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201.
Danny Vereecke Elizabeth J. Fichtner Paul Q. Lambert Peter Cooke James Kilcrease Rio A. Stamler Yucheng Zhang Isolde M. Francis Jennifer J. Randall 《Plant pathology》2021,70(3):567-583
Little is known about the epidemiology of the newly emerged disease on pistachio rootstock designated pistachio bushy top syndrome (PBTS). Here, we analysed the survival and colonization capacities of the two causative agents, Rhodococcus corynebacterioides-like PBTS1 and R. fascians PBTS2, in the different habitats they occupy. Additionally, we examined their chromosomal sequences for genes that would support their ecology and provide experimental evidence for some of their predicted functions. We demonstrate that the soil competence of PBTS2 is better than that of PBTS1 and that both bacteria behave chemotactically, allowing them to translocate from soil to the rhizoplane. Once on the rhizoplane and the phylloplane, the PBTS bacteria form extensive epiphytic biofilms, probably aided by exopolysaccharide production. From these biofilms, the bacteria colonize the plant's interior tissues through the formation of ingression sites, likely created by the localized activity of cell wall-degrading enzymes. The observed systemic spreading of the PBTS strains throughout the plant tissues is probably mediated by surface motility and agrees with the occurrence of symptoms in both the aerial and root parts of the plant host. Based on all available information, we provide a working model on this pathosystem to be used as a conceptual framework for future research. 相似文献
202.
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204.
郭珍梅 《山西农业大学学报(自然科学版)》2000,(4)
本文对英译汉中的误译现象进行了归纳总结 ,并从不同侧面剖析了误译现象发生的根源 ,找出问题的症结及规律 ,从反面给人以启迪和帮助 相似文献
205.
The effects of biofumigation and soil heating on arbuscular mycorrhizal fungi (AMF) colonisation, strawberry growth and strawberry yield in pot experiments compared with untreated soil and chemical fumigation with dazomet were tested. Three different Brassicaceae species (Brassica juncea, Eruca sativa, Sinapis alba) were used as biofumigant plant green manure and soil heating was applied to simulate soil solarisation. Half of the plants were inoculated with indigenous arbuscular mycorrhizal fungi inoculum. With one exception (E. sativa) among the uninoculated plants, the treatments significantly decreased the mycorrhizal colonisation parameters compared with the untreated control. Dazomet displayed the greatest inhibitory effects on AMF establishment. In addition, the intensity and number of bands corresponding to Glomus spp. obtained with temporal temperature-gradient gel electrophoresis were lower for strawberry plants from biofumigant treatments than from the control. For the inoculated plants, there were almost no significant differences among the mycorrhizal colonisation parameters. The mass of leaves for the uninoculated and inoculated plants was higher for almost all non-chemical soil fumigant treatments compared with the control, except for heating of the uninoculated treatments. The number of strawberry fruits for the uninoculated biofumigant treatments was the highest, being higher than the values observed for the heating treatments, the chemical disinfection treatments and the control. There were no significant differences among the inoculated treatments. Biofumigation with Brassicaceae species resulted in higher soil organic matter and mineral nutrients and had a relatively small effect on AMF colonisation (F% = 59.0, 80.3, 47.3 for Bj, Es and Sa, respectively) compared with uninoculated controls (F% = 84.3). Despite the reduced AMF colonisation, biofumigation resulted in a higher fruit number and mass of leaves. Therefore, it represents a non-chemical soil fumigation method that should be applied in sustainable strawberry production. 相似文献
206.
The tall fescue (Festuca arundinacea Schreb.) seed collection of the Centro de Investigaciones Agrarias de Mabegondo was surveyed to determine Acremonium infection rates. One hundred seeds from each of 19 accessions were microscopically examined for endophyte. Seventeen accessions (90%) contained endophyte with a range of 7 to 100%. Leaf sheaths of seedlings from the infected accessions were examined to determine the percentage of infection with viable endophyte. Only seven (41%) of the seventeen infected accessions collected and stored in 1995 at 4°C and 45–50% relative humidity contained viable endophyte with a range of 70 to 100%. While existing germplasm collections of Festuca arundinacea can provide only a small basis of Acremonium germplasm for study, newly collected Festuca arundinacea accessions will offer a greater diversity of Acremonium genotypes. 相似文献
207.
While it is well established that plants are able to acquire nitrogen in inorganic form, there is less information on their ability to ‘short circuit’ the N cycle, compete with microbes, and acquire nitrogen in organic form. Mycorrhizal fungi, known to enhance nutrient uptake by plants, may play a role in organic N uptake, particularly ericoid mycorrhizas. We asked the question—Can mycorrhizal fungi increase the ability of plants to take up organic N, compared to inorganic N? Here, we report on the abilities of three plant species, ericoid mycorrhizal Rhododendron macrophyllum and Vaccinium ovatum and arbuscular mycorrhizal Cupressus goveniana ssp. pigmaea, to acquire C and/or N from an organic and an inorganic N source. All three species are native to a California coastal pygmy forest growing in acidic, low-fertility, highly organic soils. In a pot study, glycine-α13C, 15N and 15N-ammonium were applied to pygmy forest soil for 17 or 44 h. Ericoid mycorrhizal species did not demonstrate a preference for either inorganic or organic sources of N while Cupressus acquired more NH4-N than glycine-N. For all species, glycine-N uptake did not increase after 17 h suggesting glycine uptake and glycine immobilization occurred rapidly. Both glycine-N and glycine-C were recovered in shoots and in roots suggesting that all species acquired some N in organic form. Regression analyses of glycine-N and glycine-C recovery in root tissue indicate that much of the glycine was taken up intact and that the minimum proportion of glycine-N recovered in organic form was 85% (Cupressus) and 70% (Rhododendron). Regressions were non-significant for Vaccinium. For all species, glycine-N remained predominantly in roots while glycine-C was transferred to shoots. In contrast, NH4-N remained in roots of ericoid plants but was transferred to shoots of arbuscular mycorrhizal Cupressus. Since net N mineralization rates in pygmy forest soils are low, our results suggest that organic N may be an important N source for plants in this temperate coniferous ecosystem regardless of mycorrhizal type. Acquisition of amino acid C by these species also may partially offset the carbon cost to plants of hosting mycorrhizal fungi. 相似文献
208.
王生林 《甘肃农业大学学报》1993,28(4):413-419
在定性分析的基础上,利用灰色系统模型,对兰州市主要动物性食品供求趋势进行了定量预测和分析,探讨了解决供求矛盾的基本途径和具体措施。 相似文献
209.
白菜型油菜雄性不育材料的发现和育性观察 总被引:4,自引:1,他引:4
1989年3月,我们在油菜甘白种间杂交(81008X托品)F_4代白菜型油菜品系中,发现了雄性不育株。经过两年多的观察研究,其测交和回交后代无育性分离,现有白菜型油菜品仲中存在着保持和恢复基因。初步认为,该不育材料属于核质互作的细胞质不育类型。该不育材料在盛花前总不育率为98.76%,盛花后育性有变化。与波里马不育系高温敏感型相比,其育生变化除高温因素外,对光照长度是否也有一定的诱导作用,或需要一定的积温后才能导致育性发生变化进行了讨论。后期可育株自交和兄妹交结实指数分别为0.044和0.090,低于自交不亲和结实指数1.0的标准,剥蕾自交结实指数也仅5.133。根据其雄性不育和自交不亲和双重性质、作者认为,该不育材料用于配制杂种,纯度可能优于白菜型油菜自交迟钝系和标志性状杂种。 相似文献
210.
杨光蓉 《四川农业大学学报》1990,8(2):101-107
通过四年在四川盆西北地区主产脐橙及温州蜜柑的县、市,对不同土壤类型桔园所进行的秋季地膜覆盖试验表明:①有利于土壤有机质的累积,②减少土壤氮素损失;③影响土壤含水量间接影响土壤磷、钾的释放。从土壤及树体养分测定还表明,地膜覆盖有利于罗伯逊脐橙及温州蜜柑对土壤养分的吸收利用。 相似文献