High yields and bee pollination of hermaphroditic rambutan (Nephelium lappaceumL.)in Chiapas, Mexico

Abstract

Introduction. Many cultivated plants do well with exotic pollinators, and native pollinators can also serve exotic crops. Both can be optimized for agriculture. We studied Nephelium lappaceum L. (Sapindaceae), an andro-dioecious Asian plant, in tropical Mexico. The hermaphrodite flowers were not known to shed viable pollen, and outcrossing from male pollinating plants was thought essential for efficient horticulture. Materials and methods. We used the locally developed CERI61 variety of rambutan and conducted experiments on pollination and fruit yield. An orchard of 1,000 trees was studied intensively during two flowering seasons in Chiapas, Mexico. Plantation yields were recorded for 10 years. We compared open pollination experiments with pollinator exclusion and 'induced pollination' treatments. We caged some trees with colonies of stingless bees: Scaptotrigona and Tetragonisca. Results and discus- sion. Caged flowers produced fruit, with no male plant present. Pollen dehisced and was viable on approximately 5% of flowers. Trees caged with pollinators, and open pollination treatments revealed 9.1 times more mature fruit than trees without pollinators. Fruit mass was significantly higher in induced pollination treatments. Yields exceeding 7 t ha −1 were obtained during a ten-year test period. Scaptotrigona mexicana (Apidae, Meliponini) was the main pollinator, fol- lowed by social halictid bees (Halictus hesperus). Feral Africanized honeybees were not strongly attracted to flowers. Conclusion. Both stingless bee species in open pollination treatments and within cages showed that fruit production increased nearly 10-fold in this variety of rambutan. Although outcrossing versus selfing did not affect initial mature fruit set, a superior fruit yield, in weight and size, was obtained from selfing mediated by pollinators in caged trees.