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Journal of Heredity 2003:94(4)
© 2003 The American Genetic Association 94:355-357

Brief Communication

Inheritance of Seed Color in Capsicum

Y. Zewdie, and P. W. Bosland

From New Mexico State University, Department of Agronomy and Horticulture, Las Cruces, NM 88003.

Address correspondence to P. W. Bosland at the address above, or e-mail: pbosland{at}nmsu.edu.


   Abstract
Top
 Abstract
Materials and Methods
 Results and Discussion
 References
 
The mode of seed color inheritance in Capsicum was studied via an interspecific hybridization between C. pubescens Ruiz and Pav. (black seed color) and C. eximium Hunz. (yellow seed color). Black seed color was dominant over yellow seed color. The F2 segregation pattern showed continuous variation. The generation means analysis indicated the presence of a significant effect of additive [d], dominance [h], and additive x additive [i] interaction for seed color inheritance. The estimate for a minimum number of effective factors (genes) involved in seed color inheritance was approximately 3.

One of the morphological characters to distinguish Capsicum species is seed color. Most domesticated species—C. annuum L., C. baccatum Willd., C. chinense Jacq., and C. frutescens L.—have yellow seed color, while C. pubescens Ruiz and Pav. have black seed color. There are other wild species of Capsicum that have black seed color, such as C. lanceolatum Greenm., C. buforum Hunz, and C. flexuosum Sendt. (Tong and Bosland, 2003).

Information regarding seed color inheritance in Capsicum species is not known. C. eximium Hunz., a wild relative of C. pubescens, has yellow seed color. Fortuitously, C. eximium can be hybridized with C. pubescens; this provides an opportunity to investigate the inheritance of seed color in Capsicum. This study was undertaken to determine the mode of inheritance for black seed color in Capsicum.


   Materials and Methods
Top
 Abstract
 Materials and Methods
Results and Discussion
 References
 
Plant Materials and Color Analysis
The population used for this study was produced by hybridizing C. eximium, NMCA 90002 (P1), to C. pubescens, NMCA 80049 (P2). The F1 plant was selfed and backcrossed to both parents to produce F2 and backcrossed populations, respectively. Plants of the parental lines (P1 and P2), F1, F2, and backcrosses (BCP1 and BCP2) were grown in a greenhouse in 1.25 L white plastic pots. Each pot contained one plant. The growing medium was a mixture of 1 peat : 1 silica sand : 1 sandy loam soil (v/v). In each pot, 18 g of a slow-release fertilizer (Osmocote 14N-4.2P-11.6K) was top dressed at transplanting and again at flowering.

Each plant was considered as a replication and was placed randomly on the bench. The number of plants evaluated under each family is presented in Table 1. Mature red fruits were harvested from each plant separately. The fruits were air-dried, and the seeds extracted. A sample that contained about 100 seeds was taken from each plant separately. The surface seed color (color value—L) of the samples was measured with a Minolta CR-3000 colorimeter. Three readings per sample were taken, and the average of the readings for a sample was used for subsequent statistical analyses.


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  		Table 1.. Seed color value (mean ± SE) and range for P1 (Capsicum eximium), P2 (C. pubescens), and their F1, F2, BCP1 (F1 x P1), and BCP2 (F1 x P2).

 
Statistical Analysis
By using the color value (L) data, the segregation pattern for seed color of the F2 population was examined. The data could not fit to a one- or a two-gene model. Therefore, mean, variance, and standard error of the F1, F2, BCP1, BCP2, and the parents were determined for seed color using procedure "Means" of the SAS program using the color value (L) data. Calculated means and variances estimated the mid-parent (m), additive (d), and dominance (h) gene effects as described by Rowe and Alexander (1980) following the method for three-parameter model of Mather and Jinks (1977). Adequacy of the additive-dominance model was determined by chi-square ({chi}2) test with three degrees of freedom and was accepted if P > 0.05 (nonsignificant {chi}2 value). When the three-parameter model was inadequate (significant {chi}2 value), the interaction terms [additive x additive (i), additive x dominance (j), and dominance x dominance (l)] were computed (Mather and Jinks 1977). The genetic parameters [m, (d), (h), (i), (j), and (l)] were tested for significance using an unpaired t-test.

Environmental variance ({sigma}2 E) and broad sense heritability (Hb2) were estimated using the following formula (Ito and Brewbaker, 1991).



Where

{sigma}2 E = 1/4({sigma}2 P1 + {sigma}2 P2 + 2 {sigma}2 F1),
{sigma}2 F2 = variance of the F2 family,
{sigma}2 P1 = variance of the yellow seed color parent,
{sigma}2 P2 = variance of the black seed color parent, and
{sigma}2 F1 = variance of the F1 family.

The number of effective factors (k) involved in seed color inheritance was estimated by the following method (Burton, 1951):



Where

h = (F1 - P2) / (P1 - P2),
D = P1 - P2,
k = minimum number of effective factors,
P1 = mean of the yellow seed color parent,
P2 = mean of the black seed color parent,
F1 = mean of the F1 population,
F2 = mean of the F2 population,
{sigma}2 F1 = variance of the F1 population, and
{sigma}2 F2 = variance of the F2 population.


   Results and Discussion
Top
 Abstract
 Materials and Methods
 Results and Discussion
References
 
The F1 hybrid of C. pubescens and C. eximium had black seed color, indicating black seed color is dominant over yellow (Figure 1). The average seed color value (L) for each population is presented in Table 1. Seed color of the F2 plants ranged from black to yellow with different intensities (Figure 1) and were difficult to categorize into distinct classes. The segregation pattern did not fit either a single- or two-gene model, but showed continuous variation indicating a quantitative mode of inheritance. The seed color of the backcross families had a tendency to shift towards the recurrent parents (Figure 2).



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  		Figure 1. (upper figure). Seed color for parental lines [C. pubescens, P2, (A) and C. eximium, P1, (B)], F1 (C), and F2 (D–I)

 
The joint scaling test with three parameters model showed a significant {chi}2 value indicating the additive-dominance model is not sufficient to explain the variation in the population for seed color (Table 2). Genetic estimates for six parameters model are presented in Table 3. Significant effect of additive (d), dominance (h), and additive x additive (i) interactions were observed. The negative additive x additive (i) estimate shows the gene pairs responsible for seed color are in dispersive form (Mather and Jinks 1977). This means both parents contributed the genes for seed color.


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  		Table 2.. Joint scaling test and estimates (± SE) with three parameters model using six families mean for seed color in C. eximum x C. pubescens hybridization.

 

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  		Table 3.. Joint scaling test and estimates (± SE) with six parameters model using six families mean for seed color in C. eximium x C. pubescens hybridization.

 
The broad sense heritability for seed color inheritance was 0.60. The minimum number of effective factors involved in seed color inheritance in this study was 2.8. Mather (1979) indicated that when the gene pairs responsible for the trait are in dispersive form, the number of effective factors estimate would be low. Therefore, due to the presence of a dispersive form of genes in this study, the actual number of genes controlling seed color could be higher than three in Capsicum.

The inheritance of seed color in a number of crops has been studied. For some crops seed color is under single genetic control. For example, in flax [Linum usitatissimum L.] (Saeidi and Rowland 1997), watermelon [Citrullus lantus (Thunb.) Matsum. & Nakai] (McKay 1936), lettuce [Lactuca sativa L] (Durst 1930) and Brassica carinata A. Braun (Getinet et al. 1987), a single gene controls seed color. In contrast, Vandenberg and Slinkard (1990) reported that two independent loci control seed coat color in lentil [Lens culinaris ssp. culinaris (Medik.) Williams]. Swenson (1942) also reported in biennial white sweet clover (Melilotus alba) that two independent pairs of genes controls seed color. On the other hand, McCallum et al. (1997) studied the quantitative inheritance of green seed color in field pea (Pisum sativum L.) and reported that four genomic regions were affecting seed color. Our investigation revealed that seed color inheritance in Capsicum is controlled by at least three genes.



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  		Figure 2. (lower figure). Seed color for parental lines [C. pubescens, P2, (A) and C. eximium, P1, (B)], F1 (C), backcrossed to C. pubescens (D and E), and backcrossed to C. eximium (F and G)

 

   Acknowledgments
 
The authors thank Danise Coon, the Chile Pepper Institute, New Mexico State University, for photographic assistance and Drs. Eric Votava and Chris Cramer, Agronomy and Horticulture Department, New Mexico State University, for reviewing the manuscript. A contribution of New Mexico Agriculture Experiment Station, New Mexico State University, Las Cruces.


   Footnotes
 
Corresponding Editor: Brandon Gaut Back

Received October 21, 2002
Accepted March 28, 2003


   References
Top
 Abstract
 Materials and Methods
 Results and Discussion
 References
 

    Burton GW, 1951. Quantitative inheritance in pearl millet (Pennisetum glaucum). Agron J. 43:409-417.[Free Full Text]

    Durst CE, 1930. Inheritance in lettuce. Ill Agric Exp Stn Bull 356.

    Getinet A, Rakow G, Downey RK, 1987. Seed color inheritance in Brassica carinata A. Braun, cultivar S-67. Plant Breeding. 99:80-82.[CrossRef]

    Ito GM, Brewbaker JL, 1991. Genetic analysis of pericarp thickness in progenies of eight corn hybrids. J Amer Soc Hort Sci. 116:1072-1077.

    Mather K, 1979. Historical overview: quantitative variation and polygenic systems. In: Quantitative genetic variation (Thompson JN Jr and Thody JM. eds). New York: Academic Press; 5–34.

    Mather K, Jinks JL, 1977. Introduction to biometrical genetics. London: Chapman and Hall.

    McCallum J, Timmerman-Vaughan G, Frew T, Russell A, 1997. Biochemical and genetic linkage analysis of green seed color in field pea. J Amer Soc Hort Sci. 122:218-225.

    McKay JW, 1936. Factor interaction in Citrullus. J Hered. 27:110-112.[Free Full Text]

    Rowe KE, Alexander WL, 1980. Computations for estimating the genetic parameters in joint-scaling tests. Crop Sci. 20:109-110.[Abstract/Free Full Text]

    Saeidi G, Rowland GG, 1997. The inheritance of variegated seed color and palmitic acid in flax. J Hered. 88:466-468.[Abstract/Free Full Text]

    SAS Inst. Inc.,, 1999. SAS software release 8.1. Cary, NC: SAS Inst., Inc.

    Swenson SP, 1942. Inheritance of seed color in biennial white sweet clover, Mellitus alba. J Amer Soc Agron. 34:452-459.

    Tong N, Bosland PW, 2003. Observations an interspecific compatibility and meiotic chromosome behavior of Capsicum bufforum and C. lanceolatum. Genet Resour Crop Evol 50:193–199.

    Vandenberg A, Slinkard AE, 1990. Genetics of seed coat and pattern in lentil. J Hered. 81:484-488.[Free Full Text]


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