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Evidence is presented that a number of mechanisms are involved in the resistance of commercial cultivars of potato to soft rottingErwinia spp. These include phytoalexins, phenolics, cell wall modification, and possibly proteins. The role of elicitor-active oligogalacturonides, which are released from plant cell walls by pectic enzymes, is discussed.  相似文献   
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A phytotoxic protein that evokes the typical symptoms of Verticillium wilt disease in seedlings of Gossypium hirsutum L. (Upland cotton) was isolated from culture filtrates of Verticillium dahliae. The protein was purified by ammonium sulfate precipitation, Sephadex-G100 fractionation, and native PAGE. The 18.5 kDa protein, designated VD18.5, appears to be a single subunit protein with an isoelectric point between 3 and 5. VD18.5 induces symptoms of leaf dehydration, chlorosis, necrosis and stem discoloration in seedlings of the disease susceptible cotton cultivar Siokra 1–4. The LD50 of VD18.5 on protoplasts of Siokra 1–4 was 18 μg mL−1. VD18.5 had no noticeable effect on Pima S-7, which is a disease resistant cultivar. Phytotoxic activity was partially destroyed at high temperature and was abolished by digestion with proteinase K. Mass spectrometry fingerprinting and protein sequence data from VD18.5 yielded no significant matches when submitted to the Mascot search engine and NCBI non-redundant protein databases, respectively. These results suggest that VD18.5 is a novel protein that may be involved in the development of some of the symptoms associated with Verticillium wilt disease in the cotton plant.  相似文献   
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The plant pathogenic fungus Corynespora cassiicola causes a severe leaf spot disease on more than 70 host plant species including Hevea brasiliensis . Genetic variability in 32 isolates of C. cassiicola collected from diverse hosts and locations in Sri Lanka and Australia was assessed using restriction fragment length polymorphism (RFLP) analysis of the internal transcribed spacer (ITS) region of ribosomal DNA and random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) analysis of total fungal DNA. Amplified ITS fragments from all 32 C. cassiicola isolates exhibited an identical size, and restriction analysis with seven different restriction endonucleases revealed identity in all of the detected DNA fragments. This finding of high genetic relatedness was further supported by the cloning and DNA sequencing of the ITS2 region from one Sri Lankan and one Australian isolate. However, RAPD-PCR profiles generated by 15 oligonucleotide decamer primers revealed significant polymorphism between groups of organisms. Genetic relationships among the isolates were determined by cluster analysis of the RAPD-PCR data and seven different RAPD groups were identified. Isolates showed strong correlations between the assigned RAPD group and the location and host plant genotype from which the isolate was collected. Correlations were also observed between the RAPD group, growth of the isolate and pathogenicity on different plant hosts.  相似文献   
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A puppy was evaluated for rapid growth and large stature. Extensive diagnostic evaluation suggested a growth hormone independent disorder. As the sole detected abnormality was elevated leptin concentration, an obesity syndrome causing leptin resistance was speculated to explain the puppy's condition but was not confirmed. Except for large body size, the puppy remained clinically normal.  相似文献   
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Two hundred feral cats from the inner suburbs of Sydney were examined post mortem for adult Dirofilaria immitis and circulating microfilariae, and 101 of these cats were tested for heartworm antigens by an ELISA. Only 2 cats (1%) had adult heartworms, the blood sample from another cat contained a single microfilaria. The blood of a further three cats contained small amounts of D immitis antigen. Although D immitis occurs in cats in Sydney, the prevalence is not high enough to warrant prophylactic treatment.  相似文献   
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