Resistance to Helminthosporium leaf blight and agronomic performance of spring wheat genotypes of diverse origins

Helminthosporium leaf blight (HLB), caused by a complex of Cochliobolus sativus (Ito & Kurib.) Drechsler ex Dastur and Pyrenophora tritici-repentis Died, is a serious disease of wheat (Triticum aestivum L.) in the warm lowlands of South Asia. Wheat cultivars grown in the area are either susceptible to HLB or possess low levels of resistance to it. A replicated field study was conducted in 1999 and 2000 at two sites in Nepal to determine the level of HLB resistance and other desirable traits in 60 wheat genotypes of diverse origin. The test genotypes were planted in main strips divided into two strips one of which was sprayed four times with Tilt (a.i. propiconazole) @ 125 g of a.i. ha^–1. Four readings of HLB were recorded to calculate the area under the disease progress curve (AUDPC). Other traits under investigation included biomass yield (BY), grain yield (GY), 1000-kernel weight (TKW), harvest index (HI), days to heading (DH) and maturity (DM), plant height (PHT), and effective tiller number (ETN). Wheat genotypes differed significantly for all traits. Mean AUDPC values ranged from 45 to 1268. A few exotic genotypes were highly resistant to HLB. Losses in GY due to HLB ranged from 2 to 26%, and TKW was reduced by up to 33%. A few genotypes showed HLB tolerance, i.e., relatively smaller GY and TKW reductions despite high levels of HLB. In general, medium to late maturity and higher levels of HLB resistance and low to high GY and TKW characterized genotypes exotic to South Asia. Biplot analysis identified several genotypes that were HLB-resistant and agronomically superior. Results suggest it is possible to improve HLB resistance of local wheat cultivars based on selective breeding using this pool of germplasm.     

Diversity and Traditional Knowledge Concerning Wild Food Species in a Locally Managed Forest in Nepal

This study documents wild food species in a locally managed forest by the inhabitants of nine villages in the Dolakha district, Nepal. It presents data on their diversity, and traditional knowledge on plant use, propagation and local domestication collected through household and key informant interviews, forest transects inventories and herbaria verifications. Sixty-two wild food plants belonging to 36 families were recorded; most of them (80%) have multiple uses. Many of the food plants are herbaceous (24 species) and produce fruits for consumption (46%). Most of the food plants are consumed by the local communities as snacks, and are supplementary and nutritionally important especially prior to the harvest of staple foods. Elder women (>35 years) are the most knowledgeable group, being able to describe the use of 65% of all edibles as compared to only 23% described by young men (<35 years). Many villagers also possess knowledge on the modes of propagation for the food plants that may be used in the process of domestication. The local communities expressed a strong desire for the establishment of community enterprises based on the wild food resources for long-term income generation sources. To accomplish this, development of collective co-operative strategies based on assessments of the biology, size of harvestable population, sustainable harvesting techniques, and marketing value and demand of promising species would be required. Moreover domestication potential based on species identified in this paper and other species that local communities have knowledge on ought to be encouraged through incentive and policy interventions.     

Structural and hydrological alterations of soil due to addition of coal fly ash

Purpose  

We tested the potential of using coal fly ash for improving the physical and hydrological characteristics of coarse and medium-textured agricultural soils.     

Physicochemical and structural properties of maize and potato starches as a function of granule size

Chemical composition, molecular structure and organization, and thermal and pasting properties of maize and potato starches fractionated on the basis of granule size were investigated to understand heterogeneity within granule populations. For both starches, lipid, protein, and mineral contents decreased and apparent amylose contents increased with granule size. Fully branched (whole) and debranched molecular size distributions in maize starch fractions were invariant with granule size. Higher amylose contents and amylopectin hydrodynamic sizes were found for larger potato starch granules, although debranched molecular size distributions did not vary. Larger granules had higher degrees of crystallinity and greater amounts of double and single helical structures. Systematic differences in pasting and thermal properties were observed with granule size. Results suggest that branch length distributions in both amylose and amylopectin fractions are under tighter biosynthetic control in potato starch than either molecular size or amylose/amylopectin ratio, whereas all three parameters are controlled during the biosynthesis of maize starch.     

Conservation and climate change: Assessing the vulnerability of snow leopard habitat to treeline shift in the Himalaya

Climate change is likely to affect the persistence of large, space-requiring species through habitat shifts, loss, and fragmentation. Anthropogenic land and resource use changes related to climate change can also impact the survival of wildlife. Thus, climate change has to be integrated into biodiversity conservation plans. We developed a hybrid approach to climate-adaptive conservation landscape planning for snow leopards in the Himalayan Mountains. We first mapped current snow leopard habitat using a mechanistic approach that incorporated field-based data, and then combined it with a climate impact model using a correlative approach. For the latter, we used statistical methods to test hypotheses about climatic drivers of treeline in the Himalaya and its potential response to climate change under three IPCC greenhouse gas emissions scenarios. We then assessed how change in treeline might affect the distribution of snow leopard habitat. Results indicate that about 30% of snow leopard habitat in the Himalaya may be lost due to a shifting treeline and consequent shrinking of the alpine zone, mostly along the southern edge of the range and in river valleys. But, a considerable amount of snow leopard habitat and linkages are likely to remain resilient to climate change, and these should be secured. This is because, as the area of snow leopard habitat fragments and shrinks, threats such as livestock grazing, retaliatory killing, and medicinal plant collection can intensify. We propose this approach for landscape conservation planning for other species with extensive spatial requirements that can also be umbrella species for overall biodiversity.     

Determination of phosphorus saturation level in relation to clay content in formulated pond muds

An experiment was conducted to determine the amount of P needed to saturate simulated fish pond sediments, formulated to contain six levels of clay (0, 30, 41, 64, 73 and 81% by weight). A series of cylindrical cement tanks were filled to 20 cm depth with the six sediment types and triple superphosphate (TSP) solution was added to reach P saturation in sediment. Results showed that all sediment types reached constant inorganic-P concentration in the upper 5 cm after 12 weeks of TSP application, and P adsorption capacity of sediment increased with increasing clay content. Sediment P adsorption was slower and not significant (P > 0·05) below 5 cm depth except in the sediment type containing 0% clay. Regression analysis showed that the rate and adsorption capacity of P in sediment are primarily governed by clay content and its dominant minerals. While organic-P and loosely bound-P are commonly deposited in sediment, most inorganic-P is adsorbed by cations to form cation-P complexes. The linear relationship between cation-P saturation level and the percentage of clay in sediment is highly significant (r² = 0·84, P < 0·001) and, therefore, maximum adsorption capacity of cation-P in pond sediment can be approximated by Y = 0·019X (where Y represents the 100% saturation level in mg P g⁻¹ soil, and X is the percentage of clay in the sediment). In practice, the level of P saturation in sediment can be approximated by the initial cation-P and clay contents in the top 5 cm of pond mud using the equation: P saturation (%) = initial cation-P (mg g⁻¹ soil) × 100/P adsorption capacity (mg g⁻¹ soil).     

Diversity and detection of Korean Erwinia pyrifoliae strains as determined by plasmid profiling, phylogenetic analysis and PCR

Twenty-five strains of Erwinia pyrifoliae were investigated for their plasmid profiles and genetic relatedness. Four types of plasmid profile were observed for the first time, suggesting intraspecific plasmid profile diversity in E. pyrifoliae . Moreover, BOX-PCR and phylogenetic analysis based on the 16S-23S intergenic transcribed spacer (ITS) region showed genetic variations among E. pyrifoliae strains, although all strains were clustered in one group and separated from E. amylovora . On the other hand, ERIC-PCR and phylogenetic analysis based on partial groEL gene sequences revealed close genetic relatedness among the strains. Amplification with EpSPF and EpSPR primers of a fragment of approximately 0·65 kb from the genomic DNA of all E. pyrifoliae strains, but not from E. amylovora strains, suggested that this primer set is useful for identification of this pathogen.     

Erratum to: Efficacy of vaccination with La Sota strain vaccine to control Newcastle disease in village chickens in Nepal

Tropical Animal Health and Production -     

Analysis of protease activity in <Emphasis Type="Italic">Aspergillus flavus</Emphasis> and <Emphasis Type="Italic">A. parasiticus</Emphasis> on peanut seed infection and aflatoxin contamination

Aspergillus flavus and A. parasiticus are aflatoxin-producing fungi that can infect peanut seeds in field crops. An association between A. parasiticus proteolytic enzyme activities and peanut fungal infection was examined. For this study, a model of inductive and non-inductive culture media to produce A. parasiticus extracellular protease before infection was used. These A. parasiticus cultures were used to infect peanut seeds of cultivars resistant and susceptible to aflatoxin contamination. Peanut seeds of both cultivars exposed to fungi grown on casein medium (inductive medium) showed higher internal and external infection and a higher fungal protease content than those observed on potato dextrose agar (PDA) and sucrose medium (non-inductive media). A further study showed higher fungal colonisation and aflatoxin contamination in seeds of the resistant cultivar pre-incubated with Aspergillus extracellular proteases than in those incubated without proteases. Moreover, protease activities affected the viability of non-infected resistant cultivar seeds, inhibiting germination and radicle elongation and enhancing seed tissue injury. The results strongly suggest that protease production by A. parasiticus is involved in peanut seed infection and aflatoxin contamination resulting in seed tissue damage, affecting seed viability and facilitating the access of fungi through the testa. The analysis of fungal extracellular proteases formed on peanut seed during infection showed that A. flavus and A. parasiticus produced metallo and serine proteases; however, there were differences in the molecular masses of the enzymes between both species. The greatest activity in both species was by serine protease, that could be classified as subtilase.     

Integration of biophysical and socio‐economic factors to assess soil erosion hazard in the Upper Kaligarang Watershed,Indonesia

Soil erosion is one form of land degradation, which is caused by the interacting effects of numerous factors such as biophysical characteristics and socio‐economic condition of a particular watershed. Previous erosion studies focused on the use of soil erosion models (e.g. USLE, EUROSEM, SLEMSA etc.), which have been developed under local conditions (e.g. United States, Europe, Africa, etc) and mostly use only biophysical factors as inputs to the models. In this study, a methodology that integrates both biophysical and socio‐economic aspects into a framework for soil erosion hazard assessment using principal component analysis (PCA) is described. The analysis is done at the land unit level. With the particular conditions of the study area that is characterized by Inceptisols and Alfisols soil types, nine different land uses with mixed vegetation and forest area dominant in the steep slope, high annual rainfall (>2500 mm), high population with mostly low income and low education, were considered. These were used in formulating a soil erosion hazard index (EHI) equation which relates a number of key factors consisting of biophysical and socio‐economic variables, namely soil texture, slope steepness, land cover, soil conservation practices, income and farmers' knowledge. Weighting and scoring of these key factors were used to develop the EHI equation and to calculate an index value of erosion hazard for every land unit. Results indicate that more than 60% of the area has erosion hazard ranging from moderate to very severe, and most of the land units with high erosion hazard were found at the mountain areas. It was also found that erosion hazard was severe in areas with high silt content, followed by high rainfall and steep slope, low crop cover without any soil conservation practices coupled with lack of awareness on soil erosion and low income. The key factors identified and level of erosion hazard obtained can be used to formulate conservation measures in critical areas which are prone to soil erosion. Copyright © 2007 John Wiley & Sons, Ltd.