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.

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.

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.

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.

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.

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.

Species Diversity of Arbuscular Mycorrhizal Fungi in the Rhizosphere of Hevea brasiliensis in Hainan Island,China

Hevea brasiliensis is one of the important economic trees with a great economic value for natural rubber production.Symbiosis between roots of H.brasiliensis and arbuscular mycorrhizal fungi(AMF)is widely recognized,and can provide a range of benefits for both of them.Hainan Island harbors is one of the largest plantations of H.brasiliensis in China,whereas the information regarding the diversity of AMF in the rhizosphere of H.brasiliensis on this island is scarce.The diversity of AMF species in the rhizosphere of rubber tree plantations in Hainan was investigated in this study.A total of 72 soil samples from the rhizosphere of H.brasiliensis RY7-33-97 were collected.These included 48 samples from plantations in 11 cities or counties that had been planted for 15–25 years,and 24 samples from a demonstrating plantation site of the China National Rubber Tree Germplasm Repository representing plantations with tree plantation ages from one to 40 year-old.Collectively,a total of 68 morphotypes of AMF,belonging to the genera of Archaeospora(1),Glomus(43),Acaulospora(18),Entrophospora(3),Scutellospora(2),and Gigaspora(1)were isolated and identified,as per morphological characteristics of spores presented in the collected soil samples.Glomus(Frequency,F=100%)and Acaulospora(F=100%)were the predominant genera,and A.mellea(F=63.9%)and A.scrobiculata(F=63.9%)were the predominant species.AMF species differed significantly among collected sites in spore density(SD,290.7–2,186.7 spores per 100 g dry soil),species richness(SR,4.3–12.3),and Shannon-Weiner index of diversity(H,1.24–2.24).SD was negatively correlated with available phosphorus level in the soil;SR was positively correlated with soil total phosphorus content;and H was positively correlated with levels of soil organic matter and total phosphorus.Similarly,SD,SR,and H were also correlated with H.brasiliensis plantation age,and an increasing trend was observed up to 40 years.These results suggest that the AMF community was complex and ubiquitous in the island plantation ecosystems of H.brasiliensis,with high species abundance and diversity.Soil factors and plantation age dramatically affected AMF diversity at species level.

Dynamics of Soil N<span>H</span>⁺<sub style="margin-left:-10px;">4</sub>-N and N<span>O</span>^-<sub style="margin-left:-4px;">3</sub>-N in Rubber Plantation in Wenchang, South China

In this study, the dynamics of soil available nitrogen in rubber plantations was studied to provide a basis for the sustainable management of soil nutrients in rubber plantations. Soil samples were collected from 0 - 20 cm and 21 - 40 cm depth of rubber plantations in Wenchang area of Hainan Province to determine the soil ammonium nitrogen and nitrate nitrogen in March, June, September and December. The results showed that the total available nitrogen in the rubber plantation soil was mainly composed of nitrate nitrogen (>57%), and this nitrate nitrogen was always the absolute composition advantage in the total available nitrogen composition, and this composition advantage did not change with the change of soil depth. Nitrate and ammonium nitrogen in rubber plantation soil showed obvious seasonal variation characteristics in 0 - 20 cm soil layer and 21 - 40 cm soil depth. With the seasonal time change, the contents of soil nitrate and ammonium nitrogen increased first and then decreased. Summer and autumn were the most active periods of soil nitrate and ammonium nitrogen. There was a significant positive correlation between soil nitrate nitrogen content and ammonium nitrogen content (r = 0.6532**). Based on the correlation between soil ammonium nitrogen content and nitrate nitrogen content, the content of ammonium nitrogen in soil can be estimated according to the amount of soil nitrate nitrogen.

Converting rubber seed oil into hydrocarbon fuels via supported Pd-catalyst

The one-step hydrotreatment of rubber seed oil to produce hydrocarbon fuels has been carried out via supported Pd-catalyst,and analyzed emphatically some elements affected catalytic cracking process,for example,temperature,hydrogen partial pressure and dosage of catalyst,etc.Through experimental research,the author found out the appropriate catalytic cracking conditions as follows:310℃ of reaction temperature,2 MPa of hydrogen partial pressure,15 of the ratio of oil to catalyst(m(oil)/m(catalyst)),100 r/min of stirring speed.Under these conditions,effective component of hydrocarbon fuels in the converted oil accounts for 99.49%,and the proportion of C_(8)-C_(16) can reach as high as 79.61%.The converted oil was similar to petroleum-based oil in chemical composition,and can be used for future the aviation biofuels development as the source of raw material because it contains a large amount of hydrocarbon in the range of C_(8)-C_(16).

In vitro Transient Expression System of Latex C-serum was used for Analysis of Hevein Promoter in Response to Abscisic Acid in Hevea brasiliensis

Hevein has been found to be an essential element in coagulation of rubber particles in latex of rubber trees. In a previous study, we cloned a 1 241-bp fragment of a 5＇ upstream region of the hevein gene by genome walking. This fragment was analyzed by a 5＇ end nested deletion method in the present study, fused with a uidA （gus） gene to produce a series of tested constructs, which were transferred into C-serum of latex and the Gus activities were detected. Results showed that the fragment from -749 to -292 was sufficient for expression of gus gene in latex, and the fragment from -292 to -168 was crucial in response to abscisic acid inducement. In a transient transgenic test of rubber leaf with particle bombardment, construct Hev749 conferred gus-specific expression in veins, in which the latex tubes mainly distributed. This implies that the fragment from -749 to -292 was laticiferous-specific.

Feature extraction of overlapping hevea leaves:A comparative study

Automation of rubber tree clone classification has inspired research into new methods of leaf feature extraction.In current practice,rubber clone inspectors has been using several leaf features to identify clone types.One of the unique features of rubber tree leaf is palmate leaflets.This characteristic generates different leaflet positions,where the leaves are overlapping or separated.In this research,we propose keypoint extraction and line detection methods to extract shape and axil(angle between petioles)features of leaflet positions.The results of keypoint extraction methods,namely,SIFT,Harris,and FAST,were compared and discussed for shape feature extraction.Next,Hough transformation and boundary-tracing methods were compared to identify the suitable axil detection method.The evaluation result demonstrates the proper keypoint extraction method for shape context and the clear advantages of Hough Transformation in accuracy of angle detection.