Genetic variation and realized genetic gain from rubber tree improvement

Variação genética e ganhos obtidos por meio do melhoramento genético da seringueira

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 i²) 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.

Hevea brasiliensis; variance; covariance; heritability correlation; genetic test

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