INTRODUCTION

The potato, Solanum tuberosum, originated north of Lake Titicaca in the southern Peruvian Andes between 6,000 and 10,000 years ago (CIP, 1972;Rodríguez, 2010). Wild potato relatives are distributed from the Southern United States to Northern Patagonia, with a very large genetic diversity (Haan and Rodríguez, 2016). In Paraguay, the cultivated potato was likely introduced from other regions of South America through agricultural exchanges and by the Spaniards during the colonization period (Earle, 2023;Rodriguez, 2010;Rojas, 2008).

The potato is a staple food for many countries, providing energy and essential nutrients to a significant part of the world’s population (Lutaladio and Castaldi, 2009;Raigond et al., 2020;Singh et al., 2020). The world’s largest potato producers are China, India, and Russia (FAO, 2024b). In Paraguay, potato is the second most consumed root crop after cassava. It serves as an important alternative crop by generating income and contributing to the food security of a significant number of smallholder farmers (MAG, 2016). However, domestic production does not supply domestic demand and depends almost exclusively on imports from neighboring countries (SENAVE, 2020). One of the most significant and longstanding national challenges in achieving self-sufficient potato production is the production of seed potatoes. It is difficult due to the technical complexity involved in producing virus-free seed potatoes and a distribution system of high-quality seed potatoes, both in physiological and sanitary terms.

This study aims to compile and analyze the current state of potato production in Paraguay, with a particular focus on the challenges in developing a self-sufficient system for virus-free seed potatoes. It compiles key information on edaphoclimatic conditions in potato-growing regions, assesses the risks associated with importing seed potatoes that may introduce viral diseases, and examines the country’s heavy reliance on imports to meet domestic demand. The study also highlights the technological and logistical barriers to producing high-quality seed potatoes locally. Furthermore, it examines the successes of the KOPIAIPTA project in advancing virus-free seed potato production and distribution to smallholder farmers while providing insights into the future potential for establishing a self-sufficient potato seed production system in Paraguay.

EDAPHOCLIMATIC REQUIREMENTS FOR THE CROP AND THEIR CORRESPONDENCE WITH LOCAL CONDITIONS

Understanding the potatoes’ climatic requirements and physiological responses is crucial for achieving high yields and good tuber quality under specific site conditions (Belmont et al., 2008). Potatoes are characterized as a crop sensitive to frost and are also affected by high temperatures. Their ideal temperature range is 15 to 18 °C. However, the key condition for cultivation is that, even if grown in a warm climate area, the nighttime soil temperature should be below 20 °C for optimal tuber formation (ICTA, 2021;Zuñiga et al., 2017). In the vegetative stage, stem elongation is better at 20°C, leaf growth is optimal at 25 °C, and the ideal temperature for harvest is between 20 and 24 °C (Huarte and Capezio, 2013;Zuñiga et al., 2017).

The soil requirements of the crop are porous, drained, loam, sandy-loam, and clay-loam, 30 to 50 cm deep, and an ideal pH of 5.0 to 5.4 (ICTA, 2021;INIA, 2020). The water requirements can vary between 600 and 1000 mm during the growth stage, the greatest demand being during the development and growth of tubers (ICTA, 2021;INIA, 2020;IPTA, 2019). The irrigation management for potatoes depends on factors such as the availability of water resources, irrigation method, soil type, and the phenological stage of the plant (López and Zuñiga, 2019). In this regard, determining an irrigation schedule tailored to local factors and the water demand of the varieties used would help improve tuber production (López et al., 2022).

Paraguay is divided into two major natural regions: The Eastern Region and the Western Region. These are further subdivided into various ecoregions, established by the Secretariat of the Environment (SEAM) in 2013. The Western Region, characterized by its vast plain with a 1% slope towards the Paraguay River and alluvial soils, sandy in the north and clayey in the south, comprises the ecoregions of Dry Chaco, Pantanal, Wet Chaco, Cerrado, and Médanos. In contrast, the Eastern Region is distinguished by its gently undulating terrain, with mountain ranges in the northeast and center and predominantly red volcanic soils derived from granite and basalt with medium to high fertility. This region includes the ecoregions of Aquidabán, Amambay, Central Littoral, Central Forest, Atlantic Forest of Alto Paraná (BAAPA), and Ñeembucú. These eleven ecoregions host a mosaic of diverse ecosystems, granting Paraguay a high biological and floristic diversity (Ávila et al., 2018;MAG-DIA, 2008;SEAM, 2013).

Potato is grown in various departments of the Eastern Region in Paraguay, mainly in the Department of Paraguarí, followed, however, to a lesser extent, by Cordillera (DCEA-MAG, 2023a;IPTA, 2019). Planting times may vary according to the location, from March to July in the northern, central, and eastern departments of this region, and from the end of February to August in the southern departments of this region. The optimal average temperature for potato cultivation in the northern, central, and eastern areas is between May and July, with average temperatures around 17 and 20.4 ºC. As for the climatic conditions in the southern departments, between May to August, the temperature ranges from 15.6 to 17 ºC. Total annual precipitation varies between 1,800 and 1,000 mm, with a higher concentration in the southeastern departments (DINAC-DMH, 2019-2023).

Concerning the availability of water resources, the country’s Eastern Region has a surplus due to the supply from groundwater, retention ponds, and the contribution of national and international basins (Álvarez, 2014;Benítez, 2020). The total number of farms with a water source in the country is 274,277, including natural or artesian wells, reservoirs, and mainly, water supply systems. The Department of San Pedro stands out with 20.48% of these farms. Additionally, there is a total of 4,649 farms equipped with irrigation systems nationwide, with 42.5% located in the Department of Caaguazú (DCEA-MAG, 2023b, 2023c).

Regarding soil fertility, the departments of Paraguarí and Cordillera, despite having the highest number of potato- producing farms, feature predominantly low fertility and high fertility limitations with moderate pH, low organic matter, and medium to high exchangeable acidity. (Arce, 2017;DCEA-MAG, 2023a). On the contrary, the departments with fewer soil fertility limitations are Alto Paraná, Itapúa, followed by Caaguazú, San Pedro, Concepción, Amambay, and Canindeyú (Fatecha et al., 2017;MAGIICA, 2003).

The altitude of the planting area should also be considered in seed potato production, besides temperature, soil, and precipitation. According to the International Potato Center (CIP, 2010), the planting altitude for potatoes goes from sea level to 4,700 m. However, the higher the altitude, the lower the population of aphids, which are the main virus vectors in the potato crop (Gómez et al., 2015). Elevations in the Eastern Region vary between 50 and 750 masl (meters above sea level). The highest altitudes in the Eastern Region of Paraguay are found in the northeast (Fig. 1), mainly in the Department of Amambay, with the highest altitude in the district of Pedro Juan Caballero (DGEEC, 2016;Ginkgomap, 2018). Most of the country does not have higher elevations where aphids cannot exist; therefore, production should be considered under strict sanitary conditions to minimize the possible presence of aphids as vectors of virus transmission (DGEEC, 2016;INIA, 1993).

NATIONAL PRODUCTION SITUATION

According to the results of the 2022 National Agricultural Census (CAN) carried out by the Directorate of Agricultural Censuses and Statistics (DCEA) of the Ministry of Agriculture and Livestock (MAG), the area planted or under potato cultivation in Paraguay is 773 ha, which means an increase of 188.43% compared to the periods from 2018 to 2020 where the average cultivated area of potatoes registered was 268 ha (DCEA-MAG, 2023a;MAG, 2022a). The concentration of potato production occurs among smallholder farmers in the Department of Paraguarí (Fig. 1), who are responsible for 75.68% of the total cultivated area in the country (DCEA-MAG, 2023a). From the beginning of the century to the present, Paraguay has managed to increase both the amount of total production and yield of potato crops, going from producing less than 1,250 tons and a yield of 6.4 ton/ha in 2008 to more than 4,000 tons of production and 14.3 ton/ha of yield in 2021 according to data provided by the Food and Agriculture Organization of the United Nations (FAO) statistical database as shown in Table 1. This increase is known to be due to the support for farmers under the “National Program of Support for Horticultural Production and Marketing of Paraguay Lost 2010/2014” (CAS, 2015;FAO, 2024a;MAG, 2010). Despite this, the national potato productivity is still below the productivity of the neighboring countries such as Argentina and Brazil, which maintain a productivity of 35 and 33 ton/ha, respectively (FAO, 2024a). In addition, despite having varieties introduced and adapted to Paraguay, such as Kennebec, Primicia, Spunta, Ana, Catucha, Cupido, and Eliza, no varieties have been developed domestically (CAS, 2015;IPTA, 2019).

STORAGE, DISTRIBUTION, AND INDUSTRY

The conservation of seed potatoes and potatoes for consumption must maintain their quality, health, physical, and organoleptic characteristics and guarantee their use, consumption, and marketing. Conservation is ideally carried out in cooling chambers or diffused-light storages (CIHBIPTA, 2021;Rojas, 1994). In Paraguay, potato producers are mainly smallholder farmers and are characterized by a low level of technological acquisition and low productivity. For the same reason, the storage of potatoes for consumption is still carried out in a rustic way without the use of refrigeration technology and opting for manual harvesting, classification, and packing. In addition, the production is stored in dry and open sheds or sold almost immediately after harvesting to the market and consumers (DEA-MAG, 2022;MAGP, 2021).

The dry matter content in potatoes should be between 20 and 23% for the food industry, and it depends on the variety and conditions of the crop. In this regard, the Spunta variety, which is the main one grown in Paraguay, is characterized by not having enough dry matter, which results in potatoes that are oily, not firm enough, and unsuitable for the fresh potato processing industry (Huarte and Capezio, 2013;MAGP, 2021). Among the varieties most suitable for industrialization due to their productivity and culinary qualities are Kennebec, Innovator, Atlantic, Sagitta, Daysi, Asterix, and Cherie, among others. However, these varieties are produced in limited quantities or have not yet been introduced to the country (MAGP, 2021).

Based on the analysis of the potato market in Paraguay carried out by the Southern Agricultural Council (CAS), there are no statistics related to the local industrialization of potatoes in Paraguay until 2015. However, in the last 5 years, a new market for potato processing has been emerging in Paraguay, with CMA Paraguay S.A. being the leading company. Nonetheless, 80% of their supply of raw materials is still being covered mainly by Argentina (CAS, 2015;Fustagno, 2021).

IMPORT LEVELS OF POTATOES FOR CONSUMPTION

The amount of potatoes imported represents more than 90% of the total demand for domestic consumption. According to data from the Importer’s Single Window (VUI) compiled by the National Service for Plant and Seed Quality and Health (SENAVE), potatoes for consumption top the list of imported vegetables with a total of 55,049 tons in 2020 (SENAVE, 2020). On the other hand, import data from the Central Bank of Paraguay show that, on average, the annual import of fresh or refrigerated potatoes between 2019 and 2023 was 47,738 tons (Fig. 2), of which 96.12% comes from Argentina and 3.89% from Brazil (BCP, 2024). According to the data recorded between 2019 and 2021 at the Central Supply Market of Asuncion (DAMA), the domestically produced potato is marketed between October and December only, and the demand for the rest of the year is covered by potatoes imported from Brazil and Argentina (MAG, 2022b).

IMPORT LEVELS OF SEED POTATOES

The supply of seed potatoes represents a nationwide issue because, similar to potatoes for consumption, most seed potatoes are currently imported from Argentina mainly, and to a lesser extent, Brazil. The primary variety of imported seed potatoes is the Spunta from Argentina. The average import quantity has been increasing, rising from 147 tons per year between 2015-2018 to 799.9 tons per year between 2019-2023, as seen in Fig. 2 (BCP, 2024;SENAVE, 2020).

CONTEXT OF VIRUS PREVENTION IN SEED POTATOES IMPORTED TO PARAGUAY

An important aspect of seed potato propagation is the transmission of viruses in successive generations when they are present in the propagation material, representing significant losses in yield (Salvalaggio, 2021). As previously mentioned, seed potatoes are imported mainly from Argentina, where 12 virus species have been reported between 1966 and 2022, of which the most commonly reported species are Potato Virus Y (PVY), Potato Leaf Roll Virus (PLRV), Potato Virus S (PVS) and Potato Virus X (PVX), while less commonly reported species are the Andean Potato Mottle Virus (APMoV), Potato Virus M (PVM), Potato Virus V (PVV), Tomato Chlorotic Spot Virus (TCSV), Potato Virus P - Argentine race (PVP-Arg), Tomato Spotted Wilt Virus (TSWV), Tomato Yellow Vein Streak Virus (ToYVSV) and Groundnut Ringspot Virus (GRSV). Of these, nine are shared with Brazil: PVY, PVX, PLRV, PVS, APMoV, ToYVSV, GRSV, TSWV, and PVP, with specific strains of the latter in each country. Moreover, some viruses are also shared with Bolivia: PVY, PLRV, PVX, and PVS (Salvalaggio, 2021). However, Argentina has made an effort to establish and control agroecological areas suitable and specific for seed potato production, including the provinces of Buenos Aires, Mendoza, Tucumán, Rio Negro, San Luis, and Santa Cruz (MAGP, 2021).

A study on the potato virus status in the southeast of Buenos Aires province found that while different levels of PVY, PLRV, and TSWV incidences have been observed in seed potato seedlings, there has been a decrease in infection levels and an improvement in seed potato certification categories for all viruses over the last decades (Salvalaggio et al., 2022). These measures taken by Argentina contribute to protecting potato crops from severe virus incidences. Meanwhile, in Paraguay, the Department of Phytosanitary Quarantine of SENAVE has determined that, for imports of true potato seeds (TPS, botanical) and seed potatoes (from tubers) from Argentina, the product must be accompanied by the Phytosanitary Certificate and comply with specific declarations (SENAVE, 2024). Nevertheless, the risk of smuggled potatoes entering Paraguay from Argentina is a latent problem that generates a phytosanitary alert for the crop in Paraguay (IP, 2016;Argenpapa, 2021b).

DETECTION OF VIRAL DISEASES IN POTATOES IN PARAGUAY

Viral diseases are one of the main issues in agriculture as they directly affect plant growth and overall production (Campos and Ortiz, 2020). A study carried out in Paraguay by Shohara et al. (1995) identified several viral diseases in plants with symptoms such as mosaic, dwarfism, vein necrosis, and leaf curl. Their analysis using an electronic microscope revealed the presence of flexible particles approximately 750 nm long. These particles were suspected to be PVY, although further confirmation is required. PVX was also detected in symptomatic potato leaf samples using an electronic microscope and serology. However, the current prevalence and distribution of PVX in Paraguay are unknown (Esquivel et al., 2024;Shohara et al., 1995).

In another study in the country by Shohara in the 1990s, mentioned by Esquivel et al. (2024), samples were collected from potato plants exhibiting symptoms of mosaic, dwarfism, venous necrosis, and leaf curling. Examination of the foliar extracts using an electronic microscope revealed particles resembling those of the Carlavirus, which suggested a possible presence of PVS or PVM. However, their exact identification had not yet been confirmed at that time (Esquivel et al., 2024).

Because there are limited studies on virus identification in potatoes in Paraguay, it is crucial to be acquainted with the virus status of the countries from which potatoes are imported, with Argentina being the most important source for our market.

ESTABLISHING A SEED POTATO PRODUCTION SYSTEM IN PARAGUAY THROUGH THE KOPIA-IPTA PROJECT

Through the KOPIA-IPTA cooperation, projects for the production of disease-free seed potatoes were carried out for a total of 13 years with the Paraguayan Institute of Agricultural Technology (IPTA) at the regional research center in Caacupé (IPTA-Caacupé), divided into four work stages between 2010 and 2022.

From 2010 to 2012 (Stage 1), three Brazilian varieties (Eliza, Cupido, and Catucha) were introduced to evaluate their agronomic characteristics in the cities of La Colmena, Santa Rosa de Lima, Concepción, and Caacupé. The Eliza variety obtained an average yield of 13.7 ton/ha, Catucha of 10 ton/ha, and the lowest performing was Cupido, with an average of 7.7 ton/ha (Table 2). In addition, the Kennebec and Spunta varieties, both introduced from Argentina, have also been evaluated in the cities of La Colmena, Coronel Bogado, Yhu, and Caacupé. The Spunta variety had an average yield of 15.7 ton/ha, and the Kennebec variety 12.4 ton/ha (Table 2).

From 2013 to 2015 (Stage 2), the technology for growing potato seedlings from tissue cultures and pre-basic plants was established. From 2016 to 2019 (Stage 3), mother plants obtained from Catucha, Spunta, and Kennebec varieties were analyzed using the ELISA test for PVS, PVX, PVY, and PLRV. All tested negative and were used to generate meristematic tissue culture seedlings for seed potato production and distribution to farmers. During this stage, in 2019, 118.5 tons of seed potatoes were distributed to farmers (Table 3).

From 2020 to 2022 (Stage 4), the disease-free seed potato production system and the basic technology for seed potato production through the aeroponics system (Naz et al., 2024) were established (Fig. 3). Within this stage, 202.5 kilograms of seed potatoes were produced through an aeroponics system, a process that had previously relied solely on soil cultivation. The seed potatoes were used to produce 74.7 tons of potatoes for their distribution to farmers (Table 3). In 2022, five farmers planted 5 ha in San Juan Bautista, a city in the south of Paraguay, with low yields of 16,4 ton/ha due to drought. On the other hand, higher yields of 20.0 ton/ha were found both in La Colmena, in the central area, where 35 farmers planted 30 hectares, and in Choré, in the north of the country, where 22 farmers planted 20 hectares (Table 4).

The amount of seed potatoes that IPTA-Caacupé can produce is approximately 74 to 118 tons per year. In order to be able to supply even a portion of the approximately 799.9 tons of seed potatoes required per year in Paraguay domestically, other IPTA regional research institutes in the main potato-producing areas, besides IPTA-Caacupé, such as IPTA-Choré must participate in the proliferation of tissue culture plants. Also, the local governments in the main production areas, such as Paraguarí and Cordillera, must directly produce seed potatoes to distribute in their departments.

IPTA-Caacupé is able to produces virus-free tissue-cultured plants and supplies them to other IPTA regional research centers in the main cultivation areas. The IPTA regional research centers in the main production area should supply mass-proliferated tissue culture seedlings and acclimated tissue culture plants to the local governments in the main production areas. The local governments should use the acclimated tissue cultured plants to produce pre-basic seed potato tubers in aeroponic greenhouses, and the basic potato tubers should be cultivated in mesh greenhouses to produce potato tubers for distribution to farmers.

PROSPECTS FOR SEED POTATO PRODUCTION IN PARAGUAY

The current situation of potato production in Paraguay indicates that the persistent lack of seed potato supply to farmers is one of the primary causes of the low productivity in this crop. Each year, the Ministry of Agriculture and Livestock (MAG) promotes potato production by providing farmers with imported certified seed potatoes. Consequently, several farmers in districts in the Department of Paraguarí have consolidated their technical knowledge of this crop, making it the largest potato-producing area in the country (IP, 2020). Additionally, there has been a promotion of potato cultivation as an alternative crop among smallholder farmers in other departments of the country, such as San Pedro, Ñeembucú, and Itapúa (Argenpapa, 2020-2021a;Infonegocios, 2024;MITIC, 2024). Recently, MAG has supplied refrigerated seed potatoes to develop the crop in a non-traditional location, the Amambay Department, in the northeast of the country (PotatoPro, 2024). This area is among the highest points with an average altitude of more than 300 masl, an average annual temperature of 22.8°C, an average annual rainfall of 1,500 mm, and according to the compendium of agroecological zoning of Paraguay, is classified as a ZAE 1 zone along with San Pedro. These zones are characterized by soils suitable for agricultural exploitation with medium to high fertility values. Considering the suitability of its soils and its higher altitude areas, these zones can be established as new alternatives with good potential for seed potato production (DINAC-DMH, 2019-2023;GinkgoMaps, 2018;MAG, 2018).

Establishing strategic locations for producing and supplying virus-free seed potatoes is most likely the determining factor to fully promote its self-sustainable production in the country. In this regard, to select appropriate regions for the massive production and supply of seed potatoes, they must meet some strategic criteria from a technical, logistical, and economic standpoint. Firstly, the seedbed selection should be established in an area isolated from other potato for consumption fields or other aphid-host crops that transmit viruses (INIA-CIP, 2009). The differentiation of production areas should initially be evaluated and selected by expert producers of virus-free seed potatoes, usually from research centers. Secondly, legal protection parameters must be established for these zones, a step that falls under the responsibility of the relevant public entities. As a reference, potato seed production zoning has been promoted in Argentina, where the production areas in each province are distributed under provincial decrees or laws (MAGP, 2021). Due to the previously mentioned climatic and topographic suitability, the northeast of the Eastern Region of Paraguay could be considered for zoning for seed potato production. However, logistical arrangements for producing virus-free seedlings in institutions with adequate facilities and specialized technicians should also be evaluated and considered. Additionally, criteria for distributing seed potatoes to other producing areas of potato for consumption should be analyzed, along with the technical preparation necessary for their proper management.

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