Euphytica 59: 231-234, 1992. (~) 1992 Kluwer Academic Publishers. Printed in the Netherlands.

Short communication

Inheritance of seedling colour in faba bean (Viciafaba L.)

P.L.J. Metz, A. van Norel, A.A.M. Buiel 1 & J.P.F.G. Helsper DLO-Centre for Plant Breeding and Reproduction Research (CPRO-DLO), P.O. Box 16, 6700 AA Wageningen, The Netherlands; 1present address: ICRISAT Legumes, Virology Dept., Patancheru P.O. Andhra Pradesh 502324, India

Received 6 January 1992; accepted 27 February 1992

Key words: Faba bean, inheritance, outcrossing, seedling colour, Vicia faba

Summary

The inheritance of purple seedling colour was studied, in relation to the genetic control of flower colour. It was found that purple seedling colour is likely to be controlled by a single gene and that the trait is dominant over green seedling colour. White flowering prohibited the expression of the purple seedling colour, and is therefore thought to be epistatic.

This character can be used to estimate rate of outcrossing in breeding programmes, as well as contribute to our knowledge of the biosynthesis of plant pigments and secondary metabolites such as tannins.

Introduction

Two marker traits have been widely used to mea- sure outcrossing rates in faba bean (Viciafaba L.), namely flower and seed coat colour (de Vries, 1978; Link, 1988). Coloured flowering is dominant over white flowering and a black testa is dominant over a brown one. A disadvantage of these traits is that the assessment is time and space consuming. The assessment of flower colour might take only three weeks, since a melanin spot on the stipulae can be used as an early marker for coloured flower- ing (Picard, 1976). However, it can be used only to a limited extent because many of the present day Vicia faba varieties and breeding lines are coloured flowering. The assessment of seed coat colour re- quires an entire generation, because the seed coat, being maternal tissue, can only be observed after harvest.

Flower colour has been shown to be dominant and controlled by one or two genes (Sj6din, 1971; Picard, 1976; Cabrera, 1988; Cabrera & Martin,

1989a), but also a recessive inheritance has been described (Goyal, 1965). Goyal (1965) also found that anthocyanin pigmentation in the base of the stem in faba bean was recessive to the allele for no pigmentation. Sj6din (1962, 1971), however, has described a red stem (Rs), a seedling character, which was dominant to the normal green colour. The red colour is purportedly due to the presence of anthocyanins and melanin (Rowlands & Corner, 1962), and the intensity slowly fades during plant development. A trait such as seedling stem colour can be assessed already at ten days after sowing on small seedling plants. The trait is not widely pre- sent in present day faba bean varieties.

A correlation between flower colour, seedling colour and tannin content may be expected, be- cause these traits all depend on the biosynthesis of anthocyanins or its derivatives (Hahlbrock, 1981). For flower colour the positive correlation with the presence of tannin in the seed coat has already been established (Bond, 1976; Crofts et al., 1980; Cabre- ra & Martin, 1989b). Similarly, a red-coloured,

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putatively anthocyanin-containing, seedling might also be used as an early marker for tannin content.

We found a similar characteristic as described by Sj6din (1962, 1971), purple seedling colour, in a Rumanian landrace of Vicia faba, 4717 Populatia locala, obtained from the genebank at Braunsch- weig, Germany. The objective of the present study was to establish the genetic control of this trait, and also its correlation with flower colour.

Materials and methods

For studies on the inheritance of seedling colour inbred material of Minica 1.1, Primo and (Stay- green × SVP C), which all have white flowers and green seedlings, and of Liineburger with coloured flowers and green seedlings, were crossed with a coloured flowered genotype with anthocyanin-con- taining (purple) seedlings, 4717 Populatia locala. The Ffs were grown in isolation to prevent out- crossing. In the F2 generation the segregation for seedling colour was studied.

To study the genetic interaction between seed- ling colour and flower colour a white flowered genotype selected from a cross between cv Rowena and cv Herz Freya (R x H) and two near-isogenic lines differing for flower colour, obtained from open-pollinated Mansholts wierboon (MaW (white), MaC (coloured)) were used. All above- mentioned genotypes had green seedlings and were crossed with 4717 Populatia locala. A melanin spot on the stipulae was used as an early marker for coloured flowering. All F1 plants were grown in isolation to maturity. The F2 phenotypic segrega-

tion for seedling colour and the presence or ab- sence of a melanin spot was determined.

From the emergence to scoring for seedling col- our the seedlings were kept in the dark, since with etiolated plants the contrast purple versus not-pur- ple was more pronounced as a consequence of the absence of the green background colour. To assess for the presence or absence of a melanin spot on the stipulae, plants were further grown in the light.

The distribution of phenotypic classes has been tested for goodness-of-fit. P-values were calculated using ~ { (observed - expected)2/expected} as a test criterion.

Results

Table 1 shows the F 2 segregation of purple and green seedling colour for several crosses. Except for the cross Populatia locala × Lfineburger, the results suggest a monogenic inheritance with pur- ple seedling colour being dominant. All F1 plants had purple seedlings and a melanin spot on their stipulae. No differences in seedling colour between putative homozygous and heterozygous genotypes could be observed.

Table 2 shows the F 2 segregation for seedling colour, and a melanin spot on the stipulae. The cross between the coloured flowered partner of the near-isogenic, open-pollinated 'Mansholts wier- boon' pair and Populatia locala gave a F 2 with melanin spot, as expected. In similar crosses but with a white genotype, the phenotypic combina- tions melanin spot/purple seedlings, no melanin spot/green seedlings and melanin spot/green seed-

Table 1. Fz segregation for seedling colour of crosses with Populatia locala (Pop, loc.), carrier of the purple seedling colour

Cross Seedling colour X2(3 : 1)

purple green

Minica 1.1 × Pop. loc. 245 Primo x Pop. loc. 217 (Staygreen × SVP C)× Pop. loc. 63 Pop. loc. × Lfineburger 114 Total 639

62 0.10> P> 0.05 71 0.90 > P > 0.75 29 0.20> P> 0.10 53 0.05 > P > 0.025

215 0.95> P> 0.90

lings were found, but not the combination no mela- nin spot/purple seedlings. The observed number of plants in each class strongly suggest a ratio of 9 : 4 : 3 for the first three classes respectively (Table 2). Table 2 also shows that the characters melanin spot on the stipulae and seedling colour separately, seg- regate as single gene traits.

Discussion

The results of this study strongly support a mono- genic inheritance of seedling colour. Since this trait appears to be simply inherited and expresses itself at an early growth stage, it is likely to be a very suitable marker to assay outcrossing rates. Our results are in agreement with those of Sj6din (1971) and are similar to those of Yadav (1987), who stud- ied a similar morphological character in mungbean (Vigna radiata (L.) Wilczek). These studies are in contrast to those of Goyal (1965), whose results would indicate the opposite, i.e. an unpigmented stem base being monogenic dominant over a pig- mented one.

Sj6din (1962, 1971), who obtained red-stemmed seedlings (Rs) after mutagenic treatments of the variety 'Sval6f Primus' and Goyal (1965) mention a strong anthocyanin colouration in only the lower parts of the stem. In our experiments, the purple- red colour was also observed in the first leaves of 4717 Populatia locala seedlings, but as in Sj6din's

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study the intensity of the colour decreased during plant development.

Genes controlling white flowering have been claimed to be pleiotropic over genes for flower and stem pigmentation and for absence of tannin. This might be explained by a single block in the shared biosynthetic pathways (Picard, 1976). Pleiotropy of white flowering with a low tannin content in the seed coat is strongly supported by experimental evidence (Bond, 1976; Crofts et al., 1980). The 9 : 4 : 3 ratio we observed (Table 2) and the absence of the combination white flowers plus purple seed- lings indicate that white flowering is also epistatic over the contrast purple seedling versus green seedling. This is in contrast with the results Goyal (1965) obtained, who found an independent 9 : 3 : 3 : 1 F2 segregation for both flower colour and stem base colour, unpigmented being dominant over pigmented. It might of course be possible that the combination no melanin spot/purple seedling ex- ists, but was missed in our experiments. This is, however, with the number of plants we used, un- likely, the probability being less than 10-8%. It therefore seems more likely that the seedling pig- mentation as found in Populatia locala is more related to the system described by Sj6din than to that described by Goyal.

Since the purple seedling colour character is not spread widely among breeding lines currently used in advanced breeding programmes and since it has been shown to be monogenic dominant over green seedling colour, it will be an attractive character-

Table 2. F2 segregation for seedling colour and absence or presence of a melanin spot on the stipulae in faba bean crosses involving a white flowered genotype, (R x H) or two lines from a near-isogenic pair, which were distinguishable by their flower colour (white, M a W vs. coloured, MAC), all having green seedlings, and 4717 Populatia locala (Pop. loc.), which has coloured flowers and purple seedlings

Cross Melanin spot 2 .: X(3:2 ~) z ~(9: ~ o:4) ~,(3: I) present absent (A : B : C : D) (A + B: C + D) (A: B)

Seedling colour purple green purple green A B A + B C D C + D

( R x H) x Pop. loc. 61 19 80 0 29 29 0 . 7 5 > P > 0.50 0 . 7 5 > P > 0.50 0 . 9 0 > P > 0.75 (MAW) × Pop. loc. 63 21 84 0 28 28 P = 1.00 P = 1.00 P = 1.00 (MAC) x Pop. loc. 41 15 56 0 0 0 0 . 9 0 > P > 0.75 Total 16--5 5-5 0 5-7 P = 1.00

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istic to use in experiments aimed at the detection of outcrossing rate.

Moreover, a detailed study of this character might help to unravel the biosynthesis and the ge- netic control of plant pigments and secondary me- tabolites such as tannins.

Acknowledgements

The authors acknowledge the financial support of the 'Stichting Nederlands Graancentrum' (NGC). We thank J. Hoogendoorn for critical reading the manuscript.

References

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Cabrera, A. & A. Martin, 1989b. Genetics of tannin content and its relationship with flower and testa colours in Viciafaba. J. Agric. Sci., Cambridge 113: 93--98.

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Vries, A.Ph. de, 1978. Cross-fertilization behaviour of some white flowering varieties of Vicia faba. Euphytica 27: 389- 395.

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