User:Geert Kessel/sandbox

DuRPh
DuRPh is a fundamental and applied 10-year publicly funded research project at Wageningen University and Research Centre (WUR). The project started in 2006. DuRPh is an acronym for: “Durable Resistance against Phytophthora infestans through cisgenic marker-free modification”. The DuRPh project is developing and evaluating possibilities to achieve durable, high level resistance in potato against potato late blight, the main potato disease, through cisgenic, marker free genetic modification. This in turn will offer opportunities to drastically reduce pesticide use in the potato cultivation.

Potato
Potato is among the important arable crops in the Netherlands. Dutch growers cultivate potatoes for food and non-food applications on an area around 165 thousand ha with a total yield of 7.4 million ton. Globally, potato is the fourth largest arable crop. To control potato late blight, a conventional potato field in the Netherlands is treated with fungicides 10-15 times per season. These pesticide applications are costly and a burden to the environment. Control costs for Dutch farmers are estimated to amount to € 130 million per year, equal to about 20% of the production costs. Worldwide, the costs associated with late blight (yield losses and crop protection costs) equal billions.

Potato Late Blight
Potato late blight is a potato disease caused by the fungal-like organism Phytophthora infestans. P. infestans is an oomycete that also infects tomatoes and some other Solanaceae. P. infestans in potato infects both the foliage and tubers and is able to destroy an entire crop within two weeks after first infection. Potato late blight was a major culprit in the 1840s European, the 1845 Irish and 1846 Highland potato famines. Today, potato late blight still is a difficult disease to manage often requiring daily attention from the growers. Although an Integrated Pest Management (IPM) strategy is generally adopted to control potato late blight, frequent, mainly preventive, fungicide applications form the backbone of this strategy until now.

Goal
DuRPh aims to contribute to a more sustainable potato cultivation, in the Netherlands and abroad. DuRPh wants to provide existing potato cultivars with additional resistance genes (R-genes) originating from other crossable (wild) relatives whilst keeping all other cltivar specific agronomic traits intact. When conventionally crossing cultivated potato with wild relatives, many unwanted 'wild' properties come along, such as e.g. ugly tubers, reduced yield and bitter tastes. This phenomenon, called linkage drag, is subsequently counteracted through a repetitive, time consuming and costly cycle of back crosses and selection. With genetic modification, the problem of linkage drag does not exist. The gene or genes of interest are transferred to the target cultivar while all other cultivar characteristics remain intact. The resulting new cultivar is thus “ true to type” to the original potato cultivar except for e.g. its newly acquired resistance.

Cisgenic marker-free potatoes
Incorporating genes from related, crossable species - in this case resistance genes from wild potato plants - is called cisgenic genetic modification or cisgenesis. This differs from transgenic genetic modification, whereby plants are provided with genes from other, non-crossable, species. The DuRPh project only employs cisgenic modification. The resulting newly resistant potatoes also do not receive any so-called genetic markers such as antibiotic- or herbicide resistance genes. To assess whether a modification was successful, the plant material is exposed to the pathogen, not to antibiotics or herbicides. In a recently published scientific opinion, the European Food Safety Authority (EFSA) concludes that similar hazards are associated with cisgenic and conventionally bred plants.

Durability
The use of resistance genes originating from wild potatoes is not new. Various resistance genes have been crossed into commercial varieties in the past. However, those resistances have been broken sooner or later due to adaptation by P. infestans. Thus, also the new resistance genes can be broken. Furthermore, resistance genes are a rare and valuable commodity. In the DuRPh philosophy, durability comes through clever design and proper management of resistance. To ensure that the new resistances are not easily broken, DuRPh developed a durability enhancing strategy:
 * The team works with R-gene cassettes: sets of smartly combined R-genes that are much more difficult to break than single R-genes.
 * The local P. infestans population is continuously monitored for break through of the R-genes composing the cassette.
 * The resistant crop is not protected by fungicides excep when too many of the individual R-genes in the cassette are overcome by the local P. infestans population. In that case preventive fungicide applications will be recommended under a low input control strategy specifically designed for resistant cultivars. This strategy reduces the fungicide input by a minimum of 75-80% as compared to the control strategies currently used on susceptible cultivars.
 * R-gene cassettes that are close to being overcome by P. infestans can be replaced by more effective R-gene cassettes. Thus, the cultivar stays the same, the R-gene content of the cultivar changes.
 * As a last barrier, smart spatial deployment of R-genes and R-gene cassettes can, in case of an unforeseen break through, slow down emerging late blight epidemics.

The expected advantages to society of the expected project results are:
 * Less potato production costs
 * Strongly reduced environmental burden
 * A stimulant to fundamental research
 * Maintenance of competitive abilities and employment in the planting material production sector