Genetic variation and realized genetic gain from rubber tree improvement

Abstract

Breeding cycle in rubber extends to 20-30 years between pollination and yield assessment, distributed over three selection stages. Five hectares of small scale trial of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell.-Arg.], was established in the Northwestern region of São Paulo State, Brazil. The population comprises 98 clones mostly derived from intensively selected plus tree in the natural forest of rubber tree in the Amazon. Three open pollinated progeny tests were established in three experimental stations. Seedlings from 98 progenies including a commercial check (CC) were planted in each one of the three locations. Assessments were made when the plants were one, two and three years old. The variation among progenies for girth was highly significant in all locations examined. In the combined analysis of variance over three locations, differences among progenies were also detected, while progeny × location interaction effect was not significant. Narrow sense heritability estimates on individual tree basis (h i 2 ) were variable depending on the characteristic, age of assessment and experimental location. Realized genetic gains were calculated for the plant characteristics at the age of three years, by comparing the performance of improved (selected) materials to unimproved materials (CC). The total genetic gain from the genetically tested first generation clone population at Votuporanga is estimated as 25% for girth, 14% for rubber yield and 25% for bark thickness. Improvement of rubber tree by selection, establishment of clonal population (isolated garden) and progeny testing is a very promising and profitable operation. A variação entre progênies para crescimento de perímetro do caule foi altamente significantes em todos os locais testados. Nas análises de variâncias conjuntas com os três locais também foram observadas diferenças entre progênies, e que o efeito da interação progênie × local não foi significativo. Estimativas de herdabilidade no sentido restrito em nível de árvore individual (h i 2 ) foram variáveis dependentes das características, idade de avaliação e local dos experimentos. Foram calculados ganhos genéticos para as características da planta na idade de três anos através da comparação de desempenho nos materiais selecionados para os não selecionados (CC). O ganho genético total da primeira população geneticamente testada da população clonal de Votuporanga foi calculado como 25% para perímetro caule, 14% para produção de borracha e 25% para espessura da casca. Melhoramento da seringueira por meio da seleção, implantação de uma população clonal e teste de progênie com os clones é uma operação lucrativa e muito promissora. Palavras-chave: Hevea brasiliensis, variância, covariância, herdabilidade de correlação, teste genético Rubber tree improvement 45

Adaptability and stability in rubber tree progenies under different environmental conditions

“…The CVg(%) value for PBS corroborated studies carried out in Votuporanga, SP, by Costa et al (2000Costa et al ( , 2008, Gonçalves et al (1998aGonçalves et al ( , 2005Gonçalves et al ( , 2009, Boock et al (1995) and Moretti et al (1994), in Jaú, SP, by Gonçalves et al (1998b) and in Pindorama, SP, by Gonçalves et al (2004). σ : individual phenotypic variance; 2 g ĥ = individual heritability in the restricted sense for the individual and broad analysis in the set; 2 parc ĉ : coefficient of determination of the plot effects; 2 int ĉ : coefficient of determination of the genotype x environment interaction effects; 2 mg ĥ : Heritability of the genotypic mean, assuming total survival; g ĝ r : accuracy of genotype selection, assuming total survival; gloc r : genotypic correlation among the performances in the several environments; CVg%: genotype coefficient of variation;…”

Estimation of genetic parameters in rubber progenies

“…However, the genotype-environment interaction reduces these gains. Gonçalves et al (2009b) achieved selection gains of 8.20% for rubber yield in a combined analysis at the same experimental site.…”

Physiological characteristics of IRR 400 series rubber clones (Hevea brasiliensis Muell. Arg.) on drought stress

“…3 One of the primary sources of natural rubber is found in the Amazon basin, South America. 4 Optimal conditions for the growth of rubber plants are high temperature (28 AE 2 o C), high humidity, and rainfall of 2000-4000 mm/year. 5 Rubber plantations in marginal areas, such as the northeastern states of India, southern China, northern and northeastern Thailand, and eastern Indonesia, experience abiotic stresses such as drought.…”