Variation of chemical composition of tubers of potato table cultivars grown under deficit and excess of water

Transcription

1 Mazurczyk W., Lis B. Plant Breeding and Acclimatization Institute (IHAR) Research Division at Jadwisin Variation of chemical composition of tubers of potato table cultivars grown under deficit and excess of water ABSTRACT Average chemical composition of mature tubers of 97 Polish potato table cultivars is presented. Each variety was cultivated for at least 3 years at the Experimental Station in Jadwisin, near Warsaw. About 25 cultivars were grown each year between 1974 and 1997 on light loamy sand with the same agricultural practices, without irrigation or chemical control of diseases. Contents of dry matter and starch were the most stable with mean variability coefficients (V) 8.4 and 8.8%, respectively. The least stable components were concentrations of total sugar (V=34.2%) and reducing sugar with V reaching about fifty percent. Wet vegetation conditions worsened tuber chemical composition (less dry matter, starch, protein and ascorbic acid) as compared with dry or intermediate ones. INTRODUCTION Chemical composition of potato tubers varies as far as each lengthwise and crosswise section of each individual tuber is concerned [Es & Hartmans, 1981]. Tubers differ from one another also with regard to chemical composition. This diversification occurs not only between tubers belonging to different cultivars, but also between tubers belonging to the same cultivar or even the same potato plant. To a considerable extent it results from their different size [Beukoma & Van der Zaag, 1990; Kolbe & Stephan-Beckman, 1997]. However, there are cultivars in the event of which interdependence between the size of tubers and mean content of dry matter and protein does not occur [Makuch et al., 1981]. Chemical composition of all tubers changes to a large extent within the vegetation period [Zgórska & Frydecka- Mazurczyk, 1982; Rogoziska, 1987; Roztropowicz, 1989; Leszczyski, 1994; Christensen & Hadsen, 1996; Kolbe & Stephan-Beckmann, 1997; Karadogan et al., 1999] and, to a considerably lower extent, during storage [Es & Hartmans, 1981; Zgórska & & Frydecka-

2 Mazurczyk, 1982; Rogoziska, 1987]. Modifications of chemical composition of tubers have positive or negative effect on both their nutritive and technological value. The objective of this research is to define the range of variability of chemical composition of mature potato tubers, with regard to both large genotype variety (97 table cultivars) and meteorological conditions of vegetation covering 23 years. On the basis of such rich experimental material, differences in chemical composition of tubers related to deficit and excess of water during vegetation period have been characterised and stability of the content of the examined components has been defined. MATERIALS AND METHODS Tubers samples for chemical determinations came from collection of potato cultivars grown on light loamy sand in Jadwisin near Warsaw. Each year a very similar manner of cultivation of the examined varieties was applied: organic fertilisation with manure (22t ha -1 ) and mineral N, P, K in the amount of 80, 80, 150 kg ha -1, respectively, and chemical protection against potato beetle. Irrigation and protection against potato blight were not applied. Analyses in fresh material were made within 2 to 3 weeks after gathering crops, and the following was determined: dry matter through two-stage drying at the temperature of 60 C and subsequently at 100 C to constant weight; starch by means of the Ewers method using automatic polarimeter type Polamat S; total sugars and reducing sugars by means of the Talburt and Smith s method with dinitrophenol; ascorbic acid by means of the Tillmans method with indophenol titration. After mineralization of dry material using sulfuric acid and hydrogen pyroxide the following was determined: total nitrogen with the use of Kjeldahl s method; protein nitrogen as a difference in the content between total nitrogen and non-protein nitrogen estimated also by means of the Kjeldhal s method after prior precipitation of protein with trichloroacetic acid; phosphorus with colorimetric method, using molybdenum-vanadic reagent; potassium with the use of photometeric method. The content of crude protein and pure protein was counted by means of multiplying appropriate values of total nitrogen and non-protein nitrogen by 6.25.

3 Evaluation of losses of tuber dry matter caused by limiting effect of water factor in particular vegetation periods was made according to the Mazurczyk s method [1996]. First, potential crop growth rate (CGR p ) was calculated for particular vegetation periods according to formula 1: CGR p = P p x t k x l k /1/ where: CGR p - potential crop growth rate, kg DM ha -1 d -1 P p - potential gross assimilation, kg CH 2 0 ha (soil) -1 d -1, van der Zaag [1984] t k - temperature coefficient, van der Zaag [1984] l k - sunlight coefficient, Mazurczyk [1996] Subsequently, water deficit (N) was defined using formula 2 [Roguski et al.,1988]: N = - P - ERU p + ERU k /2/ 10 Ea d= 1 Ea - daily evapotranspiration P - decade rainfall ERU p soil water retention at the beginning of decade ERU k - soil water retention at the end of decade (k) d - day Water deficit calculated in the above way was divided by the value of daily evapotranspiration (Ea) valid for given decade in which it occurred. In such a way, the number of days of the decade with water deficit was obtained. It was assumed that in such days the dry matter equal to potential biomass growth (CGR p ) could not be produced. The summarized amount of those losses for the vegetation period decreased by 20% (HI = 0.8) constituted dry matter of tubers ( d), which could not be accumulated by plants due to water deficit in particular vegetation periods. In calculations of losses of dry matter caused by water excess ( r), it was assumed that this excess had a limited effect on biomass production only when vegetation conditions in particular decades were exceptionally unfavourable, defined as very wet. Occurrence of such unfavourable configurations was established by means of biometeorological index B calculated according to formula 3 [Chomicz, 1977] with the assumption that only B values exceeding 5 are characteristic for very wet climate in Poland:

4 n x P x H B = /3/ T av x D 2 where: B n - P - H - T av - D - Chomicz coefficient; values above 5 mean very wet plant growth conditions number of days with precipitations above 1mm for a given decade decade rainfall mean air relative humidity at noon average air temperature for a given decade number of days in decade As in the situation of water deficit, the sum of potential crop growth rate (CGR p ) values decreased by 20% constituted the total dry matter of tubers ( r), which could not be accumulated by plants due to excess of water. The results were worked out statistically applying variance analysis. For each compound, weighted mean (X av ), a variability coefficient (V) and the content range X av -2s to X av +2s (s = standard deviation) were calculated. This range covers 95% of all results with 5% error risk. RESULTS AND DISCUSSION Mean values of particular components of mature tubers of 97 potato cultivars along with the range covering 95% of all results (n = 418) are presented in Table 1. Average chemical composition meets requirements defined for tubers for direct consumption [Zgórska & Frydecka-Mazurczyk, 1997]: average level of dry matter and starch, high content of ascorbic acid and low content of sugars. The presented chemical composition does not exclude the use of those tubers in production of some processed products, particularly French fries, mainly due to the content of sugars remaining below the admissible level, and the dry matter and starch level remaining in the lower part of scale of the required values in the food processing industry [Zgórska & Frydecka-Mazurczyk,1997]. The variable coefficient V presented in Table 1 can be recognised as the stability measure of particular components [Wgrzyn, 1989]. They are the measure of dispersion of the obtained results. The lower the V coefficient the lower dispersion of values of a particular

5 component achieved in such rich experimental material. The most stable features included the content of dry matter and starch with mean values V amounting to 8.4 and 8.8%, respectively. Therefore, they are features determined to the highest degree by genotype. It is confirmed by analysis of variance components according to which, in average, approximately sixty per cent of general variation can be imputed to cultivars, over twenty per cent to interdependence of years and cultivars, and a few per cent to years [Mazurczyk, 1988; Trtowski et al., 1989; Mazurczyk, 1994]. The least stable features include the level of sugars; their values V vary from 34 to 50%. The remaining components can be defined as components of average stability with the values V between 10 and 20%. Each year approximately 25 cultivars of table potatoes were cultivated on the identical type of soil with application of similar agricultural science techniques and with the use of seed-potatoes grade of SE. Variation of components presented in Table 1 stemmed out mainly from genetic diversification of grown cultivars and diversification of vegetation conditions. Effect of water deficit and excess on the chemical composition of tubers is presented in Table 2. From among cultivation years, from 1974 to 1997, 6 driest vegetation periods (1976, 1982, 1983, 1986, 1992, 1994), wet periods (1978, 1980, 1984, 1985, 1987, 1997) and intermediate periods (1974, 1990, 1991, 1993, 1995, 1996) were chosen. The criterion of choice included estimated amount of dry matter of tubers which could not be produced due to limiting effect of water factor during vegetation. That criterion is a simplified attempt of quantitative description of relations occurring between the plants, climate and soil (water retention) during vegetation which shape the amount of accumulated biomass. Various data characterising the dynamics of changes occurring in the soil-plant-atmosphere system were used in it. Dry years covered 6 vegetation periods of the greatest d values, wet years of the greatest r values, and intermediate years of the lowest d and r values. It was calculated that the average intensity of the effect of water deficit factor ( d = 41 dt ha -1 ) in the dry years approximated the mean value of effect of water excess ( r) in the wet years (37 dt ha -1, Table 2). In the dry years the effect of water excess factor was low; mean value of d amounted to 1 dt ha -1, while in the wet years the average effect of water deficit was estimated at 9 dt ha -1 of dry matter of tubers. Therefore, it can be concluded that the years referred to as wet corresponded to this name only in 75%. In intermediate years the water deficit factor was marked in a small degree indeed ( d = 3 dt ha -1, Table 2). However, at that time the water excess factor was intensive ( r =11dt ha -1 ). It is also confirmed by high positive value (+29 mm) of agricultural and climatic water balance (P-Ea) equal to the 50% of the value for wet

6 years (+58 mm). Analysis of variations proved that the contents of dry matter, crude protein, pure protein, ascorbic acid and Maercker s constant, that is the content of non-starch substances, were greater in dry years as compared with wet years. Statistically significant diversification of other components in particular types of years was not found. CONCLUSIONS 1. Chemical composition of potato tubers was significantly diversified through deficit or excess of water occurring during vegetation periods. 2. The contents of dry matter, crude protein, pure protein, ascorbic acid and Maercker s constant were greater in dry years as compared with wet years. 3. From among 12 features of chemical composition of potato tubers, the contents of dry matter and starch were the most stable. Their mean variability coefficients V did not exceed 10%. The content of sugars was a few times less stable (V from 34 to 50%). Values of V coefficients for the other features ranged between 10 and 20%. REFERENCES 1. Beukema H.P., Van der Zaag D.E., Introduction to potato production. PUDOC. Wageningen, 1990, Christensen D.H., Hadsen M.H., Changes in potato starch quality during growth. Potato Res., 1996, 39, Chomicz K., Materiały do poznania agroklimatu Polski (Materials to get acquainted with agricultural climate of Poland). PWN Warszawa, Es van A., Hartmans K.J., Structure and chemical composition of the potato. in: Storage of potatoes. (ed. Rastovski A.) Centre for Agricultural Publishing and Documentation. Wageningen, 1981, Karadogan T., Carci K., Balabanli C., Changing of nutrient elements of tuber during the growing period of potato. 14 th Triennal Conf. EAPR, 1999, Sorrento, Italy: Kolbe H., Stephan-Beckmann S., Development, growth and chemical composition of the potato crop. II. Tuber and whole plant. Potato Res., 1997, 40, Leszczyski W. Wpływ czynników działajcych w okresie wegetacji ziemniaka na jego jako (Effect of factors active in the vegetation period of potato on its quality). Post. Nauk Rol., 1994, 6, Makuch M., Olejniczak J., Staszewicz K., Trtowski J., Porównanie zakresu zmiennoci zawartoci białka i suchej masy w bulwach ziemniaka wybranych rodów pastewnych i

7 odmian wzorcowych (Comparison of variation range of protein and dry matter content in potato tubers of selected fodder lineages and model cultivars). Biul.Inst.Ziemn., 1981, 26, Mazurczyk W., Skład chemiczny dojrzałych bulw 43 odmian ziemniaka (Chemical composition of mature tubers of 43 potato cultivars). Biul.Inst. Ziemn., 1988, 37, Mazurczyk W., Skład chemiczny dojrzałych bulw 30 odmian ziemniaka (Chemical composition of mature tubers of 30 potato cultivars). Biul.Inst.Ziemn., 1994, 44, Mazurczyk W., Wyznaczanie potencjału produkcji biomasy oraz kwantyfikacja wybranych czynników kształtujcych plon ziemniaka (Determination of biomass production potential and quantification of selected factors determining potato crop). Fragm. Agron., 1996, 13, Rogoziska I., Wpływ nawoenia azotowego i warunków przechowywania na skład chemiczny oraz warto konsumpcyjn i uytkow bulw rónych odmian ziemniaka (Effect of nitrogen fertilisation and conditions of storage on chemical composition and consumer value and usable value of tubers of various potato cultivars). ART., 1987, Bydgoszcz. 13. Roguski W. et al., Instrukcja wyznaczania potrzeb i niedoborów wodnych rolin uprawnych i uytków zielonych. IMUZ, Falenty (Instruction of determining needs and water deficits of cultivated plants and grassland), Roztropowicz S., rodowiskowe, odmianowe i nawozowe ródła zmiennoci składu chemicznego bulw ziemniaka (Sources of variation of chemical composition of potato tubers relating to type of environment, cultivar and fertiliser). Fragm. Agron., 1989,6, Trtowski J., Boligowa E., Bombik A., Zmienno plonu i zawartoci skrobi u odmian ziemniaka rónych grup wczesnoci (Variation of crop and starch content of potato cultivars of different early varieties). Zesz. Probl. Post. Nauk Rol., 1989, 382, Wgrzyn S., Wyznaczanie wartoci cech mierzalnych w warunkach interakcji genotypowo-rodowiskowej (Determination of measurable features values in genotype and environment interaction). Zesz. Probl. Post. Nauk Rol., 1989, 382, Zaag van der D.E., Reliability and significance of simple method of estimating the potential yield of the potato crop. Potato Res., 1984, 27, Zgórska K., Frydecka-Mazurczyk A., Wpływ warunków wegetacji i temperatury przechowywania na zmiany cech jakoci 26 odmian ziemniaka (Effect of vegetation

8 conditions and storage temperature on changes of quality features of 26 potato cultivars). Biul.Inst.Ziemn., 1982, 26, Zgórska K., Frydecka-Mazurczyk A., Uytkowanie ziemniaków jadalnych (Use of table potatoes). W: Produkcja ziemniaków (Potato production), ed. Chotkowski J., Bonin, 1997, Table1. Mean values of the chemical composition in fresh matter of mature tubers of table potato cultivars, Jadwisin Component Unit Weighted mean X av 1-2s X av + 2s % Dry matter % Starch % Maercker`s constant % Crude protein % Pure protein % Pure protein in crude protein % Total sugars % Reducing sugars % Sucrose % Ascorbic acid mg/100g Potassium mg/100g Phosphorus mg/100g V 2 1 with range of variation, s- standard deviation 2 variability coefficient

9 Table 2. The influence of different weather conditions on the chemical composition of mature table potato tubers. Component Average content in years of different weather conditions Dry Wet Intermediate LSD 0.05 Dry matter Starch n.s Maercker`s constant Crude protein Pure protein Pure protein in crude protein n.s Total sugars n.s Reducing sugars n.s Sucrose n.s Ascorbic acid Potassium n.s Phosphorus n.s Climatic features P P- Ea d r P andea - mm ; mean rainfall and evapotranspiration during vegetation d and r - losses of tuber dry matter caused by water shortage (d) and excess (r) during vegetation, dt ha -1 n.s. - not significant differences