Clubroot disease in Latin America: distribution and management strategies

Clubroot caused by Plasmodiophora brassicae is an important disease of cruciferous crops worldwide. In Latin America (from Mexico to Chile, including the Caribbean), most of the area in cruciferous crops is devoted to oilseed rape (Brassica napus; c. 230 600 ha) in Brazil, Chile, Paraguay, Uruguay and Argentina, while cruciferous vegetables such as cabbage, cauliflower, broccoli and Brussels sprouts (40 900 ha) are cropped intensively on small acreages across the region. Although clubroot is present in most Latin American countries, there have been very few studies of P. brassicae. Clubroot research in Latin America has focused mainly on adapting disease management strategies developed in temperate climates to tropical climates, including liming, biological control and genetic resistance. This review summarizes the management strategies used in Latin America to reduce the impact of clubroot, including novel strategies when compared with temperate regions, such as a crop rotation with aromatic plant species and the use of biological control with Trichoderma spp. Latin America has unique characteristics relative to temperate countries such as high humidity, warm temperatures and acidic soil that impact the interaction between P. brassicae and its plant hosts, so more research is required.     

Incidence of lymphoma in a captive-bred colony of hamadryas baboons (Papio hamadryas)

Objective   To assess the incidence of lymphoma and wasting-related deaths in the National Baboon Colony of Australia and relate it to the presence of simian T-cell lymphotrophic virus 1 (STLV-1) infection.
Design and procedure   The records of all animals that had died since establishment of the National Baboon Colony in Australia were reviewed retrospectively. The clinical signs and histopathological findings were recorded and assessed to determine the involvement of lymphoma in the deaths. The presence of STLV-1 was recorded if known and correlated with the STLV-1 status of the colony.
Results   Of the deaths from disease or illness, 53% were diagnosed as or suspected to be lymphoma, occurring in mature animals with no sex predisposition. The most common presentation was rapidly occurring generalised lymphadenomegaly.
Conclusions   This study has described a relatively high prevalence of lymphoma in a colony of captive-bred baboons, and it is evident that STLV-1 may play a role in the disease. Management practices in baboon colonies need to take into account the possible presence of STLV-1 and aim to reduce the transmission of the virus by preventing sexual contact between positive and negative animals. Lymphoma needs to be considered as one of the more common causes of wasting and death.     

Toxicity in three dogs from accidental oral administration of a topical endectocide containing moxidectin and imidacloprid

Three dogs were presented with a history of oral administration of a topical endectocide containing imidacloprid and moxidectin. They were diagnosed with imidacloprid and moxidectin intoxication, having ingested doses ranging from 7.5 to 1.4 mg/kg of imidacloprid and 1.9 to 2.8 mg/kg of moxidectin. The three dogs were affected to different degrees of severity, but all displayed signs of ataxia, generalised muscle tremors, paresis, hypersalivation and disorientation. Temporary blindness occurred in two cases. The three dogs were tested for the presence of the multi-drug resistance 1 gene deletion, which can cause an increased sensitivity to the toxic effects of moxidectin, and were found to be negative. Treatment included gastrointestinal decontamination, intravenous fluid therapy and benzodiazepines to control muscle tremors. All three dogs made a complete recovery within 48 h of ingestion.     

Studies into primary and secondary infection processes by Plasmodiophora brassicae on canola

The early stages of infection of canola roots by the clubroot pathogen Plasmodiophora brassicae were investigated. Inoculation with 1 × 10⁵ resting spores mL^?1 resulted in primary (root hair) infection at 12 h after inoculation (hai). Secondary (cortical) infection began to be observed at 72 hai. When inoculated onto plants at a concentration of 1 × 10⁴ mL^?1, secondary zoospores produced primary infections similar to those obtained with resting spores at a concentration of 1 × 10⁵ mL^?1. Secondary zoospores caused secondary infections earlier than resting spores. When the plants were inoculated with 1 × 10⁷ resting spores mL^?1, 2 days after being challenged with 1 × 10⁴ or 1 × 10⁵ resting spores mL^?1, secondary infections were observed on the very next day, which was earlier than the secondary infections resulting from inoculation with 1 × 10⁷ resting spores mL^?1 alone and more severe than those produced by inoculation with 1 × 10⁴ or 1 × 10⁵ resting spores mL^?1 alone. Compared with the single inoculations, secondary infections on plants that had received both inoculations remained at higher levels throughout a 7‐day time course. These data indicate that primary zoospores can directly cause secondary infection when the host is under primary infection, helping to understand the relationship and relative importance of the two infection stages of P. brassicae.     

Induction of Embryogenic Callus in Gossypium barbadense L. and Gossypium hirsutum L. by Hormone Treatments

The aim of this study was to induce embryogenic callus from various cultivars of cotton in tissue culture, so that a stable and efficient regeneration system could be developed to produce new cotton varieties for cultivation in Xinjiang. The explant materials were hypocotyls of the main cotton cultivars grown in Xinjiang, i. e. Xinhai 25, Xinhai 16, Xinluzao 39, and Xinluzao 42. We tested the effects of different combinations of two hormones (kinetin, KT; 2,4-dichlorophenoxyacetic acid, 2,4-D) on induction of callus from these explants. Calli were produced by the explants under four different combinations of hormones in the media. The optimal hormone combination to induce callus from Gossypium hirsutum explants was 0.1 mg·L^-1 KT + 0.05 mg·L^-1 2,4-D, while that to induce callus from Gossypium barbadense explants was 0.1 mg·L^-1 KT + 0.1 mg·L^-1 2,4-D. Hormone-free medium and medium containing double to the normal concentration of KNO₃ promoted the emergence of embryogenic callus. Filter paper placed under the medium promoted somatic embryo growth and regeneration of the root system. The differentiation and embryogenesis processes occurred more rapidly in G. hirsutum explants than those in G. barbadense explants. Using this protocol, normal plantlets of these cotton cultivars with strong roots were produced within 10 to 12 months. These methods could be used to increase the number of cotton genotypes that can be regenerated in tissue culture.     

Pathogenic diversity of Didymella rabiei isolates from southern Alberta,Canada

Journal of Plant Diseases and Protection - Sixty-three isolates of Didymella rabiei collected from southern Alberta were analyzed for pathogenic variability using six differential chickpea...     

浅谈察哈尔右翼前旗生态旅游发展

文章在分析察哈尔右翼前旗生态环境的基础上,就生态旅游建设的必要性和总体构想进行了探讨,并提出了相应的项目规划。     

Genetic variation in Fusarium avenaceum causing root rot on field pea

Isolates of Fusarium spp. were recovered from the roots of field pea (Pisum sativum) collected from 15 commercial fields in Alberta, Canada. Most of the isolates (75 out of 96) were identified as F. avenaceum, based on morphology, phylogeny and species‐specific PCR amplification. Molecular differences in the F. avenaceum isolates were detected based on putative mating type, and on ITS and CPN60 sequences. MAT‐1 and MAT‐2 were equally distributed among the isolates. Phylogenetic analysis based on ITS and CPN60 sequences clustered most of the F. avenaceum isolates into a single group. In some cases, isolates with low aggressiveness clustered together in additional groups. There was no correlation between phylogenetic profile and either mating type or geographic origin. This population of F. avenaceum has a low level of genetic variation and consists of isolates derived from the two mating types. Isolates with low aggressiveness are also retained in the population.