Transport,deposition and in situ decay of seagrasses in a tropical mudflat area (Banc D'Arguin,Mauritania)

Extensive seagrass beds cover large areas of the mudflats and subtidal parts of the Banc d'Arguin (Mauritania, West Africa). The fate of seagrass biomass (mainly Zostera noltii and Cymodocea nodosa) was investigated during a 1-month expedition to the area (May 1988). Only minor amounts of leaf material were found to be transported by water currents at that time. Subtidal detritus depositions were not found in the area. Though conspicuous accumulations of leaf material were present on some parts of the shore, the amounts washed ashore per flood tide formed only a minor proportion of the daily seagrass production. Thus, transport of leaf litter away from the seagrass beds of the Banc d'Arguin appears insignificant. The major part of senescent leaves probably remains trapped within the seagrass beds and will decompose in situ. The observation that a large part of the particulate carbon present in the surface sediment of seagrass beds was derived from above-ground biomass (55% and 37% in Zostera and Cymodocea beds, respectively), is in agreement with this conclusion.Using the litterbag technique, the rate of leaf decomposition in a seagrass bed was investigated. The time required for 50% weight loss of Zostera and Cymodocea leaf litter in the intertidal zone of the seagrass bed was 158 and 50 days, respectively. In the subtidal zone these figures were 49 and 37 days.     

Chinese Indonesians in a rapidly changing nation: Pressures of ethnicity and identity

Abstract: Throughout periods of political instability and economic adversity – from Dutch colonial rule, through President Suharto's period in office, to more recent times – ethnic Chinese in Indonesia have been recurrent scapegoats for violence. Suharto, especially, manipulated local perceptions of the Chinese in the economic and political arenas, to suit the needs of his government. Yet, circumstances have changed since the 1998 riots in Indonesia and Suharto's departure. Subsequent presidents have introduced legislation aimed at reducing legal restrictions on Chinese Indonesians and they, in turn, are beginning to have greater public voice through a diversity of outlets. These include the growth of numerous new print and television media; a flourishing literature sphere; the rise of a variety of political parties, both ethnicity‐based and more wide‐ranging; and the development of non‐political organisations, some tackling discrimination and others focusing upon Chinese sociocultural needs. These channels are facilitating the appearance of new and re‐emerging ethnic Chinese identities, some surfacing from over 30 years of imposed dormancy. This paper is a preliminary investigation of manifestations of these identities among ethnic Chinese in Indonesia's contemporary public realm.     

On sulphide and the distribution of Arenicola marina in a tidal mud flat in the Dutch Wadden Sea

The concentrations of free sulphide in the upper 30 cm of the sediment of a tidal mud flat in the Dutch Wadden Sea were measured periodically during one and a half year. Also grain size composition and iron sulphide content were determined. In sandy sediments free sulphide values were as a rule below 5 mg S·l⁻¹ pore water throughout the year; at stations with fine sediment much higher values were found.The depth to which Arenicola marina burrowed in the sandy sediments was 22 cm at maximum. Generally sulphide concentrations at this depth were below 0.1 mg S·l⁻¹ but local contact of the animals to concentrations of 50 mg S·l⁻¹ may occur. The density of the lugworms was found to be inversely related to the free sulphide concentration at the depth of the burrows. Whether the sulphide was responsible for this distribution or other parallel changes in sediment characteristics is not clear.Iron sulphide appeared to be of no importance for the distribution of Arenicola marina although the worms were often found in contact with concentrations as high as 450 mg S·l⁻¹ sediment.     

Mapping QTLs for kernel oil content in a tropical maize population

Maize cultivars often have low kernel oil content. To increase the oil content, efficient maize breeding programs have to be developed, which require the knowledge of the inheritance of this trait. Thus, the objective of this research was to map quantitative trait locus (QTLs) and estimate their effects for kernel oil content in a tropical maize population. Two maize inbred lines, contrasting for kernel oil content, were used to develop an F₂ population. Four hundred and eight F₂ plants were self-pollinated, and their kernels (F_2:3 progenies) were used for kernel oil evaluation. A genetic map with 75 microsatellites was developed, and the QTLs were mapped using the composite interval map (CIM); also, estimates of genetic and phenotypic variances, and heritability coefficient were computed. The map presented 10 linkage groups, spanned 1,438.6 cM in length with an average interval of 19.18 cM between adjacent markers. The kernel oil content averaged 58.40 g kg^–1, and the broad-sense heritability was high (h²= 0.98). Thirteen QTLs were mapped, which were distributed into eight chromosomes, and explained 26.64% of the genetic variation. QTLs in chromosomes 1, 5, and 6 contributed the most for kernel oil content. Nine out of 13 QTLs with favorable alleles were from the parental inbred with the highest kernel oil content. The average level of dominance was partial, but gene action of the QTLs ranged from additive to overdominance. Eight out of 13 mapped QTLs were already reported for temperate maize populations.     

Postharvest characteristics of cut dahlia flowers with a focus on ethylene and effectiveness of 6-benzylaminopurine treatments in extending vase life

With the aim of extending vase life of cut dahlia flowers, we investigated the postharvest characteristics of the flowers. Our focus was on the role of ethylene on senescence and on treatments that have extended vase life of other flowers. Continuous exposure to ethylene at 2 or 10 μL L⁻¹ significantly accelerated petal abscission in cut flowers. Flowers continuously immersed in 1 or 10 μL L⁻¹ 2-chloroethylphosphonic acid (CEPA) solution wilted earlier than those treated with distilled water (DW) or 0.15 g L⁻¹ citric acid. Ethylene production from the ovary and ray petal was relatively high (4.5 and 0.9 nL g⁻¹ fresh weight h⁻¹, respectively) at harvest, but decreased gradually over 5 days. No remarkable increase in ethylene production was observed during senescence. Silver thiosulfate complex (STS), an inhibitor of ethylene action, did not extend the vase life of cut flowers, although a high silver concentration was detected in flower organs. In contrast, pulse treatment with 1-methylcyclopropene (1-MCP) and dip treatment with 6-benzylaminopurine (BA) extended the vase life of florets, and BA was more effective than 1-MCP when the flowers were held in both DW and CEPA. BA spray treatment extended vase life of cut ‘Kokucho,’ ‘Kamakura’ and ‘Michan’ flowers. These results suggest that dahlia flower senescence is partially regulated by ethylene, and BA is more effective in delaying the senescence of cut dahlia flowers than ethylene action inhibitors.     

Thermal characterization of a tropical rice soil in relation to puddling,flood-water depth and percolation rate

Effects of puddling, flood-water depth and percolation rate on the thermal properties of a tropical rice soil were studied under field and glass-house conditions. Puddling increased volumetric heat capacity (C_V), but decreased thermal conductivity (Kt), thermal diffusivity (Dt) and damping depth (D) compared to a nonpuddled soil. A percolation rate of 40 mm d⁻¹ showed higher Kt, Dt and D than zero percolation. The values of Kt, Dt and D were highest with 50 mm and lowest with 10 mm flood- water depth. The C_v did not change with different flood-water depths or percolation rates. Consequently, puddling, 40 mm d⁻¹ percolation and 50–100 mm submergence kept the maximum temperature of surface 100–150 mm soil at relatively low level under tropical conditions. These treatments also buffered soil against extreme diurnal temperature fluctuations. The time lag between maximum solar radiation and maximum temperature of submerged soil varied, on an average, between 1.2 hours at soil surface and 11.6 hours at 300 mm soil depth; which is more than that in an upland soil.     

Distribution of juvenile and adult arenicola marina on a tidal mud flat and the importance of nearshore areas for recruitment

The spatial and numerical distribution of juvenile and adult lugworm populations on an intertidal mud flat in the western Wadden Sea is described. Density of juveniles and adults appeared to be related to intertidal height and distance from the shore line. High densities of juvenile worms always occur in places where the numbers of adults are relatively low. Nearshore Arenicola nurseries are considered to be indispensible for the recruitment of the standing stock of adult worms.     

Current status of tropical fruit breeding and genetics for three tropical fruit species cultivated in Japan: pineapple,mango, and papaya

Tropical fruit crops are predominantly produced in tropical and subtropical developing countries, but some are now grown in southern Japan. Pineapple (Ananas comosus), mango (Mangifera indica) and papaya (Carica papaya) are major tropical fruits cultivated in Japan. Modern, well-organized breeding systems have not yet been developed for most tropical fruit species. Most parts of Japan are in the temperate climate zone, but some southern areas such as the Ryukyu Islands, which stretch from Kyushu to Taiwan, are at the northern limits for tropical fruit production without artificial heating. In this review, we describe the current status of tropical fruit breeding, genetics, genomics, and biotechnology of three main tropical fruits (pineapple, mango, and papaya) that are cultivated and consumed in Japan. More than ten new elite cultivars of pineapple have been released with improved fruit quality and suitability for consumption as fresh fruit. New challenges and perspectives for obtaining high fruit quality are discussed in the context of breeding programs for pineapple.     

模拟氮沉降和刈割对内蒙古典型草原土壤微生物量的影响

为探讨大气氮沉降对草原土壤微生物量的影响,采用模拟大气氮沉降的方法对试验小区进行施N处理,研究了不同施N水平下刈割对土壤微生物量C、N的影响。结果表明：不同施N水平对土壤微生物量C、N没有显著影响,但是有增加土壤微生物量C、N的趋势;在刈割和施N的交互作用下降低了土壤中微生物量C、N的含量。不同施N水平能降低草原植被根系生物量、促进土壤酸化。施N量为20g N?m-2?a-1时对土壤微生物量C、N的抑制性最强。     

Genetic-diversity assessed by microsatellites in tropical maize populations submitted to a high-intensity reciprocal recurrent selection

BR-105 and BR-106 are important tropical maize populations, which were submitted to a high-intensity reciprocal recurrent selection, generating the IG-3 and IG-4synthetics. Using 30-microsatellite loci,we measured and compared the genetic diversity of these populations and their synthetics. The populations did not differ significantly regarding the amount of genetic diversity. As a consequence of selection, genetic variability losses, in terms of mean number of alleles per locus,proportion of polymorphic loci, and gene diversity did occur and were greater in the synthetic IG-3 than IG-4. In the synthetics, the number of loci in adherence to Hardy-Weinberg proportions was superior to that observed in the populations. The Wright's mean fixation index was higher than the mean value expected for outcrossing species (5%) indicating as light excess of homozygotic individuals in both populations. The genetic distances confirmed the favourable effects of one cycle of recurrent selection, as the synthetics became more isolated in comparison to the original populations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Association between AFLP-based genetic distance and hybrid performance in tropical maize

Identifying the best inbred combinations for the development of commercial hybrid maize varieties remains the main challenge to maize breeders. The aim of this work was to study associations between the genetic distance (GD) of 21 inbreds and the corresponding F₁ phenotypic data. Furthermore, the impact of grouping lines into genetically similar clusters was investigated. The 21 inbred lines were fingerprinted using amplified fragment length polymorphism markers. Parents and 210 F₁ progeny were evaluated in the field. Joint data analysis mostly revealed a tighter association between GD and the F₁ performance or mid parent heterosis in the intergroup than in the intragroup crosses. Despite these correlations, intergoup crosses should always be field‐tested before their release. Crosses showing low GD values should be discarded to avoid field‐testing costs. Better F₁ hybrid performance predictions can be achieved by integrating molecular and F₁ phenotypic data.     

Using Co-Kriging in variability studies to predict physical land qualities of a level river terrace

On a level river terrace with only limited physiographic features in the Limagne area in France, physical measurements were conducted at 62 sample locations, focusing on the spatial variability of soil-available water. Some 280 observations on a logarithmic sample grid were taken as well to measure basic soil properties. Pedo-transfer-functions were used to estimate soil physical characteristics which are usually difficult to measure in the field. Variability is studied with emphasis on anisotropy and the nugget effect.As physical soil characteristics are closely related with crop conditions and associated spectral imagery, relations were investigated between multispectral aerial photography and soil physical land characteristics. The vegetation index showed a highly significant relationship (F-value < .001) with the available water in the profile.A predictive soil map was made by Co-kriging. Co-kriging is described in terms of increments. To compare the results of Co-kriging with those obtained with Kriging, use is made of a procedure which defines the necessary number of observations to create a predictive map of a predescribed precision. Application of Co-kriging may either lead to maps which are more precise than maps obtained by Kriging, or to a considerable reduction in costs.     

团场棉种产业的现状与良种推广的发展对策

随着社会主义市场经济体制的改革和国家新的<种子法>的出台,种子这个特殊商品也不以人们的意志为转移而面临着市场经济的挑战.目前依然受政策保护、计划经济影响甚浓的团场棉种产业,如何主动迎接市场经济的挑战,并在市场竞争中发展壮大,是一个必须正视的课题.面对这一根本性的转折,认真分析团场棉种产业的优势和弊端、研究发展对策是大有意义的.     

Effects of river discharge and vertical circulation on aquatic primary production in a turbid Louisiana (USA) estuary

Aquatic primary production was measured in stationary and moving bottles with the light/dark oxygen method at two sites in Fourleague Bay, a shallow, turbid estuary on the central Louisiana coast receiving flow from the Atchafalaya River. Riverflow strongly influenced spatial and seasonal patterns of production. Annual net production increased from 382.5 g O₂·m⁻² (119.5 g C·m⁻²) at an upper bay site near the river mouth to 1015.7 g O₂·m⁻² (317.4 g C·m⁻²) at a lower bay site distant from the river. Net production was negatively correlated with seasonal changes in riverflow at both sites. Maximum production rates occurred at intermediate salinities. At low sainities, production was apparently light-limited because of the extreme turbidity of the riverwater. At high salinities, production declined despite greater water clarity, apparently due to nitrogen limitation. At the upper bay areal production estimates from moving incubations were significantly lower than estimates from stationary incubations, but no consistent differences were found at the lower bay and in the bay as a whole. This is the first report of moving incubations yielding significantly lower estimates most of the time. The productivity differences between moving incubations and stationary incubations were significantly correlated with relative light penetration and we suggest that this was because of at least two distinct time-dependent production-versus-irradiance phenomena whose influences varied as conditions changed.     

Molecular analysis of softening and ethylene synthesis and signaling pathways in a non-softening apple cultivar, ‘Honeycrisp’ and a rapidly softening cultivar, ‘McIntosh’

A feature of ‘Honeycrisp’ apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] is that they maintain flesh firmness over extended storage. The objective of this study was to elucidate molecular mechanisms that are responsible for slow softening of ‘Honeycrisp’ as compared with a rapidly softening cultivar, ‘McIntosh’. Fruit from both cultivars were picked during the normal harvest period and stored at 20 °C for 10 d. Internal ethylene concentrations (IECs) in ‘Honeycrisp’ fruit were lower than in ‘McIntosh’, but at climacteric levels of ethylene ‘Honeycrisp’ fruit maintained their firmness over this period, while ‘McIntosh’ softened rapidly. Concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) were higher in ‘Honeycrisp’ than in ‘McIntosh’ apples. qRT-PCR analysis was carried out for genes involved in ethylene biosynthesis, perception and signaling [ACC synthase (MdACS); ACC oxidase (MdACO); ethylene receptors (MdETR and MdERS); constitutive triple response (MdCTR); ethylene response factor (MdERF)], as well as those involved in cell wall metabolism [polygalacturonase (MdPG); xyloglucan endotransglucosylase (MdXTH); expansin (MdEXP); β-galactosidase (Md β-GS); arabinofuranosidase (MdAFase); pectate lyase (MdPL)]. At comparable IECs, the expression of genes involved in ethylene synthesis, ethylene perception and signal transduction was generally much higher in ‘Honeycrisp’ than in ‘McIntosh’ fruit. However, the expression of MdAFase and MdEXP3 was generally lower in ‘Honeycrisp’ than in ‘McIntosh’, while that of MdPG and MdPL was extremely low in ‘Honeycrisp’. Expression of MdPG1 was very low, even though IECs were at climacteric levels. Absence of fruit softening in ‘Honeycrisp’ is probably associated with restricted cell wall enzyme activity. The lower maximum IECs found in ‘Honeycrisp’ compared with ‘McIntosh’ do not appear to be related to expression of genes involved in ethylene biosynthesis.     

Characteristic analysis and risk assessment of heavy metal pollution in Liangtan river, a tributary of Three Gorges Reservoir area

Surface water samples are collected throughout the upstream Liangtan River in December, 2010. The concentrations of Cu, Zn, Ni, Pb, Cr and Fe, Mn, Mg are determined using atomic absorption spectrometry (AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) respectively for the contamination characteristics analysis and preliminary risk assessment. The results demonstrate that concentrations of 8 heavy metals show significant differences in different sampling sections of the river. The average concentration of Ni, Pb, Fe and Mn are much higher than the limits value of GB 3838-2002 Ⅲ functional area and their section of over standard are 100%, 87.5%, 50% and 43.75%, respectively. Spatial distribution and correlation analysis reveal that Fe and Mn in river may have the same pollution sources. Preliminary health risk assessment results indicate that Pb is the most important pollutant leading to non-carcinogenic concerns in particular for children, and the next is Cr. Mn, Ni, Cu, Fe and Zn in sequence.     

Genetic diversity in the parental lines and heterosis of the tropical rice hybrids

Genetic diversity within and between the maintainer (B) and restorer (R) lines used in hybrid breeding programs of the Philippine was investigated with information from analysis of pedigree record, quantitative traits and SSR assays. Mean coefficients of coancestry were calculated as 0.11 within R lines, 0.27 within B lines, and 0.04 between R and B lines, indicating greater diversity among R lines than among B lines, and the significant divergence between B and R lines. These results are consistent with those obtained from quantitative trait analysis and SSR marker assays. Relative gene diversity for 37 random SSR markers averaged 0.20 within B lines,0.28 within R lines, and 0.52 between two groups of lines. There were no consistent associations among various genetic diversity measures. Random sets of SSR marker and pedigree based diversity measures had no significant correlation with mid-parent heterosis for grain yield and biomass, indicating that prediction of heterosis for complex traits based on these two genetic diversity estimates is difficult. This revised version was published online in August 2006 with corrections to the Cover Date.     

Leaf and neck blast resistance reaction in tropical rice lines under green house condition

Rice blast (Magnaporthe oryzae) is the most destructive and epidemic disease of rice. Use of host resistance is the best alternative for disease management. The leaf and neck blast resistance of 182 rice breeding lines were assessed for leaf and neck blast and classified relative to a susceptible check-Masuli and resistant check-Laxmi, from greenhouse experiment in 2005 and 2006. The test plants were inoculated with 10⁵ conidial suspension/ml of M. oryzae at 21 days old seedlings for the leaf blast, and at neck base for the neck blast. Among them, for leaf blast, 77 rice lines were resistant, 43 were moderately resistant, 39 were moderately susceptible and 23 were susceptible. While among the selected 31 rice lines evaluated for neck blast, 4 lines were resistant, 4 were moderately resistant, 16 were moderately susceptible and 7 were susceptible. Leaf and neck infection was significant and positively correlated (r = 0.30, P = 0.05). The rice lines, Barkhe 1032, Barkhe 1034, Barkhe 1035, Barkhe 1036, Barkhe 2014, Barkhe 2024, Barkhe 3019, Super 3004 were resistant to leaf blast and Barkhe 1006, Barkhe 1032, Barkhe 1035, Barkhe 3004 were resistant to neck blast. The rice lines with identification # 11, 69, 137, 168, 182 from Masuli × MT4 parentage, and Barkhe 3017 were susceptible to both leaf and neck blast. Progenies of Irradiated Pusa Basmati (IPB), Kalinga III/IR64 (KIII/IR64), and Masuli/IR64 were resistant to both leaf and neck blast. However, most progenies from Masuli/MT4 showed susceptible reaction to both leaf and neck blast. Thus, rice lines form the IPB, KIII/IR64 and Masuli/IR64 will be promising resistant sources for rice blast in breeding programme.