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[S.sup.h] and [S.sub.c]--two complementary dominant genes that control self-compatibility in buckwheat.

THE GENUS Fagopyrum is composed of 18 species (Ohsako et al., 2001) and contains both diploid (2n = 2x = 16) and tetraploid (2n = 4x = 32) forms, with two breeding systems, self-incompatibility and self-compatibility. The predominant system in Fagopyrum, self-incompatibility, was first discovered by Darwin (1877) and belongs to the sporophytic system (Dahlgren, 1922) expressed in the pin and thrum flower type. The pin flower has long styles with short stamens, whereas the thrum flower has the opposite arrangement with short styles and long stamens. The two flower types are produced on separate plants. Fertilization can only occur between pin and thrum flowers, and pollination is accomplished by insects and wind. The prevention of selling occurs as the result of the inability of selfed pollen to promote seed set, and not due to the architecture of the flower (Nettancourt, 1977). The inhibition of pollen tubes in an incompatible style can occur one to several hours after pollen germination (Nettancourt, 1977) and the expression of self-incompatibility is so strong that almost all of the pollen tubes failed to reach the base of the style (Adachi, 1990), Self-compatibility is expressed by homostylic flowers in Fagopyrum, with styles and stamens of the same height. It is believed that homostyly in this genus was derived from the breakdown of heterostyly as a general trend in evolution (Yasui et al., 1998).

Common buckwheat, the cultivated species, is a self-incompatible diploid species. It has been widely accepted that self-incompatibility in F. esculentum is controlled by one gene (Althausen, 1908; Dahlgren, 1922; Eghis, 1925; Garber and Quisenberry, 1927; Saknarov, 1946). The genetic model represents the thrum genotype as Ss and ss for pin flowers. A 1:1 ratio is produced in the progeny from crosses between thrum and pin flowers. A supergene complex has been proposed by Sharma and Boyes (1961), consisting of five subgenes corresponding to stylar incompatibility, pollen incompatibility, style length, pollen size, and stamen height. Fesenko (1985, 1986) has suggested a similar model with three subgenes controlling style length, stamen length, and pollen size. However, this model has not been confirmed in view of the report by Sharma and Boyes (1961) in which an irradiation treatment produced a thrum plant with branches bearing both pin and homostylic flowers, inferring that one of subgenes had been mutated. There is the possibility that other genes in the irradiated buckwheat were affected by the irradiation treatment (Nettancourt, 1977).

Self-incompatibility in F. esculentum, expressed in the heterostylic flowers, has been identified as one of major causes related to yield instability in buckwheat (Ruszkowski, 1990; Campbell, 1997). The self-compatible wild species F. homotropicum is the most closely related species to F. esculentum in the Fagropyrum genus (Yasui and Ohnishi, 1998) and is one possible source of the self-compatibility character for interspecific introgression into F. esculentum.

Fagopyrum homotropicum has both diploid and tetraploid forms, collected by Ohnishi (1995) in southwestern China. This species has several desirable characters in addition to its self-compatibility, including high seed set and frost tolerance, and has been hybridized with F. esculentum, with the objective of creating a new self-pollinated buckwheat (Campbell, 1995; Wang and Campbell, 1998; Woo et al., 1999). It is important to buckwheat improvement programs that the inheritance and the interaction of the two breeding systems in the interspecific crosses is understood. Since the two breeding systems exist in the two species, segregation analysis based on the interspecific hybrids would be the first step to approach the problem. The Mendelian segregation ratio is frequently aberrant in the progeny of an interspecific hybrid between a cultivated species and a wild relative (Zamir and Tadmor, 1986). However, this problem could be reduced in the interspecific hybrid between F. esculentum and F. homotropicum as the two species are closely related (Yasui and Ohnishi, 1998) and the fertile interspecific hybrids in the previous reports (Campbell, 1995; Wang and Campbell, 1998; and Woo et al., 1999) were produced due to normal cell division at meiosis.

Based on a cross between F. homotropicum diploid and F. esculentum thrum, Woo et al. (1999) proposed that self-compatibility in F. homotropicum is controlled by the same S gene locus as in F. esculentum and designated [S.sup.h] as the self-compatibility S allele. The relationship between the self-compatibility and self-incompatibility alleles is described as S > [S.sup.h] > s with S the self-incompatible (thrum) allele dominant to both [S.sup.h] for self-compatible (homostyly) and to s, the self-incompatible (pin) allele. The limitation to this study was the small population sizes, as each [F.sub.2] population contained only 10 to 14 plants, and the occurrence of one pin plant out of 11 plants in the B[C.sub.1][F.sub.1] progeny of [F.sub.1] thrum plants crossed with pin plants of F. esculentum, which could not be explained by the model.

Fesenko et al. (1998) obtained three types of flowers in a B[C.sub.1][F.sub.1] progeny of randomly mated [F.sub.1] thrum plants with F. esculentum pin. These results suggest that the homostyly of F. homotropicum is not controlled by the same alleles as the heterostyly in F. esculentum, but they did not propose a different model from Woo et al. (1999). In addition, using the self-incompatible pin type of F. esculentum in interspecific crosses is better than using the self-incompatible thrum type, as the thrum type carries the alleles of both pin and self-compatible homostyly. Use of the only the pin type plants in crosses with homostylic plants eliminates the thrum phenotype and allows the selection of homostyly from pin.

There was no genetic study conducted previously based on the cross between F. esculentum pin and F. homotropicum homostyly. Furthermore, new collections of F. homotropicum are now available that exhibit genetic diversity for morphology and allozyme patterns (Ohnishi and Asano, 1999). The interspecific hybrids derived from these new collections would not only be valuable sources of increased genetic variability for breeding programs, but could also help in the understanding of the inheritance of desirable traits such as self-compatibility.

The objectives of this study were: (i) to study the inheritance of self-compatibility in F. homotropicum through hybridization between F. homotropicum diploid and F. esculentum pin type using new accessions of F. homotropicum; and (ii) to study the genetic relationship between self-compatibility in F. homotropicum and self-incompatibility in F. esculentum. A better understanding of the genetic relationship is important for developing successful breeding strategies for buckwheat.


The two diploid (2n = 2x = 16) accessions of F. homotropicum, K980854 and K980855, were new collections and distinct from the accessions used in the previous studies (Fesenko et al., 1998; Woo et al., 1999). The three diploid (2n = 2x = 16) F. esculentum elite lines were BM940364, BM94999.1, and X98088. The homostylic flower of the two F. homotropicum accessions was homozygous as self-incompatible heterostylic flowers (pin or thrum) have never been found in the population. The F. esculentum population is heterogeneous with a 1:1 ratio of pin and thrum plants, but there were no self-pollinated homostylic flowers found in the population. The pin type of F. esculentum was used for the crosses. Fagopyrum homotropicum was used as the female parent in three of four crosses (K980854 x BM94999.1, K980854 x BM940364, and K980855 x BM940364), and as the male in one cross (X98088 x K980854) (Table 1). The self-compatible homostylic flowers of F. homotropicum were emasculated one day before crossing. No emasculation was required when a self-incompatible F. esculentum pin plant was the female parent. Pollination was performed in the morning between 9:00 and 11:30 AM and the crossed flowers were bagged for two days following pollination. In this study, the crosses were made in only one direction as there was no maternal effect on flower morphology including style length in our previous hybridization between F. esculentum and F. homotropicum (Wang et al., 2002).

Ovule Rescue

Approximately 10 d after pollination, before any seed abortion occurred, the enlarged ovaries from the crosses were harvested. The ovaries were sterilized in 70% ethanol for 30 s and in 10% commercial bleach for 50 s and then rinsed five times in distilled sterilized water in a laminar flow hood. The ovules were then carefully excised from the ovaries and plated (1 ovule per tube) in test tubes (25 by 100 mm) which contained 10 mL MS medium (Murashige and Skoog, 1962) modified with the addition of 2 mg [L.sup.-1] zeatin, 10 mg [L.sup.-1] L-tyrosine, 10 mg [L.sup.-1] L-arginine, and 3% sucrose and solidified by 0.7% agar.

The ovule cultures were maintained at 22[degrees]C under continuous light (40 [micro]mol [m.sup.-2] [s.sup.-1]). The embryos emerged from the ovules in approximately 1 to 2 wk. Some embryos formed normal plantlets which were transferred into half-strength MS medium for further growth. Other embryos produced plantlets with poorly developed shoots and roots and these plantlets were transferred into modified MS medium, as described by Samimy et al. (1996), for shoot induction. When the shoots grew to approximately 2 cm in height, plantlets were transferred onto half-strength MS medium for rooting. Fully developed plantlets were transplanted into a soil mixture with a ratio of 2:2:1 soil/perlite/peat moss in 12.7-cm (5-inch) pots (one plant per pot). These plants were covered by an inverted 10.2-cm (4-inch) pot for one day to maintain humidity during plant hardening.

Population Development and Analysis

[F.sub.1] hybrid plants were backcrossed with F. esculentum pin plants in pairwise crosses between single plants in each cross. Although a number of backcrosses were attempted for all crosses, only two backcrosses used for analysis in this study, because seed set was low. The tiny buckwheat flowers make emasculation and pollination laborious and production of large amounts of seed difficult. In addition, the interspecific barrier was still present in the first backcross. The two backcrosses which produced more than 40 seeds were used in segregation analysis. Eight [F.sub.2] populations derived from selfing single [F.sub.1] plants were produced with a population size of 80 to 117 plants for each population. Due to insufficient seed set in the [F.sub.2] single plants and the limited greenhouse space, only three of the eight [F.sub.2] populations were used for the [F.sub.2] progeny. These three populations were chosen because they represented the two types of segregation patterns in the [F.sub.2]. The populations were scored for homostylic and pin flowers to determine the segregation of self-compatibility and self-incompatibility, respectively. Chi-square analysis was used to test the goodness of fit to the expected gene segregation ratios.

All plants were grown in a greenhouse which was maintained at a minimum temperature of 22[degrees]C with natural light supplemented by high pressure sodium lamps to give a 16-h day and 8-h night photoperiod.


Segregation of [F.sub.1], [F.sub.2], and B[C.sub.1][F.sub.1]

Fifty-two [F.sub.1] hybrids were obtained from the four crosses through ovule rescue in vitro (Table 1). All [F.sub.1] plants were self-compatible with homostylic flowers, indicating that self-compatible homostyly is dominant to self-incompatible heterostylic pin.

Of the eight [F.sub.2] populations, five populations fit a 3:1 homostyly/pin ratio and did not fit a 9:7 ratio, while the remaining three populations fit a 9:7 ratio but did not fit a 3:1 ratio (Table 2). The three [F.sub.2] populations with a 3:1 ratio also fit a 13:3 ratio indicating a epistatic interaction, but the other two populations with a 3:1 ratio did not fit a 13:3 ratio ([chi square] = 6.5 and 10.76).

One B[C.sub.1][F.sub.1] population segregated in a 1:1 ratio (Table 2), confirming the corresponding 3:1 ratio in the [F.sub.2]. The other B[C.sub.1][F.sub.1] from the cross which produced the 9:7 ratio in the [F.sub.2] fit a 3:5 ratio ([chi square] = 0.05) more closely than a 1:1 ratio ([chi square] = 2.17) (Table 2). The 3:5 ratio supports a two-gene model.

The population sizes have been increased in this study with 80 to 117 plants for each [F.sub.2] population and approximately 50 plants in the two backcrosses (Table 2) compared with the previous study (Woo et al., 1999) where only 10 to 14 plants in each F2 population and 11 plants in one backcross population were used for analysis.

[F.sub.3] Progeny Testing

Fourteen [F.sub.3] lines derived from homostylic plants in three [F.sub.2] populations were used for progeny testing (Table 3). In the two [F.sub.2] families which segregated 3:1, the [F.sub.3] ratios were 1:0 and 3:1 homostyly to pin. Three segregation ratios, 1:0, 3:1, and 9:7, were produced in the [F.sub.3] progeny from the [F.sub.2] family which segregated in a 9:7 ratio (Table 3).

Genotypes of F. homotropicum and F. esculentum

These results indicated that two genes with complementary interaction were controlling the expression of self-compatibility. A single gene model could not explain three of the eight [F.sub.2] populations' segregation ratios. The one and two gene segregation ratios could be caused by heterogeneity in the cross-pollinating F. esculentum accessions.

We propose a two-gene model with three alleles at the first locus as described by Woo et al. (1999). The homostylic self-compatible allele was designated as [S.sup.h] in the one-gene model proposed by Woo et al. (1999), where the relationships between the alleles which produce the three types of flowers, were described as S > [S.sup.h] > s, that is, the thrum self-incompatible S allele was dominant to the homostylic self-compatible [S.sup.h] allele and [S.sup.h] dominant to the pin self-incompatible s allele. The second locus has two alleles, [S.sub.c] a self-compatibility allele dominant to [s.sub.c], a self-incompatibility allele. The two alleles [S.sup.h] and [S.sup.h] confer the self-compatible (homostyly) phenotype and s and [s.sub.c] represent the two alleles for the self-incompatible (pin) genotypes.

The proposed genotype for F. homotropicum is [S.sup.h][S.sup.h][S.sub.c][S.sub.c] as F. homotropicum is pure-breeding for homostyly and heterozygosity at either loci would result in the production of homozygous recessive genotypes and the expression of a pin phenotype. Fagopyrum esculentum pin and thrum plants, on the other hand, have more than one possible genotype. At the first locus, the proposed genotype for pin is homozygous recessive ss and for thrum is Ss, resulting in a 1:1 ratio between the two types of flowers in the progeny with no homostyly phenotypes produced in the species. The pin and thrum phenotypes may be homozygous or heterozygous at the second locus. Therefore, the proposed genotypes for F. esculentum pin plants are ss[S.sub.c][S.sub.c], ss[S.sub.c][s.sub.c], or ss[s.sub.c][s.sub.c] and for F. esculentum thrum plants are Ss[S.sub.c][S.sub.c], Ss[S.sub.c][s.sub.c], or Ss[s.sub.c][s.sub.c].

Using the proposed model to predict the genotypes of the three flower types in the two parental species, it is possible to explain the observed segregation ratios in the [F.sub.1], [F.sub.2], [F.sub.3], and B[C.sub.1][F.sub.1] produced in the crosses between the two species (Tables 2 and 3), including the crosses between F. homotropicum and F. esculentum pin (Fig. 1) and between F. homotropicum and F. esculentum thrum (Fig. 2). The genotype [S.sup.h]s[S.sub.c][S.sub.c] in the [F.sub.1] would result in a 3:1 ratio in the [F.sub.2], while the genotype [S.sup.h]s [S.sub.c][s.sub.c] in the [F.sub.1] would produce a 9:7 ratio in the [F.sub.2]. The [F.sub.3] progeny segregation ratios of 1:0 and 3:1 supported the occurrence of the two possible [F.sub.2] genotypes [S.sup.h][S.sup.h][S.sub.c][S.sub.c] and [S.sup.h]s[S.sub.c][S.sub.c]. The three segregation ratios in the [F.sub.3] from the 9:7 segregating [F.sub.2] population indicated that the genotypes of the [F.sub.2] homostylic plants were [S.sup.h][S.sup.h][S.sub.c][S.sub.c], [S.sup.h]s[S.sub.c][S.sub.c], and [S.sup.h]s[S.sub.c][S.sub.c].


In the cross between F. homotropicum and F. esculentum thrum (Fig. 2), a 9:7 ratio in the [F.sub.2] and the ratio of 4:3:1 (thrum/homostyly/pin) or 2:2:1 (thrum/homostyly/ pin) in the B[C.sub.1][F.sub.1] both support the existence of the second gene. The three types of flowers produced in the B[C.sub.1][F.sub.1] agree with the previous reports (Fesenko et al., 1998; Woo et al., 1999) which could not be explained by a one-gene model. The ratio of 4:3:1 fits the B[C.sub.1][F.sub.1] segregation of 5:5:1 thrum/homostyly/pin obtained by Woo et al. (1999) and provides an explanation for the occurrence of one pin plant which could not be explained by their single-gene model.

The proposed two-gene model therefore explains the controversial results in the previous reports (Fesenko et al., 1998; Woo et al., 1999). More support for this model has been provided by observations in our ongoing breeding program. With further backcrossing and crossing among selected progeny, all four genotypes, [S.sup.h][S.sup.h][S.sub.c][S.sub.c], [S.sup.h]s[S.sub.c][S.sub.c], [S.sup.h][S.sup.h][S.sub.c][s.sub.c], and [S.sup.h]s[S.sub.c][s.sub.c], for homostyly and five genotypes, [S.sup.h][S.sup.h][s.sub.c][s.sub.c], [S.sup.h]s[s.sub.c][s.sub.c], ss[S.sub.c][S.sub.c] and ss[S.sub.c][s.sub.c], and ss[s.sub.c][s.sub.c], for pin were produced. If all the possible genotypes for pin are crossed with all the genotypes for homostyly, the [F.sub.1] progeny should segregate in either a 1:0 (ss x [S.sup.h][S.sup.h]) or a 1:1 (ss x [S.sup.h]s) in the one-gene model, but five possible segregation ratios, 1:0, 1:1, 3:1, 1:3, and 3:5, could be produced in the two-gene model (Table 4). Even though it is not easy to separate the ratio of 3:5 from the ratio of 1:1, the ratios 3:1 and 1:3 can be easily separated from the 1:1 ratio statistically to differentiate between the two models. The ratios 3:1, 1:3, and 3:5 in the [F.sub.1] progeny from the crosses between pin and homostyly are the best support for the existence of the second gene [S.sub.c] or at least that two genes control the trait. In total, five F. homotropicurn accessions have been used for interspecific hybridization in our breeding program, including one accession used in the previous report (Woo et al., 1999). All five segregation patterns have been observed in the backcrosses between the hybrids and F. esculentum pin or intercrosses among the progeny of pin and homostylic plants (data not shown). To verify the proposed model, more powerful evidence such as molecular analysis would be required.

Further Study

The present study proposes that two types of segregation ratios, 3:1 and 9:7, in the [F.sub.2] correspond to the expected genotypes for one and two heterozygous gene(s) in the [F.sub.1] population. As we are proposing that the first locus of F. esculentum is fixed as either ss (pin) or Ss (thrum), a segregation ratio of 3:1 in the [F.sub.2] would imply that the first gene is heterozygous in the population (Fig. 1). On the other hand, if the [F.sub.2] has a segregation ratio of 9:7, two types of heterozygous homostylic plants could be expected among the progeny, that is, heterozygosity at both loci or heterozygosity at one of the two loci. Aii et al. (1999) developed a codominant sequence characterized amplified region (SCAR) marker for self-compatibility from an interspecific hybrid between F. homotropicum and F. esculentum pin. This marker may be linked with the first gene, as the [F.sub.2] segregation ratio obtained was 3:1. Therefore, a marker could be developed for the second gene in a population containing the two heterozygous genes ([F.sub.2] segregation ratio of 9:7) using the codominant marker of Aii et al. (1999) to distinguish the first gene from the second gene.

Application to buckwheat breeding

Introgression of self-compatibility from F. homotropicum to F. esculentum involves crosses between the homostylic and heterostylic species. In the present study, only heterostylic pin flowers were used in the interspecific crosses. Because of the differences between pin and thrum in morphology and genetics, utilizing the pin plant has advantages over thrum plants in a crop improvement program. Thrum flowers are more difficult to cross than pin flowers as the styles of thrum are imbedded among the stamens. It is also more difficult to distinguish homostyly from thrum in the small buckwheat flowers (3- to 4-mm diameter). In addition, interspecific crosses between thrum and homostylic plants could produce progeny with all three types of flowers (Fig. 2). The use of only pin type plants in crosses with homostylic plants eliminates the thrum phenotype and facilitates the selection of homostyly from pin as the style of the pin flower is conspicuous above the stamens.
Table 1. Development of interspecific hybrids from four crosses
between two accessions of F. homotropicum (2n = 2x = 16)
K980854 and K980855 and three accessions of F. esculentum
pin (2n = 2x = 16) BM940364, BM94999.1, and X98088.

                                     Flowers         Ovules
Cross ([dagger])                    pollinated       rescued   Hybrids


K980854 (F. h) x BM940364 (F. e)     582               71        29
K980854 (F. h) x BM94999.1 (F. e)     NA ([double
                                         dagger])       1         1
X98088 (F. e) x K980854 (F. h)        40                2         2
K980855(F. h) x BM940364 (F. e)      298               62        20
Total                                940              136        52

([dagger]) F. h, F. homotropicum; F. e, F. esculentum.

([double dagger]) NA, data not recorded.

Table 2. Segregation ratios (homostyly/pin) of the [F.sub.2] and the
B[C.sub.1][F.sub.1] progeny in interspecific hybrids between
F. homotropicum diploid and F. esculentum pin.

Cross                 Generation             ratio     Total   Observed

K980854 x BM94999.1   [F.sub.2]               3:1       117      95:22
X98088 x K980854      [F.sub.2]               3:1        82      69:13
K980854 x BM940364    [F.sub.2]               9:7        80      53:30
                      [F.sub.2]               3:1       104      82:22
                      [F.sub.2]               3:1       114      82:32
                      B[C.sub.1][F.sub.1]     1:1        48      27:21
K980855 x BM940364    [F.sub.2]               3:1        86      58:28
                      [F.sub.2]               9:7        84      51:33
                      [F.sub.2]               9:7        98      58:40
                      B[C.sub.1][F.sub.1]     3:5        46      18:28

                                               [chi square]


Cross                 Generation             3:1         9:7

K980854 x BM94999.1   [F.sub.2]              2.40       29.59 **
X98088 x K980854      [F.sub.2]              3.66       25.93 **
K980854 x BM940364    [F.sub.2]              5.50 *      1.95
                      [F.sub.2]              0.82       21.58 **
                      [F.sub.2]              0.57       11.39 **
K980855 x BM940364    [F.sub.2]              2.62        4.38 *
                      [F.sub.2]              9.14 **     0.68
                      [F.sub.2]             13.07 **     0.34

                                              [chi square]


Cross                 Generation            1:1      3:5        1:3

K980854 x BM94999.1   [F.sub.2]
X98088 x K980854      [F.sub.2]
K980854 x BM940364    [F.sub.2]
                      B[C.sub.1][F.sub.1]   0.75    7.20 **    25.00 **
K980855 x BM940364    [F.sub.2]
                      B[C.sub.1][F.sub.1]   2.17    0.05        4.90 **

* Indicates significance at df = 1, P = 0.05, [chi square]
[greater than or equal to] 3.84.

** Indicates significance at df = 1, P = 0.01, [chi square]
[greater than or equal to] 6.64.

Table 3. Segregation ratios (homostyly/pin) of [F.sub.3] lines derived
from [F.sub.2] homostylic plants in three [F.sub.2] populations of
interspecific hybrids between F. homotropicum diploid and
F. esculentum pin.

                         [F.sub.2]       [F.sub.3]

Cross                      Ratio     Total    Observed

X98088 x K980854            3:1       76        56:20
                                      38        31:7
                                      26        26:0
                                      42        30:12
K980854 x BM94999.1         3:1       22        17:5
                                      20        20:0
                                      24        24:0
                                      37        32:5
K980855 x BM940364          9:7       26        26:0
                                      49        35:14
                                      23        10:13
                                      30        15:15
                                      29        29:0
                                      42        31:11

                               [chi square]

Cross                     1:0      3:1        9:7      Expected     P

X98088 x K980854          --      0.07       9.39 **      3:1     >0.80
                          --      0.88       9.91 **      3:1     >0.60
                           0       --         --          1:0      1.00
                          --      0.29       3.93 *       3:1     >0.60
K980854 x BM94999.1       --      0.06       3.95 *       3:1     >0.80
                           0       --         --          1:0      1.00
                           0       --         --          1:0      1.00
                          --      2.60      13.75 **      3:1     >0.10
K980855 x BM940364         0       --         --          1:0      1.00
                          --      0.33       4.59 *       3:1      0.60
                          --     12.19 **    1.52         9:7      0.20
                          --     10.00 **    0.48         9:7      0.50
                           0       --         --          1:0      1.00
                          --      0.03       5.26 *       3:1     >0.80

* Indicates significance at df = 1, P = 0.05, [chi square]
[greater than or equal to] 3.84.

** Indicates significance at df = 1, P = 0.01, [chi square]
[greater than or equal to] 6.64.

Table 4. Possible segregation patterns (homostyly/pin) in the [F.sub.1]
progenies from pin x homostyly crosses in buckwheat.

                           Genotypes of the homostyly parents

Genotypes of the        [S.sup.h][S.sup.h]     [S.sup.h][S.sup.h]
pin parents             [S.sub.c][S.sub.c]     [S.sub.c][s.sub.c]

  [s.sub.c][s.sub.c]           1:0                    1:1
  [s.sub.c]                    1:0                    1:1
[ssS.sub.c][S.sub.c]           1:0                    1:0
[ssS.sub.c][s.sub.c]           1:0                    3:1
ssscsc                         1:0                    1:1

                           Genotypes of the homostyly parents

Genotypes of the       [S.sup.h][sS.sub.c]    [S.sup.h][sS.sub.c]
pin parents                [S.sub.c]               [s.sub.c]

  [s.sub.c][s.sub.c]           1:0                    1:1
  [s.sub.c]                    3:1                    3:5
[ssS.sub.c][S.sub.c]           1:1                    1:1
[ssS.sub.c][s.sub.c]           1:1                    3:5
ssscsc                         1:1                    1:3


The authors would like to thank Dr. Y. Yasui for his advice in the gene notation.


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Yingjie Wang, Rachael Scarth, * and Clayton Campbell

Y.J. Wang and C. Campbell, Kade Research Ltd, Research Centre, Unit 100-101 Route 100, Morden, MB, Canada R6M 1Y5; R. Scarth, Dep. of Plant Science, Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2. Received 3 Nov. 2003. * Corresponding author (Rachael_
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Author:Wang, Yingjie; Scarth, Rachael; Campbell, Clayton
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Date:Jul 1, 2005
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