Biocontrol measures against onion basal rot incidence under natural field conditions

Abstract Background The mass drug administration of ivermectin for onchocerciasis control has contributed to a significant drop in Loa loa microfilaria loads in humans that has, in turn, led to reduction of infection levels in Chrysops vectors. Accurate parasite detection is essential for assessing loiasis transmission as it provides a potential alternative or indirect strategy for addressing the problem of co-endemic loiasis and lymphatic filariasis through the Onchocerciasis Elimination Programme and it further reflects the true magnitude of the loiasis problem as excess human mortality has been reported to be associated with the disease. Although microscopy is the gold standard for detecting the infection, the sensitivity of this method is compromised when the intensity of infection is low. The loop-mediated isothermal amplification (LAMP) assay of parasite DNA is an alternative method for detecting infection which offers operational simplicity, rapidity and versatility of visual readout options. The aim of this study was to validate the Loa loa LAMP assay for the detection of infected Chrysops spp. under experimental and natural field conditions. Methods Two sets of 18 flies were fed on volunteers with either a low (< 10 mf/ml) or high (> 30,000mf/ml) microfilarial load. The fed flies were maintained under laboratory conditions for 14 days and then analysed using LAMP for the detection of L. loa infection. In addition, a total of 9270 flies were collected from the north-west, east, and south-west regions (SW 1 and 2) of Cameroon using sweep nets and subjected to microscopy (7841 flies) and LAMP (1291 flies plus 138 nulliparous flies) analyses. Results The LAMP assay successfully detected parasites in Chrysops fed on volunteers with both low and high microfilariaemic loads. Field validation and surveillance studies revealed LAMP-based infection rates ranging from 0.5 to 31.6%, with the lowest levels in SW 2 and the highest infection rates in SW 1. The LAMP assay detected significantly higher infection rates than microscopy in four of the five study sites. Conclusion This study demonstrated the potential of LAMP as a simple surveillance tool. It was found to be more sensitive than microscopy for the detection of experimental and natural L. loa infections in Chrysops vectors.

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Estimation of ascochytosis infection of samples and lines of chickpea sorts in natural field conditions in Uzbekistan

Agrarian science ◽

10.32634/0869-8155-2020-339-6-74-77 ◽

2020 ◽

pp. 74-77

Author(s):

J. T. Nakhalbaev ◽

I. Kh. Khamdamov

Keyword(s):

Field Conditions ◽

Seed Infection ◽

Natural Field ◽

The Third ◽

Experimental Station ◽

Leguminous Crops ◽

Sowing Period ◽

Research Institute

Relevance and methods. The information on the influence of samples of chickpea sorts, time of planting the lines of chickpeas on seed infection with ascochytosis and on the weight of grain on one plant bush is presented in this article. Samples of chickpea sorts and lines were studied during the first sowing period — the first decade of March and the second sowing period — the third decade of March. Ascochytosis infection was evaluated in natural field conditions. The study was conducted at the Central Experimental Station of the Galaaral Research Institute of Grain and Leguminous Crops in 2015–2017 in Uzbekistan.Results. According to the three-year study, it was found that in the years when there was a lot of precipitation days, sorts Yulduz, ILC 263 and MП 2015/1 of the lines during the first sowing were determined to be infected with acochytosis up to 6 points. During the first sowing period of this cv., there was a decrease in the weight of grains on one plant bush compared to the second sowing period. Cv. ILC 3279, Umid and line 14442 were found to be virtually undamaged in natural field conditions with ascohitosis during both planting periods. It wasfound our that the weight of cv. Мustaqillik-20, line 14442 grain on one plant bush remained high during both planting periods.

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Solar radiation use efficiency by soybean under field conditions in the Amazon region

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2009001000001 ◽

2009 ◽

Vol 44 (10) ◽

pp. 1211-1218 ◽

Cited By ~ 8

Author(s):

Paulo Jorge de Oliveira Ponte de Souza ◽

Aristides Ribeiro ◽

Edson José Paulino da Rocha ◽

José Renato Bouça Farias ◽

Renata Silva Loureiro ◽

...

Keyword(s):

Solar Radiation ◽

Leaf Area ◽

Biomass Production ◽

Amazon Region ◽

Field Conditions ◽

Radiation Use Efficiency ◽

Area Index ◽

Natural Field ◽

Use Efficiency ◽

Radiation Use

The objective of this work was to evaluate the efficiency of soybean (Glycine max) in intercepting and using solar radiation under natural field conditions, in the Amazon region, Brazil. The meteorological data and the values of soybean growth and leaf area were obtained from an agrometeorological experiment carried out in Paragominas, Pará state, during 2007 and 2008. The radiation use efficiency (RUE) was obtained from the ratio between the above-ground biomass production and the intercepted photosynthetically active radiation (PAR) accumulated to 99 and 95 days after sowing, in 2007 and 2008, respectively. Climatic conditions during the experiment were very distinct, with reduction in rainfall in 2007, which began during the soybean mid-cycle, due to the El Niño phenomenon. An important reduction in the leaf area index and biomass production was observed during 2007. Under natural field conditions in the Amazon region, the values of RUE were 1.46 and 1.99 g MJ-1 PAR in the 2007 and 2008 experiments, respectively. The probable reason for the differences found between these years might be associated to the water restriction in 2007 coupled with the higher air temperature and vapor pressure deficit, and also to the increase in the fraction of diffuse radiation that reached the land surface in 2008.

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An empirical model for drainage from soil under rain fed conditions

Soil Research ◽

10.1071/sr9770205 ◽

1977 ◽

Vol 15 (3) ◽

pp. 205 ◽

Cited By ~ 11

Author(s):

AR Aston ◽

FX Dunin

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Empirical Model ◽

Sandy Loam ◽

Empirical Relationship ◽

Field Conditions ◽

Natural Field ◽

Moisture Contents ◽

Weighing Lysimeter

An empirical relationship was derived for drainage from a podzolic sandy loam using a weighing lysimeter at Krawarree, N.S.W. The form of the equation was similar to those used to describe drainage following irrigation. The agreement between computed and measured soil moisture contents over a period of five years was good, and indicated the usefulness of such an approach to characterize drainage of soil water under natural field conditions.

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