By helping determine which genes are turned on in a tissue of citrus genes that are associated with taste, acidic content and disease, for example the chip, called the GeneChip Citrus Genome Array, could provide information useful to researchers for rectifying existing problems and making improvements to the fruit.
"The citrus array helps us quickly examine a certain trait in citrus," said Mikeal Roose, a professor of genetics in the department of botany and plant sciences at University of California Riverside (UCR) and a leader of the three-year research project.
"For a trait posing a problem for the consumer, such as an undesirable flavour, we can identify genes associated with the trait and target these for correction to improve the flavour."
The citrus family, which includes oranges, grapefruits, lemons and limes, has about 16 species, with hundreds of distant relatives, such as pummelos, trifoliate oranges, and kumquats. Food and drinks firms looking to increase sales are increasingly pushing their products as containing natural citrus flavours as a way of tapping into the burgeoning health market.
In 2003, sales of functional foods and drinks were estimated to be over six times the value of those in 1998. Unravelling the potential of health boosting components in the citrus family could therefore lead to new gains.
Citrus fruits are abundant in limonoids, phytochemicals that scientists are currently investigating for their anti-viral, anti-fungal, anti-bacterial and anti-malarial powers. Limonoids have also shown effectiveness as insecticides both in traditional farming cultures and modern biochemistry labs.
The citrus array will be used to develop new diagnostic tools for the improvement of citrus agriculture and post-harvest fruit handling, as well as to understand mechanisms underlying citrus diseases.
Researchers will also study traits pertinent to the citrus industry such as easy peeling, seedlessness, flavour components, pest and disease control, nutritional characteristics, and reproductive development.
"This industry-supported effort both added to and made use of publicly available citrus sequences to develop an entirely new tool that will benefit all citrus researchers and help sustain the citrus industry locally and worldwide," said Timothy Close, a professor of genetics at UCR and a co-leader of the project.
Manufactured by Affymetrix, the GeneChip Citrus Genome Array is made up of a glass wafer on to which nearly one million different pieces of citrus DNA are deposited on a grid or microarray using methods similar to those used to produce computer chips. The glass wafer is encased in a plastic container somewhat smaller than the size of a credit card.
The chip is the first commercial citrus microarray and allows analysis of expression of more than 20,000 different genes. The array will also be used to develop a detailed genetic map of citrus that will help researchers locate many genes.
The map location information will be used to make the development of new varieties more efficient.