Isolation of nucleotide binding site-leucine rich repeat and kinase resistance gene analogues from sugarcane (Saccharum spp.)

BACKGROUND: Resistance gene analogues (RGAs) have been isolated from many crops and offer potential in breeding for disease resistance through marker-assisted selection, either as closely linked or as perfect markers. Many R-gene sequences contain kinase domains, and indeed kinase genes have been reported as being proximal to R-genes, making kinase analogues an additionally promising target. The first step towards utilizing RGAs as markers for disease resistance is isolation and characterization of the sequences. RESULTS: Sugarcane clone US01-1158 was identified as resistant to yellow leaf caused by the sugarcane yellow leaf virus (SCYLV) and moderately resistant to rust caused by Puccinia melanocephala Sydow & Sydow. Degenerate primers that had previously proved useful for isolating RGAs and kinase analogues in wheat and soybean were used to amplify DNA from sugarcane (Saccharum spp.) clone US-01-1158. Sequences generated from 1512 positive clones were assembled into 134 contigs of between two and 105 sequences. Comparison of the contig consensuses with the NCBI sequence database using BLASTx showed that 20 had sequence homology to nuclear binding site and leucine rich repeat (NBS-LRR) RGAs, and eight to kinase genes. Alignment of the deduced amino acid sequences with similar sequences from the NCBI database allowed the identification of several conserved domains. The alignment and resulting phenetic tree showed that many of the sequences had greater similarity to sequences from other species than to one another. CONCLUSION: The use of degenerate primers is a useful method for isolating novel sugarcane RGA and kinase gene analogues. Further studies are needed to evaluate the role of these genes in disease resistance.     

Fungicide seed treatment efficacy against Microdochium nivale and M. majus in vitro and in vivo

BACKGROUND: Seed-borne Microdochium majus (Wollenweber) and M. nivale Fries are the primary pathogens responsible for Fusarium seedling blight in the UK. The two species show differences in pathogenicity, host preference and sensitivities to temperature, but their relative sensitivities to fungicide seed treatments are unknown. The aim was firstly to determine the efficacy of fungicide seed treatments towards single-spore isolates of M. majus and M. nivale using in vitro experiments, and subsequently to determine efficacy in vivo over a range of temperatures. RESULTS: Differences in EC(50) values between all seed treatments were evident from the in vitro experiments and ranged from 0.028 mg L(-1) for fludioxonil to 22.8 mg L(-1) for carboxin + thiram. The two seed treatments that showed best performance in vitro were used to examine efficacy towards seed-borne infection in vivo at 4, 8, 12 and 16 degrees C. Generally, seedling emergence improved and the severity of stem-base disease symptoms on emerged seedlings was reduced for both species through the use of the fungicides. The combination of fludioxonil + difenconazole showed improved performance compared with fludioxonil alone. Significantly less severe symptoms were observed through the use of fludioxonil and fludioxonil + difenconazole compared with bitertanol + fuberidazole at 12 degrees C and for all except one M. nivale infected seed lot at 8 degrees C. CONCLUSIONS: Differences in fungicide sensitivity between the two species in vitro were not evident in vivo. This is the first report of the effect of fungicide seed treatments on the control of seedling blight caused by M. majus and M. nivale.     

Cross-resistance between a Bacillus thuringiensis Cry toxin and non-Bt insecticides in the diamondback moth

BACKGROUND: Bacillus thuringiensis Berliner (Bt) crystal (Cry) toxins are expressed in various transgenic crops and are also used as sprays in integrated pest management and organic agricultural systems. The diamondback moth (Plutella xylostella L.) is a major worldwide pest of crucifer crops and one that has readily acquired field resistance to a broad range of insecticides.RESULTS: Selection of a subpopulation of the P. xylostella SERD4 population with the pyrethroid deltamethrin increased resistance to both deltamethrin and Cry1Ac relative to an unselected subpopulation. Selection of a second subpopulation with the Bt toxin Cry1Ac also increased resistance to both Cry1Ac and deltamethrin. A complementation test between the Cry1Ac-selected and deltamethrin-selected subpopulations suggested the presence of a common genetic locus or loci that control resistance to both insecticides. A piperonyl butoxide analogue with potent inhibitory activity against insect esterases significantly increased the toxicity of Cry1Ac and deltamethrin against the respective resistant subpopulations, but showed no such synergism with the unselected subpopulation of SERD4.CONCLUSION: Selection of one resistance phenotype resulted in the simultaneous selection of the other. This phenomenon could be due to a single mechanism acting against both classes of insecticide or to genetically linked, but separate, mechanisms.     

Integration of albedo effects caused by land use change into the climate balance: Should we still account in greenhouse gas units?

Due to impacts of albedo on climate change, benefits of afforestation/reforestation regimes are under debate. In this paper we investigate how to incorporate albedo changes in a carbon accounting tool to show the net effect of land use change on the climate. Using a study area in southern Europe, albedo and carbon sequestration modelling results are linked to determine the combined radiative forcing balance. The results show that under specific circumstances afforestation/reforestation measures may not automatically have positive impacts in a global warming context because the cooling effect of most of the carbon sequestered is neutralized by the warming effect of albedo changes. However, sensitivity analyses lead to the conclusion that improved albedo data from satellite images (MODIS) could influence and enhance outputs significantly. The paper points out that accounting based exclusively on GHG units does not, in the case of land use change, reflect the entire picture. It is highly recommended that in future global warming impacts of land use systems and biogenic products (e.g. solid biomass, liquid biofuels) should be studied using life cycle assessments (LCA) and should include these additional—non-GHG effects—on climate change.     

Carbon gain and bud physiology in Populus tremuloides and Betula papyrifera grown under long-term exposure to elevated concentrations of CO2 and O3

Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO(2) ([CO(2)]) or O(3) ([O(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. The trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwintering buds and early leaf development during the 8th-9th year of free-air CO(2) and O(3) exposure at the Aspen FACE site located near Rhinelander, WI. Net photosynthesis was enhanced 49-73% by elevated [CO(2)], and decreased 13-30% by elevated [O(3)]. Elevated [CO(2)] delayed, and elevated [O(3)] tended to accelerate, leaf abscission in autumn. Elevated [CO(2)] increased the ratio of monosaccharides to di- and oligosaccharides in aspen buds, which may indicate a lag in cold acclimation. The total carbon concentration in overwintering buds was unaffected by the treatments, although elevated [O(3)] decreased the amount of starch by 16% in birch buds, and reduced the size of aspen buds, which may be related to the delayed leaf development in aspen during the spring. Elevated [CO(2)] generally ameliorated the effects of elevated [O(3)]. Our results show that both elevated [CO(2)] and elevated [O(3)] have the potential to alter carbon metabolism of overwintering buds. These changes may cause carry-over effects during the next growing season.     

Corn protein has greater concentrations of digestible amino acids and energy than low-oil corn distillers dried grains with solubles when fed to pigs but does not affect the growth performance of weanling pigs

Three experiments were conducted to test the hypothesis that standardized ileal digestibility (SID) of amino acids (AA) and digestible energy (DE) and metabolizable energy (ME) in a new source of corn protein are greater than in corn distillers dried grains with solubles (DDGS) and that corn protein may be included in diets for weanling pigs. In experiment 1, the SID of AA was determined in two sources of DDGS (DDGS-1 and DDGS-2) and in corn protein. Results indicated that SID of most AA was greater (P < 0.05) in DDGS-2 and corn protein than in DDGS-1, but corn protein contained more digestible AA than both sources of DDGS. In experiment 2, the DE and ME in corn, the two sources of DDGS, and corn protein were determined. Results demonstrated that DE (dry matter basis) in corn protein was greater (P < 0.05) than in corn, but ME (dry matter basis) was not different between corn and corn protein. However, DE and ME in corn (dry matter basis) were greater (P < 0.05) than in DDGS-1 and DDGS-2. In experiment 3, 160 weanling pigs were allotted to four treatments in phases 1 and 2 and a common diet in phase 3. Corn protein was included at 5% to 10% in phases 1 and 2 at the expense of plasma protein and enzyme-treated soybean meal. Results indicated that although differences in average daily gain and gain to feed ratio were observed in phase 1, no differences among treatments were observed for the overall experimental period. In conclusion, the concentration of digestible AA is greater in corn protein than in DDGS; DE and ME in corn protein are also greater than in DDGS; and up to 10% corn protein may be included in phase 1 and phase 2 diets for weanling pigs.     

水稻抗稻瘟病菌防卫反应的细胞学分析与防卫基因表达

对水稻类病变坏死突变体 lmm1　(LmmKaty)与原亲本及双单倍体YT14和YT16接种稻瘟病菌24 h内的抗病反应、细胞学和分子作用机理进行了研究。人工接种实验表明,与原亲本相比,该突变体对稻瘟病菌具有更强的抗性。突变体接种20~24 h后,自动荧光检测到细胞死亡,而对照则未检测到。表明该突变体通过细胞程序性死亡阻止稻瘟病菌的蔓延,从而提高了抗病性。Northern blotting结果发现,抗病品系YT14中的防卫相关基因、苯丙氨酸解氨酶基因和β 葡聚糖酶基因在人工接种稻瘟病菌6 h后开始表达,16~24 h后上述基因表达量快速增加;而病程相关蛋白基因 PR 1和几丁质酶基因在人工接种稻瘟病菌24 h后才开始表达。与YT14相比,感病品系中上述基因的表达明显延迟。表明在人工接种稻瘟病菌24 h内水稻可启动抗病防卫反应,从而对稻瘟病菌产生抗性。     

Genetic Variability in the Potato Pathogen Colletotrichum coccodes as Determined by Amplified Fragment Length Polymorphism and Vegetative Compatibility Group Analyses

ABSTRACT Amplified fragment length polymorphism (AFLP) using three primer sets was used to characterize 211 Colletotrichum coccodes isolates from North America, 112 of which were assigned to six vegetative compatibility groups (VCGs) using nitrate nonutilizing (nit) mutants. These isolates clustered into five corresponding groups by unweighted pairgroup method with arithmetic means-based cluster analysis of AFLP banding patterns. Isolates of C. coccodes belonging to NA-VCG1 and NA-VCG3 were closely related, as were isolates belonging to NA-VCG2 and NA-VCG5. Based on bootstrap analysis of AFLP data, the two isolates originally assigned to NA-VCG4 clustered with isolates belonging to NA-VCG2 and NA-VCG5. C. coccodes isolates that clustered with two isolates belonging to NA-VCG6 were the most diverged from other groups, including seven isolates collected from hosts other than potato. As opposed to the bootstrap analysis, a quadratic discriminant analysis (QDA) of AFLP data correctly categorized the two isolates of NA-VCG4. Furthermore, in isolates where VCG determinations had been made, this model correctly classified isolates of all VCGs. QDA classifications were identical to those made by the bootstrap analysis, with the exception of VCG4. Overall, classifications made by the QDA model were strongly correlated (r = 0.970, P < 0.001) to the VCGs assigned by traditional methods. All 99 C. coccodes isolates evaluated only by AFLP also were subjected to QDA, leading to the assignment of a presumptive VCG for each isolate. No isolates of VCG4 or VCG6 were identified by QDA within this population. Symptoms of black dot developed in plants inoculated with isolates collected from both potato and non-potato hosts. However, total yield was not significantly reduced by infection with non-potato isolates. The lack of any additional groups identified by AFLP analysis may be an indicator of a limited level of genetic variation among North American C. coccodes isolates. AFLP is a much more efficient technique for subspecific characterization in C. coccodes than VCG analysis utilizing nit mutants and will provide an effective means by which the population biology of this pathogen can be further investigated worldwide.     

Identification of novel serpin isoforms and serpin polymorphisms among Australian wheat cultivars

Serpins constitute a large family of related proteins, the majority of which are serine protease inhibitors (from which their name is derived). They are known to be abundantly and polymorphically expressed in individual wheat cultivars. However, to date there lacks a detailed investigation into their inter-genotypic polymorphisms in larger wheat collections. In this study, a systematic proteomic approach, combining native polyacrylamide gel electrophoresis (PAGE), SDS-PAGE, two-dimensional gel electrophoresis, tandem mass spectrometry (MS/MS) and immunoblotting, was taken to characterize serpin polymorphisms among 177 Australian and 19 foreign hexaploid as well as 6 tetraploid wheat varieties. A total of seven serpin isoforms were identified and five unique expression patterns of these serpins were clearly revealed among varieties. In particular, the novel serpin isoforms 3a and 3b were highly polymorphic in the collection of wheat cultivars and are structurally diverse from the other serpin isoforms. The findings and methodology established in this study are not only immediately applicable in wheat breeding and varietal differentiation but may also be useful for delineation of serpin function in bread or pasta making in the future.