Cadmium in New Zealand pasture soils: toxicity to <i>Rhizobia</i> and white clover

<p>A survey of 26 pastures was conducted and soil and plant material analysed for total cadmium (Cd) and phosphorus (P), and soils further analysed for a variety of edaphic properties. Background Cd in pasture soils ranged from 0.06–0.85 mg Cd kg⁻¹ soil (mean of 0.23) and correlated closely with total P (<i>R</i>² = 65.5; <i>P</i> < 0.001), while weaker relationships with Olsen P, nitrate-N and calcium were evident. Cadmium in the pasture dry matter had no correlation to underlying soil total Cd (<i>P</i> = 0.113) or soil P (<i>P</i> = 0.75). Strains of <i>Rhizobium</i> spp. were isolated from a reference soil high in Cd (Morrinsville; 1.34 mg Cd kg⁻¹ soil) and a mid-range Cd soil (Whataroa; 0.32 mg Cd kg⁻¹ soil). The IC₅₀ of these strains, along with the commercial inoculant for white clover (<i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> TA1), to Cd were tested using a respiration sensitive assay (MicroResp). Rhizobia from the Whataroa soil had significantly greater tolerance to Cd than those from Morrinsville soil (<i>P</i> = 0.008). We propose a general stress-tolerance mechanism has evolved in the rhizobia from Whataroa, conferring metal co-tolerance. The Cd IC₅₀ of <i>Rhizobium</i> TA1 was 3.06 ppm, but levels of respiration inhibition were evident at lower concentrations. Given the importance of the legume:rhizobia symbiosis to New Zealand's pastoral sector, determination of ‘no observable effect concentrations' is required for <i>Rhizobium</i> spp., pasture legumes and, most importantly, the establishment and function of symbiosis (nodulation and N₂ fixation, respectively).</p

Comparative Genomics of Korean Infectious Bronchitis Viruses (IBVs) and an Animal Model to Evaluate Pathogenicity of IBVs to the Reproductive Organs

The K-I and nephropathogenic K-II genotypes of infectious bronchitis virus (IBV) have been isolated since 1995 and 1990, respectively, in Korea and commercial inactivated oil-emulsion vaccines containing KM91 (K-II type) and Massachusetts 41 strains have been used in the field. To date, genomic analyses of Korean IBV strains and animal models to test the pathogenicity of Korean IBVs to the reproductive organs have been rare. In the present study, comparative genomics of SNU8067 (K-I type) and KM91 IBVs was performed, and an animal model to test the pathogenicity of SNU8067 was established and applied to vaccine efficacy test. The genome sizes of SNU8067 (27,708 nt) and KM91 (27,626 nt) were slightly different and the nucleotide and amino acid identities of the S1 (79%, 77%), 3a (65%, 52%), and 3b (81%, 72%) genes were lower than those of other genes (94%–97%, 92%–98%). A recombination analysis revealed that SNU8067 was a recombinant virus with a KM91-like backbone except S1, 3a, and 3b genes which might be from an unknown virus. An SNU8067 infection inhibited formation of hierarchal ovarian follicles (80%) and oviduct maturation (50%) in the control group, whereas 70% of vaccinated chickens were protected from lesions