Ranking factors affecting emissions of GHG from incubated agricultural soils

Agriculture significantly contributes to global greenhouse gas (GHG) emissions and there is a need to develop effective mitigation strategies. The efficacy of methods to reduce GHG fluxes from agricultural soils can be affected by a range of interacting management and environmental factors. Uniquely, we used the Taguchi experimental design methodology to rank the relative importance of six factors known to affect the emission of GHG from soil: nitrate (NO₃^?) addition, carbon quality (labile and non‐labile C), soil temperature, water‐filled pore space (WFPS) and extent of soil compaction. Grassland soil was incubated in jars where selected factors, considered at two or three amounts within the experimental range, were combined in an orthogonal array to determine the importance and interactions between factors with a L₁₆ design, comprising 16 experimental units. Within this L₁₆ design, 216 combinations of the full factorial experimental design were represented. Headspace nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) concentrations were measured and used to calculate fluxes. Results found for the relative influence of factors (WFPS and NO₃^? addition were the main factors affecting N₂O fluxes, whilst glucose, NO₃^? and soil temperature were the main factors affecting CO₂ and CH₄ fluxes) were consistent with those already well documented. Interactions between factors were also studied and results showed that factors with little individual influence became more influential in combination. The proposed methodology offers new possibilities for GHG researchers to study interactions between influential factors and address the optimized sets of conditions to reduce GHG emissions in agro‐ecosystems, while reducing the number of experimental units required compared with conventional experimental procedures that adjust one variable at a time.     

Accumulation and erosion of Mars' south polar layered deposits

Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion.     

The Fusarium graminearum genome reveals a link between localized polymorphism and pathogen specialization

We sequenced and annotated the genome of the filamentous fungus Fusarium graminearum, a major pathogen of cultivated cereals. Very few repetitive sequences were detected, and the process of repeat-induced point mutation, in which duplicated sequences are subject to extensive mutation, may partially account for the reduced repeat content and apparent low number of paralogous (ancestrally duplicated) genes. A second strain of F. graminearum contained more than 10,000 single-nucleotide polymorphisms, which were frequently located near telomeres and within other discrete chromosomal segments. Many highly polymorphic regions contained sets of genes implicated in plant-fungus interactions and were unusually divergent, with higher rates of recombination. These regions of genome innovation may result from selection due to interactions of F. graminearum with its plant hosts.     

New polyether triterpenoids from Laurencia viridis and their biological evaluation

The red seaweed Laurencia viridis is a rich source of secondary metabolites derived from squalene. New polyethers, such as iubol (2), 22-hydroxy-15(28)- dehydrovenustatriol (3), 1,2-dehydropseudodehydrothyrsiferol (4), and secodehydrothyrsiferol (5) have been isolated and characterized from this alga. The structures were determined through the interpretation of NMR spectroscopic data and the relative configuration was proposed on the basis of NOESY spectrum and biogenetic considerations. All new compounds exhibited significant cytotoxic activity against a panel of cancer cell lines.     

Attempts to extend seed potato production in Israel to new areas at high altitudes

Summary Attempts were made to grow seed potatoes in the Gilboa mountains and central Golan Heights both at ca 500 m altitude. The activity of winged aphids was low between May and September, the period suitable for growing seed potatoes. Potato virus X (PVX) and potato virus Y (PVY) were rare. The highest incidence of potato leaf roll (PLRV) was 17% at Gilboa and 5% at Nov (central Golan). In both areas, spindle sprout was a severe problem in progeny tubers and it was associated with a purple top syndrome, probably caused by a mycoplasma, that appeared during growth. Activity of the probable vector, the leafhopperHyalesthes obsoletus, ceases in the Golan after June. Delaying planting until the end of May or later reduced the incidence of purple top and spindle sprout to nil. Both were reduced by Temik treatment and by covering the plots with netting but not by treatments with Rogor and Croneton. All three chemicals reduced PLRV incidence. Therefore, delayed plantings and insecticides may reduce purple top, spindle sprout and PLRV. This work was partly supported by funds of BARD 339-80.     

Detection of PVY extreme resistance genes in potato germplasm from the uruguayan breeding program

Breeding goals in potato programs encompass several important commercial traits such as market aspects (skin color, eye depth, shape), category use (fresh or processed), yield, crop duration, and pest and disease resistance. In light of medium- and long-term changes in trait requirements, breeders rely on a range of wild and commercial germplasm in their efforts to reach the multiple objectives that determine the success of a new variety. Readily selectable markers for the recognition of multiple introgressed traits in breeding populations would therefore be practical high-value tools. In subtropical countries, warm climate and the continuous cropping of potato promote high vector pressure and the spread of viruses, rendering seed certification schemes difficult.Potato virus Y (PVY) constitutes a constant problem in several developing countries and it was recently reported as a challenge for seed production in the U.S.A. and Spain, resulting in rejection of seed lots in certification programs. Here we report the simultaneous use of two molecular markers to identify genes for extreme resistance to PVY in the Uruguayan potatobreeding program germplasm. Simplicity and compatibility of the marker system (allele specificity) were emphasized in implementing a reliable and efficient procedure. Forty-four percent of the genotypes tested were shown to carry extreme resistance to PVY, in the majority of cases fromSolanum tuberosum ssp.andigena (Ry_adg). Furthermore, a single marker originating fromSolanum stoloniferum (M45) could be used to recognize both Ry_sto and Ry_adg. The molecular phenotype data corresponding to M45-Ry genotypes was in accordance with virus field exposure observations of resistance.     

Marandu Palisadegrass Mineral Nutrition and Production Related to Nitrogen and Potassium Supply

Nitrogen (N) and potassium (K) fertilization play a key role in forage crops and can significantly increase yields of ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. exA. Rich.) Stapf.], one of the most important forage crops in Brazil. This study aimed to identify the concentrations of total N and K, nitrate (NO₃^?), and ammonium (NH₄⁺), chlorophyll meter readings (SPAD), and nitrate reductase activity (At-RNA) required to maximize yield. Plants were grown in quartz substrate and treated with nutrient solutions that ranged from 2 to 33 mmol L^?1 for N and 0.5 to 11 mmol L^?1 for K. Dry matter production and At-RNA increased with increasing N and K supplies. SPAD readings correlated strongly with N leaf concentration and dry matter production and can be used to assess the N status of this species. The supply of N and K in the fertilization promoted high yield and adequate N and K concentration for plant metabolism.     

Vitamin content and amino acid composition of pickled garlic processed with and without fermentation

The effect of processing, with and without fermentation, upon the nutritional composition of pickled garlic was evaluated. On a dry basis, the fermented product had a higher content of riboflavin, alpha-tocopherol, and most individual amino acids but a lower thiamin level than the unfermented product. Ascorbic acid was totally lost during processing. The chemical scores for the unfermented and fermented product were 88 and 108%, respectively, with the limiting amino acid being leucine. Water blanching (90 degrees C for 4 min) affected only the ascorbic acid content, whereas fermentation significantly affected the contents of thiamin, ascorbic acid, and alpha-tocopherol, as well as glutamic acid and arginine. For each processing type, the effect of the preservation method and storage time on vitamins and amino acid composition was also analyzed. In the case of the fermented product, usage of the corresponding fermentation brine plus refrigerated storage was also assayed as the packing/preservation method and was found to give the best result from a nutritional standpoint.