Performance of modern and old , European and national potato cultivars in different environments

Little information on the comparative yield of the main potato cultivars (Solanum tuberosum subsp. tuberosum) used in Brazil is available. The objective of this study was to evaluate the performance of modern and old, European and Brazilian potato cultivars in different environments. Two experiments were carried in the field in 2013, in Brazil: in Guarapuava, in the state of Paraná, from January to April; and in Brasília, the Federal District, from August to November. Treatments consisted of six cultivars (origin, year of release): Bintje (European, 1910), Monalisa (European, 1982) and Agata (European, 1990); Baronesa (Brazilian, 1955), Catucha (Brazilian, 1995) and BRS Clara (Brazilian, 2010), arranged in complete blocks at random, with four replications, in both areas. Growth cycle, total and commercial yield (number of tubers and mass), tuber average weight and tuber dry matter content were evaluated. We observed significant differences in yield among cultivars, both in Guarapuava and in Brasilia. We also observed that increases in yield in Brazil are possible, the modern cultivars having higher yield potential than old cultivars. No significant differences in yield were detected between European and Brazilian cultivars, in none of the growing zones. We suggest that the use of imported cultivars by Brazilian potato growers is related to factors not associated to yield.

place due mainly to traits such as resistance to pests and diseases and yield potential, which are enhanced in new cultivars.Gebhardt (2013) refers to the development of improved potato cultivars as one of the major research goals to increase agricultural productivity and to ensure food safety.Nevertheless, Carew et al. (2009) report that in Canada potato yield has been increasing more due to the combination of good fertilization and regional effects than to the use of improved cultivars.Evans (1998), comparing the yield potential of American potato cultivars production in developing countries exceeds 150 million tons out of a total world production of 376 million tons (FAO, 2015).In Brazil, potato has expressive socioeconomic significance, with the national production reaching 3.5 million tons in 2013 (IBGE, 2015).
As years went by, there was a natural cycle of cultivar substitution, with modern cultivars replacing ancient ones.Although cultivar substitution is not a quick movement in potato worldwide, with some very old cultivars still having solid representativeness in many countries, it indeed takes P otato (Solanum tuberosum) plays an important role as a food source for human populations in different regions.The crop has gone through major changes worldwide.Until the beginning of 1990, most of consumption and production took place mainly in Europe and North America.From 2004 onwards, the area dedicated to growing potatoes has been larger in developing countries (Walker et al., 2011).Even though, production remains higher in developed countries.According to the Food and Agriculture Organization (FAO), potato annual released from 1930 to 1990 observed that modern cultivars did not outyield old cultivars mainly because, in the USA, potato breeding programs focused other traits, like tuber commercial quality.In studies carried out by Love et al. (1998), 44 North American potato cultivars for industry, released from 1876 to 1998, were compared to evaluate the progress in breeding.This study states that potato breeders have been obtaining significant progress with new cultivars, but mainly in quality of tubers for industrial purpose.Gadum et al. (2003) reported that breeding programs have been focused not only on yield potential, but also on tuber quality and disease resistance.On the other hand, studies carried out by Bradshaw (2009) reported that increases in yield in new potato cultivars are quite possible, since potato yield potential is high.
In Brazil, the dependence on imported cultivars to meet the market demands for tubers, either for fresh consumption or processing, is still high.In the city of Guarapuava, where potato production is very traditional, 2025 ha are grown yearly with the crop (IBGE, 2015).Japanese immigrants started the potato production business in the 1950s, using predominantly the Dutch cultivar Bintje, which remained as the main potato cultivar in the region for many years.It was only in the beginning of the 1990s that cultivar Bintje was replaced by another Dutch cultivar, Monalisa, which, in its turn, lasted as the main cultivar until late 1990s.From then on, cultivar Monalisa was replaced by cultivar Agata, also Dutch.Cultivar Agata is still the main cultivar used in Guarapuava, as well as in the remaining of the main potato production zones in Brazil.
The great majority of foreign cultivars used in Brazil come from breeding programs set in countries with temperate climate, places with different weather, soil, pests, and diseases.As a rule, these cultivars are not expected to suit Brazilian growing conditions.For Fontes et al. (1995), the use of welladapted potato cultivars, with desirable agronomic traits, such as upright growth habit, high stem number and density, high total and commercial potential yield and not susceptible to tuber physiological disorders, is fundamental to the success of a crop season.
In Southern Minas Gerais, a study was carried out in order to evaluate the market demands in relation to tuber appearance, quality, and yield of national and foreign potato cultivars (Carmo et al., 2009).In this study, authors observed that cultivars showed different agronomic performances depending on the growing environment.National cultivars showed higher yield and better adaptation to the local growing conditions than imported cultivars.According to Peixoto et al. (2002), the use of cultivars which are better adapted to the local environmental conditions can result in increases of regional production.Same authors state that the behavior of a cultivar in a specific environment is a result of genotypic and environmental effect and of the interaction of both, and add that trials to evaluate such interaction should be done prior to the use of national and foreign cultivars in a specific region, since the most traits are affected by environmental conditions.
In Brazil, studies on yield potential of the main potato cultivars used in the past and in the present, as well as studies comparing the yield potential of cultivars developed by national and foreign breeding programs, are scarce.Thus, this study aims to compare yield and yield components of the main modern and old, national and European potato cultivars used in Brazil, in two different environments.
Planting was carried out when we reached adequate weather conditions (temperature, rain, luminosity, and photoperiod) for the crop in each region.In both areas, we began to prepare the soil one month before planting, subsoiling once and harrowing twice.During planting, a light harrowing followed by a grooving operation was carried out.Treatments consisted of six cultivars (origin and year of commercial release), namely Agata (European, 1990), Monalisa (European, 1982), Bintje (European, 1910), BRS Clara (Brazilian, 2010), Catucha (Brazilian, 1995) and Baronesa (Brazilian, 1955), and we used seed tubers of the same size (class type III, 30-40 mm).Seed tubers were kept in a chamber at 4°C to standardize sprouting about 15 days before planting.Seed tubers were planted manually, using 0.80 m spacing between lines in both areas and 0.25 m spacing between plants in Guarapuava and 0.30 m in Brasilia.In the Brasilia experiment, we used seed tubers grown in Guarapuava.
We limited our range to six cultivars due to the historical concentration of the Brazilian market in few materials.The foreign cultivars used here are the leading ones in Guarapuava region for the last 65 years and represent about 80% of what has been planted by farmers during this period: cultivar Bintje from 1950 onwards, cultivar Monalisa, mainly in the 1990s, and cultivar Agata, from the beginning of the last decade to today.The Brazilian cultivars were selected following the same criteria of market relevance and time of release.
Each experimental plot consisted of 6 lines of 18 plants, arranged in complete blocks at random, with four replications, in both areas.Fertilizers were supplied in pre-planting, homogeneously distributed within the furrow.In Guarapuava, as liming was not necessary, fertilization consisted of 4 t/ha NPK, 04-14-08, supplying 160 kg/ ha of N, 560 kg/ha of P 2 O 5 and 320 kg/ ha of K 2 O, a practice used by producers in the region and, as checked by Queiroz et al. (2013), very close to the dose for maximum technical efficiency for cultivar Agata in the region.In Brasilia, according to the soil analysis and for yield expectations above 30 t/ha, liming was carried out using 2.5 t/ha of dolomitic limestone and fertilizers were applied to supply 40 kg/ha of N (urea), 600 kg/ha of P 2 O 5 (super triple phosphate), 90 kg/ha of K 2 O (potassium chloride), 2 kg/ha of B (borax) and 4 kg/ ha of Zn (zinc sulfate).Cultural practices (control of weeds, pests, and diseases) followed the standards adopted in each region.The experiment carried out in Brasilia received irrigation according to the traditional management used at Embrapa Hortaliças for potatoes: biweekly shifts, with 26-mm water depth.Ridges were hilled up in both areas 15 days after emergence.
To assess plant emergence, we counted the number of plants/plot in 2-3-day intervals until reaching 75% emergence.Senescence was registered when leaves in at least 75% of the plants in the plot became yellowish.To assess yield, we took 12 plants per plot from the four central lines, after physiological maturation.Tubers were harvested and split into two categories: non-commercial (tuber transversal diameter below 45 mm) and commercial (tuber transversal diameter above 45 mm), counting and weighting tubers in each category.Commercial tubers were divided into three classes: up to 100 g, 100 to 200 g and heavier than 200 g.The number of tubers, as well as fresh (FM) and dry mass (DM) were recorded.
Later, DM percentage was calculated.
Data were submitted to analysis of variance and to the Tukey test at 5% probability, for differentiation of means.Comparison between European and Brazilian cultivars was evaluated by t-test (P<0.05).For growth period, tuber DM percentage, number of total and commercial tubers, total and commercial yield, we used the relative average percentage in the regression analysis, based on the year of release of each cultivar as the independent variable, using SPSS statistical package (v.20.0).

RESULTS AND DISCUSSION
In Guarapuava, cultivar Agata was the earliest, with a 99-and 77-day cycles counting from planting and from emergence, respectively (Table 1).In Brasilia, cultivars Agata (91-; 76-day cycles) and BRS Clara (94-; 79day cycles) were the earliest.Cultivar Catucha, both in Guarapuava and Brasilia, showed the longest cycle from planting and from emergence to senescence, being about three weeks longer than the earliest cultivars.The other cultivars showed intermediate cycle.In general, cultivars showed a cycle longer cycles in Guarapuava than in Brasilia, probably due to the lowest temperatures in Guarapuava.From January to April 2013, monthly average temperatures ranged from 17.3 to 20.8°C in Guarapuava, while in Brasilia, average temperatures ranged from 24.6 to 29.2°C between August and November, in the same year.In studies carried out by Silva et al. (2013) 1).In Brasilia, there were no significant differences among cultivars and total yield ranged from the equivalent of 39 t/ha (3.9 kg/m 2 , cultivar Agata) to 23 t/ha (2.3 kg/ m 2 , cultivar Monalisa).Turning to commercial yield (tubers above 45 mm in diameter), in Guarapuava, cultivars Monalisa and BRS Clara showed the highest figures, corresponding to about 48 t/ha, differing significantly only from cultivar Bintje, whose yield in tubers/ m 2 corresponded to 26 t/ha (Table 1).In Brasilia, cultivars Agata and Baronesa had significantly the highest commercial yield, corresponding to about 32 t/ ha, whereas cultivar Bintje had the lowest yield (corresponding to 18 t/ha), significantly below all other cultivars.
In studies carried out by Pereira et al. (2013), in the Southern Brazilian Region (Canoinhas, state of Santa Catarina, and Pelotas, state of Rio Grande do Sul), cultivar BRS Clara, in five experiments in a period of three years, showed averages to total and commercial yield of 18.9 and 11.0 t/ha, respectively.Cultivar Agata, in the same set of experiments, averaged 13.3 and 7.4 t/ha as total and commercial yield respectively.Data similar to ours for total and commercial yield and number of tubers were obtained by Queiroz et al. (2013) with cultivar Agata in Guarapuava, where authors observed 45 and 39 t/ha as total and commercial yield respectively, with 36 commercial tubers/m 2 .In our experiments, cultivar Monalisa yielded the equivalent to 21 t/ha of commercial tubers in Brasília, far below the observed in Guarapuava (equivalent to 49 t/ha).According to Filgueira (2008), cultivar Monalisa is sensitive to high temperatures, which may be the reason for the low yield observed in Brasilia, where average temperatures were high during the growth cycle.
The t-test did not detect significant differences between European and Brazilian cultivars, nor in Guarapuava (p= 0.651), neither in Brasília (p= 0.858).In Guarapuava, European cultivars (Agata, Monalisa, and Bintje) showed average total yield corresponding to 43.3 t/ha, while the average total yield of Brazilian cultivars (BRS Clara, Catucha, and Baronesa) pointed to 45.6 t/ha.In Brasilia, European and Brazilian cultivars showed average total Means followed by same letters in the columns, for each area, do not significantly differ from each other, Tukey test (p<0.05).
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yields estimated in 29.0 and 31.7 t/ha, respectively.Yields in Guarapuava were higher than in Brasilia, probably due to environmental effects, mainly climatic conditions, as observed in the studies carried out by Carew et al. (2009).The yield similarity we observed between Brazilian and European cultivars in the same growth area differs from the data obtained by Carmo et al. (2009) who, studying 22 national and imported potato cultivars in the Southern region of Minas Gerais, reported higher yields with Brazilian cultivars.These results suggest that the wide use of imported potato cultivars by Brazilian producers should not be attributed to differences in yield potential between the Brazilian and foreign cultivars.We postulate that the Brazilian potato cultivars are not more widely spread due to other issues, such as low seed availability, producers' lack of knowledge about cultivars and their crop management or even due to lower acceptance of national tubers in the market.Although the Brazilian cultivars did not outyield the European material in our work, we believe that a more general use of cultivars bred and selected under Brazilian weather and soil conditions, more resistant to pests and diseases, may result in the reduction in the use of agrochemicals and fertilizes in potato production in Brazil.
Concerning tuber MS content, in    Bintje had the lowest.However, and as expected, cultivar Bintje outyielded the others in small tubers (<100 g) (Figure 1A).In Brasilia, cultivars Catucha and Baronesa had the highest yield of large tubers (>200 g), cultivars Agata, BRS Clara and again Baronesa outyielded the others concerning medium tubers (>100g) and cultivar Bintje, as it happened in Guarapuava, had the highest yield of small tubers (<100 g) (Figure 1B).
The number of commercial tubers, in Guarapuava, had a trend similar to tuber production: cultivars Monalisa and Bintje produced the highest number of large and small tubers, respectively (Figure 1C).In Brasilia, cultivar Bintje produced few large and medium tubers and cultivars Monalisa and Catucha, on their turn, produced few small tubers (Figure 1D).
When cultivars were clustered by year of release, in general, no relation was noticed between cultivar "age" and growth cycle (Figure 2A), tuber MS content (Figure 2B), total number of tubers (Figure 2C), number of commercial tubers (Figure 2D), and total yield (Figure 2E).
The lack of relationship between growth cycle and year of cultivar release might have imposed by the crop management system used in Brazil.The difficulties of growing potatoes in tropical conditions led farmers to prefer, since old days, cultivars with rather short cycles, especially if it is compared to the potato cycle in cooler countries in Europe or North America.Thus, a decrease in the potato growth period in Brazil would have been a surprise.
Considering the results obtained by Love et al. (1998), which showed that in the USA from 1876 to 1998 an increase of tuber dry mass content was observed, the absence of a relation between the year of cultivar release and tuber DM content in our study was unexpected.The discrepancy might have to do with the fact that Love et al. (1998) studied industrial cultivars, while ours are mainly for table consumption.In addition, although consumers became more demanding towards quality along the years, tuber DM content is not yet a trait consumers pay that much of attention to in Brazil.In addition, the consumption of processed potato in Brazil is still low in comparison to other countries and imports, mainly pre-fried French fries, play an important role in the supplying chain.Nevertheless, some studies have been reporting increases in the per capita consumption of industrialized processed potato, as average income in the country also increases.In fact, this trend opened room for the release of national cultivars bred for industrial purposes, like cultivars BRS Ana and BRSIPR Bel (Pereira et al., 2010(Pereira et al., , 2015)).
Despite the lack of significant relationship between year of cultivar release and total yield (Figure 2E), it was noticed that the modern cultivars used in Brazil evaluated in this study increased their commercial yield potential until the 80s (Figure 2F).From this year on, yield stabilized, corroborating the data observed by Bradshaw (2009), who relates that increases in the yield of new potato cultivars in Europe are not expected, since the crop harvest index is already high.Our data are also in agreement with Gadum et al. (2003), which reported that breeding programs have been focused not only on yield potential of new cultivars, but also on tuber quality and resistance to the main diseases.It is not known if the higher commercial yield of modern cultivars we observed is due to greater photoassimilate production or to greater photoassimilate partitioning directed to tuber formation.
When compared to the yield potential of the oldest cultivar used in this study (cultivar Bintje), we observed about 30% of commercial yield increase in the modern cultivars.Taking this into consideration, we may say that cultivar Catucha has low yield potential in relation to its year of release.On the other hand, cultivar Agata shows high yield potential, explaining why Brazilian producers increasingly adopt it.There were no significant differences in yield between European and Brazilian cultivars when comparison was carried out grouping cultivars by origin.On the other hand, when the two growth areas were compared, Guarapuava showed the highest yield.Considering it all, we may say that potato yield in Brazil has increased in the latest years by the combination of the use of good crop management practices and cultivars with high yield potential.

Figure 1 .
Figure 1.Fresh mass (kg/m 2 , A and B) and number (m 2 , C and D) of commercial tubers per class of size of modern and old potato cultivars.Guarapuava (figures A and C), and Brasilia (figures B and D).Guarapuava/Brasilia, Unicentro/Embrapa Hortaliças, 2013.Means followed by same letters, for each class of tuber size, do not differ significantly from each other, Tukey test (p<0.05).

Table 1 .
Growth cycle from planting and emergence to senescence of plants, number and fresh mass (FM) of total and commercial tubers, percentage of dry mass (DM) and average weight of commercial tubers (TW) of modern and old cultivars of potato.Guarapuava/Brasilia, Unicentro/Embrapa Hortaliças, 2013.