12个泰国玉米群体的产量配合力效应分析及其杂种优势类群的划分

对12个泰国玉米群体的配合力效应进行分析,并对其杂种优势类群进行划分。结果表明,12个泰国玉米群体的产量一般配合力(GCA)和特殊配合力(SCA)方差均存在极显著或显著差异,产量配合力总效应顺序与组合产量排序相吻合,两者成显著正相关。12个泰国玉米群体可分为2个杂种优势群,第Ⅰ类群包括Q9、Q11群体,与旅大红骨杂优群内的丹340等的SCA最高;第Ⅱ类群包括Q1等其余群体,与Reid杂优群内的掖478、7239等的SCA较高。第Ⅱ类群可分为3个亚群,第Ⅰ亚群包括Q1、Q2、Q10群体,与Reid杂优群内的掖478S CA最高;第Ⅱ亚群包括Q3、Q4、Q6、Q8、Q12群体,与塘四平头杂优群内的黄早四SCA最高;第Ⅲ亚群包括Q5、Q7群体,与Reid杂优群内的7239 SCA最高。产量排前10位的组合中以Q1、Q10、Q11为亲本的组合各2个,以Q2、Q5、Q7、Q8为亲本的组合各1个。群体Q1、Q10、Q11在广西的育种利用价值最高,可直接用于选育自交系或作为改良材料。     

Effect of replacing soybean meal with yeast‐fermented canola meal on growth and nutrient retention of Nile tilapia,Oreochromis niloticus (Linnaeus 1758)

Yeast fermentation integrated with water soaking was applied as a method to reduce the levels of some anti‐nutritional factors in canola meal. The procedure completely eliminated glucosinolates and it reduced phytic acid content by 18%. It also led to increase of 9% of crude protein and 8–32% of some minerals in the meal. A 60‐day feeding trial was conducted to evaluate replacement of dietary soybean meal protein with yeast‐fermented canola meal for Nile tilapia at ratios of 0, 25, 50, 75 and 100% respectively. Three groups of fish with an initial weight of 10 g were fed with each diet twice a day to an apparent satiation. The results showed that there were non‐significant differences (P > 0.05) in growth, survival rate, feed intake and feed conversion ratio for all fish fed with the test diets. However, replacement with 75 and 100% levels significantly reduced (P < 0.05) protein efficiency ratio and nutrient digestibility of protein, lipid, ash, Ca, Mg and P of fish compared with the lower levels. The low retention of protein, lipid, ash, Ca, Mg and P were also observed. These effects seemed to be related to an increased dietary phytic acid.     

The effect of a catastrophic flood disaster on livestock farming in Nakhon Sawan province, Thailand

In 2011, a catastrophic flood disaster in Thailand affected not only humans but also took animal lives. Data on livestock losses, including death, loss, and decreased production, were collected in Nakhon Sawan province. The time-series map of the flooded area from August to December 2011 was available online from the Geo-informatics and Space Technology Development Agency. To evaluate the high-density areas of livestock loss, a spatial hot spot analysis was performed. The Getis-Ord Gi statistic with weighted zone of indifference and the Euclidean distance measurement were employed to identify spatial clusters of species that were affected by the flood. The results indicated that the majority of livestock losses were from poultry and swine farms. The density of poultry and swine loss was significantly different between sub-districts with clusters of high-density loss alongside the river, particularly in Chum Saeng and Kao Liew. Using spatial hot spot analysis as a tool to classify and rank the areas with high flood risks provides an informative outline for farmers to be aware of potential flood damage. To avoid unexpected loss from flooding, poultry and swine farms in risk areas should be properly managed, particularly during the flooding season between August and December.     

Anthropogenic mercury enrichment in remote lakes of northern Québec (Canada)

In a sub-Arctic region of the province of Québec, at sites situated 200 to 1400 km away from the closest industrial centers, we find the ubiquitous presence of anthropogenic Hg, reflected by steadily increasing concentrations of this metal in lake sediments, since about 1940, to rates averaging 2.3 times the preindustrial levels. Mercury concentrations in lake sediments were found to be proportional to the amounts of terrestrial organic carbon from the catchment area. It would, therefore, be misleading to derive continental-scale gradients of this pollutant based on Hg concentrations in oligotrophic lake sediments, unless they are normalized to their organic carbon content. Our normalized data for sediments of remote lakes along a 1200 km transect (45 to 55°N) clearly indicate that the distribution pattern of long-range Hg contamination is independent of the latitude over the boreal forest domain. This uniform contamination contrasts with that of Pb, which decreases towards the north over the same latitudinal span, away from the industrial centers of the St Lawrence Valley and the U.S. Mid-West.     

The effects of prey depletion on dietary niches of sympatric apex predators in Southeast Asia

Resource depletion exerts opposing pressures on co-occurring consumers to expand diets while limiting overlap with competitors. Using foraging theory as a framework, we tested the effects of prey availability on diet specialization and overlap among competing Asian predators: dhole, leopard, and tiger. We used scat analysis from a prey-poor site, combined with a quantitative synthesis of 40 other diet studies, to determine biomass of different prey types consumed by each predator. We then assessed diet composition in relation to prey density, and compared diet breadth and overlap between prey-poor and prey-rich sites. In prey rich areas, all three predators specialized on energetically profitable medium and large ungulates (>30 kg), resulting in narrow, overlapping niches. Each predator shifted toward less profitable small-bodied prey (≤30 kg) as preferred ungulates declined, whereas consumption of preferred ungulates was unrelated to small prey abundance, as predicted by foraging theory. Diet breadths doubled under prey depletion (except leopard), but overlap declined as diets diverged via species-specific traits that facilitated capture of different types of alternative prey. Asia's apex predators adapt similarly to depletion of mutually preferred ungulates by switching to more numerous but less profitable small prey. Yet they can also partition a depleted prey base through intrinsic niche differences, thereby avoiding competitive exclusion. Our findings illuminate the stabilizing properties of adaptive foraging and niche differences in ecological communities, and provide insights into the behavior and resilience of Asia's endangered apex predators in response to prey depletion in the heavily poached forests of this region.     

Detection and integration of gene mapping of downy mildew resistance in maize inbred lines though linkage and association

Association mapping relies on the variation and extent of linkage disequilibrium within a species to identify genes of interest; this is an alternative to linkage mapping in traditional biparental population, which exploits only the variation in the two parents of the mapping population. This study was designed to identify association between 48 SSR markers and downy mildew (DM) resistance using a set of 60 public and private maize inbred lines in Thailand. Genetic diversity and population structure in the set were calculated. A total of 489 alleles with an average gene diversity of 0.70 revealed two subpopulations among the 60 maize inbred lines. Analysis of variance resulted in significant effects of phenotypic values of tested entries, with significant effects of inbred lines, locations, and their interaction. In addition, the analysis of variance for broad sense heritability also indicated high heritability (0.97), and association analysis revealed three significant SSR-trait associations (P < 0.05). These three significant SSR loci have not been reported in previous linkage mapping studies. Our results suggest that new allelic variants associated with DM resistance in these germplasm collections should be useful to help identify new lines carrying alleles for DM resistance in breeding marker-assisted selection programs.     

Detection of candidate R genes and single nucleotide polymorphisms for downy mildew resistance in maize inbred lines by association analysis

Downy mildew (DM) is a plant disease that strongly limits maize production. The resistance (R) genes for this disease have been identified and characterized and serve as important tools for plant disease evaluation. In this study, partial genes for PIC15, PO145579, and zmcf5 were identified and analyzed in a panel of 60 public and private maize inbred lines using bioinformatics and statistics tools. These candidate R genes exhibited an average nucleotide diversity value of 0.015. The negative Tajima’s D values for these genes suggested that purifying selection has played a role in the evolution of maize DM resistance genes. In addition, linkage disequilibrium among these genes occurred across an extent of ~ 200 bp. Using association analysis methods, a general linear model, and a mixed linear model, five polymorphisms within the partial PIC15 and PO145579 genes were detected and associated with DM disease. These are new polymorphisms that have not previously been reported in association with DM disease traits. Therefore, correlations between these new polymorphisms and DM disease in these germplasm collections could advance the development of a functional marker for marker-assisted selection of DM disease resistance in maize breeding programs.     

The partitioning of mercury in the solid components of dry and flooded forest soils and sediments from a hydroelectric reservoir,Quebec (Canada)

Upon inundation, the soils in a hydroelectric reservoir are subjected to several years of physical, biological, and chemical changes as the transition from a terrestrial to an aquatic ecosystem is achieved. It is suspected that changes in soil Eh and pH alter the metal binding capacity of organic matter, reactive iron (Fe) oxides/oxyhydroxides, and clay minerals, and may cause the mercury associated with these phases to be remobilized. Four cores were collected along a transect from an unflooded forest soil to a pre-impoundment lake bottom sediment. They were subjected to a customized sequential extraction procedure to determine the distribution of Hg between three operationally-defined solid compartments: organic carbon, reactive Fe oxides/hydroxides, and the solid (clay and sulfide) residue. Results indicate that up to 80% of the Hg in the O-horizon of forest soils and flooded soils and up to 85% of the Hg in lake sediments is bound to the NaOH-extractable organic carbon fraction. Furthermore, it was observed that the highest Hg concentrations are associated with degraded organic matter. In the B-horizon of a podzol, 40–60% of the total Hg was found associated with reactive Fe minerals. In contrast, the flooded podzol contains almost no reactive Fe at any depth and associated Hg concentrations are low. We propose that upon inundation, Fe oxides are reduced and Hg released to the pore waters where it is rapidly bound to other available substrates. Analyses of the extractions residues suggest that there is an enrichment of Hg in this fraction immediately above the B-horizon in a flooded soil.