The Handbook, richly illustrated with over a thousand photos and many hundreds of diagrams and graphs, comprises a total of five fully elaborated chapters divided into clear paragraphs and is providedwith an index. The first chapter deals with people who consume potatoes, create economic value and set up related organizations. Chapter two is based on the plant, its growth, how it uses sun, water and mineral resources and how it defends itself against diseases and pests. In the third chapter, the Handbook gives an overview of the propagation material with both a genetic and a seed material component. All aspects of the crop in its environment of soil and weather in various climates as well as the influence of climate change is described in the fourth chapter. In conclusion, chapter five deals with the cultivation and storage of the tubers with all the equipment and organization involved. Introduction 2. Plant 1 2 3 4 Crop of the future Developments to date As early as 10,000 years ago, the South American population around Lake Titicaca had domesticated the potato crop. They did so by selecting from hundreds of wild potato species the ones they liked best. When Cristopher Columbus arrived in South America around 1500, the Inca civilization was at its peak. When the conquistadors arrived later they could not apprehend that 500 years later farmers at all continents would grow the crop and that in the future, after wheat from the Middle East and rice from Asia, potato would be the third most popular food crop on earth. From the Titicaca region in Peru and Bolivia, the potato spread all over South America. Close to the equator potato only thrives in cool mountains at short days. This is the only suitable daylength for tuber formation of potato grown there. But in the South of Chile, on the island of Chiloë, species have developed that also initiate tubers at long days. So, these are also of use in regions far from the equator. The first potatoes that arrived in Spain flowered exuberantly but only produced tubers in autumn when the days started to shorten. Later shipments, in particular from Chile and also by British seafarers, broke through in Europe as they were better adapted. And from then on, the spread through Europe picked up speed. Potatoes yielded more than cereals and in Europe they took the place of rye and barley as food for both man and animals. Potato as a cheap source of food supported urbanization and the industrial revolution in England; the British introduced the crop to North America in the 18th century. The impact of this was huge as in North America the crop came into contact with late blight caused by the water mold Phytophtora infestans. This disease had its origin in the Toluca Valley in Mexico. Potatoes were transported by ship from America to Europe as 20 oduces a plant with four or five mainstems1. The more mainstems there are, the less lateral stems are formed because of competition for water, minerals and light. A mother tuber with apical dominance produces a single stemmed plant2 oduces several lateral stems, four to five here. Lateral stems are formed at the stem segment below ground or just above 3 higher up at main or lateral stem originate in axils where an inflorescence is formed. Inflorescences o because of competit oduces sever soil level. Branches of stems e still seen as peduncles with aborted flowers or fruits, best observed where a stem is cut up in segments4 e and longer days. Besides apical lateral stems, a main stem bring eases with higher temperatures and longer days main stem brings about basal lateral stems from ound or from belowground stem nodes. ound or seed tuber when planted at the start of sprout formation and with a single sprout at the apical part of the tuber often produces only one single seed tuber wh formation and w part of the tuber main stem with main stem with its lateral stems. This because the apical domi the formation of we oduces severa om several eye eye. Thus, a see comprising one acting as a diffe however compe the apical dominance of this sprout prohibits the formation of sprouts and stems from the well-sprouted seed tuber, however, oduces several main stems from sprouts om several eyes. Occasionally even two stems e generated from two sprouts from a single eye. Thus, a seed tuber yields a potato plant comprising one or several main stems each acting as a different independent plant. They do however compete, due to their proximity, for and nutrients. Single-stemmed plants om a single-sprouted tuber, as well as singleom a single-sp stemmed plants derived from a seedling from true potato seed (TPS), create more branches than closely spaced main stems emanating from a plant from a mother tuber with multiple sprouts. Leaf The composite leaves of a potato plant are attached to the stem through the petiole. This is the basal part of the midrib of the leaf. The lower pair of leaflets are rudimentary leaflets, with higher pairs of primary and secondary leaflets topped by the primary leaflet at the tip of the midrib. When the stem generates more segments, the lowest leaf levels get completely shaded, turn yellow and drop off. Drought hastens this leaf shedding as the plant economizes its water use through this mechanism. The epidermis of potato leaves has two types of hair. There are the unbranched (uniseriate) covering hairs and there are glandular hairs. The latter contain a spherical head that exudes volatile compounds. Some wild potato species exude a sticky substance from these hairs that repels insects. 125 soil level. Branches e still seen as ped The relatively rapid degeneration of potato compared to crops multiplied by seed is the main reason for the benefits of creating a comprehensive seed potato production system parallel to the production system of tubers destined for the market. It is possible to grow potato from true seed (TPS) where hardly any 0.2 1. Society 3. Propagation material crops, such as wheat and maize that also need to be sown every cropping season, the potato crop is special in several aspects. The main difference is that the potato crop is multiplied vegetatively. Like other vegetative means of reproduction of the potato crop such as planting stem cuttings or sprouts, any contamination with diseases or pests of the vegetative propagation material is also contaminating the next crop grown from it. With each field generation more and more contaminating agents, pests and diseases accumulate, leading to a gradual degeneration of the seed stock. Relative rates 1 0.8 0.6 0.4 0 0 1 2 3 4 5 number of field generations (1=mini-tubers planted) Increase of seed amount Proportion infected plants Relative yield Healthy mini-tubers are introduced into developing potato production regions with subsistence farming without a seed program. The relative yield of the potato crop generation after generation decreases less than proportional to infection. The amount of seed produced increases exponentially, but after a few generations farmers do not distinguish ware from seed anymore diseases are transmitted. Potato Spindle Tuber Viroid (PSTVd) is an exception. Establishing a crop from botanical seeds for commercial reasons is slow so far and leads to low yields compared to crops derived from seed tubers. The use of TPS as basic seed material, however, is being developed using hybrids at the diploid level. The seedling tubers produced are used as seed tubers, similar to the use of mini-tubers. Subsistence growers in the centre of origin of potato in Peru possess a very wide range of potato cultivars, thousands are named Potato Spindle Tuber Viroid (PSTVd) is transmitted through true seed and easily transmitted from plant to plant by contact and cutting stems in vivo and in vitro 38 The multiplication rate of a ware potato crop is about 20 but of a seed potato crop where more seed is planted and less is harvested has a multiplication rate of less than 10 on average. 281 6 The Potato Handbook is published in English and Dutch. It is meant for everyone who wants to delve deeper into the potato, such as growers, extensionists, technicians, students, researchers and participants in the value chain in all climates and cultivation systems. Order information / Congress A NEW AGE FOR POTATOES 11 - 12 June 2020 Hotel Amigo Brussels, Belgium Register now! With the support of Order now The most complete Potato Handbook in the world Crop of the future Anton J. Haverkort 27 11:35 Rrelative quantity of seed, proportions infection and yield Pagina 46

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