Implications of climate change for agricultural productivity in the early twenty-first century

This paper reviews recent literature concerning a wide range of processes through which climate change could potentially impact global-scale agricultural productivity, and presents projections of changes in relevant meteorological, hydrological and plant physiological quantities from a climate model ensemble to illustrate key areas of uncertainty. Few global-scale assessments have been carried out, and these are limited in their ability to capture the uncertainty in climate projections, and omit potentially important aspects such as extreme events and changes in pests and diseases. There is a lack of clarity on how climate change impacts on drought are best quantified from an agricultural perspective, with different metrics giving very different impressions of future risk. The dependence of some regional agriculture on remote rainfall, snowmelt and glaciers adds to the complexity. Indirect impacts via sea-level rise, storms and diseases have not been quantified. Perhaps most seriously, there is high uncertainty in the extent to which the direct effects of CO2 rise on plant physiology will interact with climate change in affecting productivity. At present, the aggregate impacts of climate change on global-scale agricultural productivity cannot be reliably quantified

Studies on sheep dip bacteriostatic agents

In this study of bacteriostatic agents used in sheep dips, the results of earlier relevant work were first reviewed. The literature relating to the microbiology of fleece wool, the chemicals that have been used in the control of arthropod ectoparasites of sheep, and the micro-organisms of the fleece that cause problems with plunge sheep dipping, and the in vitro methods of testing the sensitivity of bacteria to chemicals was studied. The seven bacteriostatic compounds selected for study were: lauryldimethylbenzylammonium chloride, a mixture of alkyl-, tolyl-, and methyl- trimethylammonium chlorides, 2-hydroxypropylmethanethiosulphonate, 4-chloro-2-cyclopentylphenol, 2,2'-dihydroxy-3,5,6, 3',5',6'-hexachlorodiphenylmethane, 3,4,4'-trichlorocarbanilide, and an arsenical preparation containing sodium arsenite. They were evaluated against the following indicator organisms; Escherichia coli (Migula) Castellani and Chalmers 1919, a sulphur reducing strain of E. coli Pseudomonas aeruginosa (Schroeter) Migula 1919, Erysipelothrix rhusiopathiae (Migula) Buchanan 1918, and Dermatophilus congolensis van Saceghem 1915, emend. 1916, 1934. The laboratory methods used to assess the activity of the compounds were; a broth dilution turbidimetric and agar subculture technique, an agar diffusion technique, a manometric technique, and a gradient plate procedure. A field trial was undertaken to relate the laboratory results to the practical sheep dipping situation. The quaternary ammonium compounds tested showed the greatest antibacterial activity, and their use as dip bacteriostats can be recommended. All the other compounds, except 3,4,4'-trichlorocarbanilide, have possible applications for the control of specific microbiological problems of sheep dipping or in fleece wool. Some observations are made concerning the phenomenon of hormesis as shown in agar diffusion plates. Comparisons have been drawn between the methods used in this study and assessment of their value has been made. An agar diffusion method is suggested as a standard test for sheep dip bacteriostatic agents. Finally some recommendations for further research work have been made

Global genetics and invasion history of the potato powdery scab pathogen, Spongospora subterranea f.sp. subterranea

Spongospora subterranea f. sp. subterranea (Sss) causes two diseases on potato (Solanum tuberosum), lesions on tubers and galls on roots, which are economically important worldwide. Knowledge of global genetic diversity and population structure of pathogens is essential for disease management including resistance breeding. A combination of microsatellite and DNA sequence data was used to investigate the structure and invasion history of Sss. South American populations (four countries, 132 samples) were consistently more diverse than those from all other regions (15 countries, 566 samples), in agreement with the hypothesis that Sss originated in South America where potato was domesticated. A substantial genetic differenciation was found between root and tuber-derived samples from South America. Estimates of past and recent gene flow suggested that Sss was probably introduced from South America into Europe. Subsequently, Europe is likely to have been the recent source of migrants of the pathogen, acting as a "bridgehead" for further global dissemination. Quarantine measures must continue to be focussed on maintaining low global genetic diversity and avoiding exchange of genetic material between the native and introduced regions. Nevertheless, the current low global genetic diversity of Sss allows potato breeders to select for resistance, which is likely to be durable

Infection Risk Potential of South American Spongospora subterranea f.sp. subterranea Root Gall and Tuber Lesion Inoculum on Potato (Solanum tuberosum ssp. tuberosum)

ISSN:1874-9380ISSN:0003-0589ISSN:1099-209

Trichoderma strains suppress Rhizoctonia diseases and promote growth of potato

Trichoderma spp. from New Zealand soils were evaluated (in greenhouse experiments and one field trial) for Rhizoctonia disease suppression and plant growth promotion of potato plants. Trichoderma virens LU549, T. atroviride LU144 and T. barbatum LU1482 demonstrated the greatest suppression of cankers on potato plants; the percentage of diseased stolons was reduced by 41-46%, compared with the R. solani control. Trichoderma virens LU549 also increased average tuber weight by 210%, and T. atroviride LU144 by 146%, compared with the R. solani control (in which tuber formation was highly suppressed). In plant growth promotion pot trials, the greatest proportional increases for three plant growth parameters (compared with the untreated control) were elicited by: T. harzianum LU1491 (number of tubers), T. barbatum LU1489 (total tuber weight), and Trichoderma sp. 792 LU1483 (average tuber weight). All six of these strains were selected and evaluated in all combinations in a 26 factorial greenhouse experiment. Trichoderma atroviride LU144 had positive impacts on several Rhizoctonia disease and plant growth parameters. Four of the strain combinations were subsequently tested in a field trial during the 2011/12 growing season, in which two Trichoderma strain combinations increased potato tuber yields. This research has shown potential for use of New Zealand Trichoderma strains to suppress Rhizoctonia diseases of potato and increase crop productivity

Germination and bioactivity of Trichoderma atroviride affected by culturing and storage conditions

Identification of the production and storage factors that affect conidial germination and bioactivity (fitness) will assist the success of biological control agents. Effects of culturing conditions on conidial fitness of Trichoderma atroviride LU132 were examined in different storage conditions over time. Abiotic factors (temperature, nutrients, water activity, pH) during production were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against Rhizoctonia solani in dual culture were selected to assess effects of storage condition on conidial fitness. Fitness of the test conidia was examined after storage at 30°C and at 0 or 50% relative humidity (RH) over 6 months. Fitness declined over time, and the decline was greater for 50% RH than 0% RH. The greatest number of conidia and germination percentage resulted from conidia produced at 25°C, but greatest bioactivity resulted from those produced at 30°C. Different C to N ratios (5:1 or 160:1) did not affect these parameters. However, fewer conidia were produced at 30°C, and the least germination and bioactivity resulted from conidia produced at 20°C. Conidia can be divided into two groups: those adapted to extreme culturing conditions (e.g. high temperature), and those protected by nutrients during storage. However, environmental factors are not independent. For example, conidial production at 30°C is probably accompanied by water stress, oxidation, and rapid pH change which may also affect fitness

Understanding the survival, persistence, and bioactivity of the biocontrol agent Trichoderma atroviride LU132

Identification of the production and storage factors that affect conidial germination and bioactivity (fitness) will assist the success of biological control agents. Abiotic factors (temperature, nutrients, water activity, pH) during production were studied and then the effects of culturing conditiond on conidial fitness of Trichoderma atroviride LU132 were examined in different storage conditions over time

Biological fitness of <i>Trichoderma atroviride</i> during long-term storage, after production in different culture conditions

<div><p>ABSTRACT</p><p>Identification of the production and storage factors that affect conidium germination and bioactivity (fitness) will assist the success of biological control agents. Effects of culturing conditions on conidium fitness of <i>Trichoderma atroviride</i> LU132 were examined in different storage conditions over time. Abiotic factors (temperature, nutrients, water activity and pH) during production were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against <i>Rhizoctonia solani</i> in dual culture were selected to assess effects of storage conditions on conidium fitness. Fitness of the test conidia was examined after storage at 30°C and at 0% or 50% relative humidity (RH) over 6 months. Fitness declined over time, and the decline was greater for 50% RH than 0% RH, probably through reduced metabolic activity of conidia during long-term storage. Stored conidia were probably affected by dehydration, temperature and other factors such as oxidation, before and during storage, and also by rehydration after storage. The greatest number of conidia and germination percentage resulted from production at 25°C, but greatest bioactivity resulted from those produced at 30°C. No significant effects on bioactivity were detected between the conidium production treatments C : N 5 : 1 and C : N 160 : 1, indicating that C : N ratio in culture medium is not important for conidium survival of <i>T. atroviride</i>.</p></div