1. Inheritance of seed coat color of Ethiopian mustard (Brassica carinata A. Braun) Mukhlesur Rahman, Muhammad Tahir 1 Department of Plant Science, North Dakota State University, Fargo, ND 58105, USA 1 Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada OBJECTIVES MATERIALS AND METHODS RESULTS CONCLUSIONS Monogenic inheritance with yellow seed color dominant over brown seed color in B. carinata has been identified in this research. A dominant repressor gene is present in the yellow seeded parent which blocked the function of seed coat color synthesis genes. REFERENCES Bell, J.M. 1993. Factors affecting the nutritional value of canola meal: A review. Can. J. Anim. Sci. 73:679-697. Getinet, A., Rakow, G. and Downey, R.K. 1996. Agronomic performance and seed quality of Ethiopian mustard in Saskatchewan. Can. J. Plant Sci. 76: 387–392. Getinet A. and Rakow G. 1997. Repression of seed coat pigmentation in Ethiopian mustard. Can. J. Plant Sci. 77: 501–505. U, N. 1935. Genome-analysis in Brassica with special reference to the experimental formation of B. napus and its peculiar mode of fertilization. Japan J. Bot. 7:389–452. Warwick, S.I., Gugel, R.K., McDonald, T. and Falk, K.C. 2006. Genetic variation of Ethiopian mustard (Brassica carinata A. Braun) germplasm in western Canada. Genet. Resour. Crop Evol. 53: 297–312. INTRODUCTION Table 1: Segregation ratio and Chi-square tests for seed coat color in the F2 and BC1 populations of crosses and reciprocal crosses of brown seeded and yellow seeded B. carinata cultivars. Plant materials The pure breeding brown seeded cultivar ‘ACC-8’ and the pure breeding yellow seeded cultivar ‘ACC-9’ of B. carinata were collected from Dr. M.A. Malek, Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh and were selfed for three generations. Crosses and reciprocal crosses were made between the brown and the yellow seeded lines. The F 1, F 2 and F 3 plants were grown in the green house of the Department of Plant Science, University of Manitoba, Canada, and Department of Plant Science, North Dakota State University, USA. Backcross progeny were produced by crossing the F 1 plant with the respective yellow seeded and brown seeded parental lines. The seed coat colors were classified into three groups, such as yellow, yellow-brown and brown (Figure 1). Chi-square (χ 2 ) goodness of fit tests was used to check expected versus observed phenotypic segregation ratios for F 2 and BC 1 data. The objectives of this study were to describe the seed coat color inheritance and to develop high seed yield yellow seeded B. carinata germplasm. An attempt has been taken to develop molecular marker for seed coat color gene to facilitate marker assisted selection for seed coat color in B. carinata breeding programs. Brassica carinata A. Braun, known as Ethiopian mustard is an amphidiploid (2n=34, BBCC) originated from natural hybridization between two diploid species, Brassica nigra (L.) Koch (2n=16, BB) and Brassica oleracea L. (2n=18, CC) (U, 1935). This species is more compatible with the disease-, pest- and drought-tolerant in nature (Getinet et al., 1996) and could be grown where cultivated rapeseed (e.g. B. napus) is not well adapted. Moreover, B. carinata is resistant to blackleg, white rust and alternaria leaf spot which are major diseases for B. napus (Warwick et al. 2006). Yellow seeded Brassica have an advantage over the dark-seeded ones since them resulting in higher oil content in the seed. The meal from yellow seeds contains lower dietary fiber, lower antinutritional compound and higher protein content (Bell, 1993). Cultivated varieties of B. carinata are mostly brown seeded, however, yellow seeded germplasm are also available which could be used for agronomical improvement in breeding program. Therefore, B. carinata could be improved by the development high yielding yellow seeded germplasm. RESULTS & DISCUSSION Seed coat color in B. carinata displayed primarily maternal inheritance. Seed coat color varied from yellow to yellow-brown and brown (Figure 1). The yellow-brown color is darker than the parental yellow, is the result of incomplete dominance of the yellow over brown in heterozygous condition. Monogenic inheritance was found for seed coat color gene, with yellow color trait was dominant over brown color trait. The dominant nature of yellow seed coat color of B. carinata is in contrast to many previous reports in B. napus, B. juncea, B. rapa where the yellow seed was being identified as a recessive trait. The dominant nature of the yellow seed trait in B. carinata has been explained as an interaction between seed coat color gene and dominant repressor (Rp) gene. The Rp gene repress the function of seed coat color gene resulted translucent and colorless seed coat i.e. yellow seed in B. carinata (Getinet et al., 1997). Absence of the repressor gene will allow the seed coat color gene to be functioned for synthesis of seed coat pigments in the brown seed of B. carinata. The development of molecular marker for seed coat color gene/or repressor gene is in progress (Figure 2). Yellow parentBrown parent F 1 seed F 2 seed F 3 seed Figure 1. Seed coat color segregation in different F 2 [(ACC-8 x ACC-9)] and BC 1 [(ACC-8 x ACC-9) x ACC-8] populations of B. carinata crosses. PopulationsSegregation ratio Yellow/ Yellow-brown Brown seed 3 : 1 χ2χ2 dfP F 2 Populations ACC-8 x ACC-9 ACC-9 x ACC-8 110 69 42 26 0.561 0.284 1111 0.3-0.5 0.5-0.7 Total17968 BC 1 Populations1 : 1 χ2χ2 dfP (ACC-8xACC-9)xACC-8 (ACC-8xACC-9)xACC-9 53 85 44 0 0.84410.3-0.5 Total12953 Figure 2. Development of SSR marker for seed coat color gene (in progress).