Sample of seedless rambutan, seed coat still present. Image from masalykitchen.

One of the ways to achieve food security is by improving our crops. Aside from developing disease-resistant plants with higher yields, agronomists also increase the edible portion of produce. While the sweet and succulent rambutan flesh has improved in thickness over the past decades, the big inedible seeds take up a huge portion of the fruit.

Seedless rambutan fruits occur naturally at an average of 4.45%. Scientists from Aklan State University in the Philippines discovered that gibberellic acid (GA3), a plant growth regulator, can inhibit the development of rambutan seeds. With a 50 parts-per-million (ppm) solution, the study claims that 86.67% of fruits did not develop seeds. They also claim that a 200 ppm solution can reduce seed development by nearly 100%.

In an interview with Manila Bulletin, lead researcher Dr. Marilyn Romaquin says that she discovered the reduction of seed development while evaluating effects of gibberellic acid on the yield and quality of rambutan. The research was conducted on nine eight-year-old asexually propagated Maharlika rambutan trees of uniform vigor, height, and canopy. Though discovered on accident, her adviser Dr. Danilo T. Eligio claims that “it is a breakthough”.

Aside from a reducing seeds, results show that GA3-treated rambutan branches has 18 to 28 percent more yield than untreated branches. Seedless fruits are shorter in length but has about the same diameter and weight as the seeded fruits. The weight of the edible portion was also not significantly affected. However, seedless fruits are significantly sweeter.

The study also found that the proportion of seedless fruits increases if GA3 is applied before the flower buds break. More seeds would develop if the treatment is applied during later stages of fruit growth.

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