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Hand Pollination of Cupuassu Trees (Theobroma grandiflorum)

Cupuassu (Theobroma grandiflorum, Sterculiaceae) is an Amazonian tree whose fruits are used to make juice, ice-cream, candies and chocolate. It has gained popularity recently and is considered one of the most profitable crops in the Amazon region. The species is predominantly allogamous and many flowers do not set fruit, even when pollinated with compatible pollen. The rate of natural pollination is low (estimated at 1.6% for pistils pollinated with more than 60 pollen grains). In the present work, some aspects of its pollination were studied. Hand pollination was performed close to anthesis (between 17-18:00 h) and on the morning following anthesis, in the following way: three staminodes of the flower to be pollinated were removed to allow access to the pistil; a stamen was then taken from the donor flower with a pair of tweezers and its anthers were brushed against the stigmatic branches of the receptor flower. Best results with hand pollination were obtained with recently opened flowers and attributed to a high deposition of pollen grains. Controlled pollinations between compatible plants, using a variable number of pollen grains, showed that flowers that received 60 pollen grains had a 20% probability to set fruit; flowers that received more than 400 pollen grains always set fruit. Hand pollination increased the number of harvested fruits. The number of seeds from fruits obtained by natural and hand pollination was similar. Hand pollination, therefore, can be used both for breeding and for yield enhancement of trees that would otherwise have pollination problems.

Theobroma grandiflorum; cupuassu; hand pollination

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