Seed physiological potential of “ dedo-de-moça ” pepper in relation to maturation stages and rest periods of the fruits

One of the main problems in pepper seed production is the uneven maturation of the fruits due to the continuous flowering period of the plant, making it difficult to harvest all the fruits at the same time. Thus, studies on fruit maturation stage and seed physiological potential are extremely important in order to identify the appropriate harvest time, avoiding seed deterioration. The aim of this study was to evaluate the physiological potential of five genotypes of “dedo de moça” pepper seeds (Capsicum baccatum var. pendulum) in three maturation stages (green, orange and red), with and without 10-day rest period after harvest date. Physiological potential and vigor of seeds were evaluated through germination tests (first count, accelerated aging and electrical conductivity). The observed results were submitted to variance analysis, comparing averages through Tukey test and principal components analysis. In general, red fruits reflected seed maturity since they provided maximum germination. On the other hand, even fruits harvested at a maturation stage prior to red (green and orange), showed the benefits of the rest periods on germination and vigor characteristics, being this result more evident in green fruits which, initially, had lower physiological potential. The evaluated genotypes showed lower physiological potential of fruits harvested at the green stage, without 10-day rest period.


Research
Hortic.bras., Brasília, v.36, n.4,October-December 2018 T he genus Capsicum is a vegetable dedicated to fresh consumption and condiments, spices and preserved products (Moreira et al., 2013).Based on floral characteristics, such as shape of the calyx, color of the chorolla and number and orientation of flowers per node, this genus is classified into 38 species (USDA, 2011), considering that only five are considered domesticated: C. annuum, C. frutescens, C. chinense, C. pubescens and C. baccatum (DeWitt & Bosland, 2009).
The species C. baccatum is one of the main peppers grown in Brazil by family farmers (Villela et al., 2014).Among the different types of peppers belonging to this species, "dedo-demoça", also known as "chifre-deveado", "red pepper" and "Calabrian pepper" is one of the most used in Brazilian cuisine due to its sensorial quality (color, flavor and pungency).This pepper is widely consumed both in natura as well as processed, in the form of sauces and dehydrated (Carvalho et al., 2009;Cardoso et al., 2018).
Although "dedo-de-moça" pepper is a vegetable of great acceptance in the Brazilian market, only four cultivars

Received on June 12, 2017; accepted on June 22, 2018
are available for commercialization (MAPA, 2016).According to Justino et al. (2015), the lack of interest of seed producing companies to develop new Capsicum spp.cultivars is related to deficiencies in production techniques, low yield, difficulty of extraction and problems related to seed physiological potential.
The uneven fruit ripening, resulting from plant continuous flowering is one of the main problems in production of Capsicum spp.seeds, since this makes it difficult to harvest the fruits at the same time.Thus, the knowledge about the relationship fruit ripening and seed ripening is of great relevance, since it determines the appropriate harvest time, avoiding lots of immature seeds or under advanced deterioration process.In this context, several studies have been carried out in order to determine the ripening process of pepper seeds and identify the appropriate time for harvest, which results in production of high-quality seeds (Queiroz et al., 2011;Vidigal et al., 2011;Abud et al., 2013;Pereira et al., 2014;Justino et al., 2015).
In addition to studies on maturation and harvest time, other researchers point out that seeds kept inside the fruit after harvest, for some time, continue the maturation process, reaching high levels of germination and vigor (Vidigal et al., 2009;Ricci et al., 2013).For "dedode-moça" pepper, Pereira et al. (2014), evaluating fruits in four maturation stages [15,25,35 and 45 days after anthesis (DAA)] and submitted to rest period for 0, 5 and 10 days, verified that the best germination results occurred at 45 DAA and that post-harvest rest period for 10 days improved seed physiological potential.On the other hand, Justino et al. (2015), evaluating seven ripening stages (20,30,40,50,60,70 and 80 DAA) verified that seed physiological potential occurred at 70 DAA, when the fruits showed red color.Thus, the authors verified differences in results for ripening of "dedo-de-moça" pepper, and this fact may be the cause of genotypic or environmental variation.
Thus, in this study we aimed to evaluate seed physiological potential of "dedo-de-moça" pepper (Capsicum baccatum var.pendulum) in three maturation stages (green, orange and red), without and with 10-day of postharvest rest period.
During flowering phase, pepper flowers were dated daily, and from anthesis, up to obtain from 40 to 60 fruits of each genotype.At harvest, fruits were removed from plants based on their coloration and classified as green [unripe fruits, 48 to 53 days after anthesis (DAA)], orange (intermediate, 58 to 63 DAA) and red (ripe fruits, 67 to 72 DAA).
Seeds were extracted manually, from one part of harvested fruits, right after harvest, washed in running water and kept for drying for approximately 48 hours under monitored closed environmental conditions (25±2°C).The remaining fruits were kept at rest for 10 days under 25°C temperature and 71% relative humidity, and then, the seeds were extracted manually, washed in water and dried under similar conditions to ones described previously.
The experiment was carried out in a completely randomized design in a factorial scheme 3×2×5, being three maturation stages (green, orange and red), two rest periods of the fruits (postharvest extraction or after 10 days) and five genotypes, with four replicates.
Seeds were submitted to tests to determine the degree of moisture, germination and vigor (first count, accelerated aging and electrical conductivity).Germination test was conducted in four replicates and 50 seeds per treatment distributed on two germitest paper sheets, moistened with 0.2% potassium nitrate solution (KNO 3 ) equivalent to 2.5 times the dry paper mass, in Gerbox-type plastic boxes (11×11×3.5cm).The samples were kept in a germination chamber at 30° C temperature and two evaluations were performed: the first called first germination count at day 8 and the second at day 14 after sowing.The normal seedling criterion was adopted according to criteria established by the Rules for Seed Analysis (RAS) and the results expressed in percentage (Brasil, 2009).
Accelerated aging test was installed distributing 1.0 g of single-layer seeds onto a stainless steel mesh tray coupled with Gerbox-type plastic boxes (11×11×3,5 cm), containing 40 mL distilled water.The seeds were kept in an incubator at 42°C for 96 hours (AOSA, 1983).Right after, the seeds were placed to germinate and on the 8 th day evaluated; the results were expressed in percentage of normal seedlings (Baalbaki et al., 2009).
For electrical conductivity test, the authors used four replicates of 50 seeds.These seeds were immersed in 25 mL distilled water and kept in a BOD incubator at 25°C for 48 hours; using a portable digital conductivity meter (model HI98300, Hanna), the electrical conductivity of the imbibition solution was determined.Results were expressed in µS.cm -1 g -1 of seeds (Vidigal et al., 2008).
The obtained data were tested for normality and homogeneity of variances by the Shapiro-Wilk and Bartlett tests, respectively.Germination and first count variables were transformed by arcsin to meet the assumptions of the analysis of variance.Afterwards, data were submitted to variance analysis and averages compared using Tukey test at 5%.Principal components analysis was also used as database.All analyses were done with the aid of program R (http:// www.r-project.org)using package ExpDes (Ferreira et al., 2014) and FactoMineR (Lê et al., 2008).

RESULTS AND DISCUSSION
Using variance analysis, the authors Seed physiological potential of "dedo-de-moça" pepper in relation to maturation stages and rest periods of the fruits LSA Gonçalves et al. observed a significant effect for variation sources: rest periods of the fruits (R), maturation stage (EM) and genotypes (G) for the most evaluated variables.A significant effect was observed for all variables, evaluating interactions between R x EM and EM x G showing differentiated behavior concerning rest period and maturation stages and also from genotypes and change in fruit maturity stage.For interactions R x G and EM x R x G, the authors verified a significant effect only for accelerated aging (ENV) and electrical conductivity (COND).These results show existence of genotypic variability regarding the types of treatments proposed to evaluate maturation and rest period of the pepper fruits.Coefficients of variation were 11.62, 17.87, 8.39 and 14.15% for germination, first count, ENV and COND, respectively.
For germination and first count, higher values of post-harvest extraction were obtained from red fruits with 94 and 89% germination, respectively, whereas for fruits under 10-day rest, no differences were observed for the three fruit maturity stages (Table 1).On the other hand, the authors verified significant increase in germination and in the first count, after 10-day rest period, for seeds extracted from green and orange fruits, showing that in this period the seeds had completed their maturation process (Table 1).
Post-harvest extraction from green and orange fruits interrupts the seed maturation process resulting in seeds with low physiological potential.However, the seeds remaining inside the fruits for 10 days allowed its complete maturation.Similar results were observed by Pereira et al. (2014) for "dedo-de-moça" pepper harvested in different maturation stages and stored for 0, 5 and 10 days; The 5 and 10-day postharvest storage provided an increase in seed germination.For bell pepper, another species of genus Capsicum, Teixeira et al. (2006) observed that the seeds extracted from yellowish green fruits, without storage, showed 40% and 90% germination after zero and seven-day storage, repectively.Thus, the results obtained in this study confirmed that early-harvested fruits, resting for some days, result in better physiological potential.
Genotypical effect was verified using interaction EM x G, for germination and first count, in which no differentiation of genotypes in red fruit stage was observed (Table 2).However, for green fruits, higher values were obtained for genotypes BRS Mari, Horticeres and Hortivale, whereas for orange color, higher values were observed for genotypes UEL111, UEL110, BRS Mari and Hortivale.
Some studies have shown some variability in germination and vigor of seeds in accessions belonging to same species, such as for passion fruit (Freitas, 2009), papaya (Cardoso et al., 2009) and Capsicum spp.(Pessoa et al., 2015).Pessoa et al. (2015), evaluating F 2 population of C. annuum, verified variability and high heritability for variables related to seed physiological potential, considering that these characteristics can be used in the first generations of selection aiming to obtain uniformity of emergency and seedling vigor.
For accelerated aging test, the genotypes Hortivale, Horticeres and UEL 111 obtained the highest values when evaluated at red maturation stage, without 10-day rest, whereas for fruits at orange stage, the highest values were Table 1.Average values of germination (%) and first germination count (%) of C. baccatum var.pendulum seeds, "dedo-de-moça" type, extracted from fruits after 10-day rest period, in three maturity stages (green, orange and red).Londrina, UEL, 2016.Averages followed by same uppercase letter in line and lowercase letter in column do not differ by Tukey test (p<0.5).

Treatments
Table 2. Seed germination and first germination count of five C. baccatum var.pendulum, "dedo-de-moça" type genotypes, extracted from fruits in three maturity stages (green, orange and red).Londrina, UEL, 2016.verified for genotypes UEL 111 and Hortivale (Table 3).Fruits submitted to a 10-day rest period, except for green maturation stage, did not present any difference between genotypes at red and orange stage.Among the green fruits the highest values were observed for BRS Mari and Hortivale.

Genotypes
For post-harvest extraction, the highest values for accelerated aging were observed at red maturation stage for UEL 111, Horticeres and Hortivale, whereas for UEL 111 and UEL 110 no difference at orange and red maturation stages was verified.Comparing genotypes in relation to maturity stages of fruits under a 10-day rest period, UEL 110 and Horticeres obtained higher number of normal seedlings after accelerated aging for orange maturation stage compared to green fruits (Table 3).Contrarily, no difference for orange and red maturation stages for fruits under rest period was noticed.
Comparing post-harvest extraction and 10-day rest period of the fruits, the authors observed higher values for accelerated aging in post-harvest rest period of green fruit stage, for all genotypes; orange stage fruits showed the same results, except for the genotype UEL 111.Red fruits presented a difference between post-harvest extraction and 10-day rest period only for genotypes UEL 110 and BRS Mari which obtained higher values when the fruits were in rest period.Queiroz et al. (2011), evaluating accelerated aging of Habanero Yellow pepper, verified that maximum vigor was noticed for seeds harvested at 67 DAA, 7 days of storage (rest period).This study corroborates the results in this research, in which the authors observed that 10-day rest of fruits resulted in more vigorous seeds, considering this result more evident in green fruits which initially showed lower physiological potential (Table 3).
For electrical conductivity lower values for orange and red stages for post-harvest extraction were observed (Table 3).For fruits under a 10-day rest, no differences among maturation stages for genotypes BRS Mari and Hortivale were observed, whereas in relation to other genotypes better results were obtained for orange and red stages.Comparing presence or absence of rest period of fruits for 10 days, differences for the three fruit maturity stages were noticed, considering that higher values were observed for postharvest extraction.For green fruits, the authors observed differences for genotypes UEL 110, BRS Mari and Hortivale, whereas for orange fruits, the authors observed differences for UEL 111, BRS Mari and Hortivale.For red fruits, the difference mentioned above was observed only for genotypes UEL 110 and Hortivale, showing existence of genotypic variability among the genotypes regarding the rest period in the three maturation stages.In relation to genotypes, BRS Mari obtained the lowest values for the three post-harvest maturation stages, whereas in 10-day Table 3. Accelerated aging test and electrical conductivity from seeds of five C. baccatum var.pendulum "dedo-de-moça" type genotypes, post-harvest extracted and after 10-day rest period of fruits in three maturity stages (green, orange and red).Londrina, UEL, 2016.

Genotypes
Post

-harvest extraction 10-day rest period
*Differences between two seed extraction times (post-harvest and 10-day rest period).Averages followed by same uppercase letter in line and lower case letter in column do not differ by Tukey test (p<0.05).Figure 1.Biplot raph of Principal Component Analysis of pepper genotypes C. baccatum var.pendulum.Green fruits without rest (1A); green fruits with rest (1B); intermediate-colored fruits without rest (2A); orange fruits with rest (2B); red fruits without rest (3A); red fruits with rest (3B).Londrina, UEL, 2016.