| Inheritance of seed coat color of six spring wheats
(Triticum aestivam L.) C.C. JAN and C.O. QUALSET Department of Agronomy and Range Science, University of California, Davis, California, USA It has been reported that seed coat color in wheat (Triticum aestivum L.) is controlled by three independent genes located on chromosomes 3A, 3B and 3D and the red color is dominant to the white (NILSSON-EHLE 1909, SEARS 1944, ALLAN and VOGEL 1965, METZGER and SILBAUGH 1970). Our present study was to examine the genetics of seed coat color of six spring wheat varieties, with special reference to Sharbati Sonora, presumably an induced white-seeded mutant (VARUGHESE and SWAMINANTHAN 1967), and Lerma Blanco 70, a spontaneously derived white-seeded mutant found in a population of Lerma Rojo 64 by the authors at Davis, California. Materials and Methods In 1970 four white-seeded varieties, Safed Lerma, Sharbati Sonora, Chhoti Lerma, and Lerma Blanco 70, one light red-seeded variety, Lerma Rojo 64, and one dark red-seeded variety, Sonora 64, were chosen and used in a diallel cross at Davis, California. The Indian white-seeded varieties, Safed Lerma and Chhoti Lerma, were selected from CIMMYT crosses with the parentage of II 15444 ={ (Y50 x N10-B)L52} Lerma Rojo3 for Safed Lerma and II 15929=Lerma Rojo 64 (sib) x Humantla Rojo for Chhoti Lerma. The F1's and F2's were then grown in 1971 and 1972 at Davis, respectively. One spike per plant was sampled for all the 15 F2 populations and the threshed seeds were visually observed and recorded according to the color. The X2 test was used to test the goodness of fit to the theoretical ratios. Results and Discussion Table 1 shows the seed coat color of the parents, F1 and the segregation of the F2 populations. No red-seeded plants appeared in the F1 and F2 populations of the white (W) x White (W) crosses which indicated the lack of any red alleles in Safed Lerma, Sharbati Sonora, Chhoti Lerma, and Lerma Blanco 70. For the red (R) x W or W x R crosses, the F1 plants produced red seeds with the same degree of redness of their red-seeded parents. In all these crosses, the red alleles showed very strong dominance over the white alleles. The F2 populations of R x W and W x R crosses segregated with a ratio of 3 red to 1 white indicating that both red parents have one pair of dominant red genes in homozygous condition. The F1 seed coat color of the R x R cross showed dark redness same as its dark red-seeded parent Sonora 64. Theoretically, its F2 should show darker seeds than either of the parents ; however, this could not be detected by visual observation. Probably a better method is necessary to determine the slight differences in color. The F2 population of the R x R cross segregated into 15 red to 1 white indicating that each variety carried one pair of dominant red-seed genes, probably located on different chromosomes. Based on the segregation situation discussed above, the suggested genotypes for the six varieties used are as follows : Safed Lerma. Sharbati Sonora, Chhoti Lerma, and Lerma Blanco 70, rxrxryry ; Lerma Rojo 64 RxRxryry ; Sonora 64 rxrxRyRy The intensity of red color is less with RxRx of Lerma Rojo 64 than RyRy of Sonora 64. From these results it is not possible to assign the genotypes to the specific R-loci, viz. R1,R2, and R3. The discovery of the spontaneous mutation of red-seeded Lerma Rojo 64 to white-seeded Lerma Blanco 70 indicated the possibility of utilizing naturally occurring white-seeded mutants in a breeding program and the possibility of a rather high mutation for the R-locus. Sharbati Sonora was reported by VARUGHESE and SWAMINATHAN (1967) as the direct result of gamma-irradiation without any backcrossing after being identified from an M2 population of 48,500 plants, and it resembled Sonora 64 in all respects except seed coat color. It seems quite possible that Sharbati Sonora could have also arisen as a spontaneous mutant just as Lerma Blanco 70. Literature Cited ALLAN, R.E. and O.A. VOGEL 1965. Monosomic analysis of red seed color in wheat. Crop Sci. 5: 474-475. METZGER, R.J. and B.A. SILBAUGH 1970. Location of genes for seed coat color in hexaploid wheat Triticum aestivum L. Crop Sci. 10: 495-496. NILSSON-EHLE, H. 1909. Kreuzungsuntersuchungen an Hafer und Weizen. Lunds Universitets Arsskrift, N.F., Afd. 2, Vol. 5, No. 2: 1-122. Lund. C.W.K. Gleerup. VARUGHESE, G. and M.S. SWAMINATHAN 1967. Sharbati Sonora, a symbol of the age of algeny. Indian Farming 17 (5) : 8-9. |