Rubber Tree Genotypes Research Articles

Simultaneous selection of rubber yield and girth growth in young rubber trees

The importance of the rubber yield from the rubber tree (Hevea brasiliensis) is already well known. Recently, the importance of girth growth and consequently wood rubber tree has been emphasized. Genotypes with greater girth growth produce greater volume of wood. Rubber tree timber can be used as raw material for a vast range of products, substituting wood from natural forests. Rubber tree genotypes that combine high yield and vigorous growth are of great interest for genetic improvement. Thus, the objective of the present study is the simultaneous selection in young rubber tree progenies for dual-purpose rubber yield and girth growth. Twenty-two progenies were used which were assessed at the field in two locations in a randomized experimental block design with three replicates and 3m×3m spacing. The classic selection index was used; this index is a tool that allows all the characters of interest to be used simultaneously. The progeny effect was significant for both variables and in both locations, indicating progeny genetic variability and the possibility of selection. The progeny mean heritability (hˆx¯2) was greater than the heritability based on single individual's level (hˆi2) and within plot heritability (hˆw2). The multicollinearity among the variables was low, so the variables could be used simultaneously to construct the selection index. Four progenies were selected with an 18% selection intensity, but the progenies were different in the two locations. The classic selection index was efficient in simultaneous selection of rubber yield and girth growth in progeny of young rubber trees. Simultaneous selection for rubber yield and vigor is important at the initial stages of genetic breeding and should be done per location. This selection contributes to identifying superior progeny for rubber yield and with potential for double purpose: wood and rubber production.

Genetic diversity of cultivated accessions and wild species of rubber tree using EST‑SSR markers

The objective of this work was to evaluate the efficiency of EST‑SSR markers in the assessment of the genetic diversity of rubber tree genotypes (Hevea brasiliensis) and to verify the transferability of these markers for wild species of Hevea. Forty‑five rubber tree accessions from the Instituto Agronômico (Campinas, SP, Brazil) and six wild species were used. Information provided by modified Roger's genetic distance were used to analyze EST‑SSR data. UPGMA clustering divided the samples into two major groups with high genetic differentiation, while the software Structure distributed the 51 clones into eight groups. A parallel could be established between both clustering analyses. The 30 polymorphic EST‑SSRs showed from two to ten alleles and were efficient in amplifying the six wild species. Functional EST‑SSR microsatellites are efficient in evaluating the genetic diversity among rubber tree clones and can be used to translate the genetic differences among cultivars and to fingerprint closely related materials. The accessions from the Instituto Agronômico show high genetic diversity. The EST‑SSR markers, developed from Hevea brasiliensis, show transferability and are able to amplify other species of Hevea.

Development of genomic‐derived simple sequence repeat markers in Hevea brasiliensis from 454 genome shotgun sequences

With 2 figures and 2 tablesAbstractIn an attempt to develop additional microsatellite markers in rubber tree, we employed a 454 pyrosequencing technology to obtain genomic shotgun sequences and subsequently identified over 24 000 putative simple sequence repeats (SSRs). A total of 418 potential SSR loci were chosen for an empirical validation. Two hundred and twenty‐four primer pairs yielded successful amplification, and 90 SSR markers exhibited polymorphism among the 18 rubber tree accessions evaluated. The number of alleles per locus ranged from 2 to 7, with an average of 3.44 alleles per SSR. The gene diversity of individual microsatellite loci displayed a broad range of values from 0.104 to 0.901 with a mean of 0.612. The polymorphism information content also varied greatly from 0.099 to 0.893 with an average of 0.577. We also identified a set of five highly informative markers that were able to unequivocally distinguish 18 rubber tree genotypes examined in this study.

Temporal stability of vigor in rubber tree genotypes in the pre- and post-tapping phases using different methods

Vigor is important in rubber tree cropping because of its association with early latex exploitation, resistance to wind breakage and wood production. The objective of the present study was to assess the vigor stability of 25 rubber tree genotypes in the pre- and post-tapping phases using different methods. A randomized block design was used with three replications and six plants per plot. Seven annual trunk girth increments were used in the pre-tapping and six in the post-tapping phases. Stability was assessed by the methods by Wricke, Eberhart and Russell, Lin and Binns, and the AMMI statistical model (Model Additive Main Effects and Multiplicative Interaction). The association among the different stability parameters ωι, \( \hat{S}_{di}^{2} \), Pi, and IPCA 1 was verified by the Spearman correlation. Joint ANOVA showed highly significant effects for genotypes, years, and genotypes × years interaction in the two phases. In the pre-tapping phase, the IAC 311 genotype was stable in all the methods and in the post-tapping presented stability in Eberhart and Russell, Wricke, and AMMI. In the post-tapping phase, the IAC 312 genotype was stable in Eberhart and Russell, AMMI and Lin and Binns. While in the pre-tapping the correlations were positive and significant among all the parameters, in the post-tapping it only occurred between ωι with \( \hat{S}_{di}^{2} \) and ωι with IPCA 1. In the stability assessment of rubber tree vigor, the association among the methods depended on the assessment period. Stability methods based on different principles can show agreement in identifying stable genotypes in rubber tree vigor. The tapping procedure affected vigor stability of rubber trees.

Development and characterization of 296 new polymorphic microsatellite markers for rubber tree (Hevea brasiliensis)

With 2 figures and 1 table AbstractEnriched genomic libraries in GA and GT tandem repeat motifs were generated from rubber tree (Hevea brasiliensis). Design of appropriate primer pairs in the flanking regions enables to produce amplified fragments for 310 of these sequences. The test of these genomic microsatellites on a set of 10 rubber tree genotypes allows the characterization of 296 new polymorphic markers. Expected heterozygosity ranged from 0.10 to 0.93 and allele numbers from 2 to 11. Microsatellite loci with GA motifs were more abundant, longer and more polymorphic than GT motifs. Such a high variability suggests the utility of these markers for the establishment of integrated linkage maps, as well as the characterization of linkage disequilibrium in rubber tree populations.

Temporal stability of growth and yield among Hevea genotypes introduced to a non-traditional rubber growing region of peninsular India

Extensive cultivation of Hevea brasiliensis in India now focus on non-traditional regions for rubber cultivation. As a prelude for selection of genotypes for commercial cultivation, many introduced genotypes are being tested in genotype adaptation experiments in these regions. Present study, reports for the first time, growth and yield adaptation of 28 genotypes in a non-traditional rubber growing region of peninsular India viz., the coastal Karnataka region. Agroclimate of this region was found favoring growth and establishment of all the genotypes evaluated. However, not all the genotypes grew and yielded well. Only four genotypes, RRII 203, KRS 25, PB 260 and PB 235 showed good growth and yield. On grouping, the genotypes fell into categories of moderate high yielders, moderate low yielders and low yielders. The most popular variety of the traditional region, RRII 105 did not perform well in this region. Biological stability in growth and yield of RRII 203 and PB 260 was identified as stable and these genotypes were the best adapted. KRS 25 and PB 235 had unstable yielding pattern. The best identified genotypes can be considered for extensive culture as single clone plantations or as major constituent of clone blends as well as parents in future breeding programmes. Other moderate stable yielders may be used for clone blending in smaller proportions and may be subjected to yield improvement.

Divergence and genetic variability among superior rubber tree genotypes

The objective of this work was to estimate the genetic variability and divergence among 22 superior rubber tree (Hevea sp.) genotypes of the IAC 400 series. Univariate and multivariate analyses were performed using eight quantitative traits (descriptors), including yield. In the univariate analyses, the estimated parameters were: genetic and environmental variances; genetic and environmental coefficients of variation; and the variation index. The Mahalanobis generalized distance, the Tocher agglomerative method and canonical variables were used for the multivariate analyses. In the univariate analyses, variability was verified among the genotypes for all the variables evaluated. The Tocher method grouped the genotypes into 11 clusters of dissimilarity. The first four canonical variables explained 87.93% of the cumulative variation. The highest genetic variability was found in rubber yield-related traits, which contributed the most to the genetic divergence. The most divergent pairs of genotypes are suggested for crossbreeding. The genotypes evaluated are suitable for breeding and may be used to continue the IAC rubber tree breeding program.

Genetic divergence of rubber tree estimated by multivariate techniques and microsatellite markers

Genetic diversity of 60 Hevea genotypes, consisting of Asiatic, Amazonian, African and IAC clones, and pertaining to the genetic breeding program of the Agronomic Institute (IAC), Brazil, was estimated. Analyses were based on phenotypic multivariate parameters and microsatellites. Five agronomic descriptors were employed in multivariate procedures, such as Standard Euclidian Distance, Tocher clustering and principal component analysis. Genetic variability among the genotypes was estimated with 68 selected polymorphic SSRs, by way of Modified Rogers Genetic Distance and UPGMA clustering. Structure software in a Bayesian approach was used in discriminating among groups. Genetic diversity was estimated through Nei's statistics. The genotypes were clustered into 12 groups according to the Tocher method, while the molecular analysis identified six groups. In the phenotypic and microsatellite analyses, the Amazonian and IAC genotypes were distributed in several groups, whereas the Asiatic were in only a few. Observed heterozygosity ranged from 0.05 to 0.96. Both high total diversity (HT' = 0.58) and high gene differentiation (G st' = 0.61) were observed, and indicated high genetic variation among the 60 genotypes, which may be useful for breeding programs. The analyzed agronomic parameters and SSRs markers were effective in assessing genetic diversity among Hevea genotypes, besides proving to be useful for characterizing genetic variability.

Ecophysiological factors underpinning productivity of Hevea brasiliensis

High land productivity is a must for any commercial cultivation including Hevea brasiliensis (rubber). Also, the high demand for natural rubber has placed great pressure on expanding rubber cultivation to new and non-traditional areas. Understanding the ecophysiological principles behind the measures of productivity improvements is vital for wide application of these measures and to assess their sustainability. This review discusses the ecophysiological principles and tools used, along with the measures taken, to address productivity needs in terms of: genotype selection, determination of optimum planting density, and establishment of intercropping systems. Breeding for high yields and selection of suitable genotypes for different growing conditions are a top priority throughout the research history of rubber, however, early selection tools are necessary to reduce the time required for this process. As for any crop, photosynthesis drives the productivity of the rubber crop and, therefore, factors that govern and/or parameters that indicate the efficiency of photosynthetic productivity under field conditions could be used as tools in the selection of Hevea genotypes. Particularly for the early selection of genotypes in breeding programmes, mature crop characteristics which determine crop photosynthesis and productivity, should be linked to juvenile plant characteristics. The spatial and temporal efficiency by which plants acquire growth resources determines the overall productivity of the rubber crop, hence the optimum planting density and suitable crop combinations in intercropping systems. Changes in crop microclimate influence the efficiency of resource capture and thereby can be important for determining planting density and intercrops. Research needs regarding all the above aspects are also discussed.

Age-age correlation for early selection of rubber tree genotypes in São Paulo State, Brazil

In a field trial involving 68 rubber tree (Hevea spp.) clones calculation of genotypic correlation coefficients revealed significant age-age correlation from age 1 to 6 (immature period) for girth A and for age 7 to 12 (mature period) for girth B and for age 7 to 12 (production of latex) for yield. Rank correlation coefficients between all immature ages of girth (girth A), all ages of mature girth (girth B) and all annual rubber production (yield) were significant for the three traits, with the coefficients decreasing with increasing age. Selection of the sets of best 30, 15, 10 and 5 clones from the available 68 clones at a given age was generally accompanied by a descending order of percentage success. It was suggested: (a) to have the best 30 clones of age 6, select the set of best 36 clones at age 2, (b) to have the best 15 clones of age 6, select the set of best 20 clones at age 3, (c) to have the best 5 clones of age 6, select the set of best 8 clones at age 4, and (d) to have the best 3 clones of age 6, select the set of best 3 clones at age 5. More than 80% of the targeted clones on girth A or girth B basis and more than 76.7% clones on yield basis were found to get selected at steps (a) through (d). For achieving early multiplication of the most productive clone for deployment, multiplication should be started with the best 36 (i.e. 60%) clones selected at age 2.

Early selection for growth vigor in rubber tree genotypes in northwestern São Paulo State (Brazil)

Forty-five genotypes (clones) of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Müell. Arg.] of different origins were assessed for efficiency of early selection at the Votuporanga Experimental Station in northwestern São Paulo State, Brazil, using a randomized complete block design with three replications and six plants per plot. Girth at 120 cm above the highest point of the grafting union of each tree was taken at ages 12, 24, 36, 48, 60, 72, 84 and 96 months. Highly significant differences in girth were detected among the genotypes at all ages evaluated, except for 12 months. Estimates of genetic variance for two age sets showed a substantial increase with age, while the genotype variation decreased. Selection made at 24 months proved to be the most efficient, giving a superior gain per unit of time.

AVALIAÇÃO DE GENÓTIPOS DE SERINGUEIRA (Hevea spp.) AO Microcyclus ulei VISANDO À IDENTIFICAÇÃO DE FONTES DE RESISTÊNCIA HORIZONTAL

Avaliou-se, sob condições controladas, a resistência de genótipos de seringueira ao mal-das-folhas. Empregaram-se dois isolados de Microcyclus ulei, pertencentes aos grupos I e II. Utilizaram-se mudas em sacos plásticos e inocularam-se folíolos nos estádios B1/B2 com uma suspensão de 2 χ 105conídios/ml. Incubaram-se as mudas em câmara úmida a 24° C por 24 horas. Determinaram-se o período latente (PL), diâmetro das lesões (DL), tipo de lesão (TL) e tipo de reação (TR). A maioria dos genótipos testados foi suscetível a pelo menos um isolado do patógeno. Os genótipos que apresentaram resistência moderada, com maior período latente e menor esporulação a um isolado, em geral, foram suscetíveis ao outro. Apenas o genotipo AM/86/271 exibiu resistência incompleta, caracterizada por maior PL, menor DL e baixa esporulação. Entretanto, o número de isolados testados não assegurou o caráter da resistência. Com base nos resultados obtidos concluiu-se que os genótipos avaliados não apresentaram perspectivas para utilização em programas de melhoramento visando resistência ao M.ulei.

Phylogenetic relationships within Hevea brasiliensis as deduced from a polymorphic mitochondrial DNA region

We have cloned a 4.5-kb mtDNA fragment showing a high RFLP polymorphism between various Hevea genotypes. Subcloning and sequencing of a 1.4-kb segment of this clone allowed us to design PCR amplification primers to isolate homologous mtDNA segments of about 0.9 kb from 23 representative genotypes of Hevea. Complete sequences from 4 genotypes showed between 6.7% and 20.2% of nucleotide diversity, suggesting the presence of a hypervariable, or hotspot, region. A sequence of 345 nucleotides within this region was determined for the 23 genotypes. The phylogenetic relationships inferred from the sequence comparison are in general agreement with the results obtained from mtDNA RFLP analysis, indicating that this polymorphic mtDNA region is a useful molecular marker for phylogenetic analysis within Hevea.