Study to investigate all 150 species of Passiflora that are native to Brazil

Research project will prospect for wild species and explore genetic variability to enrich germplasm banks.

By Peter Moon  |  Agência FAPESP – Some 520 species of passion flower (Passiflora spp.) are known to science. They grow as tendril-climbing vines or shrubs in tropical forests throughout the Americas but are found predominantly in the Amazon. At least 150 species are native to Brazil, and 170 to Colombia: these are the centers of Passiflora’s diversity. Despite all this variety, only two species are domesticated and have commercial value as food or as raw material for beverages, cosmetics or pharmaceuticals. These species are the relatively sour Passiflora edulis, known mainly as yellow passion fruit, and the sweeter P. alata, known as winged-stem passion flower or fragrant granadilla, which can be eaten with a spoon – hence the Tupi name of the fruit, mara kuya or moroku'ya (mburucuyá in Guarani, maracujá in Portuguese), meaning “food in the gourd bowl.” Some wild species are used as ornamental plants.

Brazil is the world’s largest producer and consumer of yellow passion fruit. According to IBGE, the national statistics office, production totaled 823,000 metric tons in 2014, with growers in the Northeast accounting for 75%. Output and acreage have both increased tenfold since the 1980s thanks to genetic improvement by EMBRAPA, the Brazilian Agricultural Research Corporation.

All this evidences the importance of researching and conserving the rich diversity of Passiflora. However, there is a problem: only two species are domesticated, and practically no research has been done on all the wild species. Their properties are unknown to science. “It’s a challenge from a conservation standpoint. We know almost nothing about the genetic variability of most wild species of Passiflora,” said Anete Pereira de Souza, a researcher at the University of Campinas’s Biology Institute (IB-UNICAMP) in São Paulo State, Brazil.

Pereira de Souza is principal investigator for the project “Genetic and molecular variability in passion fruit (Passiflora spp.) commercial and wild accessions, targeting ex situ conservation and plant breeding,” supported by FAPESP, and co-author of a review of the state of the art in knowledge of Passiflora conservation and genetic diversity, published as a chapter of the book Genetic Diversity and Erosion in Plants. The study was developed in collaboration with researchers at the Southwest Bahia State University (UESB), EMBRAPA Cerrados (Federal District), and EMBRAPA Cassava & Fruit (Bahia).

Most wild species of Passiflora prosper in warm, wet forests. “This is the main problem posed by climate change: any alteration in hydrology or temperature may mean the loss of a large number of species,” Pereira de Souza said.

Prospecting and conserving

In other words, many wild species risk simply disappearing before samples of their genetic variability can be collected for conservation, serving as a promising and irreplaceable source for future improvements to the domesticated species. “There are disease resistance genes that we could use to improve the cultivated species,” she explained. The only genomic study of Passiflora performed to date was published by researchers at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP).

“To conserve the biodiversity of Passiflora, we need genetic, genomic and phenotypic data on all species of the genus,” Pereira de Souza said. The first step is prospecting for and identifying all wild species. The second entails conserving samples in botanic collections and germplasm banks.

Another risk that arises from Passiflora’s vulnerability to climate change is its dependence on bumblebees (Bombus spp.) for pollination. There are some 250 species of bumblebee, and since 1998, a federal law has protected them against pursuit, destruction, hunting and capture, given their importance to the pollination of many plants.

“Passion flower plants bear fruit only if pollinated by bumblebees, big black bees that are increasingly rare in the wild,” Pereira de Souza said. They typically nest in hollow trees or logs, and deforestation is destroying their habitat.

Many growers of yellow passion fruit complain of a dearth of fruit, presumably owing to the waning population of bumblebees. Without flowers, there is no fruit. “Growers have had to pollinate manually for some time,” Pereira de Souza said. “To make matters worse, we know next to nothing about bee species and other insects that pollinate wild species of Passiflora.”

If any wild species of Passiflora depend on a single bee species for pollination and if the bee in question disappears because of deforestation and climate change, then the wild species of Passiflora will also disappear, which would be an irreparable loss.

“The Genetic Diversity, Conservation, and Use of Passion Fruit (Passiflora spp.),” by Anete Pereira da Silva et al. and published in Genetic Diversity and Erosion in Plants, can be read at http://link.springer.com/chapter/10.1007/978-3-319-25954-3_5.