Scientists are looking for resistance genes so kiwifruit plants can withstand the Psa bacterium’s effector genes.
Listen this RNZ audio, Kiwifruit Psa disease genetic July from 2012
Alison Ballance goes to the Mount Albert Research Centre to meet Plant & Food Research’s Matt Templeton who works at the level of genes. He shows her some scanning electron micrographs that show how Psa affects individual plants.
Plant defence system
Matt explains how pathogens cause disease and how plants defend themselves – it turns out it’s a far more complex system than was originally thought. Plants have a series of receptors on the outside of their cell walls that detect specific portions of a microbe. A receptor sends a signal to the nucleus of the cell telling it it’s got to respond. This induces the transcription of a specific subset of genes, which will be translated into proteins that will defend the plant from the pathogen.
Psa-effector proteins overwhelm plant defence
This system doesn’t work perfectly because bacteria have developed sophisticated systems for suppressing the plant defence response. They do that by injecting a subset of proteins called the effectors into the cytoplasm of the plant cell. It is Psa-effector proteins that overwhelm the kiwifruit plant’s response, so Matt is sequencing the Psa genome to identify all the crucial effectors. Effectors aren’t well characterised, so there’s a lot of work to do just to understand what exactly an effector does.
Finding resistant genes to target Psa-effectors
At the moment, existing kiwifruit cultivars don’t have genes that are resistant to Psa. Matt’s job is to find genes in the wider germplasm that have resistance to Psa, and these are the ones they want to fast-track into commercial cultivars.
Matt’s strategy is to identify the important Psa effectors and then marry that information with the information from the orchard regarding resistant plants. It is about finding the genes in resistant plants that target the crucial effectors in Psa.
For more information see this other RNZ audio: Psa-resistant kiwifruit.
Plant & Food scientists are aiming to breed kiwifruit cultivars that show resistance to Psa.
Programme details: Our Changing World.