Characteristics of Organically Grown Compared to Conventionally Grown Potato and the Processed Products: A Review

Interest in organic foods is increasing at a moment when humanity is facing a range of health challenges including the concern that some conventionally produced foods may pose possible adverse effects on human and livestock health. With the increasing human population, intensive production is increasingly trending towards high-input systems that aim to close yield gaps, increase crop yields, and develop new crop varieties with higher yield potential and tolerance to biotic and abiotic stresses, all within the context of incorporating specific traits to satisfy consumer demand. Potato (Solanum tuberosum L.) is one of the most consumed foods under different cultural diets; however, its production faces some challenges related to soilborne diseases, marketable yield and quality, sugars and dry matter content of the produced tubers, tuber content in terms of nitrate, minerals, vitamins, bioactive compounds, and antioxidants, and consumer appreciation regarding the sensory characteristics of tubers and processed products. Different studies have been investigating some of these challenges, with sometimes straightforward and sometimes conflicting results. This variability in research results indicates the general non-transferability of the results from one location to another under the same management practices in addition to differences in plant material. This review compares some characteristics of raw or boiled potato and processed products from potato tubers grown organically and conventionally. Ideally, such information may be of benefit in decision making by consumers in their dietary choices, by potato growers in their selection of crop management practices, and by scientists looking at potential areas for future research on potatoes.

Nitrogen availability to potato plants is critical to plant growth and development, tuber yield and quality. Nitrogen form and source are one of the main differences between conventional and organic potato production (Gastal and Lemaire, 2002;Wang et al., 2002;Lomardo et al., 2012Lomardo et al., , 2017. In addition, to control the numerous potential diseases and stabilize yield in potatoes, commercial growers apply a strict package of pesticides and high rate of nitrogen fertilizer (Mauromicale and Ierna, 1999 The taste and bitterness are the main sensory properties of the boiled potato tuber and the texture, color and oil content, crispiness are the main quality parameters of fried potatoes (Aguilera, 1997; Moreira et al., 1999, Thygesen et al., 2001, Ross and Scanlon, 2004. Moyano et al. (2007) found a direct relationship between potato's specific gravity, total solids content, starch content, cell size, and surface area and pectin and potato texture. For the processed product like potato chips, a very crispy texture is expected as crispness is an indicator of freshness and high quality (Moreira et al., 1999;Rosen and Hellenas, 2002;Troncoso and Pedreschi, 2007a,b). Mooreover, the color of the fresh, boiled or fried potatoes is considered one of the most important defining qualities, particularly of fried potatoes (Scanlon et al., 1994) and is the result of the Maillard reaction that is directly linked with the reducing sugars content and aminoacids or proteins at the surface, and the temperature and duration of frying (Marquezm and Anon, 1986).
For the present review, we compared some characteristics of the organically grown potato tubers to the conventional ones. We have considered only side-by-side comparative studies that include both organic and conventional farming practices to exclude some extraneous information which might not necessarily be the impact of the organic farming but the effects of uncontrolled factors. The main characteristics in our review focus on disease pressure on the potato plant and tubers, potato tuber total and marketable yields, specific gravity and dry matter content, sugar and starch contents of potato tubers, nitrate content of potato tubers, bioactive compounds and antioxidant contents in potato tubers, mineral and vitamin content, and the sensory characteristics of the potato tubers. and quality losses of the yield and ultimately decrease the net return of the production system with increased production costs. Potato cultivars with a strong, erect shoot growth habit with shorter stems, more branching, and a denser and taller canopy in the early stages of plant growth may be less susceptible to weed interference than cultivars with less lofty plant habit (Pszczółkowski and Sawicka, 2003; Baranowska et al., 2016;Barbaś et al., 2020). Commercial potato growers follow rigorous pesticide application schedules throughout the conventional potato growing season, and apply different pesticides. While conventional potato often starts by soil fumigation, organic potato often relies on the biofumigation provided by cover crops such as those of the Brassicacea family. Boydston (2010) reported that weeds should be managed in a holistic, intentional and proactive manner if no herbicide is considered. Under organic farming, crop rotation, cover crop selection, planting pattern and timing in addition to healthy and appropriate seed material are the main aspects to be considered for successful weed management. Some specific plants considered as cover crops such as sudangrass and different species of Brassica have been used as a green manure and biofumigant to reduce nematode populations preceding potatoes, and weed emergence (Boydston and Hang, 1995;Mojtahedi et al., 1993a,b). Cover crops that have reportedly suppressed weeds through direct competition or release of allelopathic compounds during decomposition of residues include: rye, oats, barley, rapeseed, mustards, sorghum-sudangrass hybrids, and buckwheat (Putnam and De-Frank, 1983;Weston et al., 1989;Lanfranconi et al., 1993;Boydston and Hang, 1995 Rubel et al., 2020). However, multiple, well-timed shallow cultivations or heat-flaming can eliminate many early season weeds and the application of new technologies for detecting crop rows and weeds coupled with precision cultivation, flaming, and application of nonselective organic herbicides are being developed and hold promise to reduce the need for labor-intensive hand weeding (Boydston, 2010). Cover crops are planted by both organic and conventional potato growers for multiple objectives: nitrogen fixation, soil hydraulic properties improvement, diseases and nematodes suppression, adding more organic matter to the soil, nutrients reclamation, etc. (Hartsema et al., 2005;Clark, 2007;Campiglia et al., 2009;Griffin et al., 2009;Larkin et al., 2021). With cultivation as the only weed management practice in potato production, weed density increased with reduction in tuber yield compared to hand weeding or herbicide application (Eberlein et al., 1997;Felix et al., 2009). VanderZaag (2010) reported that weekly scouting of all fields to determine economic thresholds before spraying and the reliance on weekly newsletters informing about the status of pests and diseases offers significant, environmentally-friendly approaches for sustainable weed, pest and disease management across the potato field. The use of neonicotinoid chemistry as a seed tuber treatment greatly reduced the need to spray insecticide, especially for Colorado potato beetle control, and the amendment with cattle or swine manure led to better crop health and reduced the need for pest and disease treatments (VanderZaag, 2010). Herbicide selection, herbicide combinations and application rates and timing determine the effectiveness of the method in weed management (Pawlonka, 2007;Lavlesh Ragha et al., 2018;Zarzecka et al., 2020;Barbaś et al., 2020). Barbaś et al. (2020) found that chemical method of controlling weeds was the most effective weed control method over a combination of mechanical methods in potato production. However, the combination of metribuzin and rimsulfuron+SN oil as a potato pre-emergence tool was more effective than the other meribuzin, ethoxylated isodecyl alcohol 0.1%, fluazyfop-P butyl, SN oil combinations.

Nutrient management
Potatoes are a special crop and not only does the organic production system affect the crop plant growth and yield but also the tuber quality during cold storage is affected by the particular production systems. Organic farming faces many challenges such as proper nutrient management, weeds, diseases, and insect pest control . Both organic and conventional systems have adopted cover cropping to improve soil organic matter content and improve soil quality. However, organic farming relies more on cover cropping to reduce weed pressure and some specific plant species (Brassicassae) are adopted for soilborne disease control in potatoes combined with improving nutrient and weed management under organic farming. Bio-fertilizers derived from microorganisms are an alternative to chemical and organic fertilizers. El-Sayed et al. (2015) compared mineral fertilizers at a rate of 285.6 kg N + 178.5 kg P2O5 + 357 K2O /ha to a combination of biofertilizers consisting of nitrogen fixers (Azospirillum brasilense and Azotobacter chroococcum), P-dissolving bacteria (Bacillus megaterium and vesicular-arbuscular mycorrhiza) and K-dissolving bacteria (Bacillus cereus) plus different rates of compost on potatoes. They found significant increases in the total and marketable yield of potato from plots treated with 50% of the recommended mineral fertilizers plus 23.8 t/ ha compost with or without bio-fertilizer as well as from plots that received compost at the rate of 35.7 t /ha, compared with plots treated with full dose of mineral fertilizer plus 11.9 t/ha compost (control), while the compost treatment at the rate of 23.8 t /ha + bio-fertilizer resulted in a significant increase in marketable yield, and conventional fertilizer showed significantly higher weight loss of potato tubers during cold storage than all other treatments (El-Sayed et al. irregularis on growth traits of the host potato plant and found that the viral particles were concentrated in the leaves but decreased the root growth, and the infection with PVY evoked prolonged oxidative stress reflected by increased level of endogenous H2O2 and alleviation of oxidative stress in PVY-infected host plants by a substantial decrease in the level of shoot-and root-derived H2O2 with asymptomatic growth depression. Carter et al. (2003) reported that the application of compost once in a 3-year potato rotation was beneficial for both soil physical and biological properties, and for potato productivity. However, due to the limited viability of compost and/or organic fertilizers in many locations and their low nitrogen content (Rembialkowska, 1999), organic fertilizer may be challenging and more emphasis should be given to cover cropping in addition to bio-fertilizers that colonize the soil under organic production in humid and sub-humid climates. The bio-fertilizers are constituted with microorganisms which solubilize the unavailable forms of inorganic-P (Venkateswarlu et al., 2007) and potassium rock through production and secretion of organic acids (Bin Zakaria, 2009). The leguminous cover crops are associated with nitrogen fixing bacteria Azotobacter spp. which are known to produce different growth hormones, vitamins and siderophores. Azotobacter is capable of converting nitrogen into ammonia, the form of nitrogen that can be taken up by plants ( Kamil et al., 2008). Jen-Hshuan (2006) reported that Azotobacter spp. can produce antifungal compounds to fight against plant pathogens. Rees et al. (2011) reported that in-season fresh poultry manure amendment increased potato total yield compared to the fall application (Bationo et al., 2004).  reported the commercial hog manure-sawdust compost (CP) and pelletized poultry manure (NW) applied at 300 and 600 kg total N /ha positively affect potato tuber yield and potato plant N uptake (112 kg N /ha) under nonlimiting soil moisture conditions. Fahmy et al. (2010) found that pulp fiber residue compost amendment increased potato plant-available phosphorus and potassium and the tuber yield was increased under supplementary irrigation while no change was observed in a rainfed setting compared to the non-amended plot. Green manure management and the recycling of organic materials may be a valid alternative to the conventional synthetic fertilizer-based management system for sustainable potato production, sustaining tuber yield without enhancing potential environmental risks due to N leaching (Canali et al., 2012). Drakopoulos et al. (2016Drakopoulos et al. ( , 2018 investigated solid cattle manure, lucerne pellets, grass/clover silage amendments on crop performance and nitrogen utilization of organic potato and found that plant-based fertilizers enhanced nitrogen utilization in terms of apparent nitrogen recovery compared to animal-based manures and the lucerne pellets resulted in the highest yield regardless of the tillage practices. In contrast, Wilson et al. (2019) reported that soil amendments with diverse wood waste and manure compost products resulted in a small increase in plant N availability in small plots experiments. The immature products resulted in net N immobilization, the composts high in K increased plant K availability with non-significant effects on tuber yield.

Potato diseases occurrence and intensity in potato
Disease management is a serious challenge and threat to organic potato management. Late blight, caused by Phytophthora infestans is commonly thought to be the factor most limiting yield under organic practices . Soilborne potato diseases include Rhizoctonia canker and black scurf, caused by Rhizoctonia solani; common scab, caused by Streptomyces scabiei; powdery scab, caused by Spongospora subterranea f. sp. subterranea; white mold, caused by Sclerotinia sclerotiorum; silver scurf, caused by Helminthosporium solani; pink rot, caused by Phytophthora erythroseptica; and Verticillium wilt, caused by Verticillium dahliae. Common scab, caused by Streptomyces scabies; silver scurf Helminthosporium solani and softrot, caused by Erwinia carotovora var. atroseptica may be detrimental to organic production systems. Organic farming relies on the agricultural practices to reduce and/or control diseases instead of applying chemical pesticides. Larkin and Halloran (2014) 2015) investigated the effect of management practices on potato tuber diseases (common scab (Streptomyces spp.), silver scurf (Helminthosporium solani), dry rot (Fusarium spp.), and soft rot (Pectobacterium spp.) and found that the organic systems had significantly more tubers (around 39 %) infected with common scab (surface cover 4-15 %) than in conventional systems (around 25 %), fewer tubers infected with silver scurf compared to all conventional farming systems, less tubers infected with dry rot in organic systems compared to the conventional systems, and the soft rot infections were not influenced by farming systems. Bernard et al. (2014) reported rapeseed rotation reduced all observed soilborne diseases such as stem canker, black scurf, common scab, and silver scurf by 10 to 52 % under organic farming.
Organic farming heavily relies on crop rotations and improved cropping systems incorporating management practices associated with soil health management (crop rotation length, cover crop species choice, and green manures, organic matter amendments, and minimum tillage). Larkin et al. (2021) found that disease suppression practices which included disease-suppressive green manures and cover crops, produced the highest yields compared to soil improvement, soil conservation and status quo practices representing yield increase from 11 to 35%. The disease suppression system consisted of a three-year rotation with the disease-suppressive Brassica "Caliente 119", Mustard Blend (blend of oriental and white mustard seeds, Brassica juncea L. and Sinapis alba L.) grown as a green manure, followed by a fall cover crop of rapeseed (Brassica napus L. " Dwarf Essex") in the first year (Larkin et al., 2021). In the second year, a disease-suppressive sorghum-sudangrass hybrid (Sorghum bicolor x S. bicolor var. sudanense) was grown as a green manure, followed by a fall cover crop of winter rye (Secale cereale L.), with potato in the third year. This combination improves disease control in potato with yield advantage. These organic management practices have been shown to significantly affect soil chemical, physical and biological properties (

Total tuber yield and marketable yield
Potato under organic production is subjected to different pests, diseases and limited available nutrient and consequently produces lower tuber yield compared to the conventionally grown potato (Clark et al., 1998 2013) found that total and marketable yields were significantly reduced by the use of both organic crop protection and fertility management. Moreover, the yield gap between organic and conventional fertilization regimes was greater and more variable due to lower or less predictable nitrogen supply in organic fertilizer pratice than that between crop protection practices (Palmer et al., 2013). Ierna and Parisi (2014) reported that organic cultivation system was less productive (5 to 50% less) than the conventional due to a less availability of nitrogen and to appearance time and severity level of late blight infection. Fiorillo, et al. (2005) and Warman and Havard (1998) found no tuber yield reduction under organic farming. Warman (1998) suggested that variation in weather has a greater influence on productivity than the kind of fertilizer adopted.

Tuber specific gravity and dry matter content
Potato tuber specific gravity is an important characteristic for processing potatoes quality and it represents the dry matter content of tubers. Potato tuber with high specific gravity shows higher dry matter content and produces potato chips or fries with light color with less oil absorption (Lulai and Orr, 1997). Dale et al. (1994) and Haase (2004) indicated that the dry matter content of potato tuber linked with specific gravity is a main determinant of potato quality. Potato dry matter content has been grouped as high dry matter content

Nitrate content of Potato Tubers
Organically grown potatoes generally contain less nitrate ( In contrast, Jiří et al. (2007) reported that mean contents of crude protein and in protein content in dry matter were significantly higher in organically grown potato tubers than in tubers from conventional practice. They found that potato genotype or cultivar was the factor with the highest direct effect on crude protein and protein contents in the potato tubers. Makaraviciute (2003) and Maggio et al. (2008) reported non-significant differences in potato content in essential amino acids between organic and conventional potato tubers. Shepherd et al. (2014) found that mass-spectrometry and gas chromatography analysis of polar compounds identified 83 metabolites showing significant differences in the metabolome between the organic and conventional farming with 62 metabolites (dominated by free amino acids) being less abundant in tuber samples from organic compared with conventionally grown plots due to the 50% lower nitrogen content of the organically grown potatoes than for conventional production. Lombardo et al. (2012) found that total protein amount was independent of the farming management system However, on the basis of peptide composition, protein quality as nutritional value is superior in the organically grown potato tubers than the conventionally grown potato tubers (Rembiałkowska, 2007).

Mineral and vitamin contents
Potato tuber content might be impacted by soil and plant management practices. Wszelaki et al. (2005) found that potassium, magnesium, phosphorus, sulfur and copper concentrations in tuber skin and flesh, were also significantly higher in the organic treatments, while iron and manganese concentrations were higher in the skin of conventionally grown potatoes. Lombardo et al. (2014) investigated early potato tuber mineral contents under organic and conventional farming and found that the potato tubers contained more phosphorus (2.8 vs. 2.3 g kg −1 of dry matter) and a comparable quantity of both magnesium and copper (on average 250 and 2.6 mg kg −1 of dry matter, respectively) under organic farming than the conventional farming. Wszelaki et al. (2005) found tuber skin and flesh to have higher concentration in potassium, magnesium, phosphorus, sulfur and copper significantly higher under organic management than conventional practices while, iron and manganese contents were higher in the skin of conventionally grown potatoes.
Contradictory data have also been reported between the organically grown and conventional grown potato with respect to vitamin C content (Asami et al., 2003;Warman et al., 1998;Wacholder and Nehring, 1940). Warman and Havard (1998) found that there was no significant difference in vitamin C content of the potato tubers grown under organic and conventional practices. Conversely, other studies have reported higher vitamin C content in the organic potato tubers than in the conventional potato tubers Potato threshold concentration in solanine of 140 µg g −1 causes bitter taste, and solanine concentration greater than 200 µg g −1 creates a burning sensations in the throat and on the tongue (Sinden et al., 1976). Gilsenan et al. (2010) found that the conventional potatoes had a lower dry matter content and a slightly softer texture than the organic potatoes. The conventional baked potato was also slightly softer, less adhesive and wetter than the organic backed potato but there was no significant difference between the organic and conventional baked potato samples for the sensory attributes of appearance, aroma, texture and taste acceptability (Gilsenan et al., 2010). Brazinskiene et al. (2014) reported that odor and taste intensity of the potato samples were not affected by farming practices. Table 2. Comparative analysis of characteristics differences between organically and conventionally grown potatoes.

References
Major research findings Locations Warman and Havard (1998) The yield and vitamin C content of the potatoes was not affected by treatments. Potatoes from organic systems had 18% more total phenolics than those from conventional systems.

Italy
The nitrate content in organically grown tubers was 34% lower than conventional products.
Ascorbic acid content of conventionally produced tubers were 23% greater than from organic systems.
Better sensory performance after frying (crispness and less browning) was observed in potatoes from organic than conventional systems. Conventional farming yield is significantly higher than that obtained by organic.
Lithuania The farming type has no significant effect on the content of phenolic acids.
No significant effect of farming type on dry matter and starch content, or sensory properties was found. The organic cultivation system was less productive than the conventional. Italy The largest starch content in the peel and the bulk of the tubers was observed in the conventional system (33.0% and 78.1%, respectively).

Serbia
The lowest contents of starch content in the peel and the bulk of the tubers were identified in the organic cropping system (22.7% and 65.2%, respectively).
The highest content of fructose, glucose, and saccharose in tubers was identified in the conventional system, followed by integral, and being the lowest in the organic cultivation system.

Zarzyńska
and Pietraszko (2015) The organic production system resulted in less than optimal plant growth, tuber yield and tuber size. Poland Maggio et al.
Organic farming caused a 25% marketable yield reduction with a higher percentage of large tubers under conventional farming.
Italy Highest starch values were found in organic Merit and conventional Agria.
The total protein content was higher in both Agria and organically grown tubers and it also corresponded to higher total amino acid contents. Specifically, organic farming increased only threonine, whereas it significantly reduced most of the other amino acids. Higher contents of polyphenols (sum), phenolic acids (sum), chlorogenic acid, p-coumaric acid, and cafeic acid were found in biodynamic and organic samples compared to the conventional tubers.

Poland
Organically and biodynamically produced potatoes were significantly richer in flavonoids and anthocyanins.
Organically and biodynamically cultivated potatoes (except the "Salad Blue" cultivar) were essentially richer in flavonoids and anthocyanins. Total and marketable yields were significantly reduced by the use of both organic crop protection and fertility management.
England yield gap between organic and conventional fertilization regimes was greater and more variable than that between crop protection practices. Bartova et al. (2013) Organic potatoes contained significantly less of nitrogen, nitrates and α-solanin.

Czech
Republic Protein content, patatin relative abundance in total tuber protein and patatin content in organically produced potato tubers were slightly lower than in conventional ones but the differences were not statistically significant.
Bernard et al.
Compost amendment had variable effects on tuber diseases, but consistently increased yield (by 9 to 15 %).

USA
Rapeseed rotation reduced all observed soil-borne diseases (stem canker, black scurf, common scab, and silver scurf) by 10 to 52 %.
Combining rapeseed rotation with compost amendment both reduced disease and increased yield.
Mean content of crude protein was significantly higher in tubers from organic crop management than in tubers from conventional system (10.92 and 9.76 % in dry matter, respectively).

Germany
Cultivar was the factor having the highest direct effect on crude protein as well as protein contents.
Tubers from conventional crop management showed an increased tendency to accumulate nitrates.
Moeller et al.
N availability was most important in limiting yields in organic potato crops.

Germany
Only 25% of this variation in yield could be attributed to the influence of late blight.
In organic farming, yields are mainly limited by nutrient availability in spring and early summer.
The higher the N status of a potato crop, the longer the growing period needed to achieve the attainable yield and the higher the probability that late blight stops further tuber growth and becomes the key tuber-yield-limiting factor.
Potato cultivars Aladin and Almera are suitable varieties for growers of Lazio region which are interested to switch from conventional to organic management system due to the highest marketable yield especially of medium size tubers ( 45-75 mm) and the low incidence of disease problems (common scab). Italy Attacks of wireworm percentage incidence was almost 9 times higher in organic system in comparison to conventional system leading to a reduction of marketable yield of medium tuber size.
The conventional potatoes had a lower dry matter content and a slightly softer texture than the organic potatoes. Ireland No significant difference between the organic and conventional baked potato samples for the sensory attributes of appearance, aroma, texture and taste acceptability. This review has explored the characteristics of organically grown potato tubers compared to the conventionally grown potatoes. Across several studies comparing potato farming practices, it can be derived that potato total tuber and marketable yield is lower under organic farming than under conventional farming. Weed and disease pressure is more intense under the organic farming and the lower nitrogen available for potato plant infers low nitrogen content in the organically grown potato tuber. Organic potato tubers contain higher sugar content compared to the conventionally grown tubers. Organic potato tubers show high polyphenol compounds content due to the stress occurring under the organic practices (limited nutrients and increasing disease pressure) compared to the conventional practices. Some contradictory results are reported on the impact of cropping systems on potato tuber content in minerals, vitamin C, sensory properties and the dependence of several characteristics on the genotypic material. For future studies, it is crucial to match the best agronomic production practices and plant genotypic material to maximize the fresh potato and processed products contents in bioactive compounds to match the health-promoting properties for more production sustainability. Consumers are showing increasing interest in organically grown potatoes due to its nutritional quality and health protection value. Due to the lower tuber yield under organic farming, for the profitability of the production system, organic products are more expensive and consumers might be willing to pay the price for health-promoting properties. Funding: This research received no external funding.

Institutional Review Board Statement
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Informed Consent Statement
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Data Availability Statement
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Conflicts of Interest
The authors declare no conflict of interest.