SAN DIEGO — In an unmarked greenhouse, leafy bushes carpet an acre of land here tucked into the suburban sprawl of Southern California. The seeds of the inedible, drought-resistant plants, called jatropha, produce a prize: high-quality oil that can be refined into low-carbon jet fuel or diesel fuel.

The mere existence of the bushes is an achievement.

Hailed about six years ago as the next big thing in biofuels, jatropha attracted hundreds of millions of dollars in investments, only to fall from favor as the recession set in and as growers discovered that the wild bush yielded too few seeds to produce enough petroleum to be profitable.

But SGB, the biofuels company that planted the bushes, pressed on. Thanks to advances in molecular genetics and DNA sequencing technology, the San Diego start-up has, in a few years, succeeded in domesticating jatropha, a process that once took decades.

SGB is growing hybrid strains of the plant that produce biofuel in quantities that it says are competitive with petroleum priced at $99 a barrel. Oil is around $100 a barrel.