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31.
Bérénice Agnola Stéphane Boury Claudie Monot Anne Quillévéré Yves Hervé Drissa Silué 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(5):471-478
A rapid resistance/susceptibility test for Peronospora parasitica (downy mildew) was established by inoculating leaf-disks of four Brassica oleracea accessions. Several conditions were tested: disk disinfection or not, agar medium with or without nutrients and with 50 or 100 ppm of benzimidazole. Using disinfected disks placed on agar (no nutrient and benzimidazole at 50 or 100 ppm), the responses of leaf-disks to four isolates were similar to those obtained using the classical cotyledon test, whereas undesired contaminations occurred in all other conditions. The possible effect of the particular leaf used for obtaining the disks was also studied. In each incompatible interaction tested, disks were resistant whatever the leaf used. In compatible interactions, susceptible phenotypes were observed on disks derived from the six lowest leaves, but disks from upper leaves were resistant. The genetic basis of resistance in a F1 hybrid broccoli was assessed, by testing six isolates on an F2 population derived from this hybrid. The cotyledon test only allows inoculation of two isolates per seedling, whereas many isolates can be tested on each plant by using leaf-disks. The segregation of the resistance to each of the six isolates was analysed: two dominant genes (tightly linked) control resistance to all isolates (one to five isolates; the other to only one isolate). 相似文献
32.
A simple procedure to evaluate relative resistance and tolerance of tomato cultivars to the begomoviruses causing tomato yellow leaf curl (TYLC) disease in Spain was developed. To estimate the resistance and tolerance levels of a cultivar, several formulae were developed based on the ratio of infected plants, virus titre (estimated by tissue–print hybridization) and symptom intensity. The formulae were applied to five commercial tomato cultivars (Amoretto, Birloque, Royesta, Tovigreen and Ulises) naturally infected by TYLC viruses. The analyses showed that Ulises, Birloque and Tovigreen exhibited a moderate resistance, and Ulises was also highly tolerant. There was a positive correlation between symptom intensity and virus titre in infected plants, suggesting that the hybridization technique could also be used as an early estimator of tolerance. Finally, molecular hybridization and nucleotide sequence analyses of the begomovirus intergenic region showed that the local TYLC virus population consisted of a single species, Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Israel), with low genetic variation (nucleotide identity between isolates higher than 97%). 相似文献
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引起糖甜菜细菌性叶斑病的萎蔫短小杆菌新致病变种 总被引:3,自引:0,他引:3
1995年在内蒙古临河市新发现了糖甜菜细菌性叶斑病,从病斑所分离的10个细菌菌株经柯赫氏法则验证,均确系该病的病原菌。采用形态观察、表型特征和生理生化特性测定、数值分析、血清学反应、细胞化学成分分析、DNA G+C mol%和DNA-DNA同源性测定进行了鉴定,并与植物病原棒形细菌15个标准菌株进行了比较。该病原菌为革兰氏阳性细菌,不规则短杆状,有一根鞭毛、亚极生或侧生,结合其生理生化特性、细胞化学成分和DNA G+C mol%和DNA-DNA同源性测定结果,认为应属于短小杆菌属(Curtobacterium)的萎蔫短小杆菌(Cur. flaccumfaciens),数值分析也支持这一结论。此外,据血清学反应结果及其对短小杆菌属的其它植物寄主的致病情况,认为该病原菌应是萎蔫短小杆菌种下的一个新的致病变种,定名为Curtobacterium flaccumfaciens pv. beticola pv. nov. Chen et al.,2000(萎蔫短小杆菌糖甜菜致病变种)。 相似文献
35.
种植方式与种植密度对大力士高粱的影响 总被引:1,自引:0,他引:1
本试验用裂区设计,研究了大力士高粱在16种不同种植密度、3种种植方式下,产草量、生产速度、茎叶比、茎粗的变化情况。结果表明,在撒播密度为18 kg/hm2、条播为22.5 kg/hm2、穴播为28.5 kg/hm2时达到最高产量;生长速度在第53-55 d时最高,达5.7 cm/d;茎叶比随着产量的增加逐渐减少;茎粗随着种植密度的增大而有减小的趋势。 相似文献
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This paper considers the relationships between the dispersal of seeds and the distribution pattern of an annual weed. A comparative study of seed dispersal by combine harvesters, with and without a straw chopper attached, was established using Lolium rigidum, a common weed in Mediterranean cereal crops. Seed dispersal distance was quantified and the relationships between dispersal and fine‐scale seedling distribution evaluated. Primary dispersal of L. rigidum seeds occurs in a very limited space around the parent plants, but the density of seed is low because most seeds do not fall from spikes spontaneously. In contrast, many seeds are spread by combine harvesters. In this study the maximum dispersal exceeded 18 m from established stands in cereal fields, although the modal distance was close to the origin. In addition, the action of the combine harvesters tended to accumulate L. rigidum seeds predominantly under the straw swath, with some lateral movement. This action could explain the fine‐scale banded pattern of L. rigidum in cereal fields. Although the treatment of straw by the standard and straw chopper combines differed, the resultant seed distribution showed few differences. 相似文献
38.
Evaluation of vegetable protein in canine diets: Assessment of performance and apparent ileal amino acid digestibility using a broiler model
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D. C. Fiacco J. A. Lowe J. Wiseman G. A. White 《Journal of animal physiology and animal nutrition》2018,102(1):e442-e448
Recent technological advances in the human food industry with respect to meat processing have decreased the availability of animal proteins to the pet food industry which typically formulates diets with an excess of animal protein. In the long term, this is not sustainable; thus, alternative protein sources need to be investigated. This study examined three canine diets, comparing a typical animal protein‐based diet (control) with two experimental diets where the animal protein was substituted in part with vegetable protein (formulated based either on total protein or amino acid content) using a broiler model. Each diet was fed to six cages each containing two birds from day 15, 18 cages in total (36 birds). Excreta were collected from days 19 to 21. On day 23, birds were euthanized and weighed, and their ileal digesta were collected and pooled for each cage. In addition, one leg per cage was collected for evaluation of muscle mass. Results showed no significant difference in animal performance (feed intake or live weight gain) or muscle to leg proportion across the diets. Birds fed the control diet and the diet balanced for amino acid content exhibited the greatest coefficients of apparent metabolizability for nitrogen (p < .001). Birds fed the diets that contained partial replacement of animal with vegetable protein generally had greater ileal digestibility of amino acids compared to birds fed the control (animal protein) diet. Analysis of excreta showed no dietary difference in terms of dry matter content; however, birds fed the diet balanced for total protein and the diet balanced for amino acid content had significantly greater excreta nitrogen than the control (p = .038). Overall, the study suggests vegetable proteins when formulated based on amino acid content are a viable alternative to animal proteins in canine diets. 相似文献
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