Shear resistance characteristics and influencing factors of root-soil composite on an alpine metal mine dump slope with different recovery periods

Artificial vegetation restoration is the main measure for vegetation restoration and soil and water conservation in alpine mine dumps on the Qinghai-Tibet Plateau,China.However,there are few reports on the dynamic changes and the influencing factors of the soil reinforcement effect of plant species after artificial vegetation restoration under different recovery periods.We selected dump areas of the Delni Copper Mine in Qinghai Province,China to study the relationship between the shear strength and the peak displacement of the root-soil composite on the slope during the recovery period,and the influence of the root traits and soil physical properties on the shear resistance characteristics of the root-soil composite via in situ direct shear tests.The results indicate that the shear strength and peak displacement of the rooted soil initially decreased and then increased with the increase of the recovery period.The shear strength of the rooted soil and the recovery period exhibited a quadratic function relationship.There is no significant function relationship between the peak displacement and the recovery period.Significant positive correlations(P<0.05)exists between the shear strength of the root-soil composite and the root biomass density,root volume density,and root area ratio,and they show significant linear correlations(P<0.05).There are no significant correlations(P>0.05)between the shear strength of the root-soil composite and the root length density,and the root volume ratio of the coarse roots to the fine roots.A significant negative linear correlation(P<0.05)exists between the peak displacement of the rooted soil and the coarse-grain content,but no significant correlations(P>0.05)with the root traits,other soil physical property indices(the moisture content and dry density of the soil),and slope gradient.The coarse-grain content is the main factor controlling the peak displacement of the rooted soil.

Increase in root density induced by coronatine improves maize drought resistance in North China

Drought stress caused by insufficient irrigation or precipitation impairs agricultural production worldwide.In this study,a two-year field experiment was conducted to investigate the effect of coronatine(COR),a functional analog of jasmonic acid(JA),on maize drought resistance.The experiment included two water treatments(rainfed and irrigation),four COR concentrations(mock,0μmol L^(-1);A1,0.1μmol L^(-1);A2,1μmol L^(-1);A3,10μmol L^(-1))and two maize genotypes(Fumin 985(FM985),a drought-resistant cultivar and Xianyu 335(XY335),a drought-sensitive cultivar).Spraying 1μmol L^(-1)COR at seedling stage increased surface root density and size,including root dry matter by 12.6%,projected root area by 19.0%,average root density by 51.9%,and thus root bleeding sap by 28.2%under drought conditions.COR application also increased leaf area and SPAD values,a result attributed to improvement of the root system and increases in abscisic acid(ABA),JA,and salicylic acid(SA)contents.The improvement of leaves and roots laid the foundation for increasing plant height and dry matter accumulation.COR application reduced anthesis and silking interval,increasing kernel number per ear.COR treatment at 1μmol L^(-1)increased the yield of XY335 and FM985 by 7.9%and 11.0%,respectively.Correlation and path analysis showed that grain yields were correlated with root dry weight and projected root area,increasing maize drought resistance mainly via leaf area index and dry matter accumulation.Overall,COR increased maize drought resistance mainly by increasing root dry weight and root area,with 1μmol L-^(-1)COR as an optimal concentration.

Challenges and Progress in Evaluating Apple Root Resistance Responses to Pythium ultimum Infection

Due to the hidden nature of roots in the soils, it is more challenging to investigate their resistance traits and defense responses as compared to those of the aerial organs. At the same time, it is self-evident that root health is fundamental to a plant’s entire life and productivity. It is also easily conceivable that root function, physiology, morphology, and architecture are constantly impacted by the complex soil environment including both biotic and abiotic factors. This report summarizes and updates the challenges and progress in evaluating resistance responses of apple root to infection from a necrotrophic oomycete pathogen, Pythium ultimum. Several obstacles impede the progress of investigating apple root resistance traits including the difficulties of direct and real-time evaluation and the lack of a continuous supply of apple plants for repeated infection assays. Systematic and detailed analyses were made possible by implementing a micropropagation procedure for continuously generating uniform apple plants for repeated infection assays. As a result, an elite panel of apple rootstock germplasm with distinct resistance levels was identified. These apple rootstock genotypes with well-defined resistance levels are the much-needed plant materials for subsequent genomics and transgenics analyses to define the functional roles of specific candidate genes. Careful microscopic examination revealed contrasting necrosis progression patterns between resistant and susceptible genotypes, which shed light on the potential mechanisms underlying resistance traits. Our continuing research will provide a clearer view regarding the genetic elements regulating resistance traits in apple roots to P. ultimum infection.

Intergeneric Somatic Hybrid Plants Between Citrus and Poncirus trifoliata and Evaluation of Their Root Rot Resistance

Protoplasts of Page tangelo (Citrus reticulata Blanco×C. paradisi Macf.) cell suspension culture were electrically fused with mesophyll protoplasts isolated from trifoliate orange (Poncirus trifoliata (L.) Raf.). More than 150 plantlets regenerated after 4-5 months of culture. The regenerated plants were trifoliate with well developed root systems. Root_tip chromosome counting of more than 20 randomly selected plants revealed that they were all tetraploids (2n=4x=36). RAPD analysis of 7 randomly selected plants verified their hybridity. Inoculation of citrus Phytophthora parasitica Dastar toxin on leaves of somatic hybrids and both parental genotypes showed that Page tangelo was moderately susceptible, and trifoliate orange was highly resistant while the somatic hybrids were resistant. The potential of this somatic hybrid as rootstock is also discussed.

Lodging Resistance Related to Root Traits for Mechanized Wet-Seeding of Two Super Rice Cultivars

Mechanical hill wet-seeded rice machine is beneficial for establishing and growing uniform rows of seedlings.However,there is limited knowledge regarding the effects of the establishment of furrows on growth,lodging and yield,and their relationships with root traits.In this study,field experiments were conducted during 2012 and 2013 using two super rice varieties(hybrid rice Peizataifeng and inbred rice Yuxiangyouzhan)under three furrow establishment treatments(T1,both water and seed furrows were established by the machine;T2,only seed furrows were established by the machine;and T3,neither water nor seed furrows were established by the machine).Lodging index,lodging-related traits,grain yield,above-ground dry weight and root traits were measured.The results showed that the lodging index was significantly affected by the treatments with furrows(T1 and T2).The strongest lodging resistance was detected in the mechanical hill wet-seeded rice with furrow treatment(T1)in both 2012 and 2013.Lodging resistance was strongly related to the breaking resistance.No significant difference was found in grain yield or dry weight of the mechanical hill wet-seeded rice.Therefore,the mechanical hill wet-seeded rice with furrow treatment increased rice lodging resistance,which was related to root traits.

Resistance Evaluation of Soybean Germplasm from Huanghuai Region to Phytophthora Root Rot

The aim of the study was to establish a set of differential strains and to identify soybean resistant genes to Phytophthora root rot and then to apply those strains for analysis of the resistant genes Rps1a,Rps1c,and Rps1k that soybean cultivars or lines may carry.Virulence formula of 125 Phytophthora sojae isolates were determined using the hypocotyls inoculation technique,the strains,which includ 6 isolates with different virulence formulas,were applied to identify the resistance of 55 soybean cultivars or lines and resistant genes were analyzed using the gene postulating procedure.Eighteen reaction types occurred in 55 cultivars or lines and results of gene postulation indicated that 2 cultivars or lines probably carried gene Rps1c and no cultivar may carry genes Rps1a or Rps1k.A few of soybean cultivars or lines from Huanghuai Region carry Rps genes Rps1a,Rps1c and Rps1k and tend to infect by P.sojae,so resistant cultivars or lines need to be bred and popularized actively.

A Phenotyping Protocol for Detailed Evaluation of Apple Root Resistance Responses Utilizing Tissue Culture Micropropagated Apple Plants

In the post-genomics era, reliable phenotypes are considered the bottleneck for unraveling the genetic control over the biology of interest. Phenotyping resistance response of roots to infection by soilborne pathogen is more challenging compared to that of plant aerial parts. In additional to the hidden nature and small stature of fine roots where infection occurs, extra obstacles exist for rosaceae tree crops such as apple. Due to self-incompatible reproduction and high-level heterozygosity of apple genome, genetically identical apple plants cannot be produced through apple seed germination. Here we report an established phenotyping protocol which includes a streamlined tissue culture procedure for micropropagation of uniform apple plants, standardized inoculation procedure using Pythium ultimum, and multilayered evaluating methods on apple root resistance traits. Because of the implementation of tissue culture based micropropagation procedure, constant availability of the uniform plants with defined genetic background, equivalent age and non-contaminated roots overcame a longstanding barrier of systematic and detailed phenotypic characterization of apple root resistance traits. Repeated infection assays by root-dipping inoculation demonstrated the reproducible and wide-range plant survival rates, from single-digit to over 90% survived plants for a given genotype. Genotype-specific values due to P. ultimum inoculation on shoot and root biomass reduction, maximum root lengths, leaf number and cumulative leaf areas were quantified between mock-inoculated and P. ultimum infected plants. Use of a glass-box container offered enhanced accessibility and minimized invasiveness for continuous and non-disruptive observation on the necrosis progression patterns along inoculated roots. With the assistance of a dissecting microscope, the genotype-specific resistance responses along the infected apple roots were captured and analyzed in detail. This reported phenotyping protocol represents a major development and should be easily adopted for other rosacea tree fruit crops with minor modifications.

Polygenic Heritability of Rose Root Rot Disease Resistance in Offspring of Rosa multiflora

Rose root rot disease caused by Pythium helicoides Drechsler has brought heavy damage to cut rose production in Japan,and it has became apparent that Rosa multiflora showed resistance to this disease.Roses have been bred by interspecies crossing with Rosa species including of R.multiflora,and many progenies of R.multiflora have been bred as determined cluster-flowered roses.However,the genetic architecture of this resistance remains.So,in this study,four kinds of R.multiflora and 21 rose cultivars that have been clarified in the cross-fertilization genealogy with R.multiflora were used as plant materials,and the inheritability of resistance to root rot disease was investigated.Four kinds of R.multiflora had all high resistance,and the resistance to root rot disease in R.multiflora was inherent characteristic of species.Five varieties not less than 50% in relatedness with R.multiflora were shown as varied ‘resistant’ and ‘moderately resistant’.Therefore,the inherent resistant characteristic in R.multiflora was not controlled by single major gene,and the resistibility in R.multiflora was not cytoplasmic but nuclear heredity.Although there was significant negative relation between relative root rot severity and relatedness with R.multiflora,the variance of relative root rot severity had tendency to expand as relatedness with R.multiflora reduced.This result,therefore,indicated that the contingency of resistance expression increased as the relatedness with R.multiflora was reduced.The varieties having low degree of relatedness with R.multiflora had similar relative root rot severity with R.multiflora.These results indicated that we would be able to select resistant roses from progenies crossed with R.multiflora.

Mitigative Effect of <i>Bacillus subtilis</i>QM3 on Root Morphology and Resistance Enzyme Activity of Wheat Root under Lead Stress

Lead (Pb) is an environmental pollutant extremely toxic to plants and other living organisms including humans. In order to research the relieve effect of Bacillus subtilis QM3 on wheat roots (Triticum aestivum L.), after wheat seeds germination for two days, wheat root caused, the experimental materials were divided into four large groups and each large group was placed in 6 petri dishes as six small groups, and then four large groups respectively cultivated with sterile water (CK), 108 CFU/ml B. subtilis QM3 (B1), 107 CFU/ml B. subtilis QM3 (B2) and 106 CFU/ml B. subtilis QM3 (B3) for 2 days, after that stressed with lead nitrate, Pb (NO)2, Pb2+ concentration calculation at five concentrations (50, 250, 500, 1000, 2000 mg/L), sterile water and different Pb2+ concentration liquid respectively cultivated the 6 small groups in each large group measuring root morpholog and assaying changes of antioxidant enzyme activity. The results showed that: with the increase of the Pb2+ concentration, root morphology index and the activity of antioxidant enzyme increased first and then decreased. Root morphology index reached the maximum in 50 mg/L Pb2+ concentration. B. subtilis QM3 clearly promoted the growth of the root and the antioxidant enzyme activity (p 0.05). Without Pb stress, B. subtilis QM3 had the best improving effect on root morphology. When Pb2+ concentration was 50 mg/L, superoxide dismutase (SOD) and ascorbate peroxidase (APX) reached the maximum. SOD activity, compared with CK, B1, B2 and B3 respectively, increased by 8.05%, 27.41% and 9.79%. APX activity, compared with CK, B1, B2 and B3 respectively, increased by 52.70%, 111.15% and 14.16%. Catalase (CAT) and peroxidase (POD) reached the maximum at the Pb2+ concentration was 500 mg/L. CAT activity, compared with CK, B1, B2 and B3 respectively, increased by 59.93%, 83.46% and 70.59%. POD activity, compared with CK, B1, B2 and B3 respectively, increased by 2.88%, 10.11% and 7.67%. Result suggested that B. subtilis QM3 could improve root growth and antioxidant enzyme activity of the wheat root under lead stress.

The OsNAC41-RoLe1-OsAGAP module promotes root development and drought resistance in upland rice

Drought is a major environmental stress limiting crop yields worldwide.Upland rice(Oryza sativa)has evolved complex genetic mechanisms for adaptative growth under drought stress.However,few genetic variants that mediate drought resistance in upland rice have been identified,and little is known about the evolution of this trait during rice domestication.In this study,using a genome-wide association study we identified ROOT LENGTH 1(RoLe1)that controls rice root length and drought resistance.We found that a G-to-T polymorphism in the RoLe1 promoter causes increased binding of the transcription factor OsNAC41 and thereby enhanced expression of RoLe1.We further showed that RoLe1 interacts with OsAGAP,an ARF-GTPase activating protein involved in auxin-dependent root development,and interferes with its function to modulate root development.Interestingly,RoLe1 could enhance crop yield by increasing the seed-setting rate under moderate drought conditions.Genomic evolutionary analysis revealed that a newly arisen favorable allelic variant,proRoLe1−526T,originated from the midwest Asia and was retained in upland rice during domestication.Collectively,our study identifies an OsNAC41-RoLe1-OsAGAP module that promotes upland rice root development and drought resistance,providing promising genetic targets for molecular breeding of drought-resistant rice varieties.

Resistant Evaluation of Kiwifruit Rootstocks to Root Zone Hypoxia Stress

In this thesis, 10 species of kiwifruit rootstocks were treated with hydroponics hypoxia to study their root zone hypoxia tolerance. The results were as follows: growth of all kiwifruit seedlings was inhibited. The max length of new root, plant height, plant biomass, root activity, relative growth rate of leaves, and content of chlorophyll in leaves under root zone hypoxia stress obviously declined comparing with control. MDA content, relative conductance in the leaves and roots all increased in 10 kinds of kiwifruit seedlings. The sensitivities of 10 kinds’ kiwifruit seedlings to hypoxia stress were obviously different. With the method of subordinate function and cluster analysis, the adversity resistance coefficient of 10 kinds’ kiwifruit seedlings, were comprehensively evaluated in order to appraise their hypoxia-tolerance abilities. According to the results, “Hayward”, “Qinmei”, “Jinxiang”, “Kuoye”, “Huayou” kiwifruit seedlings held higher tolerance to root zone hypoxia stress, while “Hongyang” kiwifruit seedlings were sensitive to root zone hypoxia stress. The others, including “Xixuan”, “Maohua”, “Jinhua”, “Shanli” kiwifruit seedlings kept moderate resistant intensity to root zone hypoxia stress. The kiwifruit seedlings’ resistance order from strong to weak was: “Hayward” > “Qinmei” > “Jinxiang” > “Kuoye” > “Huayou” > “Xixuan” > “Maohua” > “Jinhua” > “Shanli” > “Hongyang”.

Regulation of phenylpropanoid biosynthesis by MdMYB88 and MdMYB124 contributes to pathogen and drought resistance in apple

MdMYB88 and MdMYB124 have been demonstrated to be responsible for lignin accumulation in apple under drought stress.In this study,using a metabolomic approach,we identified differentially accumulated phenylpropanoid and flavonoid metabolites in MdMYB88/124 transgenic RNAi plants under control and long-term drought stress conditions in apple roots.We confirmed the regulation of phenylalanine by MdMYB88 and MdMYB124 via UPLC-MS in apple roots under both control and drought conditions.Using Electrophoretic Mobility Shift Assay(EMSA)and ChIPquantitative PCR(qPCR)analyses,we found that MdMYB88 positively regulates the MdCM2 gene,which is responsible for phenylalanine biosynthesis,through binding to its promoter region.Under long-term drought conditions,MdMYB88/124 RNAi plants consistently accumulated increased amounts of H2O2 and MDA,while MdMYB88 and MdMYB124 overexpression plants accumulated decreased amounts of H2O2 and MDA.We also examined the accumulation of metabolites in the phenylpropanoid biosynthesis pathway in the leaves of MdMYB88 and MdMYB124 transgenic apple plants after long-term drought stress.We found that metabolites responsible for plant defense,including phenylpropanoids and flavonoids,accumulated less in the RNAi plants but more in the overexpression plants under both control and drought conditions.We further demonstrated that MdMYB88/124 RNAi plants were more sensitive to Alternaria alternata f.sp.mali and Valsa mali,two pathogens that currently severely threaten apple production.In contrast,MdMYB88 and MdMYB124 overexpression plants were more tolerant to these pathogens.The cumulative results of this study provided evidence for secondary metabolite regulation by MdMYB88 and MdMYB124,further explained the molecular roles of MdMYB88 and MdMYB124 in drought resistance,and provided information concerning molecular aspects of their roles in disease resistance.

Evaluation of Cowpea Genotypes for Resistance to <i>Fusarium redolens</i>in Uganda

Fusarium redolens, a virulent fungus which causes damping off, leaf yellowing, wilting and root rots has recently been devastating cowpea fields in Uganda. This study aimed at identifying cowpea genotypes that are resistant to Fusarium redolens. Therefore, ninety cowpea genotypes were evaluated two times against a highly virulent Fusarium redolens (isolate from Zombo in Paidha district) in the screen house in 2016. Genotype effect was highly significant (P 0.001) for root rot severity. Based on the Index of Susceptibility (IS), three genotypes (Asontem, Dan1 LA and IT89KD-88) remained resistant (IS 3.5) over the two screening periods, 72 moderately resistant (3.5 ≤ IS 6.5) and 11 susceptible (IS ≥ 6.5). Resistance was found to be enhanced by presence of lateral roots above or at the ground level. Further results suggested a difference in genetic control of resistance to root rots and seed rots caused by Fusarium redolens. All the released varieties tested (SECOW 1 T, SECOW 2 W, SECOW 3 B, SECOW 4 W and SECOW 5 T) had moderate resistance to Fusarium redolens. Correlation analysis revealed root rot severity was strongly correlated to disease incidence (+0.64, P 0.001), to proportion of plants with lateral roots (-0.56, P 0.001), to amount of leaf chlorophyll (-0.53, P 0.001) and to proportion of plants that died prematurely due to Fusarium redolens infection (+0.45, P 0.001). No significant correlation was detected between root rot severity and proportion of plants that germinated. The established resistance could be exploited for improvement of farmer preferred cowpea varieties towards Fusarium redolens resistance in Uganda.

Resistance identification of bivalent fungi-resistant genes transformed soybean to Phytophthora sojae

Soybean is one of the most important sources of edible oil and proteins in the world. However, it suffers from many kinds of fungal diseases which is a major limiting factor in soybean production. The fungal disease can be effectively controlled by breeding plant cultivars with genetic transformation. In this study, the resistance to Phytophthora sojae of five bivalent transgenic soybean lines was identified using the hypocotyls inoculation technique. The lines were the T2 of the transgenic soybean which were transformed with kidney bean chitinase gene and barley ribosome inactivating protein gene, and were positive by Southern Blot analysis. The resistance difference was studied through comparing the death percentage of transgenic soybean with the control. The results showed that four lines were more resistant to P sojae, whereas other one had no significant difference in comparison with the control. These transgenic soybean lines with enhanced resistance to P sojae will be useful in soybean resistance breeding.

Molecular Marker-Assisted Backcrossing of Anthracnose Resistance Genes into Common Beans (<i>Phaseolus vulgaris</i>L.) Varieties

Anthracnose, caused by Colletotrichum lindemuthianum, is a major disease of common bean and results in high yield loss. Due to the high degree of pathogenic variability of the fungus and the continual emergence of new races, genetic resistance in the host is not durable. Gene pyramiding using Marker Assisted Selection (MAS) is proposed as a viable approach to improve the durability of major genes conditioning resistance to anthracnose. In this study a common bean line Urugezi x AND 1062 susceptible to anthracnose but already improved for Pythium root rot resistance was improved for anthracnose resistance through a backcross breeding program. Genotypic selection was done in Rubilizi laboratory in Kigali, Rwanada whereas phenotypic selection was conducted in an anthracnose hotspot at Rwerere, a research Centre of the Rwanda Agricultural and Animal Resources Development Board (RAB). Analysis of variance for effect of bean varieties and anthracnose isolates on disease expression showed significant differences (p < 0.001) among varieties and isolates and for the interaction between isolates and varieties. Developed BC2F1 plants were 41% of them resistant and 59% susceptible to anthracnose. However, the observed proportion of 26 resistants and 37 susceptible in BC2F1 plants didn’t fit the goodness of fit of the expected proportion of 75 resistants to 25 susceptible. Only 41% of BC2F1 plants inherited the resistance genes and were phenotypically resistant. Presence of SCAR-markers, SAB3 and SBB14, in the developed resistant lines h suggested successful resistance transfer of anthracnose resistance genes.

不同基因型烤烟对镰刀菌根腐病的抗性鉴定与评价

为明确不同基因型烤烟对烟草镰刀菌根腐病的抗性,利用10个烟草品种(系),采用粗毒素幼芽接种、带菌菌谷接种、孢子悬浮液培养等方法进行抗性鉴定。结果表明,供试品种对尖孢镰刀菌抗性表现出显著差异;对尖孢镰刀菌表现出抗的品种(系)有4个,分别是‘Y2001’、‘Y2002’、‘长脖黄’、‘664-01’;对尖孢镰刀菌表现出感的品种(系)有6个,分别是‘7710’‘、7713’‘、Y2007’‘、Y2008’‘、中烟100’、‘小黄金1025’。3种接种方法鉴定结果基本一致,共筛选出4个抗性品种(系)。

不同时期水分胁迫对大豆根系特性及产量的影响

为揭示抗旱基因型大豆根系应答干旱胁迫的响应机制,于2020年在辽宁省沈阳市开展盆栽试验,以抗旱基因型和干旱敏感型大豆为试材,探讨干旱(W1,土壤含水量为田间持水量的50%)、轻度干旱(W2,土壤含水量为田间持水量的60%)、适宜水分(W3,土壤含水量为田间持水量的80%)对大豆根系特性和产量的影响。结果表明:同一时期控水,W1和W2条件下,抗旱品种“辽豆14”的总根长和根表面积优于干旱敏感型品种“辽豆21”。一般情况下,平均根直径为0~0.5 mm的根长比例表现为:“辽豆21”>“辽豆14”,而平均根直径为0.5~1.0 mm的根长比例却表现为:“辽豆14”>“辽豆21”。随着生育进程的推进,大豆地上部鲜重、地上部干重、根干重逐渐累积,鼓粒期达最大值;一般情况下,同一控水时期,随着土壤含水量的增加,同一品种地上部鲜重、根鲜重、地上部干重、根干重值逐渐增加,但抗旱品种“辽豆14”的值一般优于干旱敏感型品种“辽豆21”。随着生育进程的推进,根冠比鲜重和根冠比干重值降低;土壤干旱提高了植株的根冠比。各个时期控水,品种和水分均显著影响了大豆的单株产量,干旱(W1)和轻度干旱(W2)均降低了2品种的单株产量,但抗旱品种“辽豆14”引起产量下降的值更低。干旱胁迫条件下,抗旱基因型大豆在总根长、根表面积、地上部干重、根干重、产量以及平均根直径为0.5~1.0 mm的根长比例方面,表现出优于干旱敏感型品种的优势。

牙体缺损类型与纤维桩位置对桩核冠修复上颌前磨牙抗折性能的影响

纳入120颗离体上颌前磨牙分成5组(每组24颗),制备360°牙本质肩领(A组)、颊侧180°牙本质肩领(B组)、腭侧180°牙本质肩领(C组)、远中180°牙本质肩领(D组)、近中180°牙本质肩领(E组),分别用树脂核+全冠修复、颊侧根管纤维桩+树脂核+全冠修复、腭侧根管纤维桩+树脂核+全冠修复、颊、腭侧根管纤维桩+树脂核+全冠修复。结果显示:A组样本牙的抗折破坏载荷值高于B、C、D、E组(P<0.05),颊侧根管置入纤维桩抗折强度高于腭侧(P<0.05)。提示360°完整牙本质肩领能提供最佳的抗折强度,牙本质肩领不完整时,推荐置入颊侧根管纤维桩修复。

院内感染肺炎克雷伯菌的影响因素及其耐药情况调查

【目的】探讨院内感染肺炎克雷伯菌的影响因素及耐药情况。【方法】选取2018年3月至2023年1月本院收治的87例院内感染患者作为研究对象,其中28例院内感染肺炎克雷伯菌患者纳入观察组,59例院内感染鲍曼不动杆菌的患者纳入对照组。比较两组一般资料;分析菌株来源、耐药性及毒力基因;分析院内感染肺炎克雷伯菌的影响因素及耐药情况。【结果】观察组中有21例(75.00%)为混合感染阳性,其中A型(肺炎链球菌)5例(23.81%)、B型(葡萄球菌)4例(19.05%)、C型(流感嗜血杆菌)2例(9.52%)、A型+B型4例(19.05%)、A型+C型2例(9.52%)、B型+C型3例(14.29%)、A型+B型+C型1例(4.76%)。对照组中有26例(44.07%)为混合感染阳性,其中A型6例(23.08%)、B型5例(19.23%)、C型4例(15.38%)、A型+B型3例(8.69%)、A型+C型3例(11.54%)、B型+C型4例(15.38%)、A型+B型+C型1例(3.85%)。两组年龄、性别、住院时间、白蛋白、科室分布、白细胞(WBC)计数及留置导管、侵入性操作、与感染患者住通病区≥1周、终末消毒残缺占比比较,差异无统计学意义(P>0.05);观察组长期使用广谱抗菌药物、合并其他细菌感染≥2种及前期肺炎克雷伯菌定植占比高于对照组(P<0.05)。Logistic回归分析结果:长期使用广谱抗菌药物、合并其他细菌感染≥2种、前期肺炎克雷伯菌定植是患者院内感染肺炎克雷伯菌的危险因素(P<0.05)。28株菌株主要来源于痰液、血液;肺炎克雷伯菌对哌拉西林/他唑巴坦、头孢曲松耐药性最高(100%),肺炎克雷伯菌对替加环素(3.57%)、四环素(7.14%)耐药性最低;28株菌株中高黏液性菌株6株(21.43%)、非高黏液性菌株22株(78.57%),高黏液性菌株拉丝实验阳性率高于非黏液性菌株(P<0.05);高黏液性菌株iroN、rmpA及ybtS毒力基因阳性率高于非黏液性菌株(P<0.05)。【结论】长期使用广谱抗菌药物、合并其他细菌感染≥2种、前期肺炎克雷伯菌定植是患者院内感染肺炎克雷伯菌的危险因素,肺炎克雷伯菌对常见抗菌药物耐药性较为严重。

番茄颈腐根腐病病原菌鉴定及抗性品种筛选

番茄颈腐根腐病是设施番茄冬春生产中最严重的病害之一,严重威胁我国设施番茄的安全生产。近年来番茄颈腐根腐病在我国番茄主产区发生日益严重,培育抗病品种是防治该病最经济有效的方法。本试验采集典型症状的发病植株进行病原菌分离纯化,综合运用形态学观察、分子生物学鉴定和致病性测定方法,确定病原菌为尖孢镰刀菌番茄颈腐根腐病专化型(Fusarium oxysporum f.sp.radicis-lycopersici,Forl)。之后利用分离的病原菌通过苗期人工接种鉴定结合抗性基因分子标记方法,对32个番茄商品种进行抗颈腐根腐病鉴定分析,结果显示有18个表现抗病,与分子标记Frl-ZL的鉴定结果一致,可用于番茄抗颈腐根腐病育种或生产。