Generation means analysis of traits related to lodging using two crosses of durum × emmer wheat

Genetic Resources and Crop Evolution - Lodging is one of the most important factors that affect wheat final yield. Emmer [Triticum turgidum subsp. dicoccum (Schrank ex Schübl.) Thell.] is a...     

Interpreting genotype × environment interactions for durum wheat grain yields using nonparametric methods

The objective of this study was to compare nonparametric stability procedures and apply different nonparametric tests for genotype × environment (G × E) interactions on grain yields of 15 durum wheat genotypes selected from Iran/ICARDA joint project grown in 12 environments during 2004–2006 in Iran. Results of nonparametric tests of G × E interaction and a combined ANOVA across environments indicated the presence of both crossover and noncrossover interactions, and genotypes varied significantly for grain yield. In this study, high values of TOP (proportion of environments in which a genotype ranked in the top third) and low values of sum of ranks of mean grain yield and Shukla’s stability variance (rank-sum) were associated with high mean yield. The other nonparametric stability methods were not positively correlated with mean yield but they characterized a static concept of stability. The results of correlation analysis indicated that only TOP and rank-sum methods would be useful for simultaneous selection for high yield and stability. These two methods identified lines Mrb3/Mna-1, Syrian-4 and Mna-1/Rfm-7 as genotypes with dynamic stability and wide adaptation. According to static stability parameters, the genotypes 12A-Mar8081 and 19A-Mar8081 with lowest grain yield were selected as genotypes with the highest stability.     

Seed Development,Oil Accumulation and Fatty Acid Composition of Drought Stressed Rapeseed Plants Affected by Salicylic Acid and Putrescine

Two field experiments were carried out in 2017 and 2018 to evaluate the impacts of salicylic acid (1?mM SA) and putrescine (1?mM Put) on leaf osmolytes, seed reserve and oil accumulation and fatty acid composition of rapeseed (Brassica napus L.) under different watering levels (irrigations after 70 and 150?mm evaporation as normal irrigation and severe drought stress, and 70?→?90?→?110?→?130?→?150 and 70?→?100?→?130→150 as gradual and moderately gradual water deficits, respectively). The experiments were laid out as split plot on the bases of randomized complete block design in three replications. Water stress increased the contents of glycine betaine, proline, soluble sugars, and proteins. Application of SA and Put further enhanced the contents of glycine betaine and soluble sugars, while reduced proline content of leaves. Seed filling duration, seeds per plant, plant biomass and seed yield were decreased with increasing irrigation intervals. Exogenous SA and Put enhanced all of these parameters under different irrigation intervals. Oil accumulation in seeds was diminished as water stress severed. The gradual water deficit considerably reduced the impacts of drought stress on yield related traits and oil content per seed, due to stress acclimation of plants. Oil content of seeds was augmented by SA and Put treatments through prolonging seed filling duration, particularly under limited irrigations. Percentages of palmitic acid and stearic acid (saturated fatty acids) were not affected by water limitation. However, unsaturated fatty acids of linoleic and linolenic acids were reduced, and oleic acid was enhanced due to water shortage. Unsaturation index was improved by SA and Put treatments under severe water stress as a result of decreasing oleic acid and increasing linoleic and linolenic acids contents. The SA spray was the best treatment for improving rapeseed seed and oil production under normal and stressful conditions.

     

Amiloride selectively blocks the low threshold (T) calcium channel

More than one type of voltage-gated calcium channel has been identified in muscle cells and neurons. Many specific organic and inorganic blockers of the conventional, slowly inactivating high threshold (L) calcium channel have been reported. No specific blockers of the low threshold (T) channel have been as yet identified. Amiloride, a potassium sparing diuretic, has now been shown to selectively block the low threshold calcium channel in mouse neuroblastoma and chick dorsal root ganglion neurons. The selective blockade of the T-type calcium channel will allow identification of this channel in different tissues and characterization of its specific physiological role.     

Atrionatriuretic peptide transforms cardiac sodium channels into calcium-conducting channels

The atrionatriuretic peptide (ANP) is released from atrial cells in response to increased extracellular fluid volume and reduces sodium absorption by the kidney, thus reducing the blood volume. In this report, ANP suppressed the calcium and sodium currents in rat and guinea pig ventricular myocytes. The suppression of sodium current was caused by enhanced permeability of the sodium channel to calcium without significant changes in the kinetics or the tetrodotoxin sensitivity of the channel. Thus, ANP may regulate the sodium channel by altering its cationic selectivity site to calcium, thereby repressing the sodium current. The suppression of sodium and calcium channels and the resultant depressed excitability of the atrial cells may help to regulate ANP secretion.     

Regulation of calcium release is gated by calcium current, not gating charge, in cardiac myocytes

In skeletal muscle, intramembrane charge movement initiates the processes that lead to the release of calcium from the sarcoplasmic reticulum. In cardiac muscle, in contrast, the similarity of the voltage dependence of developed tension and intracellular calcium transients to that of calcium current suggests that the calcium current may gate the release of calcium. Nevertheless, a mechanism similar to that of skeletal muscle continues to be postulated for cardiac muscle. By using rapid exchange (20 to 50 milliseconds) of the extracellular solutions in rat ventricular myocytes in which the intracellular calcium transients or cell shortening were measured, it has now been shown that the influx of calcium through the calcium channel is a mandatory link in the processes that couple membrane depolarization to the release of calcium. Thus, intramembrane charge movement does not contribute to the release of calcium in heart muscle.