected diverse locations for three years. An attempt was made to identify ideal test locations and mega-environments using GGE biplot analysis. The CSSRI sodic environment was the most discriminating location in individual years as well as over the years and could be used to screen out unstable and salt-sensitive genotypes. Genotypes CSR36, CSR-2K-219, and CSR-2K-262 were found ideal across years. Overall, Genotypes CSR-2K-219, CSR-2K-262, and CSR-2K-242 were found superior and stable among all genotypes with higher mean yields. Different sets of genotypes emerged as winners in saline soils but not in sodic soils; however, Genotype CSR-2K-262 was the only genotype that was best under both saline and alkaline environments over the years. The lack of repeatable associations among locations and repeatable mega-environment groupings indicated the complexity of soil salinity. Hence, a multi-location and multi-year evaluation is indispensable for evaluating the test sites as well as identifying genotypes with consistently specific and wider adaptation to particular agro-climatic zones. The genotypes identified in the present study could be used for commercial cultivation across edaphically challenged areas for sustainable production.

Attenuation of the self-renewal of transit-amplifying osteoblast progenitors in the murine bone marrow by 17 beta-estradiol.

In agreement with evidence that estrogens slow the rate of bone remodeling by suppressing the production of both osteoclasts and osteoblasts, loss of estrogens leads to an increase in the number of osteoclast as well as early osteoblast progenitors (CFU-osteoblasts; CFU-OBs) in the murine bone marrow. Here we show that CFU-OBs are early transit-amplifying progenitors, i.e., dividing cells capable of limited self-renewal, and that 17 beta-estradiol acts in vivo and in vitro to attenuate their self-renewal by approximately 50%. Consistent with a direct receptor-mediated action of estrogens on early mesenchymal cell progenitors, anti-estrogen receptor-alpha (anti-ER alpha) Ab's stain a small number of marrow cells that exhibit characteristics of primitive undifferentiated cells, including a high nucleus/cytoplasm ratio and lack of lineage-specific biochemical markers; the effect of 17 beta-estradiol on CFU-OB self-renewal is absent in mice lacking ER alpha. Because both osteoblasts and the stromal/osteoblastic cells that are required for osteoclast development are derived from CFU-OBs, suppression of the self-renewal of this common progenitor may represent a key mechanism of the anti-remodeling effects of estrogens.

Estradiol and progesterone influence the synthesis of gonadotropins in the absence of gonadotropin-releasing hormone in the ewe.

Acute actions of estradiol and progesterone on synthesis and secretion of gonadotropins without the confounding effects of endogenous steroids and GnRH were examined by using the ovariectomized (OVX), hypothalamic-pituitary-disconnected (HPD) ewe. Thirty-two OVX ewes were subjected to HPD and randomly assigned to eight groups (4 ewes/group). An additional four OVX ewes served as controls. Each of 12 OVX-HPD ewes received 4 s.c. implants of estradiol 24 h after HPD (implantation was designated as Time 0 h). Sixteen OVX-HPD ewes received no treatment and served as contemporary controls. The remaining four OVX-HPD ewes received implants of estradiol for 48 h and were administered 16 mg progesterone i.m. twice daily in the last 24 h of estradiol treatment. Blood samples and pituitary glands were collected from OVX-HPD control and steroid-treated ewes at 0, 12, 24, and 48 h. Amounts of gonadotropin subunit mRNAs and serum concentrations of gonadotropins were decreased at 24 h after HPD and remained unchanged thereafter in OVX-HPD controls. Although treatment with estradiol decreased pituitary content of LH and steady-state levels of mRNA for LH beta-subunit (p < 0.05) compared to contemporary controls, serum concentrations of LH were not affected. Serum concentrations and pituitary content of FSH decreased (p < 0.05) 24 h after initiating treatment with estradiol, but steady-state levels of FSH beta-subunit mRNA were unchanged. There was a transient decrease in pituitary content of FSH at 24 h of estradiol treatment. Steady-state levels of mRNA for alpha-subunit were unaffected by estradiol.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic analysis of tolerance for phosphorous deficiency in rice (Oryza sativa L.).

The inheritance of phosphorous (P) - deficiency tolerance in rice was investigated by a sevenparent diallel. The parent materials involved were four P-efficient (IR20, IR54, IR28, and Mahsuri), one moderately P-efficient (TN1), and two P-inefficient (IR31406333-1 and IR34686-179-1-2-1), genotypes. Relative tilering ability (RTA) under P-deficient and P-supplemented soil conditions was the parameter used in determining the tolerance level of the different genotypes. Diallel graph analysis revealed that tolerant parents have an excess of recessive genes, while moderate and susceptible parents possess more dominant genes. Genetic-component analysis suggested that both additive and dominance gene effects are involved in the inheritance of P-deficiency tolerance in rice. The trait exhibited over doiminance as confirmed by the graphical analysis. Narrow-sense heritability of the trait was moderate (0.50) and environmental effects were low. Both the general combining ability (GCA) and the specific combining ability (SCA) were significant, but GCA was more prevalent than SCA. Tolerant parents exhibited a high GCA whereas susceptibles have a very poor GCA, suggesting that tolerant parents were mostly enriched in additive genes and susceptible parents in non-additive genes. Crosses involving two high general combiners showed low SCA effects whereas crosses between poor general combiners manifested highly-significant SCA values.

Genetic analysis of salinity tolerance in rice (Oryza sativa L.).

The genetics of salinity tolerance in rice was investigated by a nine-parent complete diallel including reciprocals. Test materials involved susceptible (IR28, IR29, and MI-48), moderately tolerant (IR4595-4-1-13, IR9884-54-3-1E-P1, and IR10206-29-2-1), and tolerant ("Nona Bokra", "Pokkali", and SR26B) parents. Twoweek-old seedlings were grown in a salinized (EC = 12 dS/m) culture solution for 19 days under controlled conditions in the IRRI phytotron. Typical characteristics of salinity tolerance in rice were found to be Na(+) exclusion and an increased absorption of K(+) to maintain a good Na-K balance in the shoot. Genetic component analysis (GCA) revealed that a low Na-K ratio is governed by both additive and dominance gene effects. The trait exhibited overdominance, and two groups of genes were detected. Environmental effects were large, and the heritability of the trait was low. Our findings suggest that when breeding for salt tolerance, selection must be done in a later generation and under controlled conditions in order to minimize environmental effects. Modified bulk and single-seed descent would be the suitable breeding methods. Combining ability analysis revealed that both GCA and specific combining ability (SCA) effects were important in the genetics of salt tolerance. Moderately tolerant parents - e.g., IR4595-4-1-13 and IR9884-54-3-1E-P1 - were the best general combiners. Most of the best combinations had susceptible parents crossed either to moderate or tolerant parents. The presence of reciprocal effects among crosses necessitates the use of susceptible parents as males in hybridization programs. Large heterotic effects suggest the potential of hybrid rice for salt-affected lands.

More rapid restoration of pituitary content of follicle-stimulating hormone than of luteinizing hormone after depletion by oestradiol-17 beta in ewes.

To test the hypothesis that the synthesis and secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are differentially regulated after depletion by oestradiol, circulating concentrations of oestradiol were maintained at approximately 30 pg/ml for 16 days in each of 35 ovariectomized ewes. Five other ovariectomized ewes that did not receive oestradiol implants served as controls. After treatment with oestradiol, implants were removed and pituitary glands were collected from each of 5 ewes at 0, 2, 4, 8, 12, 16 and 32 days thereafter and amounts of mRNA for gonadotrophin subunits and contents of LH and FSH were quantified. Before collection of pituitary glands, blood samples were collected at 10-min intervals for 6 h. Treatment with oestradiol reduced (P less than 0.05) steady-state concentrations of LH beta- and FSH beta-subunit mRNAs and pituitary and serum concentrations of these hormones. At the end of treatment the amount of mRNA for FSH beta-subunit was reduced by 52% whereas that for LH beta-subunit was reduced by 93%. Steady-state concentrations of mRNA for FSH beta-subunit returned to control values within 2 days of removal of oestradiol, but 8 days were required for concentrations of FSH in the pituitary and serum to return to control values. Steady-state concentrations of mRNA for LH beta-subunit and mean serum concentrations of LH returned to control values by Day 8, but pituitary content of LH may require as long as 32 days to return to control levels. Therefore, replenishment of FSH beta-subunit mRNA preceded increases in pituitary and serum concentrations of FSH.(ABSTRACT TRUNCATED AT 250 WORDS)