Spring frost and decay fungi are implicated in suppressing aspen re-growth following partial cleaning in juvenile stands

? Aspen (Populus tremuloides Michx.) regenerates at high densities following manual cleaning.

? Ten-year-old stands located near Lac La Biche and Peace River, Alberta were manually cleaned to three densities (0, 500 or 1 500 stems ha^?1) at three times (bud set, dormancy or bud flush) to test the hypothesis that maintaining residual aspen reduces regeneration.

? At Lac La Biche up to 98% of the aspen regeneration died in the partially-cleaned plots compared to 67% at Peace River five years post-treatment. A spring frost in the second growing season at Lac La Biche is hypothesized to be the inciting factor predisposing the stump sprouts to infection by decay fungi such as Armillaria root rot, resulting in reduced density and height of the aspen regeneration at Lac La Biche relative to Peace River. Drought and ungulate herbivory provided additional stresses. The high mortality of aspen regeneration at Lac La Biche shifted the understory regeneration from aspen to balsam poplar (Populus balsamifera L.).

? These results indicate that maintaining 1 500 stems ha^?1 of residual aspen will not effectively control the re-sprouting of aspen; however, the vulnerability of aspen regeneration to spring frost and other stressors can nearly eradicate the re-growth of aspen.

     

The type III effector PthG of <Emphasis Type="Italic">Pantoea agglomerans</Emphasis> pv. <Emphasis Type="Italic">gypsophilae</Emphasis> modifies host plant responses to auxin,cytokinin and light

Pantoea agglomerans pvs. gypsophilae and betae are related gall-forming bacteria. While P. agglomerans pv. beta initiates gall formation on both beet and gypsophila, the gypsophila pathovar causes gall formation only on gypsophila. PthG is a type III effector determining host range of these pathogens, initiating the hypersensitivity response in beet, but is a virulence factor in gypsophila. The role of PthG and its mode of action in pathogenicity remain unclear. Transgenic Nicotiana tabacum plants expressing pthG were created. PthG over-expression was often lethal, and surviving pthG-bearing lines showed morphological and developmental abnormalities such as leaf deformation and abnormal vascular branching, dwarf stature, loss of apical dominance, seedling apical meristem loss, rapid germination, reduced fertility, plants which cease growth for several weeks later producing a new lateral shoot, and loss of endophyte resistance (bearing unusual saprophyte populations). Some transformants required light for seed germination and showed rapid seedling greening. In in vitro assays PthG expression modified responses to auxin and cytokinin, inhibiting root and shoot production but not callus formation. In vitro differentiation responses to light were modified by PthG expression. This effector may interfere in the plant auxin signalling pathways resulting in higher observed auxin and ethylene levels, and subsequent blockage of root and shoot development. Apparently PthG tunes the host response to high hormone levels, changing the developmental response. Since shoot and root development are delayed, we hypothesize that callus/gall formation is supported by this activity. However, interference by PthG with hormone and light signalling does not explain all the responses observed in pthG-bearing lines.     

Fusarium graminearum as a dry rot pathogen of potato in the USA: prevalence,comparison of host isolate aggressiveness and factors affecting aetiology

A 2004–2005 survey of potatoes from stores in the north‐central potato‐producing region of the USA showed that the predominant causes of dry rot were Fusarium graminearum and Fusarium sambucinum. Isolates of F. graminearum originally isolated from potato tubers with dry rot (n = 15), wheat kernels with scab (n = 15), and sugarbeet tap roots with decay (n = 5) were tested for aggressiveness to potato tubers. There were no significant differences in aggressiveness among isolates of F. graminearum, regardless of original host, as measured by their ability to cause dry rot. These findings may have implications for survival of F. graminearum inoculum since potatoes, wheat and sugarbeets are frequently used in crop rotation in the region. Fusarium graminearum required larger wounds for infection of potato tubers than F. sambucinum. Plug‐removal injury, simulating a stolon‐removal injury, resulted in equal incidence of dry rot caused by the two Fusarium species, whereas abrasion and bruising injury were sufficient for infection and dry rot development by F. sambucinum, but not F. graminearum. A change in harvest practices from vine‐killing prior to harvest to mechanical vine‐killing on the day of harvest may be a factor affecting the onset of dry rot caused by F. graminearum, since this process often causes large wounds at the stem end of the tubers when the stolon is forcibly removed.     

Secondary Nothofagus dombeyi forests: site index curves and dominant height in the Coastal Range of south-central Chile

Nothofagus dombeyi is distributed on very diverse sites in the temperate forests of Chile and Argentina. In Chile, studies on its dynamics and productivity in forests, where it is the dominant species, have been carried out mainly in the foothills of the Andes, but the productivity and growth of these forests in the Coastal Range are almost unknown. The objective of this study was to evaluate the construction of a single dominant height/age growth model for two homogeneous edaphoclimatic zones (ZEH 2 and 5) previously defined for this species in the Coastal Range of south­central Chile. The results showed that the Chapman-Richards model was the best candidate function, in terms of goodness of fit and predictive capabilities. Using this function, specific parameters (a, b and c) were obtained for each zone, from which site models were constructed by the Algebraic Difference Approach method for a base age of 35 years. This model is intended to contribute to better estimations of site productivity for N. dombeyi forests in the Coastal Range of south-central Chile, and thus facilitate private and public decisions regarding their management.     

Microwave-Enhanced Advanced Oxidation Treatment of Lipids and Food Wastes

Fats, oils, and grease (FOG) and source separated organics (SSO) were treated with the microwave-enhanced advanced oxidation process (MW-AOP) at 90 and 110 °C, with varying amounts of hydrogen peroxide dosages. The treatment efficiency, in terms of soluble substrates and volatile fatty acids (VFA), increased with an increase in both temperature hydrogen peroxide dosages. Fatty acids and compounds with carbonyl group and/or hydroxyl group in both initial and treated FOG samples were identified by gas chromatography-mass spectrometry. MW-AOP treatment temperatures and hydrogen peroxide dosages dictated the formation of degradation products. The degradation followed peroxidation mechanism to produce lower molecular weight substrates such as short chain fatty acids which would be less inhibitory to microbes. After the MW-AOP treatment, both SSO and FOG comprised of more soluble and low molecular weight compounds. These compounds included VFA and nutrients that would be readily available for bacterial or plant uptake.     

Assessment of Mobile Phone Usage Among Farmers in Keana Local Government Area of Nasarawa State,Nigeria

This study assessed the usage of mobile phones among farmers in the Keana Local Government Area of Nasarawa State, Nigeria. One hundred and fifty-eight respondents were selected using purposive and random sampling techniques. Primary data were used, and collected using a structured questionnaire. Research revealed that a majority of the respondents (60.1%) had a medium level of use of mobile phones. The mobile phone network preferred by respondents was MTN (32.3%). The major factor affecting the use of mobile phones is poor network coverage (22.1%). Possession of formal education, income, and sex of the respondents significantly affected their level of use of mobile phones. It is therefore recommended that network providers be supervised by the Government to ensure quality service delivery, and other network providers encouraged to improve on their services.     

Development and evaluation of a standard area diagram set for the severity of phomopsis leaf blight on eggplant

A standard area diagram set (SADs) with eight severity values ranging from 0.5 to 32% was evaluated as a tool to improve the accuracy of the estimates of Phomopsis leaf blight severity on eggplant by ten inexperienced raters. A first assessment in a 50-leaf dataset of digital images was performed unaided (UN, no SAD). Two further aided (A) assessments, conducted two (A1) and four weeks after the first (A2) unaided one were performed. The precision of the estimates, as indicated by the Pearson’s correlation coefficient (r), improved significantly when using the aid (A1: r = 0.96 and A2: r = 0.96) compared to unaided (UN: r = 0.79). However, the generalized bias (C _b) was not significantly affected because the unaided estimates were already quite accurate (C _b = 0.93). The overall concordance (ρ _c) was significantly improved due to the large gains in precision when using the SADs. The raters’ estimates were more uniform (ρ _c > 0.9) when using the aid, with progressive gains in the reliability of the estimates among them, indicated by the concordance correlation coefficient statistics. The SADs proposed in this study will be useful in severity estimation during field work involving multiple raters, especially as use of the SADs results in less variable estimates, improving accuracy and reliability among raters.     

Cover Image,Volume 73, Issue 1

The cover image, by Oscar Fernando Santos‐Amaya et al., is based on the Research Article Fitness costs and stability of Cry1Fa resistance in Brazilian populations of Spodoptera frugiperda, DOI: 10.1002/ps.4312 . Photo Credit: Dr. Oscar Santos‐Amaya.