">New Method Discovered to Make Potatoes Resistant to...

Tag : potatoes

According to researchers at Wageningen University in theNetherlands, the Sainsbury Laboratory at the John Innes Centre inthe UK and Ohio State University in the USA, the best strategy tomake potatoes resistant to the stubborn fungal pathogenPhytophthora is to develop so-called broad spectrum resistance. Intheir article, published on 6 August in the journal PLoS One, theyexplained that the current methods to discover resistance genes aretoo slow. Moreover, because they often concern only a single gene,these methods do not lead to sustainable resistance becausePhytophthora can break single-gene resistance relatively quicklyand easily.

Interaction
The newly developed method is based on the interaction of genes ofthe pathogen and genes of the potato. The response of the potatoinvolves resistance genes in the plant, and the response of P.infestans involves so-called avirulence genes. The avirulence geneproduces proteins (effectors) that are recognised by the resistancegene proteins of the potato; an interaction then takes place. Byusing effectors (proteins that are secreted by Phytophthora intothe plant after infection takes place), researchers can relativelyquickly identify and isolate the genes that are crucial to theinteraction. Because the pathogen (Phytophthora) cannot switch offthese proteins, but produces them constantly, genes that canrecognise these proteins can potentially serve as resistance genes.

In the study, a set of 54 effectors (of an estimated 500 effectorsin total) were tested on a large set of wild potato species. Inmany cases, this led to reactions from the wild potato species (thehypersensitivity response: the location where the effector proteinwas applied begins die off) and in one case to the actualidentification of the effector protein – known as IPiO. Thiseffector turned out to be directly correlated with the resistanceof three wild species, S. stoloniferum, S. papita and S.bulbocastanum. This means that a positive response against theeffector always occurred in plants that had the resistance gene. Inadditional studies, the researchers were able to show that theeffector in this case was the avirulence gene of the resistancegene. Because the researchers realised that the resistance genesfrom the three species had to be very similar, they were quicklyable to isolate the resistance genes in S. papita and S.stoloniferum by using their knowledge of the previously isolatedresistance gene from S. bulbocastanum.

Permanent threat
Since Phytophthora first ravaged the potato – an eventepitomised by the notorious Irish Potato Famine in the 19th century– this pathogen has been a permanent threat, and hasrepeatedly led to disastrous crop damage and high production costs.Until now, a very labour-intensive process of searching forsustainable resistance has yielded few or no results, and the useof fungicides has been essentially the only way to control thedisease in modern agriculture.

The methods described in the article make it possible – relatively quickly – to acquire an impression of theprevalence and nature of resistance genes that would be verydifficult or even impossible for the pathogen to break. Bycombining several of these potentially hard-to-break resistancegenes, sustainable resistance will come within reach.