Lígia Regina Lima Gouvêa

Structure of genetic diversity among common bean ( Phaseolus vulgaris L.) varieties of Mesoamerican and Andean origins using new developed microsatellite markers

A common bean genomic library was constructed using the ‘IAC-UNA’ variety enriched for (CT) and (GT) for microsatellite motifs. From 1,209 sequenced clones, 714 showed microsatellites distributed over 471 simple and 243 compound motifs. GA/CT and GT/CA were the most frequent motifs found among these sequences. A total of 123 microsatellites has been characterized. Out of these, 87 were polymorphic (73.7%), 33 monomorphic (26.8%), and 3 (2.4%) did not amplify at all. In a sample of 20 common bean materials selected from the Agronomic Institute Germplasm Bank, the number of alleles per locus varied 2–9, with an average of 2.82. The polymorphic information content (PIC) of each marker varied from 0.05 to 0.83, with a 0.45 average value. Cluster and principal coordinate analysis of the microsatellite data were consistent with the original assignment of the germplasm accessions into the Andean and Mesoamerican gene pools of common bean. Low polymorphism levels detected could be associated with the domestication process. These microsatellites could be a valuable resource for the bean community because of their use as new markers for genetic studies.

Genetic variability and selection for laticiferous system characters in Hevea brasiliensis

Six laticiferous system characters were investigated in 22 three-year-old, half-sib rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.] progenies, evaluated at three sites (Votuporanga, Pindorama and Jau, all in the Sao Paulo State, Brazil). The traits examined were: average rubber yield (Pp), average bark thickness (Bt), number of latex vessel rings (Lv), average distance between consecutive latex vessel rings (Dc), density of latex vessels per 5 mm per ring averaged over all rings (Dd) and the diameter of the latex vessels (Di). The joint analysis showed that site effect and progeny x sites interaction were significant for all traits, except Lv. Estimates of individual heritabilities across the three sites were high for Bt; moderate for Lv, Pp and Dc; low for Dd and very low for Di. Genetic correlations in the joint analysis showed high positive correlations between Pp and the other traits. Selecting the best five progenies would result in genetic gains of 24.91% for Pp while selecting best two plants within a progeny would result in a Pp genetic gain of 30.98%.

Genetic parameters and correlation in early measurement cycles in rubber trees

Knowledge of the traits present in plant populations of a species is essential to carry out selection and breeding. The objective of the present study was to estimate the genetic parameters and correlate genetically and phenotypically the variables rubber yield, annual trunk girth increase, number of latex vessel rings and bark thickness in early measurement cycles. A total of 22 rubber tree progenies (Hevea brasiliensis) were assessed in three locations during three early measurement cycles. The bark thickness variable correlated significantly for the three increase measurements made in the locations of Jaú, Pindorama and Votuporanga. The progeny mean based joint hereditability showed mean values greater than individual plants and within progeny plants of 0.848, 0.286 and 0.242, respectively. The variables annual trunk girth increase and bark thickness are genetically correlated variables. Rubber yield is correlated genetically with bark thickness that permits simultaneous selection for the two characteristics. The early measurement cycles were efficacious for finding genetic variability among the genotypes.

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.

Prediction of Hevea progeny performance in the presence of genotype-environment interaction

Twenty two open-pollinated Hevea progenies from different parental clones of the Asian origin were tested at five sites in the Northwestern Sao Paulo State Brazil to investigate the progeny girth growth, rubber yield, bark thickness and plant height. Except for the rubber yield, the analysis of variance indicated highly significant (p<0.01) genotype x environment interaction and heterogeneity of regressions among the progenies. However, the regression stability analysis identified only a few interacting progenies which had regression coefficients significantly different from the expected value of one. The linear regressions of the progeny mean performance at each test on an environmental index (mean of all the progenies in each test) showed the general stability and adaptability of most selected Hevea progenies over the test environments. The few progenies which were responsive and high yielding on different test sites could be used to maximize the rubber cultivars productivity and to obtain the best use of the genetically improved stock under different environmental conditions.

EXPRESSÃO FENOTÍPICA DE CLONES DE SERINGUEIRA NA REGIÃO NOROESTE DO ESTADO DE SÃO PAULO ( 1 )

The development of new clones with high production combined to other desirable secondary characters is fundamental for a sustainable and competitive rubber tree cultivation. The objective of this study was to evaluate, during a period of 13 years, the phenotypic expression of superior characters of 17 clones of rubber tree grown in the plateau region of Sao Paulo State, Brazil. The treatments were arranged in a randomized block design with three replicates and six plants per linear plot. The clone IAC 40 exhibed the highest yield (2.316 kg ha-1 year-1) followed by IAC 300 (1.921 kg), whereas the control clone RRIM 600 had 1.493 kg ha-1 year-1 over six years of tapping. The percentage of plants able for opening ranged from 40% for IAC 329 to 100% for IAC 327. Except for IAC 56, IAC 331 and IAN 3156, with 7.21 mm, 7.18 mm and 6.40 mm respectively, all other clones had lower thick virgin bark at opening compared to the control clone RRIM 600, which recorded 6.38 mm. Except IAN 3.156 all clones showed low incidence of panel dryness. The good performance of all clones, both from IAC and Amazone (IAN, Fx and RO) allow their recommendation for small scale cultivation, when they would be further tested in different environments of the Sao Paulo State, aiming recommendations in large scale.

Genetic parameters and estimated genetic gains in young rubber tree progenies

The objective of this work was to assess the genetic parameters and to estimate genetic gains in young rubber tree progenies. The experiments were carried out during three years, in a randomized block design, with six replicates and ten plants per plot, in three representative Hevea crop regions of the state of Sao Paulo, Brazil. Twenty-two progenies were evaluated, from three to five years old, for rubber yield and annual girth growth. Genetic gain was estimated with the multi-effect index (MEI). Selection by progenies means provided greater estimated genetic gain than selection based on individuals, since heritability values of progeny means were greater than the ones of individual heritability, for both evaluated variables, in all the assessment years. The selection of the three best progenies for rubber yield provided a selection gain of 1.28 g per plant. The genetic gains estimated with MEI using data from early assessments (from 3 to 5-year-old) were generally high for annual girth growth and rubber yield. The high genetic gains for annual girth growth in the first year of assessment indicate that progenies can be selected at the beginning of the breeding program. Population effective size was consistent with the three progenies selected, showing that they were not related and that the population genetic variability is ensured. Early selection with the genetic gains estimated by MEI can be made on rubber tree progenies.

Genetic variability and predicted genetic gains for yield and laticifer system traits of rubber tree families

The present study aimed to estimate genetic parameters in order to assess heritability, predict genetic gains, and establish genetic and phenotypic correlations among yield-related traits of 22 families of Heveabrasiliensis (Willd. ex. Adr. de Juss.) Muell-Arg, selected phenotypically for yield. Three early measurements were carried out for the traits dry rubber yield (DRY), annual girth growth (GGR), number of vassel latex rings (NVR) and bark thickness (BKT). Statistical analyses were carried out using the REML/BLUP (restricted maximum likelihood/best linear unbiased prediction) method. The additive genetic variance showed higher values than the residual variance, indicating high genetic variability in the studied population. The high values of heritability obtained indicated that the studied traits are little influenced by the environment and high gains can be obtained by selection in this population. High genetic correlation was found between GGR and BKT in the three years of evaluations suggesting that selection of families on one of these traits would lead to gains for the other trait as well. The magnitude of genetic correlation indicated greater contribution from genetic factors than environmental factors in these correlations. Gains among and within families, by selecting in the first year of assessment for rubber yield, did not vary significantly in relation to the other two years. Thus, selection could be made in the first year of assessment, thereby reducing the cost and time for the selection work with subsequent cloning.

Avaliação de clones de seringueira para a região noroeste do Estado de São Paulo

Sao Paulo e o Estado no qual clones de seringueira (Hevea brasiliensisWilld. ex Adr. de Juss.) Muell. Arg. tem apresentado maior produtividade de borracha, no Brasil. O objetivo deste estudo foi avaliar a producao de borracha e o vigor de 14 clones de seringueira, implantados na regiao de Votuporanga, alem de averiguar mudancas na tendencia da correlacao anual, para analisar a possibilidade de uma selecao precoce, com base nos caracteres estudados. Para isso, a producao de borracha, em gramas arvore-1sangria-1, foi avaliada, utilizando-se o sistema de sangria 1/2S d/4 5d/7 11m/y ET 2,5%. O periodo de avaliacao da producao de borracha foi de oito anos. O vigor, tambem, foi analisado, medindo-se o perimetro do caule por 16 anos. Os clones IRCA 111 e PB 235 tiveram os melhores desempenhos de producao de borracha. Os clones IAC 15 e IAC 44 apresentaram os melhores resultados de vigor. As correlacoes geneticas e fenotipicas foram significativas e positivas entre todos os anos de producao. Para o vigor, a significância dos coeficientes de correlacao genotipica e fenotipica diferiram na pre-sangria e na pos-sangria. Pelos valores de producao de borracha observados, os clones IRCA 111 e PB 235 sao considerados favoraveis a recomendacao em pequena escala para a regiao de Votuporanga. Com base nos resultados obtidos, e possivel realizar uma selecao precoce para o carater de produtividade, usando-se os dados obtidos no primeiro ano de avaliacao. Por causa das diferencas observadas entre os periodos de pre-sangria e pos-sangria, nao e aconselhavel realizar uma selecao precoce no periodo de pre-sangria, visando ao carater de vigor.

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.