Identification of dspEF, hrpW, and hrpN loci and characterization of the hrpN Ep gene in Erwinia pyrifoliae

Erwinia pyrifoliae, the causal pathogen of shoot blight in the Asian pear tree (Pyrus pyrifolia cv. Singo), is host-specific and endemic to Korea. To identify the genes associated with the hypersensitive response (HR) and pathogenicity, a genomic library of E. pyrifoliae WT3 was constructed, and the cosmid clone Escherichia coli (pCEP33) was selected. Sequence analysis of 19.7-kb pCEP33 determined disease-specific (dsp) region homolog and approximately 40% of the hrp genes, which included hrpW, hrpN_Ep, hrpV, hrpT, hrcC, hrpG, hrpF, and partial hrpE homologs, with respect to the cluster of Erwinia amylovora. Additionally, two open reading frames, ORFD and ORFE, were found downstream of the dspEF region. The results of the sequence analysis showed that the pCEP33 did not contain any hrp regulatory genes or most of the genes encoding components of the Hrp protein secretion system. The hrpN_Ep gene of E. pyrifoliae contained five intergenic nucleotide fragment insertions (INFIs) and produced the HR elicitor protein harpin_Ep, with a molecular mass of approximately 44kDa. The purified HrpN_Ep protein elicited faster and stronger HR when infiltrated into tobacco leaves than did HrpN_Ea from E. amylovora. To observe the role of the hrpL gene in the expression of HrpN_Ep, the pEL2 containing hrpL was used to transform E. coli (pCEP33). Expression of HrpN_Ep in E. coli (pCEP33 + pEPL2) was detected with an immunoblot using antiserum raised against HrpN_Ep, indicating a role of hrpL gene in enhancing the expression of HrpN_Ep.     

Epidemiology of foliar blights (spot blotch and tan spot) of wheat in the plains bordering the himalayas

ABSTRACT Helminthosporium leaf blight (HLB), a complex of spot blotch caused by Cochliobolus sativus and of tan spot caused by Pyrenophora tritici-repentis, is a major wheat disease in South Asia. This 2-year study elucidated HLB development and its impact on yield. Symptoms caused by C. sativus and P. tritici-repentis were first observed at the seedling and tillering stages, respectively. The number of airborne conidia and leaves infected by the two pathogens remained low for several weeks under lower temperatures, followed by a sharp rise as temperatures increased. The number of airborne conidia of C. sativus and incidence of infection by C. sativus were higher compared with P. tritici-repentis. The disease complex caused an average 30% reduction in yield, with greater losses under delayed seeding. Delayed seeding increased disease severity even in resistant genotypes and caused higher yield losses. 'Milan/Shanghai-7' was the most resistant among six genotypes evaluated. Despite higher disease severity, 'BL 1473' showed relatively lower yield losses, indicating its tolerance to foliar blight. The findings of this study bear implications for integrated foliar blight management in the warmer areas of South Asia by combining optimum seeding date, seed treatment and foliar spray of fungicides, and resistant wheat genotypes.     

Biodegradation of Toluene Under Seasonal and Diurnal Fluctuations of Soil-Water Temperature

An increasing interest in bioremediation of hydrocarbon polluted sites raises the question of the influence of seasonal and diurnal changes on soil-water temperature on biodegradation of BTEX, a widespread group of (sub)-surface contaminants. Therefore, we investigated the impact of a wide range of varying soil-water temperature on biodegradation of toluene under aerobic conditions. To see the seasonal impact of temperature, three sets of batch experiments were conducted at three different constant temperatures: 10°C, 21°C, and 30°C. These conditions were considered to represent (1) winter, (2) spring and/or autumn, and (3) summer seasons, respectively, at many polluted sites. Three additional sets of batch experiments were performed under fluctuating soil-water temperature cases (21<>10°C, 30<>21°C, and 10<>30°C) to mimic the day-night temperature patterns expected during the year. The batches were put at two different temperatures alternatively to represent the day (high-temperature) and night (low-temperature) times. The results of constant- and fluctuating-temperature experiments show that toluene degradation is strongly dependent on soil-water temperature level. An almost two-fold increase in toluene degradation time was observed for every 10°C decrease in temperature for constant-temperature cases. Under fluctuating-temperature conditions, toluene degraders were able to overcome the temperature stress and continued thriving during all considered weather scenarios. However, a slightly longer time was taken compared to the corresponding time at daily mean temperature conditions. The findings of this study are directly useful for bioremediation of hydrocarbon-polluted sites having significant diurnal and seasonal variations of soil-water temperature.     

Influence of tillage,planting date,and Bt cultivar on seasonal abundance and within-plant distribution patterns of thrips and cotton fleahoppers in cotton

Abstract

Thrips (Thysanoptera: Thripidae( and cotton fleahoppers, Pseudatomoscelis seriatus (Reuter( (Hemiptera: Miridae(, are considered to be significant economic pests of cotton in Texas, USA. A 2-year field study evaluated the influence of planting date, tillage practice, and Bt cotton on seasonal abundance patterns of thrips and cotton fleahoppers and their within-plant distribution patterns in cotton. Thrips were sampled visually while fleahoppers were sampled both visually and with a ‘beat bucket’ at weekly intervals throughout the growing season. Thrips infestations had two distinct peaks, with the first peak at the one to two main stem node leaf stage and the second peak during the flowering stage. Cotton fleahoppers had only one infestation peak at 13 – 15 weeks after planting (after crop cutout(. Average seasonal abundance of each pest was significantly influenced by tillage practice with higher numbers in conventional tillage compared with that in conservation tillage plots. Thrips abundance was similar between the two cultivars, whereas cotton fleahopper abundance was significantly higher in non-Bt cotton compared with that in Bt cotton. Thrips average seasonal abundance was significantly higher in timely planted cotton compared with that in late-planted cotton. Thrips were more prevalent in upper one-third vertical stratum (51%( followed by middle stratum (33%( and the lower stratum (16%(. Cotton fleahopper within-plant distribution was similar to that for thrips, with 65, 24, and 11% of the total abundance found in upper, middle, and lower one-third of the plant, respectively.     

Mitigating soil erosion through farm-level adoption of soil and water conservation measures in Samanalawewa Watershed,Sri Lanka

Abstract

Soil erosion by water is currently one of the most notable types of land degradation in Samanalawewa Watershed in Sri Lanka, creating copious environmental and socioeconomic impacts. Thus, with the aim of detecting and mapping the rates of human-induced soil erosion in the watershed, remote sensing and geographic information system based modelling and field experiments were carried out. The results of the assessment disclosed that the present rate of human-induced soil erosion varies from 0 to 289 t ha^?1 yr^?1 with the majority of the area exceeding the natural rate of soil erosion by 14 to 33 times at present. However, the average rate of human-induced soil erosion has declined dramatically from 19.8 to 4.3 t ha^?1 yr^?1 from 1986 to 2008. In order to analyse the significant determinants of farm-level adoption of soil and water conservation measures, binary logistic regression procedure was applied using the data collected through a household survey (n = 201). The most significant (p<0.01) variables of the study were the farmers’ perceptions of soil erosion problems, gender of the household head, training on soil and water conservation, and ascertained advice from agricultural extension officers while the variables regarding past awareness about soil conservation technologies and off-farm income were significant at p<0.05. Furthermore, the study revealed that the majority (60.2%) of the farmers in the study area had been adopting different types of soil and water conservation measures for a prolonged period of time. Therefore, owing to the current decreasing rate of soil erosion, the soil and water conservation costs and the ratios of human-induced soil erosion vs natural soil erosion had declined significantly while the productivity of their lands had gone up.     

Community-based forest management and its role in improving forest conditions in Nepal

The status of forest conditions before and after intervention of the forestry projects in community forest in three districts of Nepal is examined. Benefits are observed from the adoption of adaptive collaborative management and collective learning and action research in three sampled districts. The adoption of regular silvicultural treatments has increased the availability of forest products to local users. Moreover, improved forest condition and smallholder livelihoods have improved, as has environmental sustainability. However, the community forestry program has several limitations and shortcomings. Elite capture, social disparity, inequitable benefit-sharing and exclusion of poor and marginalized groups from the community forestry program are notable challenges to be solved in coming years. Special attention is needed to make community forestry inclusive with equitable benefit-sharing and a pro-poor focus.     

Growth and development of fall- and spring-planted populations of Conyza canadensis and C. bonariensis

The growth and phenological development of spring- and fall-planted Conyza canadensis and C. bonariensis were studied in Fresno, CA, USA. A glyphosate-resistant (GR) and a glyphosate-susceptible (GS) population of each species were used. Time taken by each plant to reach the rosette, bolting, appearance of first bud, appearance of first open flower, and initial seed set were converted to growing degree days (GDDs). The fall- and spring-planted C. canadensis required similar GDDs to complete their life cycles but the GR type required fewer GDDs than the GS type. In C. bonariensis, the GDDs required to complete its life cycle differed between the fall- and spring-plantings but not between the GR and GS types. The total aboveground biomass of both fall- and spring-planted Conyzas at initial seed set was similar but the spring-planted GS C. canadensis produced more biomass than the GR type, whereas the fall-planted GS C. bonariensis produced more biomass than the GR type. Plant development based on GDD models can have global implications and help in planning for timely applications of post-emergence herbicides.     

Use of nondestructive sensors to quantify ornamental kale nitrogen status

Greenhouse production of ornamental kale is popular for fall sales. The objective of this study was to evaluate if nondestructive handheld sensors could be used to quantify nitrogen (N) status in Brassica oleracea ‘Nagoya Red’. Topdressed fertilizer treatments of 0, 2.5, 5, 10, 15, and 20 g of 16-9-12 controlled release fertilizer (CRF) were utilized. Individual plants were scanned from 10 pots per treatment for Normalized Difference Vegetative Index (NDVI) values using a prototype NDVI pocket sensor, the recently released commercial GreenSeeker? handheld, and a Soil-Plant Analyses Development (SPAD) chlorophyll meter at three different rating dates starting 25 d after fertilizer treatment application (DAT). Linear and quadratic trends were observed within sampling dates. All three sensors showed correlations with leaf N depending on sampling time. Results indicated that 10 g CRF would be recommended for potted production.