Ethylene and jasmonate as stimulants of latex yield in rubber trees(Hevea brasiliensis):Molecular and physiological mechanisms.A systematic approximation review

The rubber tree Hevea brasiliensis(Willd.Ex Adr.De Juss.)Müell Arg.]is an important source of latex for the production natural rubber.Natural rubber is an important biopolymer used in various industries,but aspects related to hormonal regulation in biosynthesis are still unknown,which would allow optimizing its production.We review the molecular and physiological mechanisms of increases latex regeneration and flow by the stimulation of rubber trees with exogenous applications of ethylene and jasmonate.We found that the increase in latex regeneration by ethylene is due to the increase in gene level expression and enzymatic activity of key photosynthesis and glycolysis enzymes for the generation of precursors in the first phase of rubber biosynthesis.Latex flow is supported by up-regulated genes in sucrose metabolism such as invertases,induction of sucrose transporters(SUT),and aquaporins(PIP)to maintain flow and turgor pressure in laticifers.Meanwhile,the increase in latex yield mediated by jasmonate may be due to the induction of laticifer differentiation in the long term and in the short term be mediated by the induction of small rubber particles(SRPP)as non-enzymatic cofactors in the production of latex.This information contributes to the knowledge of latex biosynthesis,which allows for a greater support for the exogenous application of jasmonates and ethylene to regulate its production.

Development and Characterizations of EST-SSR Markers in Rubber Tree(Hevea brasiliensis)

To further develop EST-SSR marker in rubber tree, we assembled the sequences downloaded from NCBI and Malaysia EST databases of rubber tree. By analyzing the assembled 3 733 unigenes, we identified 566 potential SSR sites in this study. That is to say, there was one EST-SSR in every 3.96 kb. The di-nu-cleotide repeat was the most abundant type, fol owed by tri-, hexa-, tetra- and pen-ta-nucleotide repeat. The most common number of repeat units was 5, fol owed by more than 12, 6 and 7. Of 51 SSR motifs identified in this study, di-, tri-, tetra-, penta- and hexa-nucleotide repeats were 6, 26, 5, 3 and 11 types, respectively. The GA/CT di-nucleotide repeat was the most abundant motif, fol owed by TC/AG, AT/TA, CTT/GAA, TTC/AAG and TCT/AGA. In total, 158 new EST-SSRs were developed and amplified with the DNA of RRIM600 as a template. The results showed that the PCR products of 99 EST-SSRs generated clear amplifying bands. The EST-SSR markers developed in this study further enrich the number of molecular marker in rubber tree, and they wil be widely applied in DNA fingerprinting, genetic diversity, marker-assisted selection and genetic mapping, etc.

Comparative Proteomics Analysis of the Sieve Tube from Rubber Tree(Hevea brasiliensis) Seedlings under Contrasting Ethylene Treatments

[Objective]To elucidate the role of ethylene(ET),a latex yield stimulant of the rubber tree,on the sieve tube(ST)transport efficiency of materials(especially sucrose)needed for natural rubber biosynthesis.[Method]Rubber tree seedlings were treated with ET solution or water which was used as a control on the bark,and latex samples and ST tissue samples were collected for proteomic analyses and latex sucrose content determination respectively.[Results]After ET treatment,the sucrose content of the latex was found significantly decreased.A total of 66 ethylene-responsive proteins(ERPs)were distinguished by two-dimensional gel electrophoresis(2-DE),and 54 were successfully identified by MALDI-TOF/TOF and database searching.The majority of these ERPs were involved in carbohydrate transport and metabolic processes in the ST.[Conclusion]Our findings suggest that the application of ET may increase the transport efficiency of the ST and that the application of ET promotes the consumption of energy and sucrose in the ST.

Short-term effects of organic amendments on soil fertility and root growth of rubber trees on Hainan Island, China

Rubber[Hevea brasiliensis(Willd.ex A.Juss.)Müll.Arg.]plantations are the largest cultivated forest type in tropical China.Returning organic materials to the soil will help to maintain the quality and growth of rubber trees.Although many studies have demonstrated that organic waste materials can be used to improve soil fertility and structure to promote root growth,few studies have studied the eff ects of organic amendments on soil fertility and root growth in rubber tree plantations.Here,bagasse,coconut husk or biochar were applied with a chemical fertilizer to test their eff ects on soil properties after 6 months and compared with the eff ects of only the chemical fertilizer.Results showed that the soil organic matter content,total nitrogen,available phosphorus and available potassium after the chemical fertilizer(F)treatment were all signifi cantly lower than after the chemical fertilizer+bagasse(Fba),chemical fertilizer+coconut husk(Fco)or chemical fertilizer+biochar(Fbi)(p<0.05).Soil pH in all organic amendments was higher than in the F treatment,but was only signifi cantly higher in the Fbi treatment.In contrast,soil bulk density in the F treatment was signifi cantly higher than in treatments with the organic amendments(p<0.05).When compared with the F treatment,soil root dry mass increased signifi-cantly by 190%,176%and 33%in Fba,Fco and Fbi treatments,respectively(p<0.05).Similar results were found for root activity,number of root tips,root length,root surface area and root volume.Conclusively,the application of bagasse,coconut husk and biochar increased soil fertility and promoted root growth of rubber trees in the short term.However,bagasse and coconut husk were more eff ective than biochar in improving root growth of rubber trees.

Microorganism Characteristics in Decomposition Process of Rubber Tree Leaves Litter in Hainan Island

Microorganism plays an irreplaceable role in litter decomposition,and the dynamics of microbial activity in litter is of ecological significance in understanding the mechanism of litter decomposition. Therefore,the dynamic characteristics of microorganism in rubber litter decomposition were studied during 300 and 240 days by mesh bag method under different control measures in plantations. And the results were as following:(1) Microbial populations were closely related to litter residues and decomposition environments. The microbial population has been rising firstly and then falling on the ground but directly dropping under the ground by time.(2) Microbial populations under different environments as follows:0.07 mm aperture of mesh bag > 1 mm aperture of mesh bag,non-fertile hole > fertile hole,underground group > ground group. During the entire process of decomposition,the quantity of bacteria holed absolute superiority,then actinomycetes,finally fungi.(3) Through the correlation analysis,the total number of bacteria,fungi and microorganism in aboveground group was significantly associated with the decomposition rate,but there was little correlation to actinomycetes. It's suggested that fungi and bacteria are the main participants in litter decomposition on the ground. In underground group,the microbial groups were significantly or extremely significantly related to the dry weight of residues,but was not correlated to decomposition rate significantly,which suggested that litter provided food for underground microbes,and litter decomposition was more dependent on comprehensive effect of microbes,soil animals and soil environments.

Rubber Tree Distribution Mapping in Northeast Thailand

In many parts of mainland Southeast Asia rubber plantations are expanding rapidly in areas where the crop was not historically found. Monitoring and mapping the distribution of rubber trees in the region is necessary for developing a better understanding of the consequences of land-cover and land-use change on carbon and water cycles. In this study, we conducted rubber tree growth mapping in Northeast Thailand using Landsat 5 TM data. A Mahalanobis typicality method was used to identify different age rubber trees. Landsat 5 TM 30 m non-thermal reflective bands, NDVI and tasseled cap transformation components were selected as the model input metrics. The validation was carried out using provincial level agricultural statistical data on the rubber tree growth area. At regional (Northeast Thailand) and provincial scales, the estimates of mature and middle-age rubber stands produced from 30 m Landsat 5 TM data compared well (high statistical significance) with the provincial rubber tree growth statistical data.

First characterization of endophytic Corynespora cassiicola isolates with variant cassiicolin genes recovered from rubber trees in Brazil

Corynespora cassiicola is the causal agent of Corynespora Leaf Fall(CLF)disease.CLF is one of the most important fungal diseases of rubber trees in Asia and Africa but disease outbreaks have not been reported in South America.Cassiicolin,a small cysteine-rich glycoprotein secreted by the pathogenic C.cassiicola isolate CCP,was previously identified as a potential disease effector in rubber tree.Recently,the cassiicolin-encoding gene(Cas1)was characterized and shown to be expressed in the early phase of infection.In this study,we investigated whether previously undetected strains of C.cassiicola are present in South American rubber plantations by examining the fungal endophyte population found in asymptomatic rubber tree leaves.Four isolates were identified as C.cassiicola.Genes encoding new forms of the cassiicolin precursor protein(Cas3 and Cas4)were identified from these isolates.Three of four isolates were able to induce symptoms on the cultivar they were isolated from in a detached leaf assay,with different kinetics and intensities.One isolate had the same pathogenicity profile as the pathogenic isolate CCP;the other two isolates developed symptoms late during the course of infection,suggesting saprotrophic capabilities.However,no Cas3 or Cas4 transcripts could be detected upon inoculation with the endophytic isolates,whereas the reference gene Cas1 was expressed upon inoculation with the CCP isolate.This work demonstrated that C.cassiicola is present in South America in an endophytic form and that it may evolve from an endophytic to a saprophytic or even potentially pathogenic life style.

Electrical treeing behaviors in silicone rubber under an impulse voltage considering high temperature

In this paper,work was conducted to reveal electrical tree behaviors（initiation and propagation）of silicone rubber（SIR） under an impulse voltage with high temperature.Impulse frequencies ranging from 10 Hz to 1 k Hz were applied and the temperature was controlled between 30 °C and 90 °C.Experimental results show that tree initiation voltage decreases with increasing pulse frequency,and the descending amplitude is different in different frequency bands.As the pulse frequency increases,more frequent partial discharges occur in the channel,increasing the tree growth rate and the final shape intensity.As for temperature,the initiation voltage decreases and the tree shape becomes denser as the temperature gets higher.Based on differential scanning calorimetry results,we believe that partial segment relaxation of SIR at high temperature leads to a decrease in the initiation voltage.However,the tree growth rate decreases with increasing temperature.Carbonization deposition in the channel under high temperature was observed under microscope and proven by Raman analysis.Different tree growth models considering tree channel characteristics are proposed.It is believed that increasing the conductivity in the tree channel restrains the partial discharge,holding back the tree growth at high temperature.

Studies on Rubber (<i>Hevea brasiliensis</i>) Trees Exist Plant Type after Planting and Available Tapping Tree of Rubber Plantation in China

Existing plant types of rubber tree after planting and available tapping tree were investigated, and there were about 28 rubber plantations with different tapping years of 8 varieties “CATAS7-33-97”, “CATAS8-79”, “CATAS7-20-59”, “PR107”, “RRIM600”, “GT1”, “INA873”, “93-114”in South China. The results showed that there were six kinds of existing plant types of rubber tree after planting of rubber plantations, which were available tapping trees, wind damaged trees, cold damaged trees, tapping panel dryness trees, absent trees and weak trees, respectively. These data investigated also showed rubber trees under available tapping, stoppage due to tapping panel dryness, absence, wind damage, cold damage and weakness were counted and calculated and made up for 72.21%, 14.75%, 5.61%, 3.86%, 2.68% and 1.89%. Tapping panel dryness trees, wind damage and absent trees are major factors for the loss of tapping rubber trees in the rubber plantations. Of these investigated varieties, available tapping trees per 100 trees of rubber plantation of “PR107”at the 1st, 12th, 14th, 16th, 20th, 24th tapping year were 96, 67, 70, 75, 66, 46 trees in Hainan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “RRIM600”at the 9th, 15th, 20th, 22nd tapping year were 88, 62, 55, 36 trees in Yunnan planting zone, respectively. Available tapping trees per 100 trees of rubber plantation of “93-114” at the 10th, 19th, tapping year were 94, 62 trees in Guangdong planting zone. These results showed that available tapping trees of rubber plantation decreased with increasing tapping age under different planting zones in China.

Isolation and Analysis of Rubber Hevein Gene and Its Promoter Sequence

Hevein, a lectin_like protein, is a major factor of lutoids in the latex of rubber trees ( Hevea brasiliensis Muell._Arg.). This factor is involved in coagulation of the latex and has the ability to bind chitin. The hevein gene with a length of 680 bp was cloned by the method of RT_PCR. Its promoter region with 1 306 bp of this gene was also isolated by genome walking, and its sequence included the typical TATA and CAAT boxes as well as the homologous sequence of abscisic acid (ABA) response elements. Expression of the hevein gene in the latex and leaves was detected by Northern blot. After treatment of the trees with ethylene and ABA, the results showed that the hevein gene was expressed principally in latex, and the expression could be induced by ethylene and ABA.

The legacy effects of rubber defoliation period on the refoliation phenology,leaf disease,and latex yield

The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.

Exploration and Practice of Rubber Based Agroforestry Complex Systems in China

Agroforestry ecosystems are constructed by simulating natural ecosystems, applying the principles of symbiosis in nature, and organizing multiple plant populations to coexist, while conducting targeted cultivation and structural control scientifically. Rubber agroforestry complex ecosystems aim for sustainable development in terms of industry, ecology, resource utilization, and the livelihoods of producers. Rubber agroforestry complex ecosystems create a complex production structure system that integrates biology, society, and the economy through species combinations. Rubber trees and associated biological components coordinate with each other, mutually promote growth, and yield a variety of products for producers. Cultivation techniques and patterns of rubber agroforestry are essential components of these ecosystems. This study analyzes the production practices of rubber agroforestry complex cultivation, with a focus on the development and characteristics (complexity, systematicity, intensity, and hierarchy) of rubber agroforestry systems using a literature analysis and a survey approach. It explores the types and scales of complex planting, specifications and forms, and major effects of complex cultivation. This study identifies successful rubber agroforestry cultivation patterns and practical techniques, as well as the potential benefits of developing rubber agroforestry cultivation. It also points out the shortcomings in the development of complex planting, including an emphasis on production practices but insufficient theoretical research, a focus on production but inadequate attention to the market, and an emphasis on yield while overlooking the improvement of standards, brands, and added value. There are various complex patterns for young rubber plantations, but relatively fewer for mature plantations. Based on this analysis, this study suggests that future efforts should focus on in-depth research on interspecies and environmental interactions in rubber agroforestry ecosystems, clearly define key roles, accelerate the innovation of development patterns, and strengthen the foundation for development. It recommends promoting and demonstrating successful rubber agroforestry complex patterns and providing technical training, developing product branding for rubber agroforestry patterns, enhancing product value, expanding the application functions of rubber-forest mixed crop products, and establishing a stable and sustainable industry chain. This study provide practical experience and theoretical insights in rubber agroforestry complex systems from China the potential to enrich the knowledge of rubber agroforestry composite systems, provide practical experience to improve the operating income of smallholders, and even promote the sustainable development of rubber plantations.

Detection of the yellow-leaf disease of rubber trees using low-altitude digital imagery from UAV

Efficient and non-destructive detection of rubber tree diseases is of great significance for optimizing disease control measures for pesticide application and fertilization.In this study,the feasibility of rubber yellow-leaf disease monitoring based on a low-altitude unmanned aerial vehicle(UAV)remote sensing platform was explored,and a low-cost method for detecting yellow-leaf disease based on visible light sensors was proposed.We compared the difference between the spectral response of each band of the visible light sensor in the diseased area and the healthy area,and then decorrelated and stretched the image in the RGB color space,thereby enhancing the color separation between highly correlated channels and enhancing the color difference of the image.Then we converted the image to the HSV color space,comparing the detection effect of different morphological parameters on yellow-leaf diseases and optimizing the extraction of the diseased area.The experimental results showed that this study provides the distribution information of yellow-leaf disease of rubber trees,and the R2 of the regression model of rubber trees was greater than 0.8.This study holds significance for optimizing disease control and sustainable development of the rubber industry.

橡胶树体胚苗质量调查与分析

天然橡胶是我国重要的战略物资和工业原料,主要来源于橡胶树。橡胶树生长周期长,其苗木质量直接影响天然橡胶产业的发展,橡胶树体胚苗在前期研究中表现一致性好,且具有速生、高产的优势。海南省天然橡胶新型种植材料创新基地是当前规模生产的橡胶树体胚苗的基地,现生产品种有热研73397和热研917。本研究分析比较了热研73397体胚试管苗在2018—2020年间的株高、茎粗、叶片数、主根长等指标的差异性,比较了2020年2个品种各指标的差异性,并对不同年份不同品种进行分级比较,以期阐明橡胶树体胚苗规模生产的情况。结果表明:(1)2018—2020年,热研73397的株高、茎粗、叶片数、主根长度在各区间的比例相当;株高、叶片数、主根长度在3 a间的差异不显著;茎粗在2018和2019年之间差异显著,且3 a均值均在2.00 mm以上,最大值和最小值的差值仅为0.09 mm。(2)2020年,热研73397和热研917体胚苗的株高一致,均值均为8.0 cm,且大部分集中在5.0~10.0 cm,分别占66.13%、66.91%;热研73397和热研917的茎粗范围分别为0.80~4.23 mm、1.13~3.73 mm,均值分别为2.11 mm和2.18 mm,2个品种的茎粗在1.50~3.00 mm之间高度集中,分别占85.94%、83.82%;热研73397和热研917叶片数范围分别为0~6片和1~4片,2个品种叶片数绝大多数为1~3片,分别占88.82%、96.32%,其中热研917叶片数为2片的占比高达52.94%;热研73397的主根长度均值为9.5 cm,而热研917的为9.1 cm,2个品种的主根长度多数集中在8.0~12.0 cm之间,分别占74.12%、79.41%;方差分析结果表明,2020年2个品种的株高、茎粗、叶片数差异不显著,主根长度差异显著(P<0.05)。(3)2018—2020年调查的橡胶树体胚苗中,不同年份不同品种的橡胶树体胚苗,一级苗比例为19%~22%,二级苗比例为56%~62%。据此,规模化生产橡胶树体胚试管苗质量稳定,为橡胶树体胚苗生产工艺的推广应用提供参考。

控释尿素与普通尿素配施对橡胶树叶片和胶乳养分及产量的影响

为了明确控释尿素与普通尿素配施在橡胶树上的应用效果,通过2年田间试验,研究了减氮条件下控释尿素与普通尿素不同比例配施对橡胶树产量、叶片和胶乳矿质养分及土壤氮含量的影响,为橡胶树栽培管理中合理施氮提供技术支撑。结果表明:控释尿素与普通尿素配施可提高橡胶树干胶产量和叶片氮含量,与常规施肥相比,橡胶树干胶产量增幅为16.28%~39.13%(2021年)和7.94%~9.69%(2022年),叶片氮含量增幅为10.54%~19.17%(2021年)和10.24%~21.50%(2022年),控释尿素与普通尿素配施处理叶片氮含量均处于正常值以上。控释尿素与普通尿素配施还能够增加胶园肥穴土壤碱解氮含量,较常规施肥增加了11.27%~80.36%。控释尿素与普通尿素配施比例为50∶50时,橡胶树干胶产量(2022年)、叶片氮含量(2021—2022年)和土壤碱解氮含量(2021—2022年)均显著高于常规施肥。综上所述,在本试验条件下,控释尿素与普通尿素配施比例为50∶50能够获得较高的干胶产量,可改善叶片营养状况,维持土壤氮水平,有利于实现橡胶树施肥管理的绿色协同增效。

橡胶树白粉病拮抗放线菌的筛选及田间防效评价

为筛选对橡胶树白粉病菌具有拮抗作用的生防放线菌,本研究从云南省主要植胶区橡胶树根际土壤中分离放线菌,以橡胶树主要病害病原菌为靶标菌,采用平板对峙培养法初步筛选出1株抑菌效果良好的放线菌菌株,命名为DL5C,其对橡胶树尖孢炭疽菌Colletotrichum acutatum、胶孢炭疽菌C.gloeosporioides、橡胶树白根病病菌Rigidoporus lignosus、橡胶树褐根病病菌Phellinus noxius的抑菌率分别为58.35%、60.97%、60.03%、74.00%;DL5C菌株发酵滤液对橡胶树白粉病菌Oidium heveae孢子萌发的抑制率达72.40%;田间试验结果表明,处理7 d后,DL5C菌株发酵液对橡胶树白粉病的相对防效为80.93%。通过菌株形态特征、培养特征、生理生化特性以及16S rRNA基因序列分析,放线菌菌株DL5C被鉴定为不吸水链霉菌Streptomyces ahygroscopicus。

中国橡胶树北移栽培研究的历史考察

以20世纪50-80年代中国开展的橡胶树北移栽培研究作为研究对象,从科学史的视角,系统梳理了在西方国家对我国实行橡胶禁运的背景下,中国科学院相关研究所与当时林垦部下辖地方农垦系统、地方科研院所面对国家需求,在华南与云南分别开展系统的中国热带生物资源考察,并在此基础上确定橡胶宜林地,开展橡胶树抗寒抗风研究,最终成功实现橡胶树北移栽培,满足了国家对橡胶这一战略物资需求的过程。这有助于深入理解20世纪50-80年代国家实施的“任务带动学科”的科学发展方针,同时对于认识当代科学研究如何满足国家需求、重大科学研究中不同机构如何更好开展协同攻关,具有重要的现实借鉴价值。

胶园间作不同马铃薯品种对土壤性质及微生物多样性的影响

本研究以橡胶单作为对照,采用生物化学分析方法和高通量测序技术,分析间作不同马铃薯品种后胶园土壤化学性质、酶活性以及微生物多样性的变化规律。研究结果表明:胶园间作不同马铃薯相比橡胶单作能显著提高土壤有机质、全氮、全磷、全钾、碱解氮和有效磷含量及土壤β-葡萄糖苷酶、N-乙酰-β-D-葡萄糖苷酶、酸性磷酸酶和芳基硫酸酯酶活性,不同品种间存在显著差异,对土壤养分影响排序为:剑川红>紫薯>大牛角,对土壤酶活性影响排序为:大牛角>剑川红>紫薯。胶园间作马铃薯显著提高土壤微生物的丰富度指数和多样性指数,品种间不存在显著差异。但不同品种对土壤特定菌群丰度影响存在显著差异,总体趋势是显著降低特有细菌如绿弯菌门(Chloroflexi)、脱硫菌门(Desulfobacterota)等的丰度,显著增加特有真菌如被孢菌门(Mortierellomycota)、壶菌门(Chytridiomycota)、梳霉门(Kickxellomycota)等的丰度。LEfSe分析发现间作马铃薯富集了一些参与物质循环或具有拮抗植物病原菌的有益微生物,大牛角、紫薯和剑川红分别富集了16、26和31种标志微生物。冗余分析和相关性分析发现,土壤养分和酶活性与胶园土壤特定细菌、真菌门丰度有显著相关性,养分和酶活性增加,降低细菌门丰度,增加真菌门丰度。综上所述,间作马铃薯显著提高了胶园土壤养分、酶活性以及土壤微生物群落多样性,降低特定细菌门和增加特定真菌门的丰度;不同马铃薯品种对土壤养分和酶活性的影响存在显著差异,可能与其富集不同有益微生物相关。本研究为胶园林下间作提供了新的思路和数据支撑。

减量施氮对橡胶树——葛藤间作模式结瘤固氮及氮素吸收利用的影响

【目的】研究接种根瘤菌后,减量施氮对橡胶树与葛藤间作模式结瘤固氮及氮素吸收利用的影响,为胶园减少氮肥施用量、实现绿色发展提供理论依据。【方法】在幼龄胶园中,采用随机区组设计,设5个处理:橡胶树单作,配合正常氮肥施用量(对照,CK1);橡胶树间作葛藤但不接种根瘤菌,配合正常氮肥施用量(对照,CK2);橡胶树间作葛藤并接种根瘤菌后,配合正常氮肥施用量(T100)、减施25%氮肥(T75)和减施50%氮肥(T50);分析不同处理下根瘤固氮效果、作物生长状况、作物氮含量、葛藤氮累积量及表层(0~30 cm)土壤全氮含量。【结果】与T100处理相比,T75和T50处理的葛藤根瘤数量、根瘤鲜重、固氮酶活性、固氮潜力和豆血红蛋白含量均增加,其中T50处理与T100处理差异显著(P<0.05,下同);T75和T50处理的葛藤地上部干重和根系干重均与CK2无显著差异(P>0.05,下同),而T50处理的葛藤根系氮含量和地上部氮累积量均较CK2显著增加,分别是其1.10和1.49倍。与CK1和CK2相比,接种根瘤菌配合减施氮肥对橡胶树的树围、树高和叶片氮含量均无显著影响,但T50处理的胶园0~10 cm、10~20 cm和20~30 cm土层土壤全氮含量均较CK1显著提高15%以上。相关分析结果表明,根瘤固氮酶活性与葛藤植株干重、氮含量和氮积累量呈显著正相关。【结论】在橡胶树与葛藤间作模式中,接种根瘤菌配合减施50%氮肥,可增强葛藤根瘤的固氮能力,从而提高表层土壤全氮含量,促进葛藤对氮素的吸收和累积,并维持橡胶树叶片氮素含量,保证了葛藤和橡胶树的正常生长。

防治橡胶树褐根病0.5%戊唑醇膏剂的研制

由木层孔菌属有害层孔菌Phellinus noxius Corner引起的褐根病是我国橡胶树的主要根部病害之一。生产上常用挖隔离沟和灌根施药方式进行防治,但其耗费人力物力,防治成本高。为了寻求经济高效且环保的新技术,本研究通过对不同杀菌剂、填料、增稠剂、渗透剂和保湿剂进行筛选,制备了一种防治橡胶树褐根病的膏剂。随后,通过对外观、附着性、黏度、pH值、稳定性、成膜性及固含量流失率等性能指标的综合评价,确定了膏剂的最佳配方为:0.5%(质量分数,余同)戊唑醇、20%纳米硅藻土、2%羧甲基纤维素钠、6%乌迪尔树皮穿透剂、5%凡士林、5%棕榈油、5%乙二醇,余量为水。制备的膏剂为乳白色黏稠状,呈弱碱性,附着性强,黏度高,冷热储合格,成膜薄且有韧性,膜的固含量流失率为13.95%,耐雨水冲刷能力强。0.5%戊唑醇膏剂经过橡胶植株茎基部施药,通过气相色谱-串联质谱(GC-MS/MS)结合QuEChERs法检测橡胶根中戊唑醇的含量。结果表明,施药后24 h即可在植株根部检测到戊唑醇,96 h含量达到5.49 mg/kg,说明戊唑醇能穿透茎部树皮向下传导至根部。综上所述,膏剂剂型的研制为橡胶树褐根病的化学防治提供了一种新途径。