Hevea Brasiliensis Clones Research Articles

Productivity evaluation of 10 Hevea brasiliensis clones in Ecuador under escape conditions for South American leaf blight

Productivity evaluation of 10 Hevea brasiliensis clones in Ecuador under escape conditions for South American leaf blight

Leaf thermotolerance of Hevea brasiliensis clones: intra- versus interclonal variation and relationships with other functional traits.

Land surface temperature is predicted to increase by 0.2°C per decade due to climate change, although with considerable regional variability, and heatwaves are predicted to increase markedly in the future. These changes will affect where crops can be grown in the future. Understanding the thermal limits of plant physiological functioning and how flexible such limits are is thus important. Here, we report on the measurements of a core foliar thermotolerance trait, T50, defined as the temperature at which the maximum quantum yield (Fv/Fm) of photosystem II declines by 50%, across nine different Malaysian Hevea brasiliensis clones. We explore the relative importance of interclonal versus intraclonal variation in T50 as well as its association with leaf and hydraulic traits. We find very low variation in T50 within individual clones (mean intraclonal coefficient of variation (CoV) of 1.26%) and little variation across clones (interclonal CoV of 2.1%). The interclonal variation in T50 was lower than for all other functional traits considered. The T50 was negatively related to leaf mass per area and leaf dry matter content, but it was not related to hydraulic traits such as embolism resistance (P50) or hydraulic safety margins (HSM50). The range of T50 observed (42.9-46.2°C) is well above the current maximum air temperatures Tmax,obs (T50 - Tmax,obs>5.8 °C), suggesting that H. brasiliensis is likely thermally safe in this south-east Asian region of Malaysia.

Influence of different protein contents from several clonal varieties of Hevea brasiliensis latex on the properties of cured natural rubber film using glutaraldehyde (GA) as a curing agent

Natural rubber films were prepared from four different Hevea brasiliensis clones, namely RRIM600, RRIT251, PB235, and BPM24, using the creamed concentrated latex method. The creamed latexes were characterized by their protein content and particle sizes. The rubber particle surface characteristics were monitored using transmission electron microscopy (TEM). It was observed that the particle sizes of all clones varied in the range of 1.0–2.5 µm. Moreover, the RRIT251 clone exhibited higher protein content than the other clones. The influence of protein content on the properties of cured natural rubber (NR) was investigated using glutaraldehyde as a cross-linking agent. Mechanical properties, crosslink density, relaxation behavior, and heat resistance indicated by T90 (temperature scanning stress relaxation, TSSR) were considered. The crosslink density of cured NR increased with higher protein content. This phenomenon can be attributed to the strong formation of rubber chains with GA cross-links through the amino groups of proteins present in rubber molecules. Consequently, Hevea brasiliensis clones with higher protein content facilitate improved crosslink formation within the GA system, resulting in enhanced mechanical and thermo-oxidative degradation properties (T90 from TSSR test).

Determination of antioxidant enzymes level in healthy and tapping panel dryness (TPD) syndrome affected bark tissues of rubber tree (Hevea brasiliensis Muell. Arg.)

Oxidative stress may lead to overproduction of reactive oxygen species (ROS) which are highly toxic ultimately cause stimulation of antioxidant enzymes and damages to proteins, lipids, carbohydrates and DNA molecules in bark tissue of Hevea brasiliensis during onset of Tapping panel dryness syndrome (TPD). In this study, Antioxidant enzymes level in bark tissues of seven different healthy and TPD affected clones of Hevea brasiliensis namely RRII 105, PB 217, PB 235, PB 285, PB 5/51, PCK2 and GT1 was determined to monitor TPD occurrence. The results revealed that increased level of antioxidant enzymes activity was noticed in bark tissues of TPD affected clones while it was found to be low in healthy clones. Maximum level of superoxide dismutase (SOD) activity noticed was 0.634 U/mg FW in healthy PB 5/51 clone compared with its TPD affected clone. The CAT activity was also found to be high in healthy PB 5/51 clone (1.988 U/mg) than TPD affected clone. In the case of peroxidase (POX) activity, it was found to be low in all healthy clones while the activity was significantly increased in TPD affected clones and maximum activity was noticed in PCK2 followed by PB285. Antioxidant enzymes level was also determined by native PAGE analysis and its results showed that isoenzymes of SOD and POX banding pattern are directly correlated with biochemical assays activity. This research correlates the activities of antioxidant enzymes between healthy and TPD affected clones and paves the path to understand the role of SOD, CAT and POX during onset of TPD and leads to future genetic studies on antioxidant enzymes and its genes in Hevea brasiliensis.

Latex yield variation among Hevea brasiliensis clones grown under the agro- climate of South-West Ethiopia

Hevea brasiliensis is the primary commercial source of natural rubber in the world and its latex is a source for many industrial inputs. The latex yield potential of rubber tree plantations has been lower than the estimated potential due to latex yield variation among rubber tree clones. Nine introduced and one indigenous Hevea brasiliensis clones were evaluated in Ethiopia Guraferda district from July 2018 to May 2020 to determine which clones provide a better latex yield for future rubber tree plantations. Ten Hevea brasiliensis clones were evaluated with ten trees of the same age selected randomly from the same plantation site for each clone. The latex yield was significantly varied both from clone to clone and from month to month during the study period. Mixed, RRIC101, and Malawi clones of Hevea brasiliensis produced the highest latex yield, whereas the TOLIK.B clone had the lowest. The highest average latex yield was obtained in June, which has a high rainfall with moderate temperature. The results of this study indicate that latex yield potential could be increased by mass planting of rubber tree clones which give more yield and resistance to diseases.

Physiological and biochemical characteristics of two contrasting clones of Hevea brasiliensis under cold stress

Physiological and biochemical responses of two Hevea clones, differing in cold tolerance potential, namely, RRII 105 (susceptible) and SCATC 88/13 (tolerant) were assessed under low temperature exposure. They were accustomed under controlled conditions (30°C/22°C day/night) for one week before the actual low temperature treatment (15°C/7°C day/night) for two weeks and then allowed for a recovery period (30°C/22°C day/night) of three days. The objective of the experiment was to evaluate the changes in physiological and biochemical characteristics and to determine the ability of the genotypes to recover from cold injury upon exposure to subsequent normal temperature. Photosynthetic pigment contents were more sensitive to cold stress induced photo-oxidation; however, the clone SCATC 88/13 could maintain better level of pigments and remained green with less level of leaf yellowing even after two weeks of stress imposition. A fast recovery of growth on re-warming was noticed in this clone than RRII 105. Cold stress induced leaf injury resulted in significant inhibition of photochemical efficiency (Fv/Fm) and effective quantum yield (O PS II) of PS II in both the clones but the decline was comparatively lesser in SCATC 88/13. During stress recovery periods the rate of PS II repairing was better in SCATC 88/13 than susceptible clone. Comparatively the level of antioxidant, glutathione and rate of antioxidant enzymes activities such as total peroxidase and SOD were high during stress and recovery periods in SCATC 88/13 than RRII 105. The clone SCATC 88/13 maintained a low level of lipid peroxidation during all the phases. Low temperature stress could impair different physiological activities such as antioxidant defense systems and photochemical reactions of photosynthesis and enhance the rate of lipid peroxidation, pigments degradation and photo-inhibition. The results obtained indicate lesser cold injury and faster stress recovery on re-warming in clone SCATC 88/13.

Evolution of the Rate of Live and Tapped Trees of Hevea brasiliensis Clones, Muell. Arg. the First 15 Years of Plantation Establishment

The density of tapped rubber trees in a plantation is a determining parameter of its productivity. It is related to the number of trees planted per hectare, the evolution of which can be influenced by several factors that act on the trees from the year of establishment to the time of tapping. To this end, a study to determine the evolution of the rate of live trees and tapped trees of eight rubber clones during the first fifteen years of establishment was carried out in southwestern Côte d'Ivoire. At opening, rubber trees planted at 510 trees/ha (7 m x 2.80 m) were bled in a descending half-spiral at different tapping and stimulation frequencies. The experimental design was a Fisher block design with 6 treatments (d2, d3/4y, d4/4y, d4/8y, d5/8y, d6/10y) and 3 replications. The results revealed that the rate of live trees and tapped trees was not influenced by either clone or latex harvesting treatment. The rate of live trees decreased progressively from the immature phase of the plantation (94.71 ± 1.34%) to the end of the downward tapping (91.55 ± 0.67%). The rate of tapped trees increases from the time of planting (69.51 ± 8.03%), over the years (92.00 ± 1.39%) until it equals the rate of live trees (92.00 ± 1.08%) before gradually decreasing to 88 ± 3.78%. It should be noted that the factors influencing the evolution of the rates of live and taped trees caused less damage to the rubber trees. And this influence is not dependent on clone, metabolic activity class and latex harvesting system.

Determination of the Influence of Cultural Techniques "Densities and Opening Standardʺ on Agrophysiological Parameters of Clones Pb 260, Irca 111 and Rrim 703

To find out the effect of cultural techniques on agrophysiological parameters, four combinations ̏planting densities (low density or DF at 350 t/ha, normal density or DN at 510 t/ha) and opening standards (opening at 65cm and opening at 50 cm) ̋ were tested on Hevea brasiliensis clones PB 260, IRCA 111 and RRIM 703. This study was conducted for nine years with a split-plot experimental design of two treatments and two subtreatments repeated three times. The different combinations of treatments and subtreatments tested were low density (DN-50 cm), low density (DN-65 cm), normal density (DF-50 cm), normal density (DF- 65 cm). The parameters evaluated were the production at bleeding and per hectare, the average annual increase in circumference, the rate of tree losses and the rate of trees with dry notches. Production per tree was significantly higher at 350 t/ha and 65 cm opening (DF-65 cm), while per hectare production was higher at 510 t/ha. The girths of the different clones are stronger at DF and at the 65 cm opening. The rate of tree loss and the rate of trees with dry notch were low at the 510 t/ha density and the 65cm opening. The appropriate density and opening standard was "normal density 510 t/ha and opening to circumference 50 cm". The cultivation techniques especially the density and opening standard judiciously applied can participate in the sustainable improvement of rubber productivity of rubber plantations.

Hydraulic traits predict stem growth across Hevea brasiliensis clones in a Malaysian climatically marginal area

Competition for land resources is forcing rubber (Hevea brasiliensis Müll. Arg.) production into more agroclimatically vulnerable zones, which are more likely to be affected by drought. It is therefore of interest to determine whether there are particularly drought resistant rubber genotypes. Established plant drought-resistance indicators include xylem resistance to embolism under water stress (P50, water potential at which 50% xylem conductivity is lost), and hydraulic safety margins (HSM50), defined as the difference between P50 and minimum leaf water potential (Pmin) under driest conditions in the year. We report here on measurements of in-situ growth performance of nine mature rubber clones at an agro-climatically marginal site in North-Western Malaysia and their hydraulic, leaf and stem traits to investigate inter-clonal variation in drought resistance and growth rate. We find that P50 varies substantially across clones, between −3.05 and −1.37 MPa, while HSM50 varied within the range of −0.11 MPa to 1.37 MPa. Similar to what has been reported across species, we find a growth-hydraulic safety trade-off between rubber clones with faster growth rates associated with a lower HSM50 and less negative P50, with one exception. Based on hierarchic linear regression we find that almost all of the best growth models include hydraulic traits, besides morphological traits, indicating that hydraulic traits are important to predict growth accurately. Furthermore, rubber genotypes with high growth rate and low hydraulic safety margin (HSM50) were associated with lower wood density, higher leaf to sapwood area and larger leaf area. Overall while there are clones that are more drought resistant and are thus suited for plantation in marginal areas, they tend to be less productive.

Effect of Late Upward Tapping on the Productivity of the Metabolically Active Hevea brasiliensis Clone PB 260 in Southwestern Cote d'Ivoire

In order to evaluate the improvement of rubber productivity of rubber trees by late upward tapping. A study was conducted at SCASO (Société Civile Agricole du Sud-Ouest) on the PB 260 clone of the active metabolic class. The experimental set-up is a Fisher block design with eight treatments and three replications. The treatments compared were bled in reverse in the eleventh year of harvest, in quarter spiral every 3, 4, 5 and 6 days, with stimulation frequencies of 6, 8, 10, 12 and 13 times a year. The parameters measured were rubber production, isodiametric growth, sensitivity to dry notching of trees and physiological profile. The results show that the different latex harvesting technologies improve the rubber productivity of PB 260 (5469 kg.ha-1.yr-1) with a low dry-nut rate (1.2%) and satisfactory radial vegetative growth (3.9cm.yr-1). The physiological profile of the trees is balanced, but the treatments significantly influenced the different parameters except sucrose. Trees bled in S/4U d3 gave better results due to their high yield with an acceptable dry notch rate. Late reverse tapping is therefore a good latex harvesting technology for improving rubber productivity after down tapping.

Technological potential of fibers from 20 Hevea brasiliensis clones for use as pulp, paper, and composite materials

Based on the use of Hevea brasiliensis in latex production, the species has a consolidated role in the Brazilian economy. However, at the end of the production cycle, which lasts from 25 to 30 years, resulting wood, in general, has no added value and is normally used for firewood, without further exploring its technological properties. Seeking to introduce this species into the pulp and paper industry, we aimed to determine the fiber quality of 20 commercial clones. Wood samples were collected from planted trees (11 to 12 years old) in the municipality of Selvíria - MS. We calculated wood quality indexes of H. brasiliensis for cellulose and paper, including Flexibility coefficient, Wall proportion, Runkel ratio, Slenderness ratio (Aspect ratio), and Luce's Shape Factor. The fiber quality indexes that best indicate the potential use of wood from Hevea brasiliensis clones for cellulose and paper production were Wall Fraction, Runkel Ratio and Luce's Shape Factor, indicating that H. brasiliensis fibers, if used for proper industrial purposes, will give origin of a rigid paper with greater bonding contact on the surface. The clones that presented better results for fiber quality indexes were IAC 311, IAC 41, IAN 873, IAC 326, IAC 40 and RRIM 725. Enabling the use of wood after the latex exploratory cycle for pulp and paper will serve as a basis for genetic improvement of these clones and expansion of forest plantations for this purpose.

Identification of yeasts in different rubber leaf (Hevea brasiliensis) clones and their effects on the physical properties of fermented glutinous rice tapai

Tapai is one of the most popular traditional desserts in Malaysia and other Asian countries. Traditionally, tapai is wrapped in a rubber leaf to enhance the smell and increase its palatability. The study focused on identifying the yeasts present before and after the production of glutinous rice tapai wrapped in different rubber leaves clones, namely RRIM 2025, RRIM 2002, PB 260 and PB 350. The identification of the yeast was carried out using API 20C AUX test strips for all rubber leaves clones, glutinous rice tapai wrapped in RRIM 2025, RRIM 2002, PB 260, PB 350 and in a container (control). The results showed that Crytococcus laurentii, Rhodotorula mucilaginosa 2, Candida famata, Rhodotorula minuta were present in rubber leaf clones. While the yeasts that had been identified in tapai wrapped in rubber leaf were Candida guilliermondii, Rhodotorula mucilaginosa 2, Candida parapsilosis and Trichosporon mucoides and only C. guilliermondii was found in the container. The physical properties of the tapai that are wrapped in rubber leaves have a difference in texture, pH value and total soluble solids content compared to the control sample. The tapai sample wrapped in RRIM 2025 and RRIM 2002 had a high total soluble solid content of 45.8±0.14% and 45.78±0.16% °Bx, respectively. Meanwhile, the control sample has the highest pH value and the hardest rice kernels, which were 4.71±0.05 and 218.19±25.39 N, respectively. The results showed that the different yeasts present in the rubber leaf may cause changes in the physical properties of glutinous rice tapai.

ANATOMICAL RADIAL VARIATION AND DENSITY IN WOOD OF RUBBER TREE [Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.] CLONES

The anatomical structure and physical properties of wood change signifcantly among trees of the same species and even among different parts of the same tree. However, studies that characterize radial variation of anatomical characteristics and wood density among clones are scarce, specifcally for the rubber tree [Hevea brasiliensis (Will. ex Adr. De Juss.) Muell]. Thus, the objective of the research was evaluating the anatomical radial variation and density in wood of Hevea brasiliensis clones. For this study, 30 trees, three of each progeny from 10 clones were used. For most clones, we noticed an increase in fber length and vessel diameter towards the bark. For vessel frequency, ray height, width and frequency, we observed a decrease towards the bark. Fiber wall thickness was the most distinctive anatomical characteristic, compared to the others, presenting a trend of thicker walls in the middle position, consequently infuencing basic density clones.

Field evaluation of Hevea brasiliensis clones for the incidence of white root disease in Nigeria

Incidence and severity of white root disease affecting rubber trees were determined in ûve rubber clones of 10 and 35 years old. The percentage of infection, aggregate failure, level of infectivity and gross economic loss were evaluated. There were variations in resistance to white root disease among rubber clones studied. However, no rubber clone was free from this disease even though there were signiûcant (P>0.05) differences in the ability of the pathogen to attack different clones. Results of disease index in the multiclonal plot were compared with those from plots of specific clones of rubber. Percentage infection in 35-year-old rubber plots was signiûcantly (P>0.05) higher than 10-year-old rubber trees. The level of infectivity of white root disease pathogen was generally high with the lowest value for missing stands of 3.33 ± 1.67 (representing 41.63 per cent of expected neighbouring stands) and as many as 6.00 ± 0.56 (representing 75 per cent of expected neighbouring stands) in 10 and 35-year-old rubber plots, respectively. The estimated gross economic losses (N 113,652.30 to 274,734.30) per year recorded in the study were high. This study indicates the need for regular monitoring of white root disease in rubber plantations so that the disease can be managed and controlled at an early stage of the disease occurrence.

Quantitative Assessment of the Agro-physiological Advantages of Upward Tapping in Relation to the Downward Tapping of the GT 1 and PB 260 Rubber Clones [Hevea brasiliensis, Muell. arg. (Euphorbiaceae)] in Southwest Côte d'Ivoire

The downward tapping on virgin bark of the lower panel (BO) is immediately followed by the upward tapping on virgin bark of the upper panel (HO), consecutively. To determine the agro-physiological advantages of one tapping over another, a study of the downward and upward tapping of the GT 1 and PB 260 clones of Hevea brasiliensis was carried out in southwestern Côte d'Ivoire. For this purpose, the rubber trees were tapped in a downward half-spiral (S/2) at the opening for nine consecutive years, followed by upward quarter-spiral tapping (S/4U) for four consecutive years. The agronomic parameters (rubber production and vegetative growth), tapping panel dryness and the latex micro-diagnosis, were evaluated. For GT 1 clone, the transition from the downward tapping panels to the upward tapping panels resulted rubber productivity gain of 35%. Meanwhile for PB 260, rubber productivity gain was 37%. Regardless of the clone and tapping direction, the higher the rubber productivity of a respective tapping panel, the lower the isodiametric growth of the tree trunk was recorded. Latex harvesting systems, and clone’s combination, did not influence the tapping panel dryness or the physiological profile of the trees. Finally, it should be concluded that upward tapping is more productive than downward tapping, but the quantification of the gains in this rubber production depends on the clone.

Effect of Exogenous Hormonal Stimulation on the Metabolic Partition between Plant Growth and Rubber Production of Hevea brasiliensis Clones According to the Class of Metabolic Activity in Cote d'ivoire

Aims: In order to achieve a good and sustainable harvest of Hevea brasiliensis rubber, the effect of exogenous hormonal stimulation on the metabolic partition growth-production of clones according to the class of metabolic activity was made.
 Place and Duration of Study: The study was conducted for 9 years in the San-Pedro region in south-west Ivory Coast, precisely in the experimental industrial plantations of the former HEVEGO, now Southwestern Agricultural Civil Society Société (SCASO).
 Methodology and Results: The rubber trees were planted at a density of 510 trees/ha in a completely randomised system. They were bled in S/2 d4 and stimulated to 2.5% Etephon at annual frequencies of 0, 1, 2, 4, 6, 8, 13, 18, 26, 39 and 78. The parameters measured were rubber production, trunk circumference, sucrose content, inorganic phosphorus, thiol groups and dry notch rate. The results showed that productivity increased with the intensity of stimulation (58.96 - 68.49 g.a-1.s-1 ; 39.83 - 66.69 g.a-1.s-1) over the intervals [0.6] and [0.26] stimulations respectively in clones with active and slow metabolism. The circumference of the trunk was marked by a less pronounced decrease in growth in slow metabolizing clones (0.52%) with good protection of the laticigene system (R-SH : 0.815 mmol.l-1) and low sensitivity to dry notching (1.6). Whatever the classes of metabolic activity of the clones, the agrophysiological parameters were strongly correlated with each other by a degree 2 polynomial function.
 Conclusion: This polynomial function seems to reflect the existence of a good state of equilibrium between laticigenic metabolism and vegetative growth according to the class of metabolic activity of the Hevea brasiliensis clones.

Transcriptome dataset from bark and latex tissues of three Hevea brasiliensis clones.

Hevea brasiliensis is exploited for its latex production, and it is the only viable source of natural rubber worldwide. The demand for natural rubber remains high due its high-quality properties, which synthetic rubber cannot compete with. In this paper, we present transcriptomic data and analysis of three H. brasiliensis clones using tissue from latex and bark tissues collected from 10-year-old plant. The combined, assembled transcripts were mapped onto an H. brasiliensis draft genome. Gene ontology analysis showed that the most abundant transcripts related to molecular functions, followed by biological processes and cellular components. Simple sequence repeats (SSR) and single nucleotide polymorphisms (SNP) were also identified, and these can be useful for selection of parental and new clones in a breeding program. Data generated by RNA sequencing were deposited in the NCBI public repository under accession number PRJNA629890.

Long term performance of certain ortets and hybrid clones of Hevea brasiliensis in a high altitude region in Kerala, India

Long term performance of four hybrid Hevea clones and ten ortet selections including nine from a high elevation site within the traditional rubber growing tract of Kerala was studied. Significant variability was observed among the hybrids and ortets for all major agronomic traits. Growth of rubber trees was invariably poor in the high altitude region and tappability by the tenth year of planting was less than 50 per cent. The hybrid clones RRII 203 and RRIC 100 showed highest growth vigour with 80 per cent tappability by the 13th year of planting. Among the ortets, P 270 and Iritty 1 recorded the highest tappability of 64 per cent. The ortet P 270 was the best performer with the highest girth at the opening (61 cm), girth increment during immaturity (5.5 cm) on tapping (3.4 cm) and bole volume (0.1 m3). RRII 203 was the highest yielding clone with 56 g tree-1 tap-1 over eight years of tapping. High annual yield (48 g tree-1 tap-1) and lean season yield of P 270 combined with high drc on par with the highest yielding clone RRII 203 indicated the specific adaptability of this ortet to high elevation areas. The ortets P 213 and Iritty 1 and hybrid clone RRIC 100 were the other promising clones exhibiting growth adaptation and high yield potential under high altitude conditions.

Metabolic partition between radial vegetative growth and rubber production of Hevea brasiliensis clones of different metabolic classes, bled at unstimulated d4 frequency in Côte d’Ivoire

Metabolic partition between radial vegetative growth and rubber production of Hevea brasiliensis clones of different metabolic classes, bled at unstimulated d4 frequency in Côte d’Ivoire

Structural and Functional Annotation of Transposable Elements Revealed a Potential Regulation of Genes Involved in Rubber Biosynthesis by TE-Derived siRNA Interference in Hevea brasiliensis.

The natural rubber biosynthetic pathway is well described in Hevea, although the final stages of rubber elongation are still poorly understood. Small Rubber Particle Proteins and Rubber Elongation Factors (SRPPs and REFs) are proteins with major function in rubber particle formation and stabilization. Their corresponding genes are clustered on a scaffold1222 of the reference genomic sequence of the Hevea brasiliensis genome. Apart from gene expression by transcriptomic analyses, to date, no deep analyses have been carried out for the genomic environment of SRPPs and REFs loci. By integrative analyses on transposable element annotation, small RNAs production and gene expression, we analysed their role in the control of the transcription of rubber biosynthetic genes. The first in-depth annotation of TEs (Transposable Elements) and their capacity to produce TE-derived siRNAs (small interfering RNAs) is presented, only possible in the Hevea brasiliensis clone PB 260 for which all data are available. We observed that 11% of genes are located near TEs and their presence may interfere in their transcription at both genetic and epigenetic level. We hypothesized that the genomic environment of rubber biosynthesis genes has been shaped by TE and TE-derived siRNAs with possible transcriptional interference on their gene expression. We discussed possible functionalization of TEs as enhancers and as donors of alternative transcription start sites in promoter sequences, possibly through the modelling of genetic and epigenetic landscapes.