Effect of Photoselective Screens in the Development and Productivity of Red and Yellow Sweet Pepper

Effect of Photoselective Screens in the Development and Productivity of Red and Yellow Sweet Pepper J.Q. Santana, M.A. Balbino, T.R. Tavares, R.S. Bezerra, J.G. Farias and R.C. Ferreira Agronomy and Food Engineering College Federal University of Goiás Goiânia Brazil Keywords: Capsicum annuum var. annuum, protected cultivation, crop ecology, photosynthetically active radiation Abstract Photoselective screens promote better solar radiation quality and attenuate the extreme climatic conditions allowing greater efficiency in the vegetables production in protected crops. In Brazil the sweet pepper is traditionally cultivated in field conditions, but recently there have been investments in screenhouses and greenhouses. This research evaluated the effect of photoselective blue and red screens on the vegetative development and productivity of yellow and red sweet peppers. The experiment was conducted from 19 June to 29 October 2011, in Goiânia, Goiás, Brazil (16 35 47 S; 49 16 47 W, 730 m). The Eppo (yellow) and Margarita (red) hybrids from Syngenta Seeds were cultivated in three treatments: two shading screenhouses with field plots as control. Stem diameter and length, number of leaves, leaf area, total plant mass and mass of leaves were measured. At 40 days the total number, weight, length, diameter and number of fruits lost by sunscald or rotting were measured. The blue and red screens have promoted greater stem growth and smaller number of leaves and fruits. There was no statistical difference for leaf area, showing there is compensation between number and leaf area. The total fruit production per plant occurred in decreasing order from field conditions, to red screen followed of blue. However, the losses by sunscald and rotting was greater than 35% in field conditions, while in the screenhouses the losses were less than 5%. In this way, the production of commercial fruits per plant was higher under red screenhouse than under the blue screenhouse and in the field. The photoselective red screen promoted greater plant growth and a slight increase (4%) in the commercial fruits yield for Brazilian Midwest climatic conditions. INTRODUCTION In the north, south and in the southeast Brazilian regions, where the climate is temperate and semi-tempered, the cultivation in protected environment aimed to minimize the effects of winter ensuring that way, continuous production of food. In tropical regions as the midwest of Brazil the average annual temperature is above 20 C, with only two defined seasons (dry and wet). Thus, the production of vegetables is predominantly in open conditions, with high productivity, especially in the dry season. However, in the last 10 years the use of screened and greenhouses to produce vegetables and fruits of high commercial value has increased in order to gain in productivity and quality, especially in the rainy season. The market has launched several models of screens to replace the black shading whose main objective is to protect the plants from direct solar radiation. These materials of low density polyethylene (LDPE) are of various colors (blue, red, yellow, gray) with specific functions. The red color screens transfer more of the solar radiation wave spectrum in the red and far red and diffuse solar radiation passing through the screen, being efficient in plant development (Li, 2006). The blue screens of the spectrum providing solar radiation at a wavelength of 440-490 nm, intensify the phototropism and photosynthesis (Rodrigues, 2002). Several studies (Shahak et al., 2006; Rajapakse and Shahak, 2007; Shahak et al., Proc. 7 th IS on Light in Horticultural Systems Eds.: S. Hemming and E. Heuvelink Acta Hort. 956, ISHS 2012 493

2008) demonstrated the use of photoselective screens causes an increase in productivity and quality of tomato, pear, apple, strawberry, grape and green pepper. However, there are few papers that focus on the tropical regions as midwest Brazil. The aim of this study was to evaluate the development and productivity of two hybrid peppers, red and yellow, under red and blue photoselective screens, at the bioclimatic conditions of the tropical Brazilian region. MATERIALS AND METHODS The experiment was conducted from 19 June 2011 to 31 October 2011 in Goiânia, Goiás, Brazil (16 35 47 S; 49 16 47 W, and 730 m). The climate is classified as Aw for the Köppen-Geiger climatic classification (Kottec et al., 2006). It is hot and semi-humid with well-defined dry season, from May to September, with average annual temperature of 23.2 C, with average maximum and minimum of 29.8 and 17.9 C, respectively. The average annual rainfall is 1,575.9 mm and the average total annual sunshine is 2,588.1 h. Eppo (yellow) and Margarita (red) hybrids were grown, from Syngenta Seeds. Two screenhouses were used, each of 16 12 2.2 m in height (installed in the SE-NW direction). Both red and blue photoselective screens (Polysack, Israel) were characterized with 40% shade rating. As control field conditions (opened area) were used demarked with the same dimensions of the screenhouses. For the three treatments six beds were prepared 1.0 m wide, 14.0 m long and 0.3 m high, with 1.0 m spacing between them. Transplant in double rows was carried out, with plant spacing of 50 50 cm in the plot (approximately 26,666 plants/ha). Altogether 140 plants were transplanted for each cultivar per treatments, providing six independent populations. Polyethylene mulching film with double-sided and drip irrigation was used. The fertilizations were carried out in accordance with the recommendations for this crop. The plants were tutored and driving was done in vertical wires with horizontal ribbon. Meteorological parameters, such as, the solar radiation (SR), photosynthetically active radiation (PAR), temperature and air relative humidity were obtained from continuous records by sensors coupled to dataloggers (Spectrum, model Series 2000). The measurements were taken every ten seconds and their average values were recorded every 15 minutes. The SR and PAR were measured by pyranometers and quantum sensors, respectively. All sensors were installed in the center of each screenhouse and in open field at a height of 1.5 m tall. Average air temperature, average air humidity, and accumulated degrees-day, rate of real shading, SR and PAR accumulated averages were determined. Moreover, in order to verify the PAR use efficiency the ratio of PAR accumulated for the fruits per plant was calculated. The degree-days were calculated using basal body temperature of 10 C (Goto and Tivelli, 1998). ANOVA was performed as a completely randomized design (three environment as treatment and day as repetition) and the averages were compared by Scott-Knott test at 5% significance level. At 120 days after transplanting, and 24 days after the beginning of the productive period the diameter and stem length, leaf number, leaf area, total plant mass and mass of leaves for a sample of 32 plants of each population were measured. From the 96 th to 135 th days after transplanting the number of fruits per plant and total yield per plant in another sample of 32 plants were determined. It was adopted as the fruit harvest point that over 50% of red or yellow. In the same period were determined the production of commercial fruits per plant and the percentage of fruits lost by blight in another 32 plants. For such classification is hoped that the fruits reach the commercial standard (more than 90% of the fruit in red or yellow). In addition for 100 fruits of each population were determined the mass, length and diameter. Statistical analysis was performed by comparing independent populations and to compare the means using the Student t test at 5% significance level. RESULTS AND DISCUSSION The red screen promoted higher meteorological data (Table 1) than blue screen. 494

The red screen promoted less shading (48.23 and 59.27% for SR and PAR, respectively) than the blue screen (38.58 and 52.68% for SR and PAR, respectively). This difference between the nominal shading (40%) and the measured one may be due either to interaction between the colors screens or to the meteorological factors (Stamps, 2009). The 10% difference in shading between the screens, is certainly the main factor that explains the lower values of SR, average temperature and degree days, and relative humidity of blue screen over the red one. The PAR, in turn, over the rate of shading may have been influenced by the color of the screen. Experiments conducted in southern Brazil (Costa et al., 2011), have shown that the PAR level under the blue screen on the cloudy days was lower than the values measured under red and blue screen measured with the same nominal shading between 8:00 am and 5:00 pm. These results also agree with another experiment (Leite et al., 2008) carried out in the Brazilian southeastern region, monitoring the PAR between 9:00 am and 5:00 pm in the cultivation of several Phalaenopsis and hybrids. About the effect of treatments on the vegetative plant growth, there was no significant difference between the hybrid pepper for stem diameter, stem length, stem mass, leaf mass, leaf area and chlorophyll total plant content (Table 2). The hybrid Eppo had lower stem mass in blue screen and the Margarita hybrid showed no difference between the treatments. There was difference between the treatments for stem length, leaf mass and leaf number. Plants under the screens showed greater stem length, fewer leaves and less total leaf mass. Thus, there is the typical behavior of plants in low light saturation; the plants were taller, with fewer leaves, but leaves with greater area. Rajapakse and Shahak (2007) suggested 30% or less shading rate instead of 40% because of the limitation caused by excessive shading on the vegetable development. For the production characteristics (Table 3), there was no difference between hybrids for pepper fruit number per plant, fruit weight and total yield per plant. About the treatments, the number of fruits per plant and total production occurred in decreasing order from field conditions to red and blue screens, respectively; in turn, the fruit mass average was higher in blue screen surpassing the red screen and field condition that did not differ. Comparing colored screens such as, red, blue, reflective (aluminized) and absence of shading in the greenhouse, Costa et al. (2011) obtained yield per strawberry plant, in decreasing order from the treatment without shadowing to red, blue, and reflective screens, respectively. The highest yields occurred in the field conditions and under red screen over blue one can be explained by greater exposure to red and far red radiation during growth and leaf development. According to Kasperbauer and Hamilton (1984) the relationship between red and far red solar radiation influences the development of chloroplasts to ensure the most efficient plant survival, which possibly influenced the photosynthetic capacity, promoting a higher productivity. Atkinson et al. (2006) explained the lower productivity obtained under blue screen due to the redirection of photoassimilates for leaf area production in order to increase the solar radiation gathering, leaving less energy for the formation of fruit. In turn, the ratio between the PAR and the cumulative fruit total production per plant (Fig. 2) indirectly informs the PAR conversion efficiency in fruit mass. There was no difference between the screens, which were more efficient than field conditions. This result supports the hypothesis that production of peppers were inherent by the shading and not by the changes in the spectrum of solar radiation promoted by the colored screens. For fruit diameter and its length (Table 3) there was no difference between hybrids. But, there is interaction between screens and hybrids. The hybrid Margarita promoted diameter in descending order from blue screen (which it was also greater than Eppo ), followed by field conditions and red screen (in both they were lower than Eppo ). The hybrid Eppo had a greater diameter in the red screen. But, in the other treatments did not differ. For fruit length, the hybrid Margarita had higher averages than Eppo under blue screen and field conditions. But it did not differ in the red screen. Thus, 495

there is positive interaction between blue screen and red sweet pepper, which Margarita reached greater length and diameter in blue screen. Likewise, there was positive interaction between red screen and yellow sweet pepper. Eppo had a greater diameter in red screen. On the percentage of fruit loss (Table 3), Eppo hybrid showed higher losses than Margarita in field conditions. This demonstrates the Eppo blight sensitivity under the sun. When comparing the treatments for the two hybrids, the screens did not differ from each other and the greatest losses were observed in the field conditions. In literature several studies (Rajapakse and Shahak, 2007; Stamps, 2009) demonstrated improvement in fruit quality and an increase in commercial fruit production due to the use of colored shading screens. In addition to protection against direct solar radiation avoiding damage to the fruit epidermis, these screens promote better solar radiation distribution within the plant canopy, improving the size, ripeness, color and taste of the fruits. On the production of commercial fruits per plant (Table 3), hybrids differed only in field conditions, where Margarita was more productive than Eppo, considering the further loss of Eppo. Regarding the treatment, it was found for Margarita that the red screens did not differ to field conditions, but both outperformed the blue screen. For the Eppo hybrid, the red screen promoted greater production (increase of 4%) than field conditions and blue screens, which did not differ from each other. Fallik et al. (2009) comparing red and black screen on the sweet pepper production, found an increased production of commercial fruits in red screens. However, if the economic feasibility would be calculated of investing in a screened structure to achieve a real increase in production of only 4% (Table 3), certainly it does not recommend the use of screens in the Brazil midwest weather conditions. Maybe using 30% shading would be able to achieve higher productivity (Rajapakse and Shahak, 2007). In an experiment carried out in Serbia with sweet pepper 40 and 50% shading were compared (Ilić et al., 2011). The authors also concluded that lower rates of shading promote increased production, regardless of the screen colors. The complexity and variability of natural radiation on one side, and the multiple reactions of plant response on the other one, make it difficult to predict how a given manipulation of natural solar radiation will affect vegetative responses (Stamps, 2009). Thus, this study confirms the need for further studies regarding the use of photoselective screens in tropical regions as the midwest of Brazil, especially regarding the most appropriate rate of shading and color interaction between the screens and the different cultures and cultivars. CONCLUSIONS 1. The use of 40% shading screens or more shading rate in the bioclimatic conditions of Goiânia, Goiás, Brazil leads the etiolation plants, greater length of stem and fewer leaves, when compared to field conditions. 2. There is no difference between hybrids Margarita and Eppo for most features. The hybrids differ only in fruit shape, as expected, and on the Eppo susceptibility to the blight, causing greater loss percentage of fruits. 3. The photoselective screens, especially the blue one, promote reduction on the number of fruits and total yield per plant. In contrast, they promote more fruit mass. 4. The use of screens reduces losses by sun blight in sweet peppers production, especially for the Eppo hybrid. 5. The blue screen had the lowest commercial fruits production per plant. 6. The red screen promotes slight increase in the commercial fruits yield per plant, compared to the field conditions, mainly for the Eppo hybrid, which promoted an increase of 4%. ACKNOWLEDGEMENTS The authors are grateful for the Coordination of Improvement of Higher Education 496

Personnel (CAPES), for the scholarship granted to the first author. Literature Cited Atkinson, C.J., Dodds, P.A.A., Ford, Y.Y., Miére, J.L.E., Taylor, J.M., Blake, P.S. and Paul, N. 2006. Effects of cultivar, fruit number and reflected photosynthetically active radiation on Fragaria ananassa productivity and fruit ellagic acid and ascorbic acid concentrations. Annals of Botany, Londres 97(3):429-441. Costa, R.C., Calvete, E.O., Reginatto, F.H., Cecchetti, D., Loss, J.T., Rambo, A. and Tessaro, F. 2011. Telas de sombreamento na produção de morangueiro em ambiente protegido. Horticultura Brasileira 29:98-102. Costa, R.C. 2009. Teores de clorofila, produção e qualidade de frutos de morangueiro sob telas de sombreamento em ambiente protegido.. Dissertação de Mestrado. Universidade de Passo Fundo. Disponível em http://www.upf.br/ppgagro/download/ rosianicastoldi.pdf. Acesso em Janeiro de 2012. Fallik, E., Alkalai-Tuvia, S., Parselan, Y., Aharon, Z., Elmann, A., Offir, Y., Matan, E., Yehezkel, H., Ratner, K., Zur, N. and Shahak, Y. 2009. Can colored shade nets maintain sweet pepper quality during storage and marketing? Acta Hort. 830:37-44. Goto, R. and Tivelli, S.W (org.). 1998. Produção de hortaliças em ambiente protegido: condições subtropicais. São Paulo: UNESP. 319p. Ilić, Z., Milenković, L., Đurovka, M. and Kapoulas, N. 2011. The effect of color shade nets on the greenhouse climate and pepper yield. 46 th Croatian and 6 th International Symposium on Agriculture. Opatija. Croatia, p.529-532. Leite, C.A., Ito, R.M., Lee, G.T.S., Ganelevin, R. and Fagnani, M.A. 2008. Light spectrum management using colored nets to control the growth and blooming of Phalaenopsis. Acta Hort. 770:177-184. Li, J.C. 2006. Uso de mallas en invernaderos. Horticultura Internacional n. extra: 8691. Kasperbauer, M.J. and Hamilton, J.L. 1984. Chloroplast structure and starch grain accumulation in leaves that received different red and far-red levels during development. Plant Physiology 74:967-970. Kottek, M., Grieser, J., Beck, C., Rudolf, B. and Rubel, F. 2006. World map of the Köppen-Geiger climate classification updated. Meteorologische Zeitschrift 15(3):259-263(5). Rodrigues, L.R.F. 2002. Técnicas de cultivo hidropônico e de controle ambiental no manejo de pragas, doenças e nutrição vegetal em ambiente protegido. Jaboticabal: Funep. Rajapakse, N.C. and Shahak, Y. 2007. Light quality manipulation by horticulture industry. p.290-312. In: G. Whitelam and K. Halliday (eds.), Light and Plant Development, Blackwell Publishing, UK. Shahak, Y., Yehezkel, H. and Matan, E. 2006. Colored shade nets improve production in bell peppers. Gan Sade Vameshek April, p.37-40 (in Hebrew). Shahak, Y., Ratner, K., Giller, Y.E., Zur, N., Or, E., Gussakovsky, E.E., Stern, R., Sarig, P., Raban, E., Harcavi, E., Doron, I. and Greenblat-Avron, Y. 2008. Improving solar energy utilization, productivity and fruit quality in orchards and vineyards by photoselective netting. Acta Hort. 772:65-72. Stamps, R.H. 2009. Use of colored shade netting in horticulture. J. HortScience 44(2):239-241. 497

498 Tables Table 1. Averages weather data for each treatment during the experimental period (19 June to 10 October 2011). Goiânia, Goiás, Brazil. Treatments RH T SR PAR Accumulated SR Accumulated PAR Degree-days Real Shading (%) (%) ( C) (MJ m -2 ) (MJ m -2 ) (MJ m -2 ) (MJ m -2 ) ( C day) SR PAR Red screen 65.12 a 21.43 b 13.47 b 4.28 b 1819.26 578.17 1543.31 38.58 48.23 Blue screen 66.62 a 20.95 c 11.35 c 3.65 c 1533.56 493.96 1478.47 52.68 59.27 Field condition 62.90 b 22.92 a 21.94 a 9.05 a 2962.19 1221.89 1745.19 - - CV (%) 15.38 8.48 19.48 19.53 - - - - - Legend: RH relative humidity; T temperature; SR global solar radiation; PAR photosynthetically active radiation. Averages with the same letter within the column do not differ by Scott-Knott test at 5%. Table 2. Average vegetative characteristics of Margarita and Eppo sweet pepper hybrid grown in Goiânia, Goiás, Brazil. Treatments Stem diameter (mm) Stem lenght (cm) Stem mass (g) Leaf mass (g) Leaf number (u) Foliar area (m 2 ) Chlorophyll (Spad Index) RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP Red screen 16.54 aa 17.92 aa 78.11 aa 83.50 aa 417.89 aa 483.50 aa 266.00 ab 297.25 ab 330 ab 323 ab 1.13 aa 1.15 aa 59.60 aa 62.67 aa Blue screen 16.90 aa 17.40 aa 80.33 aa 77.67 aa 398.00 aa 355.33 ab 242.67 ab 223.00 ab 319 ab 273 ab 1.16 aa 0.88 aa 58.33 aa 60.47 aa Field condition 19.47 aa 19.67 aa 64.33 ab 60.00 ab 469.67 aa 471.00 aa 333.67 aa 359.67 aa 447 aa 411 aa 1.04 aa 0.94 aa 57.13 aa 60.33 aa CV (%) 6.99 8.13 8.62 16.12 12.20 14.30 13.34 18.92 16.00 17.24 10.37 16.23 6.84 6.77 Legend: RSP red sweet pepper ( Margarita hybrid); ASP yellow sweet pepper ( Eppo hybrid). Averages with the same minuscule letter within the line and capital letter within the column do not differ by Scott-Knott test at 5%. Chlorophyll measured with SPAD-502 (MINOLTA). 498

Table 3. Average productive characteristics of Margarita and Eppo sweet pepper hybrid grown in Goiânia, Goiás, Brazil. Treatments Fruits/plant (unit) Fruit mass (g) Fruit diameter (mm) Fruit lenght (cm) Total fruit mass/plant (kg) Discarded fruit (%) Commercial fruit mass/plant (g) RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP RSP YSP Red screen 9.59aB 9.06aB 194.8aB 246.3aA 64.8bC 75.82aA 13.25aB 13.13aA 1.86aB 1.79aB 5aB 6aB 1.77aA 1.74aA Blue screen 6.88aC 7.06aC 245.26aA 232.86aA 76.03aA 71.74bB 15.46aA 13.41bA 1.65aC 1.58aC 4aB 5aB 1.62aB 1.56aB Field 12.25aA 12.71aA 191.74aB 202.83aB 68.42bB 71.79aB 13.75aB 12.98bA 2.32aA 2.36aA 20bA 35aA 1.88aA 1.68bB condition CV (%) 28.06 28.38 22.25 19.30 11.41 7.50 12.46 10.13 18.61 17.94 22.45 23.72 18.96 17.64 Legend: RSP red sweet pepper ( Margarita hybrid); ASP yellow sweet pepper ( Eppo hybrid). Averages with the same minuscule letter within the line and capital letter within the column do not differ by Scott-Knott test at 5%. 499 499

Figures Fig. 1. Regression of PAR SR within each treatment (FC Field Conditions; RSc Red Screen; BSc Blue Screen). 120 Accumulated PAR / Yield per plant 100 80 60 40 20 0 1 2 3 RSP YSP Environment Fig. 2. PAR efficiency use. Legend: 1 Red Screen; 2 Blue Screen; 3 Field Conditions. RSP red sweet pepper ( Margarita hybrid); ASP yellow sweet pepper ( Eppo hybrid). 500