The evaluation of rhizomania resistant sugar beet for the UK

Sugar beet rhizomania disease, caused by Beet necrotic yellow vein virus and transmitted by the soil‐borne parasite Polymyxa betae, was first recorded in the UK in 1987. Recently, breeding lines and cultivars with partial resistance to the virus derived from the ‘Holly’ source of resistance have been developed and their suitability for use under UK conditions is explored in this paper. Virus multiplication in the roots of resistant lines exposed to severe disease pressure in glasshouse tests, when quantified by ELISA, was less than one third of that in susceptible controls. More recently developed resistant lines had a lower virus content, on average, largely due to a reduced frequency of susceptible individuals. There was no evidence for resistance to the vector, P. betae, in virus resistant lines. However, the proportion of viruliferous P. betae resting spores in the roots, estimated using the most probable number (MPN) technique, was reduced by at least one third in resistant lines compared with the most susceptible control. A novel line, containing an additional gene to that in ‘Holly’, was the most effective, reducing the infection level to 3% of that in the susceptible control. In two field experiments on severely infested sites, the rate of infection of a resistant line, when assessed by ELISA, was reduced by half compared with a susceptible cultivar and sugar yields of resistant lines were consistently 2–3 times higher than those of susceptible cultivars. In 41 trials on rhizomania‐free sites, several recently introduced resistant lines exhibited sugar yields and agronomic performance comparable to that of three selected high yielding, susceptible cultivars. Results are discussed in relation to the specific UK requirements for rhizomania resistant cultivars. One resistant line, Beta 805 (cv. Concept), fulfilled the requirements for widespread use to control the disease.     

A field cage method for assessing resistance to turnip root fly in brassicas

A field cage method was evaluated as an alternative to field trials for identifying sources of resistance to turnip root fly in brassicas. This involved the controlled release of adult flies and the use of egg traps to quantify egg-laying on potted plants. Overall levels of resistance to Delia floralis, and its components, were assessed for 15 swede genotypes. Significant levels of antixenosis and antibiosis type resistance were identified in several cultivars and breeding lines. There was a close agreement between the field cage results and those from previous field trials, using comparable susceptible and resistance control cultivars. Compared with field selection, the field cage method reduced by c. 40% the time required to quantify resistance and each of its components.     

Fiji disease resistance in sugarcane: Relationship to cultivar preference in field populations of the planthopper vector Perkinsiella saccharicida

Populations of the planthopper vector Perkinsiella saccharicida on sugarcane cultivars resistant (cvs QUO and Q87), moderately resistant (cvs Q90 and Q124) and susceptible (cvs NCo310 and Q102) to Fiji disease with known field resistance scores were monitored on the plant (2000–2001) and ratoon (2001–2002) crops. In both crops, the vector population remained very low, reaching its peak in the autumn. The vector population was significantly higher on cultivars susceptible to Fiji disease than on cultivars moderately resistant and resistant to Fiji disease. The number of P. saccharicida adults, nymphs and oviposition sites per plant increased with the increase in the Fiji disease susceptibility. The results suggest that under low vector density, cultivar preference by the planthopper vector mediates Fiji disease resistance in sugarcane. To obtain resistance ratings in the glasshouse that reflect field resistance, glasshouse‐screening trials should be conducted under both low and high vector densities, and the cultivar preference of the planthopper vector recorded along with Fiji disease incidence.     

Tests for resistance to Aphis fabae in field beans (Viciafaba)

Two lines of Viciafaba were as resistant to Aphis fabae as Rastatt, one of their progenitors, when compared with susceptible control varieties in glasshouse experiments. In short experiments, fewer adult aphids settled on plants of resistant varieties, which subsequently bore smaller total numbers of aphids. In a longer experiment, the aphids multiplied more slowly on the resistant varieties, which survived after susceptible beans had been killed. The bean varieties did not vary in numbers of aphids on the stem or growing point but resistant varieties had markedly smaller proportions of the total on the abaxial surface of the leaves; in particular the smaller veins supported fewer aphids. V. narbonensis was very resistant to A. fabae but was susceptible to Myzus persicae, indicating that its resistance mechanism is distinct from that within V. faba. In infested field trials most of the variation in yield of bean varieties was attributable to the size of A. fabae colonies, and resistant varieties outyielded susceptible varieties. Yields of resistant varieties in the presence of large numbers of aphids were, however, less than those from trials without aphids. In uninfested trials susceptible varieties usually gave the largest yields. The significance of these observations is discussed in relation to policies and methods for breeding for resistance to A. fabae in V. faba.     

Additional sources of resistance to groundnut rosette disease in groundnut germplasm and breeding lines

Groundnut rosette, a virus disease of groundnut (Arachis hypogaea) transmitted by the aphid, Aphis craccivora Koch, reduces yield in susceptible cultivars by 30–100%. Additional sources were sought in germplasm accessions involving 2301 lines from different sources and from 252 advanced breeding lines derived from crosses involving earlier identified sources of resistance to rosette. The lines were evaluated in field screening trials using an infector row technique during 1996 and 1997 growing seasons. Among the germplasm lines, 65 accessions showed high levels of resistance while 134 breeding lines were resistant. All rosette disease resistant lines were susceptible to groundnut rosette assistor virus. This work identified germplasm and breeding lines that will contribute to an integrated management of groundnut rosette disease. These new sources also provide an opportunity to eliminate yield losses due to the rosette disease.     

丛枝菌根真菌与深色有隔内生真菌对姜瘟病的防效及抗病机理初探

【背景】青枯劳尔氏菌(Ralstonia solanacearum,R.S)引发的姜瘟病是生姜产业发展的瓶颈问题。丛枝菌根真菌(arbuscular mycorrhiza fungi, AMF)与深色有隔内生真菌(dark septate endophytes,DSE)是两类重要的共生微生物。【目的】前期研究发现,AMF与DSE可提高生姜对姜瘟病的抗性,但其抗病机制尚不清楚,极大地限制了利用这两类共生真菌对该病的防治。【方法】在温室条件下做盆栽试验,以生姜组培苗为材料,设立接种AMF、DSE和不接种AMF、DSE的对照(CK)处理,并在上述处理下的植物生长4周后淋入病原菌液,病原菌接种1周后,通过测定菌根侵染率、发病率、叶绿素含量、光合指标、磷(P)含量、防御性酶活性及丙二醛(malondialdehyde, MDA)含量,研究AMF和DSE互作对病原菌侵染后生姜生长和生理生化指标的影响。【结果】AMF和DSE分别使姜瘟病发病率降低了45.27%和52.04%(P<0.05)。AMF+DSE组合处理抑病效果更好,发病率较对照降低60.87%(P<0.05)。AMF、DSE及...     

Variation in host susceptibility among and within populations ofPlantago lanceolata L. infected by the fungusPhomopsis subordinaria (Desm.) Trav.

Summary Susceptibility toPhomopsis stalk disease ofPlantago lanceolata genotypes, sampled in three different populations with a variable degree of infection by the fungusPhomopsis subordinaria, was determined under greenhouse conditions. Susceptibility of the host varied within, but not among populations. No relationship between the intensity of the disease in the field and the mean susceptibility of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of different (uncorrelated) plant characteristics. Determining whether host genotypes are highly or slightly susceptible can only be achieved by field trials, where the plants are exposed to the whole set of disease inducing factors. The relevance of host susceptibility to the intensity of disease in the field is discussed in relation to the variation in pathogenicity of the fungus and the variation in environmental factors prevailing inP. lanceolata populations underP. subordinaria pathogen pressure. Grassland Species Research Group Number 123     

Biological control of Sclerotinia disease by Aspergillus sp. on oilseed rape in the field

Sclerotinia sclerotiorum causes serious yield losses to many crops worldwide. Aspergillus sp. Asp-4, previously shown to inhibit germination of sclerotia of S. sclerotiorum in vitro and in the field, was evaluated in field trials for suppression of this pathogen on oilseed rape. Spray application of Asp-4 to the soil prior to sowing rice in a rice–oilseed rape rotation resulted in a significant reduction in incidence of Sclerotinia stem rot on oilseed rape compared with the non-treated control in two field trials. This application of Asp-4 also resulted in a significant reduction in germination of sclerotia relative to the non-treated control in these field trials, suggesting that this reduction in sclerotial germination led to disease control. Microscopic examination demonstrated that Asp-4 could effectively colonise external and internal portions of sclerotia of S. sclerotiorum in vitro. Incubation of Asp-4 with sterile sclerotial material induced production of β-glucanase and chitinase activities by this isolate; β-glucanase and chitinase being potentially capable of degrading the glucan and chitin polymeric components of sclerotia. Incubation of Asp-4 with sterile sclerotial material also resulted in a significant reduction in dry weight of this sclerotial material relative to the non-treated control in 96?h in vitro experiments. Experiments reported here indicate that Aspergillus sp. Asp-4 has promise as a biological control agent for S. sclerotiorum on oilseed rape. Experiments reported here suggest that disease control results from inhibition of germination of sclerotial resting structures due to mycoparasitic colonisation by Asp-4.     

Evaluation of some Iranian wheat elite lines’ reaction to Septoria tritici leaf blotch

Septoria tritici blotch is an important wheat disease in many areas of the world including Iran’s warm, humid regions. In this study, reaction of 79 lines from elite regional wheat yield trials of the Cereal Research Department from four climate zones was evaluated to S. tritici leaf blotch in adult plant stage under an artificial field inoculation in Khuzestan province in the south of Iran for two years (2008–2009 and 2009–2010). Nurseries were artificially inoculated by spreading infected plant debris (from last growing season). Taking notes was performed with a modified Saari and Prescott method in 00–99 double-digit scale. Wheat lines were classified in groups of immune (00), highly resistant (11–14), resistant (15–34), moderately resistant (35–44), moderately susceptible (45–64), susceptible (65–84) and highly susceptible (85–99). Result showed that from 79 lines, 37 lines had susceptible reaction; 2 lines had moderately susceptible; and 40 lines showed immune.     

Relationship between onion thrips (Thrips tabaci) and Stemphylium vesicarium in the development of Stemphylium leaf blight in onion

Stemphylium leaf blight caused by Stemphylium vesicarium and onion thrips (Thrips tabaci) are two common causes of leaf damage in onion production. Onion thrips is known to interact synergistically with pathogens to exacerbate plant disease. However, the potential relationship between onion thrips and Stemphylium leaf blight is unknown. In a series of controlled laboratory and field trials, the relationship between thrips feeding and movement on the development and severity of Stemphylium leaf blight were examined. In laboratory assays, onions (“Avalon” and “Ailsa Craig”) with varying levels of thrips feeding damage were inoculated with S. vesicarium. Pathogen colonisation and leaf dieback were measured after 2 weeks. In pathogen transfer assays, thrips were exposed to S. vesicarium conidia, transferred to onion and leaf disease development was monitored. In field trials, insecticide use was examined as a potential indirect means to reduce Stemphylium leaf blight disease and pathogen colonisation by reducing thrips damage. Results from laboratory trials revealed that a reduction in thrips feeding decreased S. vesicarium colonisation of onion leaves by 2.3–2.9 times, and decreased leaf dieback by 40–50%. Additionally, onion thrips were capable of transferring S. vesicarium conidia to onion plants (albeit at a low frequency of 2–14% of plants inoculated). In field trials, the symptoms and colonisation of Stemphylium leaf blight were reduced by 27 and 17%, respectively with the use of insecticide to control thrips. These results suggest that onion thrips may play a significant role in the development of Stemphylium leaf blight, and thrips control may reduce disease in commercial onion fields.     

Mitigating amphibian chytridiomycosis with bioaugmentation: characteristics of effective probiotics and strategies for their selection and use

Probiotic therapy through bioaugmentation is a feasible disease mitigation strategy based on growing evidence that microbes contribute to host defences of plants and animals. Amphibians are currently threatened by the rapid global spread of the pathogen, Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis. Bioaugmentation of locally occurring protective bacteria on amphibians has mitigated this disease effectively in laboratory trials and one recent field trial. Areas still naïve to Bd provide an opportunity for conservationists to proactively implement probiotic strategies to prevent further amphibian declines. In areas where Bd is endemic, bioaugmentation can facilitate repatriation of susceptible amphibians currently maintained in assurance colonies. Here, we synthesise the current research in amphibian microbial ecology and bioaugmentation to identify characteristics of effective probiotics in relation to their interactions with Bd, their host, other resident microbes and the environment. To target at‐risk species and amphibian communities, we develop sampling strategies and filtering protocols that result in probiotics that inhibit Bd under ecologically relevant conditions and persist on susceptible amphibians. This filtering tool can be used proactively to guide amphibian disease mitigation and can be extended to other taxa threatened by emerging infectious diseases.     

Aromatherapy in the Mediterranean fruit fly (Diptera: Tephritidae): sterile males exposed to ginger root oil in prerelease storage boxes display increased mating competitiveness in field-cage trials

Previous research showed that exposure to ginger root, Zingiber officinale Roscoe, oil increased the mating success of mass-reared, sterile males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This work, however, involved the exposure of small groups of males (n = 25) in small containers (volume 400 ml). Several sterile male release programs use plastic adult rearing containers (so-called PARC boxes; hereafter termed storage boxes; 0.48 by 0.60 by 0.33 m) to hold mature pupae and newly emerged adults before release (approximately = 36,000 flies per box). The objective of the current study was to determine whether the application of ginger root oil to individual storage boxes increases the mating competitiveness of sterile C. capitata males. Irradiated pupae were placed in storage boxes 2 d before adult emergence, and in the initial experiment (adult exposure) ginger root oil was applied 5 d later (i.e., 3 d after peak adult emergence) for 24 h at doses of 0.0625, 0.25, 0.5, 1.0, and 2.0 ml. In a second experiment (pupal-adult exposure), ginger root oil was applied to storage boxes immediately after pupal placement and left for 6 d (i.e., 4 d after peak adult emergence) at doses of 0.25 and 1.0 ml. Using field cages, we conducted mating trials in which ginger root oil-exposed (treated) or nonexposed (control) sterile males competed against wild-like males for copulations with wild-like females. After adult exposure, treated males had significantly higher mating success than control males for all doses of ginger root oil, except 2.0 ml. After pupal-adult exposure, treated males had a significantly higher mating success than control males for the 1.0-ml but not the 0.25-ml dose of ginger root oil. The results suggest that ginger root oil can be used in conjunction with prerelease, storage boxes to increase the effectiveness of sterile insect release programs.     

Repellent activity of essential oils on adults of Halyomorpha halys (Heteroptera: Pentatomidae) in different physiological-behavioural phases

The brown marmorated stink bug Halyomorpha halys is an invasive agricultural pest in North America and Europe, and also a dwelling nuisance in autumn, due to the overwintering adults aggregating inside buildings. The repellent potential of ginger, clove, vetiver and turmeric essential oils (EOs) was tested on H. halys adults of three different physiological-behavioural phases: exiting overwintering (EXOV), active during summer (SUMM) and entering overwintering (ENOV). In a two-choice apparatus, fresh food was used as an attractant in both sides, together with three males when testing ENOV individuals. A filter paper with different concentrations of the EOs was the treatment side, and a filter paper with ethanol acted as control. The position of the individually tested bugs was recorded after 1, 6 and 24 hr. All tested EOs were repellent at concentrations higher than 3%, independent of sex or length of exposure. Turmeric and clove were the most repellent EOs, whereas ginger and vetiver showed on average a medium-to-low repellency. Significant differences emerged among the physiological-behavioural phases, with SUMM individuals showing a greater repellency to many of the tested concentrations, and EXOV individuals being overall the least susceptible to these substances. The response to vetiver oil was ambiguous, as at 25%, it elicited both a strong repellency in SUMM and a strong attraction in EXOV. Turmeric and clove EOs are promising candidates in integrated pest management strategies to reduce attacks by H. halys to susceptible crops especially during summer, as well as to prevent the entrance of overwintering bugs in buildings in autumn.     

Tolerance as a mechanism of resistance to Thrips palmi in common beans

Tolerance as a mechanism of resistance to the melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), in common beans, Phaseolus vulgaris L., was evaluated under field and greenhouse conditions. Seven resistant (Brunca, BH‐5, BH‐60, BH‐130, BH‐144, EMP 486, and FEB 115) and five susceptible (PVA 773, EMP 514, BAT 477, APN 18, and RAZ 136) bean genotypes were assessed according to adult and larval populations, visual damage and reproductive adaptation scores, and yield components in field trials. From these genotypes, four resistant (Brunca, BH‐130, EMP 486, and FEB 115) and two susceptible (APN 18 and RAZ 136) genotypes were selected for quantification of proportional plant weight and height increase changes due to thrips infestation in greenhouse tests. Under medium to high thrips infestation in the field, most resistant genotypes tended to have higher reproductive adaptation and lower yield losses, though they did not always suffer less damage, as compared to susceptible genotypes. In the greenhouse, resistant genotypes showed less reduction in plant dry weight and height increase than did some susceptible ones under the same infestation pressure. Results from both field trials and greenhouse tests suggest the possible expression of tolerance as a mechanism of resistance to T. palmi in the resistant genotype EMP 486, and confirm the existence of antixenosis in FEB 115, whereas tolerance might be combined with other resistance mechanisms in Brunca.     

Integrated biological control of bacterial speck and spot of tomato under field conditions using foliar biological control agents and plant growth-promoting rhizobacteria

Integration of foliar bacterial biological control agents and plant growth promoting rhizobacteria (PGPR) was investigated to determine whether biological control of bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, and bacterial spot of tomato, caused by Xanthomonas campestris pv. vesicatoria and Xanthomonas vesicatoria, could be improved. Three foliar biological control agents and two selected PGPR strains were employed in pairwise combinations. The foliar biological control agents had previously demonstrated moderate control of bacterial speck or bacterial spot when applied as foliar sprays. The PGPR strains were selected in this study based on their capacity to induce resistance against bacterial speck when applied as seed and soil treatments in the greenhouse. Field trials were conducted in Alabama, Florida, and California for evaluation of the efficacy in control of bacterial speck and in Alabama and Florida for control of bacterial spot. The foliar biological control agent P. syringae strain Cit7 was the most effective of the three foliar biological control agents, providing significant suppression of bacterial speck in all field trials and bacterial spot in two out of three field trials. When applied as a seed treatment and soil drench, PGPR strain Pseudomonas fluorescens 89B-61 significantly reduced foliar severity of bacterial speck in the field trial in California and in three of six disease ratings in the field trials in Alabama. PGPR strains 89B-61 and Bacillus pumilus SE34 both provided significant suppression of bacterial spot in the two field trials conducted in Alabama. Combined use of foliar biological control agent Cit7 and PGPR strain 89B-61 provided significant control of bacterial speck and spot of tomato in each trial. In one field trial, control was enhanced significantly with combined biological control agents compared to single agent inoculations. These results suggest that some PGPR strains may induce plant resistance under field conditions, providing effective suppression of bacterial speck and spot of tomato, and that there may be some benefit to the integration of rhizosphere-applied PGPR and foliar-applied biological control agents.     

Evaluation of neem (Azadirachta indica) seed and ginger (Zingiber officinale) as potential control agents of yam (Dioscorea rotundata Poir.) tuber rot fungi

Yam is an important crop which serves as a source of income to small-holder farmers as well as a foreign exchange earner. Among the constraints faced by yam farmers are pests and diseases, especially deterioration caused by microbes during storage. Since over dependence on pesticides is being discouraged, neem seed and ginger extracts were evaluated as potential control agents against rot-causing fungi. The study was conducted in the Spanish laboratory, at the Faculty of Agriculture, University for Development Studies, Nyankpala Campus. Isolations were made from rotted yam tubers sampled from the Tamale Central market with potato dextrose agar (PDA) as the growth medium. Growth inhibition of the isolates was determined by growing pure cultures on PDA plates amended with 2?ml each of ethanol and aqueous extracts of neem seed and ginger as well as carbendazim. A pathogenicity test proved that Aspergillus flavus, A. niger, A. ochraceus and Penicillium digitatum isolated from the rotted tubers were responsible for the rot. A. niger had a significantly higher (p?<?0.05) occurrence (40%) than the others. Growth inhibitions by carbendazim and ethanol extracts of neem seed and ginger were comparable but significantly higher (p?<?0.05) than the aqueous extracts of neem seed and ginger as well as the control. However, the aqueous extracts of neem seed and ginger had a significantly higher (p?<?0.05) inhibition than the control. For instance, growth inhibition of A. niger by carbendazim, ethanol neem seed and ginger extracts were 70.5, 69.6 and 65.5%, respectively, while inhibition by aqueous neem seed and ginger extracts were 33.9 and 24.8%, respectively. Since aqueous extracts of neem seed and ginger significantly inhibited (p?<?0.05) growth of the rot-causing fungi, they can be used as surface protectants of stored tubers.     

The Effect of Ginger (Zingiber officinale) on Platelet Aggregation: A Systematic Literature Review

BackgroundThe potential effect of ginger on platelet aggregation is a widely-cited concern both within the published literature and to clinicians; however, there has been no systematic appraisal of the evidence to date.MethodsUsing the PRISMA guidelines, we systematically reviewed the results of clinical and observational trials regarding the effect of ginger on platelet aggregation in adults compared to either placebo or baseline data. Studies included in this review stipulated the independent variable was a ginger preparation or isolated ginger compound, and used measures of platelet aggregation as the primary outcome.ResultsTen studies were included, comprising eight clinical trials and two observational studies. Of the eight clinical trials, four reported that ginger reduced platelet aggregation, while the remaining four reported no effect. The two observational studies also reported mixed findings.DiscussionMany of the studies appraised for this review had moderate risks of bias. Methodology varied considerably between studies, notably the timeframe studied, dose of ginger used, and the characteristics of subjects recruited (e.g. healthy vs. patients with chronic diseases).ConclusionThe evidence that ginger affects platelet aggregation and coagulation is equivocal and further study is needed to definitively address this question.     

Advances in understanding the mechanism of resistance to anthracnose and induced defence response in tea plants

The tea plant (Camellia sinensis) is susceptible to anthracnose disease that causes considerable crop loss and affects the yield and quality of tea. Multiple Colletotrichum spp. are the causative agents of this disease, which spreads quickly in warm and humid climates. During plant–pathogen interactions, resistant cultivars defend themselves against the hemibiotrophic pathogen by activating defence signalling pathways, whereas the pathogen suppresses plant defences in susceptible varieties. Various fungicides have been used to control this disease on susceptible plants, but these fungicide residues are dangerous to human health and cause fungicide resistance in pathogens. The problem-solving approaches to date are the development of resistant cultivars and ecofriendly biocontrol strategies to achieve sustainable tea cultivation and production. Understanding the infection stages of Colletotrichum, tea plant resistance mechanisms, and induced plant defence against Colletotrichum is essential to support sustainable disease management practices in the field. This review therefore summarizes the current knowledge of the identified causative agent of tea plant anthracnose, the infection strategies and pathogenicity of C. gloeosporioides, anthracnose disease resistance mechanisms, and the caffeine-induced defence response against Colletotrichum infection. The information reported in this review will advance our understanding of host–pathogen interactions and eventually help us to develop new disease control strategies.