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Making Lychee and Longan Harvests Predictable

By Marcia Wood
September 22, 2004

Beneath the thin, crisp peel of an exotic tropical lychee, sweet, delicious fruit is ready to eat. To growers in Hawaii, however, lychee and its smaller cousin, longan, present a problem. Harvests are unpredictable, yielding too much fruit one year and too little the next.

Studies led by Agricultural Research Service horticulturist Tracie Matsumoto at the agency's U.S. Pacific Basin Agricultural Research Center in Hilo, on Hawaii Island, may resolve the problem. That would be a boon not only for Hawaii's growers, but also for shoppers in Hawaii and elsewhere who simply can't get enough of these delectable fruits.

Matsumoto's research is a fusion of old and new. Research elsewhere has shown that a compound in Chinese firecrackers, which have been used for hundreds of years at religious ceremonies or other special events, triggers longan trees to flower and bear fruit. That happens--even out of season--to trees growing where these events take place, such as at a temple.

In Matsumoto's research, the firecracker finding fits neatly with new discoveries from plant geneticists. Those scientists, who are investigating the genetic makeup of thale cress, or Arabidopsis thaliana--the "lab rat" of contemporary plant genetic research--have discovered that a gene called FLC can block flowering, but is typically suppressed by other genes.

Matsumoto wants to see if lychee or longan have an anti-flowering gene, or genes, similar to FLC. If they do, she'll next determine if the culprit genes can be squelched by applying a less-explosive version of the firecracker compound.

Matsumoto estimates that the first phase of the research--in which she'll determine if lychee or longan has an FLC-like anti-flowering gene--could be completed in about three to four years.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.