Protecting oranges from going green

U. FLORIDA (US) — Assembling the genome sequences for two citrus varieties for the first time is expected to unravel the mystery behind diseases such as greening while improving fruit flavor and quality.

Since its discovery in Florida in 2005, greening has caused havoc in the citrus industry; wiping out citrus crops in Asia, Africa, the Arabian Peninsula, and Brazil. Greening slowly weakens and kills all types of citrus trees, while rendering fruit malformed and discolored.

But while genome sequences of the sweet orange and Clementine mandarin may provide scientists with the tool needed to solve the greening crisis, having them is “really much, much, bigger than that,” says Fred Gmitter, professor of horticultural sciences at the University of Florida.

The discovery could also lead to citrus trees with more beautiful fruit, better disease resistance, more phytonutrients, and tolerance for salt, bad soil, or extreme temperatures.

The higher quality Clementine mandarin genome came from a haploid, meaning it has a single set of chromosomes. Scientists used a more detailed method of obtaining its genome sequence, which was more expensive, but provides longer strings of DNA, Gmitter says.

“For us, it means it gives you longer reads, longer pieces—so that you’re assembling a jigsaw puzzle out of a million pieces, instead of out of 25 million smaller pieces,” says Gmitter.

“What’s most important is to have this high-quality, original haploid reference sequence. And we did that.”

Researchers from Georgia Institute of Technology contributed to the research.

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