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Pesquisa Agropecuária Brasileira

Print version ISSN 0100-204XOn-line version ISSN 1678-3921

Pesq. agropec. bras. vol.52 no.9 Brasília Sept. 2017

https://doi.org/10.1590/s0100-204x2017000900006 

GENETICS

Fruit color and post-harvest shelf life in tomato affected by the ogc, nor A, and rin alleles

Coloração e conservação pós-colheita de frutos de tomateiro influenciadas pelos alelos ogc, norA e rin

Betsabé Antezana Poma(1) 

Wilson Roberto Maluf(2) 

Beatriz Tome Gouveia(2) 

Alisson Marcel Souza de Oliveira(2) 

Rodolfo de Paula Duarte Ferreira(2) 

Regis de Castro Carvalho(1) 

(1)Universidade Federal de Lavras (Ufla), Departamento de Biologia, Caixa Postal 3.037, CEP 37200-000 Lavras, MG, Brazil. E-mail: luciantezana@gmail.com, regisccarvalho@hotmail.com

(2)Ufla, Departamento de Agricultura, Caixa Postal 3.037, CEP 37200-000 Lavras, MG, Brazil. E-mail: wrmaluf@dag.ufla.br, biatgouveia@hotmail.com, alisson182001@yahoo.com.br, rodolfopdf@hotmail.com


Abstract:

The objective of this work was to evaluate the effects of the mutant alleles alcobaça (nor A ), ripening inhibitor (rin), and old gold crimson (og c ), in heterozygosity or homozygosity, on the expression of color and on the postharvest quality of fruit of experimental tomato hybrids. Fourteen hybrids with contrasting genotypic constitutions in the nor A , rin, and og c loci were evaluated in a randomized complete block design with four replicates. The following fruit postharvest quality traits were evaluated: firmness in the breaker stage, color, and soluble solids content. The rin +/rin and nor +/nor A genotypes increased firmness of tomato fruit at harvest (breaker stage). The rin + /rin genotypes displayed the worse internal fruit color. There was a positive effect of og c+ /og c in improving the internal color of rin + /rin and nor + /nor A fruit, making the color similar to that of the normal genotypes. The combination of the og c /og c rin + /rin nor + /nor A genes is effective to improve tomato fruit firmness, besides maintaining or improving internal color.

Index terms: Solanum lycopersicum; alcobaça; nonripening; old gold crimson; plant breeding; ripening inhibitor

Resumo:

O objetivo deste trabalho foi avaliar os efeitos promovidos pelos alelos mutantes alcobaça (nor A ), ripening inhibitor (rin) e old gold crimson (og c ), em heterozigose ou homozigose, na expressão da coloração e da conservação pós-colheita de frutos de híbridos experimentais de tomateiro. Quatorze híbridos com contituições genotípicas contrastantes entre si nos locos nor A , rin e og c foram avaliados em delineamento em blocos ao acaso, com quatro repetições. As seguintes características de qualidade pós-colheita dos frutos foram avaliadas: firmeza no estádio de amadurecimento incipiente, coloração e teor de sólidos solúveis. Os genótipos rin + /rin e nor + /nor A condicionaram a maior firmeza dos frutos de tomate no ponto de colheita (estádio de amadurecimento incipiente). Os genótipos rin + /rin apresentaram as piores colorações internas de frutos. Houve efeito positivo de og c+ /og c na melhoria da coloração interna dos frutos rin + /rin e nor + /nor A , que tornou a coloração semelhante à dos genótipos normais. A combinação dos genes og c /og c rin + /rin nor + /nor A é eficiente para melhorar a firmeza dos frutos de tomate, além de manter ou melhorar a coloração interna.

Termos para indexação: Solanum lycopersicum; alcobaça; nonripening; old gold crimson; melhoramento genético; ripening inhibitor

Introduction

Tomato (Solanum lycopersicum L.) is one of the most highly consumed vegetable crops in the world. Brazil ranks eighth in the worldwide ranking for tomato production (FAO, 2013). Tomato fruit is highly perishable, with losses of up to 21% after harvest (Rinaldi et al., 2011); it has high-water content, about 90 to 95%, which makes it fragile (Rocha et al., 2009). In tomato breeding programs, the main studied aspects are yield increase, pest and disease resistance, and the improvement of fruit quality. One of the factors associated with this last aspect is the greater natural conservation of the fruit postharvest, and this conservation may be achieved by the production of F1-hybrid fruit that is firmer and has better color (Andrade Júnior et al, 2001).

An alternative to extend the shelf life of tomato fruit has been to affect the natural maturation process of Solanum lycopersicum lines by the incorporation of mutant genes, such as rin (ripening inhibitor), nor (nonripening), Nr (never ripe), and nor A (alcobaça) (Barry & Giovannoni, 2006). These genes block and retard the maturation process, which lends a longer life to fruit. Currently, most post-harvest long-life tomato hybrids are heterozygous for the gene rin, nor, and nor A , which may lead to reduced quality because of the pleiotropic effects on other metabolic pathways involved in promoting fruit color, flavor, aroma, and texture (Kovács et al., 2009). However, alleles such as high pigment (hp) and old gold crimson (og c ) increase lycopene production in the fruit, which improves color, and they can be used simultaneously with mutant maturation alleles (Andrade Júnior et al., 2005).

Araújo et al. (2002) have shown that the alcobaça allele in homozygosity (nor A /nor A ) prolongs the post-harvest shelf life by the reduction of weight loss and the increase of firmness, and reduces the lycopene and beta-carotene concentrations, besides increasing the Brix/acidity ratio, mainly in association with the genotypes hp/hp and hp + /hp or with og c /og c ; however, its outside color limits its commercial use. Cá et al. (2006) in the evaluation of the viability of simultaneous use of mutant genes, for maturity and for color in tomato hybrids, in the loci nor A , rin, og c , or hp, found that these genotypes exhibited better fruit conservation in the post-harvest than the normal genotypes, and concluded that the genotypic constitutions nor + /nor A og c+ /og c , together with nor + /nor A og c+ /og c hp + /hp, were considered most promising, both for improving post-harvest conservation and for maintaining or improving the internal color of tomato fruit.

Faria et al. (2006) showed that the use of the mutants og c or hp, in heterozygosity, improves the color and increases the concentrations of beta-carotene and lycopene of fruit in rin + /rin and rin + /rin nor + /nor A long shelf life hybrids. Andrade et al. (2015) concluded that the best combination of high beta-carotene (B) in heterozygosity for the hue angle and chroma depends on the mutant gene og c in heterozygosity; they also showed that the og c homozygous genotypes in the absence of high beta-carotene had a significant shift in the red direction in the placenta and in the columella, which confirms their effect on improving the internal color of fruit.

The objective of this work was to evaluate the effects of the mutant alleles alcobaça (nor A ), ripening inhibitor (rin), and old gold crimson (og c ), in heterozygosity or homozygosity, on the expression of color and on the postharvest quality of fruit of experimental tomato hybrids.

Materials and Methods

The study was carried out in a greenhouse and in the field, at the experimental station of HortiAgro Sementes S.A., in the Palmital farm (21°14'16"S, 45°08'00"W, at 920 m altitude), Ijaci, Minas Gerais state, Brazil, as well as in the Departamento de Agricultura, of Universidade Federal de Lavras (Ufla), and in the laboratory of vegetable crop post-harvest, of Departamento de Ciências dos Alimentos of Ufla.

The experiment in the greenhouse was carried out in a randomized complete block design, with 14 treatments, and four replicates. Homozygous lines for the genes rin, nor A , and og c , from the germplasm bank of HortiAgro Sementes S.A., were used as parent lines for different combinations in the loci rin, nor A , and og c , and the following hybrids were obtained: TEX-432=F1(TOM-667 x TOM-756), TEX-433=F1 (TOM-591 x TOM-756), TEX-434=F1(TOM-714 x TOM-756), TEX-435=F1(TOM-756 x TOM-761), TEX-436=F1(TOM-713 x TOM-761), TEX-437=F1 (TOM-591 x TOM-761), TEX-438=F1(TOM-756 x TOM-762), TEX-439=F1(TOM-713 x TOM-762), TEX-440=F1(TOM-591 x TOM-762), TEX-441=F1 (TOM-763 x TOM-TOM-713), TEX-442=F1(TOM-757 x TOM-713), and TEX-443=F1(TOM-758 x TOM-713). These hybrids, all with determinate growth habit, together with two commercial hybrids as controls ('Giselle' and 'Colono', also of determinate growth habit), constituted 14 treatments that were placed in five different categories, in relation to their genotypic constitutions in the loci rin, nor A , and og c (Table 1).

Table 1. Description of the treatments. 

Treatment Characteristics
Giselle Normal (rin + /rin + nor + /nor + og c+ /og c+ )
Colono rin heterozygote (rin + /rin)
TEX-432
(TOM-667 x TOM-756)
rin heterozygote (rin + /rin)
TEX-433
(TOM-591 x TOM-756)
nor A heterozygote;
og c heterozygote (nor + /nor A ogc + /og c )
TEX-434
(TOM-714 x TOM-756)
Normal (rin + /rin + nor + /nor + og c+ /og c+ )
TEX-435
(TOM-756 x TOM-761)
rin heterozygote;
og c heterozygote (rin + /rin ogc + /og c )
TEX-436
(TOM-713 x TOM-761)
rin heterozygote;
og c heterozygote (rin + /rin ogc + /og c )
TEX-437
(TOM-591 x TOM-761)
nor A heterozygote; rin heterozygote;
og c homozygote (nor + /nor A rin + /rin og c /og c )
TEX-438
(TOM-756 x TOM-762)
rin heterozygote;
og c heterozygote (rin + /rin ogc + /og c )
TEX-439
(TOM-713 x TOM-762)
rin heterozygote;
og c heterozygote (rin + /rin og c+ /og c )
TEX-440
(TOM-591 x TOM-762)
nor A heterozygote; rin heterozygote;
og c homozygote (nor + /nor A rin + /rin og c /og c )
TEX-441
(TOM-763 x TOM-713)
Normal (rin + /rin + nor + /nor + og c+ /og c+ )
TEX-442
(TOM-757 x TOM-713)
Normal (rin + /rin + nor + /nor + og c+ /og c+ )
TEX-443
(TOM-758 x TOM-713)
Normal (rin + /rin + nor + /nor + og c+ /og c+ )

The plots consisted of a single row of 10 plants. The 14 genotypes were sown on 27/04/2015, and seedlings were produced in 128-cell expanded polystyrene trays that contained the commercial substrate Topstrato. Plants were thinned to one seedling per cell, at 15 days after sowing. Seedlings were transplanted in the field at 30 days after sowing. The experiment was conducted in the field according to the commercial growing recommendations for tomato under field conditions (Alvarenga, 2013), with a 0.5 m spacing between plants and 1.5 m between rows. The plants were tied on a half-length stake and the experiment was irrigated by drip. The plants were pruned up to the height of the first flowering shoot, and from that point on, they were not pruned. Fertilization at planting and topdressing, and plant health control treatments were also performed, according to the specific recommendations for the tomato cropping.

The soluble solids content (°Brix) was evaluated through direct reading in a refractometer. Post-harvest conservation of fruit was evaluated (N m-2) by fruit firmness collected at the beginning of the maturity stage, which is characterized by change of the fruit green color to the appearance of slightly red spots in the region of the stem scar - “breaker stage”) using the applanation technique described by Calbo & Nery (1995).

The same samples harvested at the beginning of the maturity stage for the firmness evaluation were used for color evaluation. Fruit were stored at 15°C and 60% relative humidity until reaching full maturity. Color readings were made at 4 parts of the fruit - epidermis, pericarp, placenta, and columella - with the Minolta CR-400 colorimeter in the CIE mode L*, a*, and b*, in which L* (lightness) is the coordinate of brightness (z axis), which ranges from -100 (black) to +100 (white), in which the higher values indicate brighter colors; a* is the hue coordinate (x axis), which ranges from +60 (red) to -60 (green); b* is the hue coordinate (y axis), which ranges from +60 (yellow) to -60 (blue). From the a* and b* values, the hue angle [defined as arc tg (b/a)] and chroma or saturation [the square root of (a2+b2)] were obtained. The hue angle is considered from the ‘a’ axis and is expressed in degrees: 0° is defined as +a (red); 90°, as +b (yellow); 180° as -a (green), and 270° as -b (blue). Mature tomato fruit in general range from 0° (red) to 90° (yellow); the nearer the values are to zero (0°), the redder the fruit; and the nearer to 90°, the yellower the fruit (Konica Minolta, 2014). For saturation or chroma, the values range from 0 to 60. Values equal to zero correspond to the origin center of the coordinates; values near zero indicate little saturated colors, and the value of 60 indicates the maximum saturation (Konica Minolta, 2014).

Data were subjected to the analysis of variance, and means were compared by the Tukey test’s, at 5% probability, by the SAS statistical application (SAS Institute, Inc., Cary, NC, USA). Experimental precision was checked by the estimate of selection accuracy (Resende & Duarte, 2007). Contrasts of interest were also calculated for comparisons between genotypes with different genotypic constitutions in the loci rin, og c , and nor A .

Results and Discussion

In the evaluated fruit quality characteristics - firmness, soluble solids content, and fruit color -, significant differences were observed between treatments, and all the quality traits showed accuracy higher than 70% (Table 2). Experimental precision was, therefore, considered high, according to Resende & Duarte (2007). The content of soluble solids, in the evaluated genotypes, varied from 3.72 °Brix, for 'Colono', to 4.72 °Brix for TEX-435 and TEX-441, respectively (Table 2). Only the differences between these extreme values were significant. The other genotypes, with intermediate °Brix values, did not differ from either of the two extreme values; this indicates that all the hybrids used were satisfactory for soluble solids content, and similar to the controls 'Giselle' or 'Colono'. Fruit firmness was affected by both the genotypic constitution in the loci (rin, nor A , and og)c and the genetic base (Table 2). The normal genotypes proved to be less firm at the beginning of the maturity stage than the heterozygous genotypes rin (C1, Table 3), og c and nor A (C3), and the genotypes og c /og c rin + /rin nor + /nor A (C4); besides, they did not differ significantly from the genotypes og c+ /og c rin + /rin (C2). These results confirmed reports on rin + /rin and nor + /nor A as responsible for the shelf life increase of the fruit (Araújo et al., 2002; Faria et al., 2003; Santos Júnior et al., 2005; Cá et al., 2006). These reports also showed that the genetic base also plays an important role in fruit firmness, when considering, for instance, the amplitude of the firmness values found among the normal genotypes 'Giselle', TEX-434, TEX-441, TEX-442, and TEX-443, among the heterozygous genotypes rin ('Colono', TEX-432), and among the genotypes og c+ /og c rin + /rin (TEX-435, TEX-436, TEX-438, TEX-439). The og c allele in heterozygosity seems not to have a direct effect on firmness, since the heterozygous hybrids og c and rin were less firm than the heterozygous genotypes rin alone (C5, Table 3). Heterozygous genotypes og c and nor A were firmer than the heterozygous rin (C6). However, simultaneous heterozygosity in the loci rin and nor A seems to be the most effective combination for increasing firmness in relation to the presence of only one of these heterozygotes, when the magnitude and significance of the contrasts C7, C8, and C9 and of the negative signal (though nonsignificant) of the C10 contrast are considered.

Table 2. Mean values of firmness in the breaker stage and of soluble solids in tomato (Solanum lycopersicum) fruit(1)

Treatment Firmness (104 N m-2) Soluble solids (°Brix)
Giselle 2.40bcd 4.35ab
Colono 3.50a 3.72b
TEX-432 (TOM-667 x TOM-756) 2.02d 4.01ab
TEX-433 (TOM-591 x TOM-756) 3.06abcd 3.98ab
TEX-434 (TOM-714 x TOM-756) 2.03d 3.97ab
TEX-435 (TOM-756 x TOM-761) 2.70abcd 4.72a
TEX-436 (TOM-713 x TOM-761) 2.12d 4.44ab
TEX-437 (TOM-591 x TOM-761) 3.31abc 4.15ab
TEX-438 (TOM-756 x TOM-762) 2.33bcd 4.29ab
TEX-439 (TOM-713 x TOM-762) 2.35bcd 4.42ab
TEX-440 (TOM-591 x TOM-762) 3.44ab 4.13ab
TEX-441 (TOM-763 x TOM-713) 2.21cd 4.72a
TEX-442 (TOM-757 x TOM-713) 2.52abcd 4.62ab
TEX-443 (TOM-758 x TOM-713) 2.30bcd 4.25ab
Accuracy (%) 92.97 76.60

(1)Mean values followed by equal letters, in the columns, do not differ by the Tukey’s test, at 5% probability.

Table 3. Estimates of contrasts of interest for firmness (2x104 N m-2) in tomato (Solanum lycopersicum) fruit. 

Contrast Description Firmness estimate (N m-2)
C1 Normal genotypes vs heterozygous genotypes rin -0.47*
C2 Normal genotypes vs heterozygous genotypes og c and rin -0.08ns
C3 Normal genotypes vs heterozygous genotype og c and nor A -0.77**
C4 Normal genotypes vs homozygous genotypes og c and heterozygous rin and nor A -1.08**
C5 Heterozygous genotypes rin vs heterozygous genotypes og c and rin 0.39*
C6 Heterozygous genotypes rin vs heterozygous genotype og c and nor A -0.30ns
C7 Heterozygous genotypes rin vs homozygous genotypes og c and heterozygous rin and nor A -0.61**
C8 Heterozygous genotypes og c and rin vs heterozygous genotype og c and nor A -0.68**
C9 Heterozygous genotypes og c and rin vs homozygous genotypes og c and heterozygous genotypes rin and nor A -1.00**
C10 Heterozygous genotype og c and nor A vs homozygous genotypes og c and heterozygous genotypes rin and nor A -0.31ns

og c , presence of the old gold crimson allele; rin, ripening inhibitor allele; nor A , alcobaça allele. ** and *Significant by the Tukey’s test, at 1 and 5%, respectively. nsNonsignificant. Normal genotypes: rin + /rin + nor + /nor + og c+ /og c+ .

Among the experimental hybrids, TEX-440 had the firmest fruit, and the fact that it has the genotypic constitution og c /og c rin + /rin nor + /nor A confirms the effectiveness of obtaining firm hybrids through the homozygous genotype og c and heterozygous genotypes for both rin and nor A .

As to fruit color, differences were observed among the treatments for all the evaluated characteristics (epidermis, pericarp, placenta, and columella) for both hue angle and chroma values (Table 4). The hue angle was affected both by the presence of the mutants rin, nor A , and/or og c and by the genetic base. Evidence of the effect of the genetic base can be observed in the difference between the normal genotypes - 'Giselle' had a significantly greater hue angle (therefore, lower tendency to red) - in the placenta than the other normal hybrids: TEX-434, TEX-441, TEX-442, and TEX-443.

Table 4. Mean values of hue angle (in degrees) for epidermis, pericarp, placenta, and columella of tomato (Solanum lycopersicum) fruit(1)

Treatment Epidermis Pericarp Placenta Columella
Giselle 38.77ab 38.90abcd 58.63a 39.11ab
Colono 38.34abcd 39.76ab 59.08a 34.81bc
TEX-432 (TOM-667 x TOM-756) 38.58abc 41.02a 55.21ab 34.43bc
TEX-433 (TOM-591 x TOM-756) 33.84e 35.10d 52.99bc 39.09ab
TEX-434 (TOM-714 x TOM-756) 35.32de 36.79bcd 51.31bc 34.73bc
TEX-435 (TOM-756 x TOM-761) 37.89abcd 36.78bcd 50.05c 35.03bc
TEX-436 (TOM-713 x TOM-761) 38.92a 38.65abcd 55.36ab 40.66a
TEX-437 (TOM-591 x TOM-761) 35.81bcde 36.06bcd 49.27c 39.13ab
TEX-438 (TOM-756 x TOM-762) 38.47abc 38.17abcd 52.38bc 32.66c
TEX-439 (TOM-713 x TOM-762) 38.33abc 39.73abc 55.57ab 37.87abc
TEX-440 (TOM-591 x TOM-762) 37.20abcd 37.13abcd 48.89c 37.99abc
TEX-441 (TOM-763 x TOM-713) 35.53cde 35.93cd 51.06bc 36.64abc
TEX-442 (TOM-757 x TOM-713) 36.85abcde 37.55abcd 51.91bc 40.62a
TEX-443 (TOM-758 x TOM-713) 36.68abcde 37.82abcd 52.71bc 38.52ab
Accuracy (%) 89.53 85.03 95.41 85.47

(1)Mean values followed by equal letters, in the columns, do not differ by the Tukey’s test, at 5% probability.

Differences were detected in the external color (epidermis) and internal color (pericarp, placenta, columella) of the fruit due to the presence of the loci rin, nor, and og c (Table 5). The heterozygosity in the locus rin increased the hue angle in relation to the normal genotypes (C1), in both the external and internal parts of the fruit, which shows the detrimental effect of rin + /rin on color. The detrimental effects of rin + /rin on internal color of the fruit were however reversed by the presence of og c in heterozygosity (C2 and C5).

Table 5. Estimates of contrasts of interest for hue angle of the epidermis (EP), pericarp (PE), placenta (PL), and columella (CO) of tomato (Solanum lycopersicum) fruit. 

Contrast Description Estimates
EP PE PL CO
C1 Normal genotypes vs heterozygous genotypes rin -1.83** -2.99** -4.02** 3.30**
C2 Normal genotypes vs heterozygous genotypes og c and rin -1.77** -0.93ns -0.22ns 1.37ns
C3 Normal genotypes vs heterozygous genotypes og c and nor A 2.79** 2.30* 0.13ns -1.16ns
C4 Normal genotypes vs homozygous genotypes og c and heterozygous genotypes rin and nor A 0.12ns 0.80ns 4.04** -0.63ns
C5 Heterozygous genotypes rin vs heterozygous genotypes og c and rin 0.06ns 2.05** 3.80** -1.93*
C6 Heterozygous genotypes rin vs heterozygous genotypes og c and nor A 4.62** 5.29** 4.15** -4.47**
C7 Heterozygous genotypes (HG) rin vs homozygous genotypes og c and HG rin and nor A 1.95** 3.79** 8.07** -3.94**
C8 Heterozygous genotypes og c and rin vs heterozygous genotypes og c and nor A 4.56** 3.23** 0.35ns -2.54ns
C9 Heterozygous genotypes (HG) og c and rin vs homozygous genotypes og c and HG rin and nor A 1.90** 1.74* 4.26** -2.00*
C10 Heterozygous genotypes (HG) og c and nor A vs homozygous genotypes og c and HG rin and nor A -2.67** -1.50ns 3.92** 0.53ns

og c , presence of the old gold crimson allele; rin, ripening inhibitor allele; nor A , alcobaça allele. ** and *Significant by the Tukey’s test at 1 and 5% probability, respectively. nsNonsignificant. Normal genotypes: rin + /rin + nor + /nor + og c+ /og c+ .

In the present study, it was not possible to measure the effect of the genotype nor + /nor A , separately, on the internal and external colors, due to the absence of a heterozygous genotype nor A in the absence of og c . However, it is clear that this detrimental effect, if it exists, is counterbalanced by the presence of og c in heterozygosity because the combination og c+ /og c nor + /nor A improved the epicarp and placenta colors in comparison to the normal genotypes (C3, Table 5). The possible detrimental effect of nor + /nor A , if it exists, appears to be less than that brought about by rin + /rin because the beneficial effects of ogc + /og c are more accentuated in the first case (C6) than in the second one (C5).

The simultaneous presence of heterozygosity in rin and nor A besides homozygosity in og c /og c provided not only a red color comparable to that of normal genotypes in the epidermis, pericarp, and columella, but also improved it in the placenta (C4, Table 5). Andrade et al. (2015) found that homozygous genotypes og c did not differ from the normal genotypes for the hue angles in the epidermis and pericarp, but had a significant shift in the red direction in the placenta and columella.

As to the genotype rin + /rin alone, the combination og c /og c rin + /rin nor + /nor A exhibited color nearer to red in all the measured points (C7, Table 5), and the same happened in the combination og c+ /og c rin + /rin (C9). In relation to the genotype og c+ /og c nor + /nor A , the genotypic combination og c /og c rin + /rin nor + /nor A brought about the best color in the placenta and the worse color in the epidermis (C10). Araújo et al. (2002) reported that the mutants og c and hp, with a genetic base in 'Floradade', isolated or in combination, in both homozygosity and in heterozygosity, brought about significant increases in internal and external colors.

From these results it can be inferred that the allele og c , both in homozygosity and in heterozygosity, is able to counterbalance the negative effects of the heterozygotes rin + /rin or nor + /nor A in fruit color, mainly in internal color. Similar effects on fruit color were found by Faria et al. (2003) and Cá et al. (2006). In fact, the three smallest chromaticity angles (nearest to red) among the studied genotypes were TEX-435 of the genotype og c+ /og c rin + /rin, and TEX-437 and TEX-440 of the genotype og c /og c rin + /rin nor + /nor A .

The chroma saturation seems to have been less affected than the hue angle among the studied genotypes (Table 6), particularly in the epidermis, pericarp, and placenta, whereas the normal genotype control 'Giselle' had the lowest numerical chromas among the treatments, and the hybrid TEX-441, which is also of normal genotype, had some of the highest chromas at these points.

Table 6. Mean values of chroma for epidermis, pericarp, placenta, and columella of tomato (Solanum lycopersicum) fruit. 

Treatment Epidermis Pericarp Placenta Columella
Giselle 28.23ab 27.39a 24.22ab 31.68abcd
Colono 26.72b 26.15a 21.87b 25.93d
TEX-432 (TOM-667 x TOM-756) 28.91ab 28.74a 23.51ab 32.77abc
TEX-433 (TOM-591 x TOM-756) 29.81ab 30.13a 26.08ab 32.19abc
TEX-434 (TOM-714 x TOM-756) 27.90ab 31.38a 27.40a 35.55a
TEX-435 (TOM-756 x TOM-761) 29.66ab 30.89a 25.46ab 32.99abc
TEX-436 (TOM-713 x TOM-761) 31.98a 29.76a 24.96ab 30.95abcd
TEX-437 (TOM-591 x TOM-761) 29.89ab 31.03a 23.86ab 29.54bcd
TEX-438 (TOM-756 x TOM-762) 28.26ab 28.98a 24.46ab 31.60abcd
TEX-439 (TOM-713 x TOM-762) 30.14ab 29.76a 23.79ab 32.08abc
TEX-440 (TOM-591 x TOM-762) 30.26ab 29.58a 25.15ab 29.10cd
TEX-441 (TOM-763 x TOM-713) 30.32ab 30.41a 27.61a 35.31ab
TEX-442 (TOM-757 x TOM-713) 28.72ab 29.12a 27.09a 30.48abcd
TEX-443 (TOM-758 x TOM-713) 28.13ab 27.20a 25.24ab 29.59bcd
Accuracy (%) 75.43 70.53 75.79 90.32

(1)Mean values followed by equal letters, in the columns, do not differ by theTukey’s test, at 5% probability.

The most significant differences in the chromas occurred in the columella (Table 7). The genotypes rin + /rin had significantly lower chromas than the normal genotypes (C1), but due to the magnitude of variation among the normal genotypes themselves, it is possible that this difference arises mainly from the effect of different genetic bases, and not from the allele rin only. Nevertheless, the effect of the allele og c in heterozygosity is clear as for the increasing of the chroma of the hybrids rin + /rin, both in the external and internal part of the fruit (C5). Genotypes og c+ /og c nor + /nor A also showed greater internal chroma than the rin + /rin (C6). Under the simultaneous presence of rin + /rin and nor + /nor A , the allele og c in homozygosity increased the chroma in the epidermis and in the pericarp of tomato fruit (C7).

Table 7. Estimates of contrasts of interest for chroma of the epidermis (EP), pericarp (PE), placenta (PL), and columella (CO) of tomato (Solanum lycopersicum) fruit. 

Contrast Description Estimates
EP PE PL CO
C1 Normal genotypes vs heterozygous genotypes rin 0.84ns 1.66ns 3.62** 3.17**
C2 Normal genotypes vs heterozygous genotypes og c and rin -1.35ns -0.75ns 1.65* 0.62ns
C3 Normal genotypes vs genotypes og c /og c nor +/nor A -1.15ns -1.03ns 0.23ns 0.33ns
C4 Normal genotypes vs genotypes og c /og c rin + /rin nor +/nor A -1.42ns -1.20ns 1.81* 3.20**
C5 Heterozygous genotypes rin vs heterozygous genotypes og c and rin -2.19* -2.41* -1.98* -2.55*
C6 Heterozygous genotypes rin vs heterozygous genotype og c and nor A -2.00ns -2.69* -3.39** -2.84*
C7 Heterozygous genotypes (HG) rin vs homozygous genotypes og c and HG rin and nor A -2.26* -2.86* -1.82ns 0.03ns
C8 Heterozygous genotypes og c and rin vs heterozygous genotype og c and nor A 0.20ns -0.28ns -1.42ns -0.29ns
C9 Heterozygous genotypes (HG) og c and rin vs homozygous genotypes og c and HG rin and nor A -0.07ns -0.46ns 0.16ns 2.58*
C10 Heterozygous genotype (HG) og c and nor A vs homozygous genotypes og c and HG rin and nor A -0.26ns -0.17ns 1.58ns 2.87ns

og c , presence of the old gold crimson allele; rin, ripening inhibitor allele; nor A , alcobaça allele. ** and *Significant by the Tukey’s test, at 1 and 5% probability, respectively. nsNonsignificant. Normal genotypes: rin + /rin + nor + /nor + og c+ /og c+ .

Conclusions

  1. The genotypic constitutions rin + /rin nor + /nor A are responsible for providing greater firmness to tomato (Solanum lycopersicum) fruit at the time of harvest, and the allele og c does not have a direct effect on firmness.

  2. Heterozygosity in the locus rin has a detrimental effect on color of the external and internal parts of the fruit. The og c allele is able to counterbalance the negative effects of the heterozygotes rin + /rin or nor + /nor A on internal color.

  3. The genotypic constitutions og c /og c rin + /rin nor + /nor A or og c+ /og c nor + /nor A are considered the most promising ones, improving the firmness and the internal or external color of tomato fruit.

  4. The simultaneous presence of heterozygous alleles rin and nor A , associated with og c /ogc, is effective in developing tomato hybrids with better post-harvest conservation.

Acknowledgments

To Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes), for scholarships granted; to Universidade Federal de Lavras and to HortiAgro Sementes S.A., for technical personnel help in conducting the experiments, and for permitting the use of infrastructure; and to Fundação de Amparo à Pesquisa do Estado de Minas Gerais (Fapemig) and to Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq), for financial support.

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Received: April 09, 2016; Accepted: September 09, 2016

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