Multilocus sequence typing analysis of Italian Xanthomonas campestris pv. campestris strains suggests the evolution of local endemic populations of the pathogen and does not correlate with race distribution

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot in Brassicaceae. It is widespread in Italy and severe outbreaks occur under conditions that favour disease development. In this study a multilocus sequence typing approach (MLST) based on the partial sequence of seven loci was applied to a selection of strains representative of the main areas of cultivation and hosts. The aim was to investigate whether the long tradition of brassica crops in Italy has influenced the evolution of different Xcc populations. All loci were polymorphic; 14 allelic profiles were identified of which 13 were unique to Italian strains. Based on the seven loci, the most common genotype within the Italian Xcc strains (AP1) was also the most representative genotype found in worldwide Xcc strains. This genotype was included in a new clonal complex in addition to three other clonal complexes already identified in Xcc populations. The phylogenetic reconstruction using a concatenated dataset of four conserved protein-coding genes, dnaK, fuyA, gyrB and rpoD, showed that the Italian strains belonged to two genetic groups. Physiological races were also investigated for the first time in Italy. The race structure of Xcc was determined by inoculating eight differential Brassica lines belonging to five species and showed that, in Italy, race 4 is the most widespread, followed by races 1 and 6. No correlation was found between allelic profiles, host of isolation, geographical origin and races, although a prevalent race was identified within the same clonal complex.     

Studies on pesticides based on coumarin. II. Synthesis and antifungal activity of ten 2-alkyl-7, 8-dihydro-3-hydroxynaphtho[1,2-c]chromen-6-ones

A series of 2-alkyl-7, 8-dihydro-3-hydroxynaphtho[1,2-c]chromen-6-ones was synthesised by the condensation of ethyl 3, 4-dihydro-1-oxonaphthalene-2-carboxylate with substituted phenols in the presence of POCl₃. The compounds were characterised and tested for their toxicity towards the mycelial growth of seven phytopathogenic fungi in culture. Drechslera oryzae, Rhizoctonia solani and Colletotrichum falcatum exhibited maximum sensitivity to these compounds whereas Macro-phomina phaseolina, Fusarium solani, Alternaria alternata and Pythium aphanidermatum were less sensitive. 2-Ethyl-7, 8-dihydro-3-hydroxy-naphtho[1,2-c]chromen-6-ones possessed greatest toxicity with EC₅₀ values ranging from 0.2 to 2.5 μg ml^?1 against all fungi except A. alternata and P. aphanidermatum.     

Resistance to foliage-feeding insects in conifers: implications for pest management

The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence.     

Hepatomas in Atlantic tomcod Microgadus tomcod (Walbaum) collected in the Hudson River estuary in New York

Abstract. Incidental observations of Atlantic tomcod during routine laboratory processing revealed that a portion of the adult population collected during the 1977–78 spawning season had enlarged livers containing dark coloured tumours and other abnormalities. Of the total of 264 livers collected between 16 January and 27 February 1978 and grossly examined for prevalence of abnormalities, 25% appeared to contain neoplastic nodules and hepatocellular carcinoma. One liver contained a massive tumour (7 × 12 mm) that involved approximately 60% of the liver. The exact causes of the high prevalence of hepatocellular carcinoma are unknown but poly-chlorinated biphenyls (PCBs) are suspected of having a possible role. The Hudson River is known to contain elevated concentrations of PCBs. Twelve tomcod livers from the 1977–78 spawning population representing both normal and hepatoma conditions contained concentrations of PCBs ranging from 10–9 to 98–2 ppm (mean of 37–5 ppm).     

Interactions of Pratylenchus thornei and Fusarium oxysporum f. sp. ciceris on Chickpea

ABSTRACT Fusarium oxysporum f. sp. ciceris and the root-lesion nematode Pratylenchus thornei coinfect chickpeas in southern Spain. The influence of root infection by P. thornei on the reaction of Fusarium wilt-susceptible (CPS 1 and PV 61) and wilt-resistant (UC 27) chickpea cultivars to F. oxysporum f. sp. ciceris race 5 was investigated under controlled and field conditions. Severity of Fusarium wilt was not modified by coinfection of chickpeas by P. thornei and F. oxysporum f. sp. ciceris, in simultaneous or sequential inoculations with the pathogens. Root infection with five nematodes per cm(3) of soil and 5,000 chlamydospores per g of soil of the fungus resulted in significantly higher numbers of propagules of F. oxysporum f. sp. ciceris with the wilt-susceptible cultivar CPS 1, but not with the wilt-resistant one. However, infection with 10 nematodes per cm(3) of soil significantly increased root infection by F. oxysporum f. sp. ciceris in both cultivars, irrespective of fungal inoculum densities (250 to 2,000 chlamydospores per g of soil). Plant growth was significantly reduced by P. thornei infection on wilt-susceptible and wilt-resistant chickpeas in controlled and field conditions, except when shorter periods of incubation (45 days after inoculation) were used under controlled conditions. Severity of root necrosis was greater in wilt-susceptible and wilt-resistant cultivars when nematodes were present in the root, irrespective of length of incubation time (45 to 90 days), densities of nematodes (5 and 10 nematodes per cm(3) of soil), fungal inocula, and experimental conditions. Nematode reproduction on the wilt-susceptible cultivars, but not on the wilt-resistant one, was significantly increased by F. oxysporum f. sp. ciceris infections under controlled and field conditions.     

Effect of Caffeine Added to the Activating Solution on Sperm Motility of Fresh and Thawed Semen of Pacu,Piaractus mesopotamicus,and Curimba,Prochilodus lineatus

The aim was to evaluate the effect of different concentrations of caffeine added in activating solution over sperm motility in fresh and thawed semen of pacu, Piaractus mesopotamicus, and curimba, Prochilodus lineatus. The activating solutions were prepared with sodium bicarbonate solution of 0.76% (NaHCO₃) and caffeine was added at concentrations of 2.5, 5.0, 10.0, and 20.0 mM. As control, a solution of NaHCO₃ 0.76 without caffeine was used. Eight males of pacu and 20 males of curimba were used. Aliquots of 200 μL of semen were diluted in 800 μL extender solution (DMSO 10% and BTS 5%), placed in 0.5 mL straws and cryopreserved for 7 d in a liquid nitrogen tank. There was a linear increase in sperm motility for fresh semen of pacu, and for curimba fresh and thawed semen (P < 0.05), due to the increase in the concentration of caffeine. There was a quadratic response for duration of motility for thawed semen of pacu and for fresh semen of curimba (P < 0.05), respectively. These results indicate that addition of caffeine in the activator solution can improve sperm motility parameters, however, is dependent on the species and concentration used.     

Top 20 environmental weeds for classical biological control in Europe: a review of opportunities, regulations and other barriers to adoption

Classical biological control remains the only tool available for permanent ecological and economic management of invasive alien species that flourish through absence of their co‐evolved natural enemies. As such, this approach is recognized as a key tool for alien species management by the Convention on Biological Diversity (CBD), the European and Mediterranean Plant Protection Organization (EPPO) and the European Strategy on Invasive Alien Species (ESIAS). Successful classical biological control programmes abound around the world, despite disproportionate attention being given to occasional and predictable non‐target impacts. Despite more than 130 case histories in Europe against insect pests, no exotic classical biological control agent has been released in the EU against an alien invasive weed. This dearth has occurred in the face of increasing numbers of exotic invasive plants being imported and taking over National Parks, forests and amenity areas in this region, as well as a global increase in the use of classical biological control around the world. This paper reviews potential European weed targets for classical biological control from ecological and socioeconomic perspectives using the criteria of historical biological control success, taxonomic isolation from European native flora, likely availability of biological control agents, invasiveness outside Europe and value to primary industry and horticulture (potential for conflicts of interest). We also review why classical biological control of European exotic plants remains untested, considering problems of funding and public perception. Finally, we consider the regulatory framework that surrounds such biological control activities within constituent countries of the EU to suggest how this approach may be adopted in the future for managing invasive exotic weeds in Europe.