A. J. Haverkort

Societal Costs of Late Blight in Potato and Prospects of Durable Resistance Through Cisgenic Modification

In the European Union almost 6xa0Mha of potatoes are grown representing a value of close to €6,000,000,000. Late blight caused by Phytophthora infestans causes annual losses (costs of control and damage) estimated at more than €1,000,000,000. Chemical control is under pressure as late blight becomes increasingly aggressive and there is societal resistance against the use of environmentally unfriendly chemicals. Breeding programmes have not been able to markedly increase the level of resistance of current potato varieties. New scientific approaches may yield genetically modified marker-free potato varieties (either trans- and/or cisgenic, the latter signifying the use of indigenous resistance genes) as improved variants of currently used varieties showing far greater levels of resistance. There are strong scientific investments needed to develop such improved varieties but these varieties will have great economic and environmental impact. Here we present an approach, based on (cisgenic) resistance genes that will enhance the impact. It consists of five themes: the detection of R-genes in the wild potato gene pool and their function related to the various aspects in the infection route and reproduction of the late blight causing pathogen; cloning of natural R-genes and transforming cassettes of single or multiple (cisgenic) R-genes into existing varieties with proven adaptation to improve their value for consumers; selection of true to the wild type and resistant genotypes with similar qualities as the original variety; spatial and temporal resistance management research of late blight of the cisgenic genetically modified (GM) varieties that contain different cassettes of R-genes to avoid breaking of resistance and reduce build-up of epidemics; communication and interaction with all relevant stakeholders in society and transparency in what research is doing. One of the main challenges is to explain the different nature and possible biological improvement and legislative repercussions of cisgenic GM-crops in comparison with transgenic GM-crops. It is important to realize that the present EU Directive 2001/18/EC on GM crops does not make a difference between trans- and cisgenes. These rules were developed when only transgenic GM plants were around. We present a case arguing for an updating and refinement of these rules in order to place cisgenic GM-crops in another class of GM-plants as has been done in the past with (induced) mutation breeding and the use of protoplast fusion between crossable species.

Applied Biotechnology to Combat Late Blight in Potato Caused by Phytophthora Infestans

Potato is an important crop, grown worldwide. It suffers from many pests and diseases among which late blight, caused by the oomycete Phytophthora infestans, is the worst. The disease is still causing major damage in many potato production areas and control is only possible by applying fungicides frequently. The knowledge on the molecular biology and genetics of the interaction between the plant and the oomycete is developing rapidly. These are relevant fields of study, currently dominated by the discovery of many resistance genes and numerous effector proteins and the analysis of their specific mode of action. These studies may yield essential information needed for the development of durable resistance. The long-term and worldwide effort to breed for resistance so far has had little effect. A novel breeding approach may change this. It is based on cisgenic modification (CM) consisting of marker-free pyramiding of several resistance genes and their spatial and temporal deployment yielding dynamic varieties that contain potato genes only. It is envisioned that this CM approach with potato’s own genes will not only prove societally acceptable but may also result in simplifications in the legislation on use of the CM approach. Various parties in the potato research arena intend to cooperate in this novel approach in a number of developing countries where potato substantially contributes to food security. The use of resources such as land, water and energy improves when the effect of late blight is markedly reduced.

Climate Change and Its Repercussions for the Potato Supply Chain

Since the onset of the industrial revolution, in 1750, the concentration of carbon dioxide rose from 290 to 380 parts per million. Especially during the last decennia, the effects of increased greenhouse gases concentrations are being felt. The last 14xa0years worldwide contained the warmest 13xa0years since weather recording started. For southern Europe, the major effects reported by the International Panel on Climate Change are reduced water availability and a shorter suitable winter time slot for potato production. For northern Europe, climate change will bring a decreasing number of days with frost and a lengthening of the growing season. It will be associated with more rain in winter and less in summer, with more erratic but heavier rain storms. For potato production in Mediterranean and Sahelian types of climate, during the heat-free period of the year, yields will go down as the suitable period becomes shorter. With a higher evaporative demand, the resource water will be used less efficiently. Potato yields in temperate climates may increase—provided that water for irrigation is available—due to a longer growing season and higher carbon dioxide concentrations in the air. The quality may be affected as larger tubers with a higher dry matter concentration are expected. Problems with pests and diseases are expected to increase with a longer growing season at higher temperature which allows more cycles of multiplication and greater pressure. Late blight will also have a longer period to build up and erratic rains will make control more difficult. Seed production with increased vector pressure will become more costly because fewer field generations will follow the rapid multiplication stage and seed production may move further north. Present potato areas in Europe, however, are more affected by economic factors such as inadequate farm size, changing habits, and remoteness of markets than by climate determined suitability of growing conditions. To remain competitive, the industry will have to invest in strengthening existing production areas and assess the potential of new potato production areas (further north), in new varieties adapted to extremes in weather (heat, drought), in irrigation equipment, in equipment better adapted to wet soil conditions to assure accessibility, and in improved stores with more stores equipped with refrigeration as higher winter temperatures more frequently will make it impossible to keep ware potatoes cool with ambient air. Assessment of both climate change and market liberalization in Europe shows other roads ahead than when only climate effects are taken into consideration.

The Canon of Potato Science

The 50th volume of Potato Research includes a special double-issue in which the Canon of Potato Science is presented. The Canon of Potato Science, in this context, can be defined as the body of knowledge that every potato scientist should possess to be able to understand what is on offer in conferences, journals and at scientific meetings of the EAPR and thus what is needed to interact effectively with colleagues in the potato research community. The Canon of Potato Science also offers a concise overview of what is relevant to potato science and thus a rapid and easy-to-read introduction into this discipline. We have identified 50 topics that together form the core of potato science, with a slight bias towards crop science, as this has been the focus of the journal over the last 50 years. Each of these 50 topics has been described in a condensed form by highly regarded experts in the field. The topics can be subdivided into six sections: Genetics (8), Diseases, pests, and weeds (13), Multiplication (8), Agronomy (7), Physiology (10) and Utilization (4). Each of the descriptions has the following general structure: What is it? Why is it important in potato science? Why is it important for the potato industry? Scientific developments. Further reading.

Durable Late Blight Resistance in Potato Through Dynamic Varieties Obtained by Cisgenesis: Scientific and Societal Advances in the DuRPh Project

From 2006 through 2015, a research project on Durable Resistance in potato against Phytophthora (DuRPh) was carried out at Wageningen University and Research Centre. Its objective was to develop a proof of principle for durable resistance against late blight by cisgenesis. This public-funded project aimed at stimulating research on genetic modification and public debate on innovative genetic techniques. It was decided to clone and transfer late blight resistance (R) genes of crossable wild potato species (cisgenes) by Agrobacterium tumefaciens-mediated transformation without non-potato genes. A stack of multiple R genes were planned to be inserted into established varieties, thereby creating a dynamic variety in which the composition of the stacks may vary over space and time. Cisgenic plants were selected based on the expression of all inserted R genes and trueness-to-type. Within the project, 13 R genes from wild potato species were genetically mapped and three of them were cloned. Four varieties were transformed with one to three R genes. This was initially done using kanamycin resistance provided by a selectable marker gene of synthetic origin in order to quickly test the performance and stability of the introduced R genes and stacked R gene combinations. Once the functioning thereof was confirmed, marker-free transformations were conducted; thus, true cisgenic events were selected. The results about the different R genes, their chromosomal location, their specificity, the background dependence, the maximum size of a stack, its regeneration time and associated somaclonal variation frequency and its stability were studied. After selection and characterisation in the laboratory, the best cisgenic events were assessed in field trials for late blight resistance. This showed that inserted R genes were capable of turning a susceptible variety into a resistant one. Maximising longevity of the resistance was assured through resistance management research. It was shown that stacking of multiple R genes and monitoring how to deploy these stacks spatially and temporally could reduce fungicide use by over 80%. Communications through media and field demonstrations were manifold to allow public and policymakers to decide if cisgenesis is an acceptable tool to make potato farming more sustainable. Future deployment of the DuRPh strategy will depend largely on its status as a genetically modified crop or its exemption thereof. Worldwide near eradication of late blight would increase global annual potato production by close to 80xa0millionxa0tons, thereby contributing considerably to the needed additional global future food supply.

AGRO-ECOLOGICAL ZONING AND POTENTIAL YIELD OF SINGLE OR DOUBLE CROPPING OF POTATO IN ARGENTINA

Potato is the most important horticultural crop in Argentina and at present 100,000 ha are grown in different regions and seasons. The four possible growing seasons are defined as early (June–October), medium-early (July–November), medium-late (October–March) and late (February–June) and have already been characterized by assessing weather, soil and crop type, yield level and yield determining, yield limiting and yield reducing factors. However, there is scarce or no information on the possibilities of expanding actual crop frontiers, either at regional or national level and on the potential yield of the crop in different agro-ecological zones. Hence, in this work, we (1) characterize agro-ecological zones for potato production, (2) establish potential duration of the crop cycle and potential growing seasons, (3) estimate the potential yield of the crop in these zones and seasons and (4) demonstrate how Geographic Information Systems (GIS) for land evaluation and simulation models that establish potential yield of the crop can be used together to assess possibilities for increasing crop production at regional or national scales. Seven potential growing seasons ranging from 3500°C day were identified for areas where one crop can be grown per year, whereas four areas were identified where there is a potential for a second crop of potatoes. In these areas and seasons, potential tuber yields ranged from 20 Mg ha−1 dry matter. The study identified suitable soils and ascertained the corresponding potential duration of the growing seasons and the potential yield for each of the suitable sites and seasons.

Organizing data in arable farming : towards an ontology of processing potato

Arable farmers and their suppliers, consultants and procurers are increasingly dealing with gathering and processing of large amounts of data. Data sources are related to mandatory and voluntary registration (certification, tracing and tracking, quality control). Besides data collected for registration purposes, decision support systems for strategic, tactical and operational tasks yield enormous amounts of mainly digital information. Data of similar nature but with often varying definitions are collected and processed separately for different purposes. This paper describes for an important arable crop – the processing potato – which data requirements and flows exist at present and how they could possibly be described in a unifying ontology. An ontology describes the concepts, attributes and relations in a specific knowledge domain using a standardized representation language. Important concepts in this domain are for example crop, parcel, soil, treatment and farm. The ontology – once elaborated – will reduce the overlap between information models and helps to overcome the problem of data definition and representation. It is a key element for the development of systems that can automatically learn either with the help of expert knowledge or through adequate numerical techniques.

Analysis of a complex crop production system in interdependent agro-ecological zones: a methodological approach for potatoes in Argentina

This paper shows how a highly complex potato production system, like the Argentinian one, can be surveyed and analysed. A survey was complemented with the use of a Geographic Information System and a simulation model approach which improves the understanding of the possibilities for increasing future crop production by expanding the area cropped with potatoes and/or the yield. A yield gap analysis was also a useful and comprehensive tool to identify and rank yield defining, yield limiting and yield reducing factors for those agro-ecological zones where the potato is currently grown. With these procedures, the physiological age of seed tubers and virus diseases were identified as the most relevant factors limiting and reducing yield. Specific strategies can be developed to counteract their limiting and reducing effects upon seed quality and tuber yield. The approach of this work does not only apply for the specific situation of the potato crop in Argentina, but this framework could be successfully applied to other crops or production systems elsewhere.

The Canon of Potato Science: 36. Potato Ontology

– Mandatory registration of data required by legal regulations to obtain a licence to produce. Location and size of the fields and mineral balances may be part of these data as government bodies often require them. Other mandatory data are those regarding food safety – timing of application and dose and type of hazardous chemicals applied – and those required by procurement agents. – Voluntary registration data are needed if growers volunteer to obtain certificates and labels, as required by the purchaser (e.g., organic) as a license to deliver to wholesale or to the processing industry. – Data from operations registered by growers for future reference by advisors, for example in decision support systems (DSS). DSS need input based on measurements of soil, air and crop variables, together with a quantitative model or database. Also data from observations in samples of the produce delivered to the processing factory are operational data. – Generic data, for example data that do not pertain to a specific potato field but still have importance to growers, such as weather conditions, information about market development and financial information on leasing land or labour costs.

The Canon of Potato Science: 46. Potato Crop Modelling

What is it? Potato crop performance can be described in terms of development and growth. Developmental stages are tuber initiation, tuber growth, maturity, dormancy, sprouting, emergence (after planting), development of leaves, stems and roots. Development is mainly determined by temperature and day length and is variety dependent. These factors determine the moment of organ initiation and the subsequent relative allocation of dry matter to them. Higher temperatures reduce the time between the various stages and shorter photoperiods lead to earlier tuber initiation, more dry matter allocated to the tubers – hence less to the foliage – and earlier maturing crops. Temperatures above the optimum for growth disfavour tuber growth and thus exert an influence on dry matter distribution. Crop growth – the difference between assimilation and respiration – is determined by yield determining factors: the amount of photosynthetically active radiation and the carbon dioxide level in the air provided temperatures are in an optimal range and all resources such as water and minerals are in ample supply. Temperatures below optimum slow down assimilation processes and too high temperatures speed up respiration; both reducing growth. Carbon dioxide levels are the same everywhere in the world but gradually increase over the years thereby leading to higher intracellular CO2 levels in the leaves which accelerates photosynthesis. The stomata need slightly less aperture because of higher carbon dioxide levels which leads to a reduction of transpiration and increased water-use efficiency. At a higher level of aggregation than photosynthesis and respiration, growth may be described as the dry matter produced by the foliar apparatus following interception of photosynthetically active radiation (about half of global radiation).