A review of the effect of implement geometry on soil failure and implement forces

This article reviews the basic relationships between the geometry of tillage tools and soil physical properties on the nature of the soil disturbance ahead of the tool. These relationships are valuable to designers and operators of cultivation equipment in selecting the optimal design of the soil working elements and their supporting frame. In addition to the disturbance, the magnitude and direction of the resulting soil forces are important when both designing and using such equipment. Reference is made to an integrated model to predict these forces using a number of spreadsheets, which predict the draught force of a range of implements to within 20% of the measured value.     

塑性土壤的弯曲破碎

弯曲加载是需要最小力及最少能耗使塑性土壤破碎的一种有效的加载方式。进一步的试验表明，使用由旋转切割刀片和支承板组成的弯曲加载装置能很好地产生弯曲破碎，只要支承板和旋转刀片的位置选择合适，其切割阻力及能耗与在水田耕作中得到广泛应用的旋耕刀片相比，约分别为后者的５０％～６５％和２０％。     

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North-eastern USA

In recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K₂O ha^?1 cut^?1) under optimum N management (112–168 kg N ha^?1 cut^?1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg^?1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K₂O ha^?1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg^?1 for the first cutting in 2002 to 15 g kg^?1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K₂O ha^?1 cut^?1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.     

Nitrogen, Phosphorus, Potassium, Magnesium and Calcium Removal by Brown Midrib Sorghum Sudangrass in the Northeastern USA

For the long‐term sustainability of the dairy industry in the Northeastern USA, manure nutrient application rates should not exceed crop nutrient removal once above‐optimum soil fertility levels are reached. Dairy producers have shown a growing interest in brown midrib (BMR) forage sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (S × S) as a more environmentally sound alternative to maize (Zea mays L.) but data on S × S nutrient removal rates are scant. Our objectives were to determine N, P, K, Ca and Mg removal with harvest as impacted by N application rate, using six N rate studies in New York. One of the six sites had a recent manure history. Although site‐to‐site differences existed, N application tended to decrease P and K and increase N, Ca and Mg concentrations in BMR S × S forage. Nutrient removal and yield were highly correlated for all sites except one location that showed a K deficiency. The crop removed large amounts of P and K in the manured site, suggesting that BMR S × S is an excellent scavenger of these nutrients. If manure is applied mid‐season, forage K levels are likely too high for feeding to non‐lactating cows.     

Impacts of Kafirin Allelic Diversity,Starch Content,and Protein Digestibility on Ethanol Conversion Efficiency in Grain Sorghum

Seed protein and starch composition determine the efficiency of the fermentation process in the production of grain‐based ethanol. Sorghum, a highly water‐ and nutrient‐efficient plant, provides an alternative to fuel crops with greater irrigation and fertilizer requirements, such as maize. However, sorghum grain is generally less digestible because of extensive disulfide cross‐linking among sulfur‐rich storage proteins in the protein– starch matrix. Thus, the fine structure and composition of the seed endosperm directly impact grain end use, including fermentation performance. To test the hypothesis that kafirin (prolamin) seed storage proteins specifically influence the efficiency of ethanol production from sorghum, 10 diverse genetic lines with allelic variation in the β‐, γ‐, and (δ‐kafirins, including three β‐kafirin null mutants, were tested for ethanol yield and fermentation efficiency. Our selected lines showed wide variation in grain biochemical features, including total protein (9.96–16.47%), starch (65.52–74.29%), and free amino nitrogen (FAN) (32.84–73.51 mg/L). Total ethanol yield (ranging from 384 to 426 L/metric ton), was positively correlated to starch content (R² = 0.74), and there was a slight positive correlation between protein digestibility and ethanol yield (R² = 0.52). Increases in FAN content enhanced fermentation efficiency (R² = 0.65). The highest ethanol producer was elite staygreen breeding line B923296, and the line with the highest fermentation efficiency at the 72 h time point was inbred BT×623. A large‐seeded genotype, KS115, carrying a novel γ‐kafirin allele, was rich in FAN and exhibited excellent short‐term fermentation efficiency at 85.68% at the 20 h time point. However, the overall ethanol yield from this line was comparatively low at 384 L/metric ton, because of insufficient starch, low digestibility, and high crude protein. Multivariate analysis indicated an association between the β‐kafirin allele and variation in grain digestibility (P = 0.042) and FAN (P = 0.036), with subsequent effects on ethanol yield. Reversed‐phase HPLC profiling of the alcohol‐soluble kafirin protein fraction revealed diversity in protein content and composition across the lines, with similarities in peak distribution profiles among β‐kafirin null mutants compared with normal lines.     

Insights into Sorghum Starch Biosynthesis from Structure Changes Induced by Different Growth Temperatures

The effects of high growth temperature on sorghum starch structures were examined from the grains of three inbred lines (BTx623, IS8525, and Karper669), and the possible mechanism by which the growth of amylopectin molecules is terminated was discussed. Sorghum plants were grown at high temperature (38/21°C day/night) and control temperature (32/22°C day/night) from sowing to maturity. The grains sampled from plants grown at high temperature had significantly lower starch weights per grain (except BTx623) and smaller starch granule sizes than those grown at control temperature. Nevertheless, the amylose contents were similar. BTx623 and IS8525 samples grown at high temperature also had higher ratios of long to short amylopectin branches and lower degree of branching than their control counterparts. These results suggested that the activities of starch biosynthetic enzymes were evidently affected by elevated growth temperature. However, the weight‐average molecular weight and the z‐average radius of gyration of sorghum starch molecules were not significantly affected by the growth temperatures, suggesting that the effects of growth temperature on starch yield, starch granule size, and the branching structure of amylopectin molecules did not influence the events that stopped the overall growth of amylopectin molecules. This observation was consistent with the cessation of whole‐molecule growth being through increasing hindrance to enzyme access as the size of the starch molecule increases, controlled largely by the molecular density of the outermost part of an amylopectin molecule.     

Paired-end mapping reveals extensive structural variation in the human genome

Structural variation of the genome involves kilobase- to megabase-sized deletions, duplications, insertions, inversions, and complex combinations of rearrangements. We introduce high-throughput and massive paired-end mapping (PEM), a large-scale genome-sequencing method to identify structural variants (SVs) approximately 3 kilobases (kb) or larger that combines the rescue and capture of paired ends of 3-kb fragments, massive 454 sequencing, and a computational approach to map DNA reads onto a reference genome. PEM was used to map SVs in an African and in a putatively European individual and identified shared and divergent SVs relative to the reference genome. Overall, we fine-mapped more than 1000 SVs and documented that the number of SVs among humans is much larger than initially hypothesized; many of the SVs potentially affect gene function. The breakpoint junction sequences of more than 200 SVs were determined with a novel pooling strategy and computational analysis. Our analysis provided insights into the mechanisms of SV formation in humans.     

Descriptive and multivariate analyses of morphotaxonomic and yield-related traits in inflorescence dichotomous cultivars of Musa species (AAB genome)

Genetic Resources and Crop Evolution - Genetic diversity in Musa species (AAB genome) has been collected and conserved in several germplasm banks in different parts of the world. However, not many...     

Characterizing the Saltol Quantitative Trait Locus for Salinity Tolerance in Rice

This study characterized Pokkali-derived quantitative trait loci (QTLs) for seedling stage salinity tolerance in preparation for use in marker-assisted breeding. An analysis of 100 SSR markers on 140 IR29/Pokkali recombinant inbred lines (RILs) confirmed the location of the Saltol QTL on chromosome 1 and identified additional QTLs associated with tolerance. Analysis of a series of backcross lines and near-isogenic lines (NILs) developed to better characterize the effect of the Saltol locus revealed that Saltol mainly acted to control shoot Na⁺/K⁺ homeostasis. Multiple QTLs were required to acquire a high level of tolerance. Unexpectedly, multiple Pokkali alleles at Saltol were detected within the RIL population and between backcross lines, and representative lines were compared with seven Pokkali accessions to better characterize this allelic variation. Thus, while the Saltol locus presents a complex scenario, it provides an opportunity for marker-assisted backcrossing to improve salt tolerance of popular varieties followed by targeting multiple loci through QTL pyramiding for areas with higher salt stress.     

Characterization,inheritance, and molecular study of opaque leaf mutant in mungbean (<Emphasis Type="Italic">Vigna radiata</Emphasis> (L.) Wilczek)

Chlorophyll-deficiency mutants are useful as genetic markers and as materials for studying the photosynthesis process. We characterized the inheritance of the gene controlling an opaque leaf (OL) trait in mungbean (Vigna radiata (L.) Wilczek). An F₂ population was developed from the cross between the OL mutant and ‘Berken’, an Australian mungbean cultivar, to study inheritance and molecular tagging. The population was advanced by selfing to produce F₅ lines from which two normal lines and two OL lines were randomly chosen to study chlorophyll content, seed growth and development, and seed cell morphology. The chlorophyll content in opaque leaf was lower than normal and thus was expected to have lower photosynthetic activity. This resulted in yellowish and shrinking pods and seeds within 15 days after flowering, while those from normal plants extended their growth up to 18 days. The cotyledon transfer cells of the OL plants deformed at 12 days and deteriorated at 14 days after flowering. The OL trait was controlled by a single recessive ol gene which was independent from the genes controlling petiole color and growth habit. We used 193 AFLP primer combinations to tag this gene and found that the marker AGG/ATA was linked with the ol gene at a distance of 3.4 cM.